Water

21 pages, 3420 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Secondary Currents with Scour Hole at Grade Control Structures

by Mouldi Ben Meftah, Diana De Padova, Francesca De Serio and Michele Mossa

Water 2021, 13(3), 319; https://doi.org/10.3390/w13030319 - 28 Jan 2021

Cited by 6 | Viewed by 2502

Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of [...] Read more.

Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of flow velocities in clear water scours downstream of a grade control structure in a channel with non-cohesive sediments, in this study, we attempted to investigate the generation and turbulence properties of secondary currents across a scour hole at equilibrium condition. The flow velocity distributions through the cross-sectional planes at the downstream location of the maximum equilibrium scour depth clearly show the development of secondary current cells. The secondary currents form a sort of helical-like motion, occurring in both halves of the cross-section in an axisymmetric fashion. A detailed analysis of the turbulence intensities and Reynolds shear stresses was carried out and compared with previous studies. The results highlight considerable spatial heterogeneities of flow turbulence. The anisotropy term of normal stresses dominates the secondary shear stress, giving the impression of its crucial role in generating secondary flow motion across the scour hole. The anisotropy term shows maximum values near both the scour mouth and the scour bed, caused, respectively, by the grade control structure and the sediment ridge formation, which play fundamental roles in maintaining and enhancing the secondary flow motion. Full article

(This article belongs to the Special Issue Flow Hydrodynamic in Open Channels: Interaction with Natural or Man-Made Structures)

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21 pages, 850 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Blue Water Visitor Monitoring Potential: A Literature Review and Alternative Proposal

by Ross G. Andrew, Robert C. Burns, Danielle Schwarzmann, Mary E. Allen and Jasmine Cardozo Moreira

Water 2021, 13(3), 305; https://doi.org/10.3390/w13030305 - 27 Jan 2021

Cited by 4 | Viewed by 3609

Abstract

This review presents a summary of existing visitor monitoring methods and relevant studies in land and marine-based areas, with a focus on the application to unique aquatic settings. Various opportunities and challenges exist with respect to the use of each method in different [...] Read more.

This review presents a summary of existing visitor monitoring methods and relevant studies in land and marine-based areas, with a focus on the application to unique aquatic settings. Various opportunities and challenges exist with respect to the use of each method in different marine settings. These methods differ in terms of the complexity, costs, level of accuracy, and detailed information they provide. Furthermore, the feasibility of applying these methods also depends on the site attributes of a marine area. Since each marine area varies in geographical scale and environmental and social conditions, some methods will be more appropriate or perform more successfully than others in a particular location. Therefore, the consideration of these methods should be part of a proposed alternative process, focused on adaptive monitoring that scales to address visitor ebbs and flows in these aquatic areas. The proposed alternative seeks to develop consensus around quantitative goals for visitor monitoring and estimating techniques in marine settings, using a customizable mix of methods and techniques. This alternative effort progresses to subsequent tasks and discussions, and recommendations are made considering the feasibility and confidence of using these methods in particular marine settings and future pilot sites. Full article

(This article belongs to the Special Issue The Blue Economy: Evaluating the Human Benefits from and Pressures on Marine and Coastal Environments)

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25 pages, 7917 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Significance of Vertical and Lateral Groundwater–Surface Water Exchange Fluxes in Riverbeds and Riverbanks: Comparing 1D Analytical Flux Estimates with 3D Groundwater Modelling

by Gert Ghysels, Christian Anibas, Henock Awol, Abebe Debele Tolche, Uwe Schneidewind and Marijke Huysmans

Water 2021, 13(3), 306; https://doi.org/10.3390/w13030306 - 27 Jan 2021

Cited by 18 | Viewed by 4258

Abstract

Riverbed temperature profiles are frequently used to estimate vertical river–aquifer exchange fluxes. Often in this approach, strictly vertical flow is assumed. However, riverbeds are heterogeneous structures often characterised by complex flow fields, possibly violating this assumption. We characterise the meter-scale variability of river–aquifer [...] Read more.

Riverbed temperature profiles are frequently used to estimate vertical river–aquifer exchange fluxes. Often in this approach, strictly vertical flow is assumed. However, riverbeds are heterogeneous structures often characterised by complex flow fields, possibly violating this assumption. We characterise the meter-scale variability of river–aquifer interaction at two sections of the Aa River, Belgium, and compare vertical flux estimates obtained with a 1D analytical solution to the heat transport equation with fluxes simulated with a 3D groundwater model (MODFLOW) using spatially distributed fields of riverbed hydraulic conductivity. Based on 115 point-in-time riverbed temperature profiles, vertical flux estimates that are obtained with the 1D solution are found to be higher near the banks than in the center of the river. The total exchange flux estimated with the 3D groundwater model is around twice as high as the estimate based on the 1D solution, while vertical flux estimates from both methods are within a 10% margin. This is due to an important contribution of non-vertical flows, especially through the riverbanks. Quasi-vertical flow is only found near the center of the river. This quantitative underestimation should be considered when interpreting exchange fluxes based on 1D solutions. More research is necessary to assess conditions for which using a 1D analytical approach is justified to more accurately characterise river–aquifer exchange fluxes. Full article

(This article belongs to the Section Hydrology)

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15 pages, 4003 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Impacts of Irrigation Water on the Hydrodynamics and Saline Behavior of the Shallow Alluvial Aquifer in the Senegal River Delta

by Abdoul Aziz Gning, Philippe Orban, Raymond Malou, Joost Wellens, Johan Derouane, Mansour Gueye and Serge Brouyère

Water 2021, 13(3), 311; https://doi.org/10.3390/w13030311 - 27 Jan 2021

Cited by 1 | Viewed by 2475

Abstract

The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by [...] Read more.

The Senegal River Delta located in north-western Senegal is a strategic region for the development of irrigated rice cultivation for achieving rice self-sufficiency. The presence of a shallow salty water table is often considered as a brake to the development of irrigation, by causing salinization of the soil, although the mechanisms of operation are not well known. An experimental study was carried out in a rice paddy located in the village of Ndiaye, 35 km north from Saint Louis, to characterize the water and solute flux processes below the irrigated plots. The objective was to better understand the irrigation-driven dynamics of soil salinization processes. An experimental monitoring network was installed for monitoring the transit of water at the plot level, in the unsaturated zone and in the aquifer. The results show that the supply of water by irrigation contributes to significantly recharging the water table, as shown by the rise in piezometric level, with a concomitant dilution of the water salinity in the soil zone and in the shallow groundwater. However, when irrigation is stopped, the groundwater level and salinity return within a month to their initial level and salinity status because of the evaporative recovery, which strongly governs these processes. Thus, water flow and solute transfers operate in the delta following a recharge–discharge and dilution–concentration cycle controlled by the water balance, and we do not expect to observe in the short- to middle-term any significant reduction in soil salinization processes by drainage. Full article

(This article belongs to the Section Hydrology)

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21 pages, 4882 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

An RF-PCE Hybrid Surrogate Model for Sensitivity Analysis of Dams

by Mohammad Amin Hariri-Ardebili, Golsa Mahdavi, Azam Abdollahi and Ali Amini

Water 2021, 13(3), 302; https://doi.org/10.3390/w13030302 - 26 Jan 2021

Cited by 34 | Viewed by 5284

Abstract

Quantification of structural vibration characteristics is an essential task prior to perform any dynamic health monitoring and system identification. Anatomy of vibration in concrete arch dams (especially tall dams with un-symmetry shape) is very complicated and requires special techniques to solve the eigenvalue [...] Read more.

Quantification of structural vibration characteristics is an essential task prior to perform any dynamic health monitoring and system identification. Anatomy of vibration in concrete arch dams (especially tall dams with un-symmetry shape) is very complicated and requires special techniques to solve the eigenvalue problem. The situation becomes even more complicated if the material distribution is assumed to be heterogeneous within the dam body (as opposed to conventional isotropic homogeneous relationship). This paper proposes a hybrid Random Field (RF)–Polynomial Chaos Expansion (PCE) surrogate model for uncertainty quantification and sensitivity assessment of dams. For different vibration modes, the most sensitive spatial locations within dam body are identified using both Sobol’s indices and correlation rank methods. Results of the proposed hybrid model is further validated using the classical random forest regression method. The outcome of this study can improve the results of system identification and dynamic analysis by properly determining the vibration characteristics. Full article

(This article belongs to the Special Issue Soft Computing and Machine Learning in Dam Engineering)

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17 pages, 10459 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Water Lice and Other Macroinvertebrates in Drinking Water Pipes: Diversity, Abundance and Health Risk

by Günter Gunkel, Ute Michels and Michael Scheideler

Water 2021, 13(3), 276; https://doi.org/10.3390/w13030276 - 24 Jan 2021

Cited by 14 | Viewed by 5629

Abstract

Activities to ensure and maintain water quality in drinking water networks, including flushing, are presented after standardized hydrant sampling combined with a stainless-steel low pressure–high flow rate (NDHF) filter and a 100 µm mesh size was used to separate pipe inhabitants. A databank [...] Read more.

Activities to ensure and maintain water quality in drinking water networks, including flushing, are presented after standardized hydrant sampling combined with a stainless-steel low pressure–high flow rate (NDHF) filter and a 100 µm mesh size was used to separate pipe inhabitants. A databank of more than 1000 hydrant samples in European lowland areas was developed and used to analyze the diversity and abundance of macroinvertebrates in drinking water networks. Load classes for water louse (Asellus aquaticus) and oligochaetes are given with three evaluation classes: normal colonization, increased colonization, and mass development. The response of Asellus aquaticus in drinking water networks to environmental conditions are presented as are their growth and reproduction, promotion of a third generation by climate change effects, food limitations, and the composition and stability of their feces. Finally, the health risks posed by dead water lice and water lice feces with bacterial regrowth and the promotion of microbe development on house filters are analyzed. Full article

(This article belongs to the Special Issue Multi-Quality Water Distribution Systems Analysis: Simulation and Management)

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18 pages, 307 KiB

Open AccessEditor’s ChoiceArticle

Equity vs. Efficiency and the Human Right to Water

by Manuel Prieto

Water 2021, 13(3), 278; https://doi.org/10.3390/w13030278 - 24 Jan 2021

Cited by 15 | Viewed by 5415

Abstract

One of the most crucial discussions within water resource management is the debate between those who defend the concept of economic efficiency and those who privilege notions of social equity. This tension is located at the core of binary categories that currently constitute [...] Read more.

One of the most crucial discussions within water resource management is the debate between those who defend the concept of economic efficiency and those who privilege notions of social equity. This tension is located at the core of binary categories that currently constitute the public debate within comparative water law and policy. These categories are commodity/human right, private property/common property, free-market/state regulation, and market value/community value. This paper explores this tension by studying how neoclassical economics understands efficiency and tracing its rise as a key hegemonic principle for water resource management. I also present equity as a conceptual opposition to efficiency and describe its institutionalization through the human-right-to-water frame. A problematization of both the equity approach and the human-right-to-water frame follows. Finally, I propose a political ecology approach to better understand the tension between efficiency and equity and offer recommendations for informing the water research agenda on efficiency/equity. Full article

(This article belongs to the Special Issue The Politics of the Human Right to Water)

23 pages, 14115 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Performance Improvement of a Drag Hydrokinetic Turbine

by Mabrouk Mosbahi, Mariem Lajnef, Mouna Derbel, Bouzid Mosbahi, Costanza Aricò, Marco Sinagra and Zied Driss

Water 2021, 13(3), 273; https://doi.org/10.3390/w13030273 - 23 Jan 2021

Cited by 19 | Viewed by 5262

Abstract

Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a [...] Read more.

Hydropower is at present in many locations, among all the other possible renewable energy sources, the best one for net cost per unit power. In contrast to traditional installation, based on water storage in artificial basins, free flow river turbines also provide a very low environmental impact due to their negligible effect on solid transport. Among them, kinetic turbines with vertical axis are very inexpensive and have almost zero impact on fish and local fauna. In application to tidal waves and sea waves, where vertically averaged velocities have alternate direction, a Savonius rotor also has the advantage of being productive during the whole time cycle. In this work, the effect of an upstream deflector system mounted upstream of a twisted Savonius rotor inside a channel has been investigated through numerical simulations and experimental tests. Numerical simulations were carried on using the ANSYS FLUENT 17.0 software. Based on this numerical study, it is shown that the proposed deflector system has improved the power coefficient of the Savonius rotor by 14%. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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21 pages, 7330 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on Landslides in Terraced Fields in the Chinese Loessial Region under Extreme Rainfall

by Yongfu Wen, Peng Gao, Xingmin Mu, Mengzhen Li, Yongjun Su and Haixing Wang

Water 2021, 13(3), 270; https://doi.org/10.3390/w13030270 - 22 Jan 2021

Cited by 15 | Viewed by 3729

Abstract

Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow [...] Read more.

Due to the development of the scale of tractor-ploughed terraces, terraces have been increasing in number, while global climate change is causing frequent extreme rainfall events in the Loess Plateau, resulting in many terrace landslides. To study the mechanism and process of shallow landslides and deep slip surface of terraces induced by extreme rainfall in loess hill and gully area, we conducted a laboratory model test of a terrace under artificial rainfall and used the Swedish arc strip method. The research results are as follows. The mechanism of shallow landslides in terraces is rill erosion accelerating rainfall infiltration, suspending the slope, and increasing its bulk density. The destruction process of shallow landslides can be roughly divided into six processes, and the earth volume of the landslide is 0.24 m³. The mechanism of the deep sliding surface in terraces occurs under the combined action of water erosion and gravity erosion. The soil moisture content increases, which decreases the anti-sliding moment and increases the sliding moment, and the safety factor becomes less than the allowable limit for terraces. The deep sliding deformation area of the terrace was 0~1.0 m below the slope surface, slip surface radius was 1.43 m, the slip surface angle was 92^°, and the deep sliding surface began to form earlier than terraced shallow landslides. The displacement of the characteristic points increased from the slope top, to the slope center, and to the slope foot, with maximum displacements of 40.3, 15.5, and 6.0 mm, respectively. Full article

(This article belongs to the Special Issue Soil–Water Conservation, Erosion, and Landslide)

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18 pages, 1408 KiB

Open AccessEditor’s ChoiceReview

The Impacts of Hydropower Dams in the Mekong River Basin: A Review

by Akarath Soukhaphon, Ian G. Baird and Zeb S. Hogan

Water 2021, 13(3), 265; https://doi.org/10.3390/w13030265 - 22 Jan 2021

Cited by 141 | Viewed by 38941

Abstract

The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams [...] Read more.

The Mekong River, well known for its aquatic biodiversity, is important to the social, physical, and economic health of millions living in China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. This paper explores the social and environmental impacts of several Mekong basin hydropower dams and groupings of dams and the geographies of their impacts. Specifically, we examined the 3S (Sesan, Sekong Srepok) river system in northeastern Cambodia, the Central Highlands of Vietnam, and southern Laos; the Khone Falls area in southern Laos; the lower Mun River Basin in northeastern Thailand; and the upper Mekong River in Yunnan Province, China, northeastern Myanmar, northern Laos, and northern Thailand. Evidence shows that these dams and groupings of dams are affecting fish migrations, river hydrology, and sediment transfers. Such changes are negatively impacting riparian communities up to 1000 km away. Because many communities depend on the river and its resources for their food and livelihood, changes to the river have impacted, and will continue to negatively impact, food and economic security. While social and environmental impact assessments have been carried out for these projects, greater consideration of the scale and cumulative impacts of dams is necessary. Full article

(This article belongs to the Special Issue Channels for Change: Integrating Multiple Disciplines for New Frontiers in Managing the Mekong River Basin)

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17 pages, 3718 KiB

Open AccessEditor’s ChoiceArticle

Estimating the Pan Evaporation in Northwest China by Coupling CatBoost with Bat Algorithm

by Liming Dong, Wenzhi Zeng, Lifeng Wu, Guoqing Lei, Haorui Chen, Amit Kumar Srivastava and Thomas Gaiser

Water 2021, 13(3), 256; https://doi.org/10.3390/w13030256 - 21 Jan 2021

Cited by 42 | Viewed by 4241

Abstract

Accurate estimation of pan evaporation (E_p) is vital for the development of water resources and agricultural water management, especially in arid and semi-arid regions where it is restricted to set up the facilities and measure pan evaporation accurately and consistently. Besides, [...] Read more.

Accurate estimation of pan evaporation (E_p) is vital for the development of water resources and agricultural water management, especially in arid and semi-arid regions where it is restricted to set up the facilities and measure pan evaporation accurately and consistently. Besides, using pan evaporation estimating models and pan coefficient (kp) models is a classic method to assess the reference evapotranspiration (ET₀) which is indispensable to crop growth, irrigation scheduling, and economic assessment. This study estimated the potential of a novel hybrid machine learning model Coupling Bat algorithm (Bat) and Gradient boosting with categorical features support (CatBoost) for estimating daily pan evaporation in arid and semi-arid regions of northwest China. Two other commonly used algorithms including random forest (RF) and original CatBoost (CB) were also applied for comparison. The daily meteorological data for 12 years (2006–2017) from 45 weather stations in arid and semi-arid areas of China, including minimum and maximum air temperature (T_min, T_max), relative humidity (RH), wind speed (U), and global solar radiation (R_s), were utilized to feed the three models for exploring the ability in predicting pan evaporation. The results revealed that the new developed Bat-CB model (RMSE = 0.859–2.227 mm·d⁻¹; MAE = 0.540–1.328 mm·d⁻¹; NSE = 0.625–0.894; MAPE = 0.162–0.328) was superior to RF and CB. In addition, CB (RMSE = 0.897–2.754 mm·d⁻¹; MAE = 0.531–1.77 mm·d⁻¹; NSE = 0.147–0.869; MAPE = 0.161–0.421) slightly outperformed RF (RMSE = 1.005–3.604 mm·d⁻¹; MAE = 0.644–2.479 mm·d⁻¹; NSE = −1.242–0.894; MAPE = 0.176–0.686) which had poor ability to operate the erratic changes of pan evaporation. Furthermore, the improvement of Bat-CB was presented more comprehensively and obviously in the seasonal and spatial performance compared to CB and RF. Overall, Bat-CB has high accuracy, robust stability, and huge potential for E_p estimation in arid and semi-arid regions of northwest China and the applications of findings in this study have equal significance for adjacent countries. Full article

(This article belongs to the Section Hydrology)

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15 pages, 3737 KiB

Open AccessEditor’s ChoiceArticle

Climate Control of Multidecadal Variability in River Discharge and Precipitation in Western Europe

by Isabel Jalón-Rojas and Bruno Castelle

Water 2021, 13(3), 257; https://doi.org/10.3390/w13030257 - 21 Jan 2021

Cited by 14 | Viewed by 3428

Abstract

The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices [...] Read more.

The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices in this region. Results show that winter river flow is characterized by large interannual variability, best correlates with (a) the North Atlantic Oscillation (NAO) at the far-northern (R up to 0.56) and southern latitudes (R up to −0.72), and (b) the West Europe Pressure Anomaly (WEPA) at the middle and northern latitudes, from 42° N to 55° N (R up to 0.83). These indices also explain the interannual variability in autumn and spring discharge in rivers characterized by secondary floods. Compared to the other leading modes of atmospheric variability, WEPA increases the correlations with winter precipitation up to 0.8 in many regions of western and central Europe. A positive WEPA corresponds to a southward shift and an intensification of the Icelandic-Low/Azores-High dipole, driving enhanced precipitation and river discharge in these regions. The correlations with precipitation are slightly higher than those with river discharge, particularly in France, with clear latitudinal gradient. This trend suggests that water storage variability and other catchment characteristics may also influence the interannual variability of river discharge. Seasonal forecasting of the WEPA and NAO winter indices can become a powerful tool in anticipating hydrological risks in this region. Full article

(This article belongs to the Section Hydrology)

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13 pages, 2599 KiB

Open AccessEditor’s ChoiceArticle

Increase in Daily Household Water Demand during the First Wave of the Covid-19 Pandemic in Germany

by Deike U. Lüdtke, Robert Luetkemeier, Michael Schneemann and Stefan Liehr

Water 2021, 13(3), 260; https://doi.org/10.3390/w13030260 - 21 Jan 2021

Cited by 90 | Viewed by 8075

Abstract

Precautionary measures and governmental regulations during the COVID-19 pandemic’s first wave have drastically altered daily activities and hence water consumption patterns. Many people had to change their working routines, the organization of childcare and hygiene practices. While first evidence appears on the impacts [...] Read more.

Precautionary measures and governmental regulations during the COVID-19 pandemic’s first wave have drastically altered daily activities and hence water consumption patterns. Many people had to change their working routines, the organization of childcare and hygiene practices. While first evidence appears on the impacts of COVID-19 on, e.g., carbon emissions, energy demand and water treatment, even indicating an unexpected increase in water consumption during that period, no study has investigated the pandemic’s sole and in-depth implications for water supply so far. This paper investigates hourly and daily water consumption volumes of a utility in northern Germany for the first wave of the pandemic. We performed a linear mixed model to compare the 2020 daily water consumption volumes with previous years. We eliminated the effects of climate using Bayesian statistic in order to carve out and estimate the original COVID-19 effect. We also compared hourly water consumption of similar time periods and calculated the percentage difference between 2020 and the two previous years. Our results reveal about 14.3% (3 968 m³) higher residential water consumption per day with higher morning and evening demand peaks during the day. We hypothesis that the reasons for the increasing water demand may be found in changed behavioral routines with an important question for water utilities, if and which of these new dynamics may persist after COVID-19 and hence pose a challenge for long-term infrastructure planning. Full article

(This article belongs to the Section Water Use and Scarcity)

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15 pages, 9838 KiB

Open AccessEditor’s ChoiceArticle

How Much Does Water Management Cost? The Case of the Water Market in the Ñuble River of South-Central Chile

by Bratian Buzolic, José Luis Arumí and Jorge Jimenez

Water 2021, 13(3), 258; https://doi.org/10.3390/w13030258 - 21 Jan 2021

Cited by 8 | Viewed by 3742

Abstract

Economic and population growth has increased the demand for freshwater worldwide, generating pressure on the environment and creating conflicts among users. Water markets have emerged as a solution for managing this resource, and Chile has been a pioneer in implementing this approach. However, [...] Read more.

Economic and population growth has increased the demand for freshwater worldwide, generating pressure on the environment and creating conflicts among users. Water markets have emerged as a solution for managing this resource, and Chile has been a pioneer in implementing this approach. However, most Chilean water markets are inefficient due to incomplete information, the poor flexibility of the water distribution system, and high transaction costs. This study analyzes the Ñuble River water market and estimates the economic and social costs of its inefficiencies through a methodology based on the marginal profitability of water, which simulates the operation of a perfect market for the Ñuble River irrigation system. Net benefit losses from market inefficiencies were estimated at 7.6 million dollars annually, which is equivalent to a 25% increase in the net returns of the current river water distribution strategy. Losses of economic benefits are even greater as the availability of water flow decreases. This is important considering that in the last decade the water flows of the Ñuble River have decreased by more than 30% compared to their historical average. Full article

(This article belongs to the Special Issue Analysis, Evaluation and Optimization of Infrastructures Serving Water Systems)

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27 pages, 6709 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Optical Methods for River Monitoring: A Simulation-Based Approach to Explore Optimal Experimental Setup for LSPIV

by Dario Pumo, Francesco Alongi, Giuseppe Ciraolo and Leonardo V. Noto

Water 2021, 13(3), 247; https://doi.org/10.3390/w13030247 - 20 Jan 2021

Cited by 15 | Viewed by 4219

Abstract

Recent advances in image-based methods for environmental monitoring are opening new frontiers for remote streamflow measurements in natural environments. Such techniques offer numerous advantages compared to traditional approaches. Despite the wide availability of cost-effective devices and software for image processing, these techniques are [...] Read more.

Recent advances in image-based methods for environmental monitoring are opening new frontiers for remote streamflow measurements in natural environments. Such techniques offer numerous advantages compared to traditional approaches. Despite the wide availability of cost-effective devices and software for image processing, these techniques are still rarely systematically implemented in practical applications, probably due to the lack of consistent operational protocols for both phases of images acquisition and processing. In this work, the optimal experimental setup for LSPIV based flow velocity measurements under different conditions is explored using the software PIVlab, investigating performance and sensitivity to some key factors. Different synthetic image sequences, reproducing a river flow with a realistic velocity profile and uniformly distributed floating tracers, are generated under controlled conditions. Different parametric scenarios are created considering diverse combinations of flow velocity, tracer size, seeding density, and environmental conditions. Multiple replications per scenario are processed, using descriptive statistics to characterize errors in PIVlab estimates. Simulations highlight the crucial role of some parameters (e.g., seeding density) and demonstrate how appropriate video duration, frame-rate and parameters setting in relation to the hydraulic conditions can efficiently counterbalance many of the typical operative issues (i.e., scarce tracer concentration) and improve algorithms performance. Full article

(This article belongs to the Section Hydrology)

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16 pages, 3044 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Interaction of Very Large Scale Motion of Coherent Structures with Sediment Particle Exposure

by Sencer Yücesan, Daniel Wildt, Philipp Gmeiner, Johannes Schobesberger, Christoph Hauer, Christine Sindelar, Helmut Habersack and Michael Tritthart

Water 2021, 13(3), 248; https://doi.org/10.3390/w13030248 - 20 Jan 2021

Cited by 6 | Viewed by 3451

Abstract

A systematic variation of the exposure level of a spherical particle in an array of multiple spheres in a high Reynolds number turbulent open-channel flow regime was investigated while using the Large Eddy Simulation method. Our numerical study analysed hydrodynamic conditions of a [...] Read more.

A systematic variation of the exposure level of a spherical particle in an array of multiple spheres in a high Reynolds number turbulent open-channel flow regime was investigated while using the Large Eddy Simulation method. Our numerical study analysed hydrodynamic conditions of a sediment particle based on three different channel configurations, from full exposure to zero exposure level. Premultiplied spectrum analysis revealed that the effect of very-large-scale motion of coherent structures on the lift force on a fully exposed particle resulted in a bi-modal distribution with a weak low wave number and a local maximum of a high wave number. Lower exposure levels were found to exhibit a uni-modal distribution. Full article

(This article belongs to the Special Issue Advanced Modelling Strategies for Hydraulic Engineering and River Research)

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21 pages, 5660 KiB

Open AccessEditor’s ChoiceArticle

Spatially Variable Precipitation and Its Influence on Water Balance in a Headwater Alpine Basin, Nepal

by Taufique H. Mahmood, Jaakko Putkonen and Aaron Sobbe

Water 2021, 13(3), 254; https://doi.org/10.3390/w13030254 - 20 Jan 2021

Cited by 2 | Viewed by 2481

Abstract

The current knowledge of the spatial variability of precipitation in High Mountain Asia is based on the remotely-sensed estimates (coarse spatial and temporal resolution) or data from sparsely-distributed rain gauges. However, as precipitation is strongly affected by topography in mountainous terrain, the spatially [...] Read more.

The current knowledge of the spatial variability of precipitation in High Mountain Asia is based on the remotely-sensed estimates (coarse spatial and temporal resolution) or data from sparsely-distributed rain gauges. However, as precipitation is strongly affected by topography in mountainous terrain, the spatially varying precipitation and the resulting water balances are currently poorly understood. To fill this gap in knowledge, we studied the spatial variation of the precipitation and its impact on water balance in a small headwater basin located in the foothills of the Himalaya, Nepal. We deployed ten rain gauges and climate stations, spanning the whole elevation range 700–4500 m above sea level (masl) for a period of four years. Our results show a quadratic polynomial relationship between annual precipitation and station elevation, which are used to produce annual precipitation maps. The performance of the elevation-based precipitation estimates is adequate in closing the water balance while the performances of average precipitation and Thiessen polygon method are poor and inconsistent in closing the water balance. We also demonstrate that precipitation estimates from one or two gauges at the lowest basin elevation substantially underestimate the water balance. However, the precipitation from one or two rain gauges at 2000–3000 masl provide a significantly better estimate of the water balance of a small headwater basin. Full article

(This article belongs to the Section Hydrology)

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13 pages, 2208 KiB

Open AccessEditor’s ChoiceArticle

A Canopy Transpiration Model Based on Scaling Up Stomatal Conductance and Radiation Interception as Affected by Leaf Area Index

by Muhammad Shahinur Alam, David William Lamb and Nigel W. M. Warwick

Water 2021, 13(3), 252; https://doi.org/10.3390/w13030252 - 20 Jan 2021

Cited by 14 | Viewed by 5324

Abstract

Estimating transpiration as an individual component of canopy evapotranspiration using a theoretical approach is extremely useful as it eliminates the complexity involved in partitioning evapotranspiration. A model to predict transpiration based on radiation intercepted at various levels of canopy leaf area index (LAI) [...] Read more.

Estimating transpiration as an individual component of canopy evapotranspiration using a theoretical approach is extremely useful as it eliminates the complexity involved in partitioning evapotranspiration. A model to predict transpiration based on radiation intercepted at various levels of canopy leaf area index (LAI) was developed in a controlled environment using a pasture species, tall fescue (Festuca arundinacea var. Demeter). The canopy was assumed to be a composite of two indistinct layers defined as sunlit and shaded; the proportion of which was calculated by utilizing a weighted model (W model). The radiation energy utilized by each layer was calculated from the PAR at the top of the canopy and the fraction of absorbed photosynthetically active radiation (fAPAR) corresponding to the LAI of the sunlit and shaded layers. A relationship between LAI and fAPAR was also established for this specific canopy to aid the calculation of energy interception. Canopy conductance was estimated from scaling up of stomatal conductance measured at the individual leaf level. Other environmental factors that drive transpiration were monitored accordingly for each individual layer. The Penman–Monteith and Jarvis evapotranspiration models were used as the basis to construct a modified transpiration model suitable for controlled environment conditions. Specially, constructed self-watering tubs were used to measure actual transpiration to validate the model output. The model provided good agreement of measured transpiration (actual transpiration = 0.96 × calculated transpiration, R² = 0.98; p < 0.001) with the predicted values. This was particularly so at lower LAIs. Probable reasons for the discrepancy at higher LAI are explained. Both the predicted and experimental transpiration varied from 0.21 to 0.56 mm h⁻¹ for the range of available LAIs. The physical proportion of the shaded layer exceeded that of the sunlit layer near LAI of 3.0, however, the contribution of the sunlit layer to the total transpiration remains higher throughout the entire growing season. Full article

(This article belongs to the Special Issue Evapotranspiration Measurements and Modeling)

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15 pages, 8150 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Distribution Uniformity in Intensive Horticultural Systems of Almería and Influence of the Production System and Water Quality

by Juana Isabel Contreras, José Roldán-Cañas, Maria Fatima Moreno-Pérez, Pedro Gavilán, David Lozano and Rafael Baeza

Water 2021, 13(2), 233; https://doi.org/10.3390/w13020233 - 19 Jan 2021

Cited by 9 | Viewed by 3389

Abstract

The high productivity and efficiency of the use of irrigation water that characterizes greenhouse horticultural crops can be affected by poor irrigation distribution uniformity. The objective of this work was to estimate the average irrigation distribution uniformity (DU) of the greenhouses in Almería, [...] Read more.

The high productivity and efficiency of the use of irrigation water that characterizes greenhouse horticultural crops can be affected by poor irrigation distribution uniformity. The objective of this work was to estimate the average irrigation distribution uniformity (DU) of the greenhouses in Almería, determining the influence of the irrigation water quality as well as the production system on this uniformity. A prospective study was carried out in which commercial farms were selected that used different water qualities (groundwater vs. reclaimed) with different production systems (organic vs. conventional/integrated). The average irrigation distribution uniformity in the greenhouses of Almería was 80%. The farms with organic production systems presented a drastic DU reduction with respect to conventional farms (48% vs. 88%). The DU of the irrigation water presented in commercial farms irrigated with reclaimed water presented a lower DU than those irrigated with groundwater (76% vs. 86%). The distribution of irrigation depth of water in the greenhouses showed slight variations (from 3.2 to 2.9 mm) depending on the emitter position, with the highest values being at the head of the sub-main pipe and dripper line and the lowest at the end of the sub-main pipe and dripper line. The depth of water values was very close to the theoretical average of 3 mm. Water quality affects the distribution pattern of the depth of water in greenhouses. Installations irrigated with reclaimed water showed greater oscillation of the water depth within the sub-unit, varying from 3.6 to 2.0 mm, although the average depth was located close to the theoretical depth (3 mm). The production system affected the distribution of the depth of water—in the organic system, the depth underwent greater variation depending on the position of the emitter in the sub-unit, ranging from 1.7 to 3.3 mm. In addition, within this production system, the median depth of water was close to 2.5 mm, lower than the theoretical depth (3 mm), which denoted a certain generalized filling that was accentuated at the end of the dripper line and sub-main pipe. Full article

(This article belongs to the Special Issue Water and Irrigation Management in Arid and Semiarid Zones)

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27 pages, 6797 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Flood Susceptibility Assessment Using Novel Ensemble of Hyperpipes and Support Vector Regression Algorithms

by Asish Saha, Subodh Chandra Pal, Alireza Arabameri, Thomas Blaschke, Somayeh Panahi, Indrajit Chowdhuri, Rabin Chakrabortty, Romulus Costache and Aman Arora

Water 2021, 13(2), 241; https://doi.org/10.3390/w13020241 - 19 Jan 2021

Cited by 129 | Viewed by 7422

Abstract

Recurrent floods are one of the major global threats among people, particularly in developing countries like India, as this nation has a tropical monsoon type of climate. Therefore, flood susceptibility (FS) mapping is indeed necessary to overcome this type of natural hazard phenomena. [...] Read more.

Recurrent floods are one of the major global threats among people, particularly in developing countries like India, as this nation has a tropical monsoon type of climate. Therefore, flood susceptibility (FS) mapping is indeed necessary to overcome this type of natural hazard phenomena. With this in mind, we evaluated the prediction performance of FS mapping in the Koiya River basin, Eastern India. The present research work was done through preparation of a sophisticated flood inventory map; eight flood conditioning variables were selected based on the topography and hydro-climatological condition, and by applying the novel ensemble approach of hyperpipes (HP) and support vector regression (SVR) machine learning (ML) algorithms. The ensemble approach of HP-SVR was also compared with the stand-alone ML algorithms of HP and SVR. In relative importance of variables, distance to river was the most dominant factor for flood occurrences followed by rainfall, land use land cover (LULC), and normalized difference vegetation index (NDVI). The validation and accuracy assessment of FS maps was done through five popular statistical methods. The result of accuracy evaluation showed that the ensemble approach is the most optimal model (AUC = 0.915, sensitivity = 0.932, specificity = 0.902, accuracy = 0.928 and Kappa = 0.835) in FS assessment, followed by HP (AUC = 0.885) and SVR (AUC = 0.871). Full article

(This article belongs to the Special Issue Flash-Flood Susceptibility, Forecast and Warning)

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19 pages, 11278 KiB

Open AccessEditor’s ChoiceArticle

Mechanisms of Flood-Induced Levee Breaching in Marumori Town during the 2019 Hagibis Typhoon

by Nguyen Xuan Tinh, Hitoshi Tanaka, Gen Abe, Yuka Okamoto and Kwanchai Pakoksung

Water 2021, 13(2), 244; https://doi.org/10.3390/w13020244 - 19 Jan 2021

Cited by 3 | Viewed by 3777

Abstract

Typhoon Hagibis, which occurred at the beginning of October 2019, was one of the largest and most powerful tropical cyclones and was considered to be the most devastating typhoon to hit Japan in recorded history. Extreme heavy rainfall caused massive impacts to Japan [...] Read more.

Typhoon Hagibis, which occurred at the beginning of October 2019, was one of the largest and most powerful tropical cyclones and was considered to be the most devastating typhoon to hit Japan in recorded history. Extreme heavy rainfall caused massive impacts to Japan in general and to Marumori Town, Miyagi Prefecture in particular. In the present study, the detailed flood characteristics at Marumori Town were investigated by using field observation and numerical simulations. The obtained data immediately after the flood has clearly shown that most levee breaches were caused by the water overflow on the river embankment at the constriction areas such as the tributaries’ junction and the intersection of the river embankment. Numerical simulations were performed to investigate the mechanism of levee breaching in Marumori Town. According to the simulation results, the flooding water from the upstream levee breach locations flowed into the paddy field area and caused the levee to breach at the river embankment interaction in the downstream area. A new levee breach criterion in terms of overflow depth and its duration on the river embankment was proposed. In addition, a sensitivity analysis was also performed to understand the effect of the backwater and phase lag of water level rise between the mainstream and tributaries. Although there have been many studies on flood disasters, the typhoon’s flood-induced disasters on the river and coastal infrastructures have still remained a big challenge. The present study outcomes provide useful information not only to understand how the river embankment of tributaries is vulnerable to water level rise, but also to support the river authorities to prepare better mitigation plans for future flood disasters. Full article

(This article belongs to the Section Water Erosion and Sediment Transport)

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13 pages, 1459 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Drip Irrigation on Soil Water Balance and Water Use Efficiency of Maize in Northwest China

by Yahui Wang, Sien Li, Yaokui Cui, Shujing Qin, Hui Guo, Danni Yang and Chunyu Wang

Water 2021, 13(2), 217; https://doi.org/10.3390/w13020217 - 18 Jan 2021

Cited by 26 | Viewed by 6133

Abstract

Drip irrigation (DI) has been widely utilized for crops and its water-saving effect has been confirmed by numerous studies. However, whether this technology can save so much water under the field scale during practical application is still uncertain. In order to answer this [...] Read more.

Drip irrigation (DI) has been widely utilized for crops and its water-saving effect has been confirmed by numerous studies. However, whether this technology can save so much water under the field scale during practical application is still uncertain. In order to answer this question, evapotranspiration (ET), soil water content, transpiration and evaporation over the DI and border irrigation (BI) in an arid area of NW China were continuously measured by two eddy covariance systems, micro-lysimeters, the packaged stem sap flow gauges and CS616 sensors during 2014–2018 growing seasons. The results showed that the DI averagely increased crop water use efficiency (CWUE) by 11% per year against BI. The deep drainage under DI treatment was lower than BI by 8% averagely for the five-year period. While for the ET, the DI averagely decreased ET by 7% and 40mm per year against the traditional BI. The decrease in ET was mainly due to the significant reduction in soil evaporation instead of transpiration. Oppositely, we found that DI may increase maize (Zea mays L.) transpiration in some year for the better preponderant growth of crop. Thus, the accelerating effect on transpiration of DI and its reducing effect on soil evaporation should be considered simultaneously. In our experiment, DI only improved CWUE and WUE (water use efficiency) by 11% and 15% on average in a large farmland scale, unable to always be more than a 20% improvement, as concluded by many other field experiments. Consequently, the water-saving effect of DI should not be overestimated in water resource evaluation. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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27 pages, 4609 KiB

Open AccessEditor’s ChoiceArticle

Evapotranspiration Response to Climate Change in Semi-Arid Areas: Using Random Forest as Multi-Model Ensemble Method

by Marcos Ruiz-Aĺvarez, Francisco Gomariz-Castillo and Francisco Alonso-Sarría

Water 2021, 13(2), 222; https://doi.org/10.3390/w13020222 - 18 Jan 2021

Cited by 17 | Viewed by 4005

Abstract

Large ensembles of climate models are increasingly available either as ensembles of opportunity or perturbed physics ensembles, providing a wealth of additional data that is potentially useful for improving adaptation strategies to climate change. In this work, we propose a framework to evaluate [...] Read more.

Large ensembles of climate models are increasingly available either as ensembles of opportunity or perturbed physics ensembles, providing a wealth of additional data that is potentially useful for improving adaptation strategies to climate change. In this work, we propose a framework to evaluate the predictive capacity of 11 multi-model ensemble methods (MMEs), including random forest (RF), to estimate reference evapotranspiration (ET

_{0}

) using 10 AR5 models for the scenarios RCP4.5 and RCP8.5. The study was carried out in the Segura Hydrographic Demarcation (SE of Spain), a typical Mediterranean semiarid area. ET

_{0}

was estimated in the historical scenario (1970–2000) using a spatially calibrated Hargreaves model. MMEs obtained better results than any individual model for reproducing daily ET

_{0}

. In validation, RF resulted more accurate than other MMEs (Kling–Gupta efficiency (KGE)

M = 0.903

,

S D = 0.034

for KGE and

M = 3.17

,

S D = 2.97

for absolute percent bias). A statistically significant positive trend was observed along the 21st century for RCP8.5, but this trend stabilizes in the middle of the century for RCP4.5. The observed spatial pattern shows a larger ET

_{0}

increase in headwaters and a smaller increase in the coast. Full article

(This article belongs to the Special Issue Evapotranspiration Measurements and Modeling)

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25 pages, 9879 KiB

Open AccessEditor’s ChoiceArticle

Checking the Plausibility of Modelled Nitrate Concentrations in the Leachate on Federal State Scale in Germany

by Tim Wolters, Nils Cremer, Michael Eisele, Frank Herrmann, Peter Kreins, Ralf Kunkel and Frank Wendland

Water 2021, 13(2), 226; https://doi.org/10.3390/w13020226 - 18 Jan 2021

Cited by 15 | Viewed by 3757

Abstract

In Germany, modelled nitrate concentrations in the leachate are of great importance for the development of scenarios for the long-term achievement of the groundwater quality target according to the specific requirements of the EU Water Framework Directive as well as within the context [...] Read more.

In Germany, modelled nitrate concentrations in the leachate are of great importance for the development of scenarios for the long-term achievement of the groundwater quality target according to the specific requirements of the EU Water Framework Directive as well as within the context of the recently adopted general administrative regulation for the designation of nitrate-polluted areas in Germany. For the German federal states of North Rhine-Westphalia (NRW) and Rhineland-Palatinate (RLP), an area-covering modelling of mean long-term nitrate concentrations in leachate with high spatial resolution was carried out using the model system RAUMIS-mGROWA-DENUZ. Hotspot regions with nitrate concentrations in the leachate of 50 mg NO₃/L and more were identified for intensively farmed areas in the Münsterland, Lower Rhine, and Vorderpfalz. The validity of modelled values was checked using measured values from 1119 preselected monitoring stations from shallow springs and aquifers filtered near to the surface with oxidizing properties. For the land use categories of urban areas, arable land, grassland, and forest, an at least good agreement of modelled nitrate concentrations in the leachate and measured nitrate concentrations in groundwater was obtained at numerous sites. An equally good agreement was obtained for 1461 measuring stations from the area of responsibility of the Erftverband, which is a major water supplier in the Lower Rhine region. Here, discrepancies have been analyzed in detail due to profound regional knowledge on observation sites. It turned out that in most cases, accuracy limitations of input data (e.g., N balance surpluses of agriculture at the municipal level, 1:50,000 soil map) have been the reason for larger deviations between observed and modelled values. In a broader sense, the case study has shown on the one hand that the model system RAUMIS-mGROWA-DENUZ is able to reliably represent interrelationships and influencing factors that determine simulated nitrate concentrations in the leachate. On the other hand, it has been proven that observed nitrate concentrations in groundwater may provide a solid data source for checking the plausibility of modelled nitrate concentrations in leachate in cases where certain preselection criteria are applied. Full article

(This article belongs to the Special Issue Geo-Environmental Approaches for the Analysis and Assessment of Groundwater Resources at Catchment-Scale)

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18 pages, 13426 KiB

Open AccessEditor’s ChoiceArticle

Monetary Valuation of Flood Protection Ecosystem Service Based on Hydrological Modelling and Avoided Damage Costs. An Example from the Čierny Hron River Basin, Slovakia

by Igor Gallay, Branislav Olah, Zuzana Gallayová and Tomáš Lepeška

Water 2021, 13(2), 198; https://doi.org/10.3390/w13020198 - 15 Jan 2021

Cited by 12 | Viewed by 5605

Abstract

Flood protection is considered one of the crucial regulating ecosystem services due to climate change and extreme weather events. As an ecosystem service, it combines the results of hydrological and ecosystem research and their implementation into land management and/or planning processes including several [...] Read more.

Flood protection is considered one of the crucial regulating ecosystem services due to climate change and extreme weather events. As an ecosystem service, it combines the results of hydrological and ecosystem research and their implementation into land management and/or planning processes including several formally separated economic sectors. As managerial and economic interests often diverge, successful decision-making requires a common denominator in form of monetary valuation of competing trade-offs. In this paper, a methodical approach based on the monetary value of the ecosystem service provided by the ecosystem corresponding to its actual share in flood regulating processes and the value of the property protected by this service was developed and demonstrated based on an example of a medium size mountain basin (290 ha). Hydrological modelling methods (SWAT, HEC-RAS) were applied for assessing the extent of floods with different rainfalls and land uses. The rainfall threshold value that would cause flooding with the current land use but that would be safely drained if the basin was covered completely by forest was estimated. The cost of the flood protection ecosystem service was assessed by the method of non-market monetary value for estimating avoided damage costs of endangered infrastructure and calculated both for the current and hypothetical land use. The results identify areas that are crucial for water retention and that deserve greater attention in management. In addition, the monetary valuation of flood protection provided by the current but also by hypothetical land uses enables competent and well-formulated decision-making processes. Full article

(This article belongs to the Special Issue Long-Term Monitoring and Research in Forest Hydrology: Towards Integrated Watershed Management)

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14 pages, 15115 KiB

Open AccessEditor’s ChoiceArticle

Transport of Cu²⁺ in Unsaturated Porous Medium with Humic Acid/Iron Oxide Nanoparticle (Fe₃O₄) Amendment

by Shanshan Lin, Mengdi Shi, Qi Wang, Junlin Yang, Gubin Zhang, Xiangru Liu and Wei Fan

Water 2021, 13(2), 200; https://doi.org/10.3390/w13020200 - 15 Jan 2021

Cited by 7 | Viewed by 2564

Abstract

Humic acid (HA) and iron oxide (such as Fe₃O₄) nanoparticles are widely distributed in soil, and their complex embedded in soil might affect the transport and fate of Cu²⁺ in the vadose zone, while Cu²⁺ is a [...] Read more.

Humic acid (HA) and iron oxide (such as Fe₃O₄) nanoparticles are widely distributed in soil, and their complex embedded in soil might affect the transport and fate of Cu²⁺ in the vadose zone, while Cu²⁺ is a serious threat to the underlying groundwater. In this study, we synthesized a composite of Fe₃O₄ nanoparticles coated with HA (HA@NPs) using as an amendment a packed sand matrix in the transport column experiments. The impacts of HA content and ion strength (IS) on Cu²⁺ transport in the unsaturated columns were investigated. The results showed that HA exhibited a stronger inhibition effect on Cu²⁺ transport, and a higher IS enhanced the mobility of Cu²⁺ in an unsaturated porous medium in the presence of HA@NPs. The recovery ratio (R_r) of Cu²⁺ breakthrough in the column decreased from 66.56% to 3.94% while the mass concentration ratio C_HA/C_NPs increased from 0 to 50 in the HA@NPs complex. The R_r increased by 1.64 times while the IS increased from 0 to 100 mM. Batch adsorption experiments, kinetics and isotherm models, and Fourier transform infrared (FTIR) spectra analysis were implemented to elucidate the underlying mechanism. It was found that HA embedded in the sand matrix could bind Cu²⁺ by forming stable chelate, while the IS-dependent Cu²⁺ transport could be attributed to the competitive adsorption between Na⁺ and Cu²⁺. Our study demonstrates that the physicochemical environment, as well as the presence of iron oxide nanoparticles and natural organic matter, can significantly impact Cu²⁺ transport in unsaturated porous medium. Full article

(This article belongs to the Section Hydrology)

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15 pages, 338 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Water Stress and Water Footprint Accounting

by Dan Wang, Klaus Hubacek, Yuli Shan, Winnie Gerbens-Leenes and Junguo Liu

Water 2021, 13(2), 201; https://doi.org/10.3390/w13020201 - 15 Jan 2021

Cited by 93 | Viewed by 16734

Abstract

Production and consumption activities deplete freshwater, generate water pollution and may further lead to water stress. The accurate measurement of water stress is a precondition for sustainable water management. This paper reviews the literature on physical water stress induced by blue and green [...] Read more.

Production and consumption activities deplete freshwater, generate water pollution and may further lead to water stress. The accurate measurement of water stress is a precondition for sustainable water management. This paper reviews the literature on physical water stress induced by blue and green water use and by water pollution. Specifically, we clarify several key concepts (i.e., water stress, scarcity, availability, withdrawal, consumption and the water footprint) for water stress evaluation, and review physical water stress indicators in terms of quantity and quality. Furthermore, we identify research gaps in physical water stress assessment, related to environmental flow requirements, return flows, outsourcing of water pollution and standardization of terminology and approaches. These research gaps can serve as venues for further research dealing with the evaluation and reduction of water stress. Full article

(This article belongs to the Special Issue In Memory of Prof. Arjen Y. Hoekstra)

26 pages, 7741 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Transport of Gaseous Hydrogen Peroxide and Ozone into Bulk Water vs. Electrosprayed Aerosol

by Mostafa Elsayed Hassan, Mário Janda and Zdenko Machala

Water 2021, 13(2), 182; https://doi.org/10.3390/w13020182 - 14 Jan 2021

Cited by 28 | Viewed by 5916

Abstract

Production and transport of reactive species through plasma–liquid interactions play a significant role in multiple applications in biomedicine, environment, and agriculture. Experimental investigations of the transport mechanisms of typical air plasma species: hydrogen peroxide (H₂O₂) and ozone (O₃ [...] Read more.

Production and transport of reactive species through plasma–liquid interactions play a significant role in multiple applications in biomedicine, environment, and agriculture. Experimental investigations of the transport mechanisms of typical air plasma species: hydrogen peroxide (H₂O₂) and ozone (O₃) into water are presented. Solvation of gaseous H₂O₂ and O₃ from an airflow into water bulk vs. electrosprayed microdroplets was measured, while changing the water flow rate and applied voltage, during different treatment times and gas flow rates. The solvation rate of H₂O₂ and O₃ increased with the treatment time and the gas–liquid interface area. The total surface area of the electrosprayed microdroplets was larger than that of the bulk, but their lifetime was much shorter. We estimated that only microdroplets with diameters below ~40 µm could achieve the saturation by O₃ during their lifetime, while the saturation by H₂O₂ was unreachable due to its depletion from air. In addition to the short-lived flying microdroplets, the longer-lived bottom microdroplets substantially contributed to H₂O₂ and O₃ solvation in water electrospray. This study contributes to a better understanding of the gaseous H₂O₂ and O₃ transport into water and will lead to design optimization of the water spray and plasma-liquid interaction systems. Full article

(This article belongs to the Special Issue Applications of Plasma Activated Water and Media in Medicine and Agriculture)

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15 pages, 23160 KiB

Open AccessEditor’s ChoiceArticle

Vertical Electrical Sounding (VES) for Estimation of Hydraulic Parameters in the Porous Aquifer

by Andreia de Almeida, Daiane Ferreira Maciel, Karen Félix Sousa, Carlos Tadeu Carvalho Nascimento and Sérgio Koide

Water 2021, 13(2), 170; https://doi.org/10.3390/w13020170 - 13 Jan 2021

Cited by 23 | Viewed by 7289

Abstract

Similarities in both water and electric current flows allow the relation of hydraulic and geoelectric parameters of porous aquifers. Based on this assumption and the importance of the hydraulic parameters for groundwater analyses, this study aimed to estimate hydraulic conductivity (K) and transmissivity [...] Read more.

Similarities in both water and electric current flows allow the relation of hydraulic and geoelectric parameters of porous aquifers. Based on this assumption and the importance of the hydraulic parameters for groundwater analyses, this study aimed to estimate hydraulic conductivity (K) and transmissivity (T) with vertical electrical sounding (VES) in the porous aquifer at the experimental farm of the University of Brasilia, Brazil. VES is a geophysical technique that provides electrical resistivity (ρ, Ω m) and thickness (h) of the subsurface layers. The ρ and h aquifer data, associated with lithology, water table level (WTL), and groundwater electrical resistivity (ρ_w, Ω m), allowed the calculation of complementary geoelectric parameters (formation factor, F, and Dar Zarrouk parameters) and the relation with K and T, determined via slug test. VES data allowed the elaboration of geoelectric models, with mean absolute percentage error (MAPE) below 6% compared to field data, and the identification of the aquifer in each VES station. Significant exponential regression models (R² > 0.5 and p-value < 0.05) showed the possibility of using geoelectric parameters to estimate hydraulic parameters. This study allowed the verification of the applicability of consolidated models and the identification of appropriate empirical relationships for hydrogeological characterization in the Brazilian tropical porous aquifers. The results of this work, besides the rapid sampling and low cost of performing vertical electrical sounding (VES), may justify the use of this geophysical technique for preliminary porous aquifer characterization, especially in regions absent of or with insufficient monitoring wells. Full article

(This article belongs to the Special Issue Advanced Technologies and Methods for Soil Water Monitoring and Management)

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24 pages, 5783 KiB

Open AccessEditor’s ChoiceArticle

Comparative Analysis of Climate Change Impacts on Meteorological, Hydrological, and Agricultural Droughts in the Lake Titicaca Basin

by Ricardo Zubieta, Jorge Molina-Carpio, Wilber Laqui, Juan Sulca and Mercy Ilbay

Water 2021, 13(2), 175; https://doi.org/10.3390/w13020175 - 13 Jan 2021

Cited by 33 | Viewed by 9559

Abstract

The impact of climate change on droughts in the Lake Titicaca, Desaguadero River, and Lake Poopo basins (TDPS system) within the Altiplano region was evaluated by comparing projected 2034–2064 and observed 1984–2014 hydroclimate time series. The study used bias-corrected monthly climate projections from [...] Read more.

The impact of climate change on droughts in the Lake Titicaca, Desaguadero River, and Lake Poopo basins (TDPS system) within the Altiplano region was evaluated by comparing projected 2034–2064 and observed 1984–2014 hydroclimate time series. The study used bias-corrected monthly climate projections from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenarios. Meteorological, agricultural, and hydrological droughts were analyzed from the standardized precipitation, standardized soil moisture, and standardized runoff indices, respectively, the latter two estimated from a hydrological model. Under scenarios of mean temperature increases up to 3 °C and spatially diverse precipitation changes, our results indicate that meteorological, agricultural, and hydrological droughts will become more intense, frequent, and prolonged in most of the TDPS. A significant increase in the frequency of short-term agricultural and hydrological droughts (duration of 1–2 months) is also projected. The expected decline in annual rainfall and the larger evapotranspiration increase in the southern TDPS combine to yield larger projected rises in the frequency and intensity of agricultural and hydrological droughts in this region. Full article

(This article belongs to the Special Issue Hydro-Meteorological Hazards under Climate Change)

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21 pages, 11728 KiB

Open AccessEditor’s ChoiceArticle

Natural Pans as an Important Surface Water Resource in the Cuvelai Basin—Metrics for Storage Volume Calculations and Identification of Potential Augmentation Sites

by Robert Arendt, Christian Reinhardt-Imjela, Achim Schulte, Leona Faulstich, Tobias Ullmann, Lorenz Beck, Sandro Martinis, Petrina Johannes and Joachim Lengricht

Water 2021, 13(2), 177; https://doi.org/10.3390/w13020177 - 13 Jan 2021

Cited by 10 | Viewed by 4362

Abstract

Numerous ephemeral rivers and thousands of natural pans characterize the transboundary Iishana-System of the Cuvelai Basin between Namibia and Angola. After the rainy season, surface water stored in pans is often the only affordable water source for many people in rural areas. High [...] Read more.

Numerous ephemeral rivers and thousands of natural pans characterize the transboundary Iishana-System of the Cuvelai Basin between Namibia and Angola. After the rainy season, surface water stored in pans is often the only affordable water source for many people in rural areas. High inter- and intra-annual rainfall variations in this semiarid environment provoke years of extreme flood events and long periods of droughts. Thus, the issue of water availability is playing an increasingly important role in one of the most densely populated and fastest growing regions in southwestern Africa. Currently, there is no transnational approach to quantifying the potential storage and supply functions of the Iishana-System. To bridge these knowledge gaps and to increase the resilience of the local people’s livelihood, suitable pans for expansion as intermediate storage were identified and their metrics determined. Therefore, a modified Blue Spot Analysis was performed, based on the high-resolution TanDEM-X digital elevation model. Further, surface area–volume ratio calculations were accomplished for finding suitable augmentation sites in a first step. The potential water storage volume of more than 190,000 pans was calculated at 1.9 km³. Over 2200 pans were identified for potential expansion to facilitate increased water supply and flood protection in the future. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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30 pages, 24612 KiB

Open AccessEditor’s ChoiceArticle

Effects of Climatic Drivers and Teleconnections on Late 20th Century Trends in Spring Freshet of Four Major Arctic-Draining Rivers

by Roxanne Ahmed, Terry Prowse, Yonas Dibike and Barrie Bonsal

Water 2021, 13(2), 179; https://doi.org/10.3390/w13020179 - 13 Jan 2021

Cited by 4 | Viewed by 3353

Abstract

Spring freshet is the dominant annual discharge event in all major Arctic draining rivers with large contributions to freshwater inflow to the Arctic Ocean. Research has shown that the total freshwater influx to the Arctic Ocean has been increasing, while at the same [...] Read more.

Spring freshet is the dominant annual discharge event in all major Arctic draining rivers with large contributions to freshwater inflow to the Arctic Ocean. Research has shown that the total freshwater influx to the Arctic Ocean has been increasing, while at the same time, the rate of change in the Arctic climate is significantly higher than in other parts of the globe. This study assesses the large-scale atmospheric and surface climatic conditions affecting the magnitude, timing and regional variability of the spring freshets by analyzing historic daily discharges from sub-basins within the four largest Arctic-draining watersheds (Mackenzie, Ob, Lena and Yenisei). Results reveal that climatic variations closely match the observed regional trends of increasing cold-season flows and earlier freshets. Flow regulation appears to suppress the effects of climatic drivers on freshet volume but does not have a significant impact on peak freshet magnitude or timing measures. Spring freshet characteristics are also influenced by El Niño-Southern Oscillation, the Pacific Decadal Oscillation, the Arctic Oscillation and the North Atlantic Oscillation, particularly in their positive phases. The majority of significant relationships are found in unregulated stations. This study provides a key insight into the climatic drivers of observed trends in freshet characteristics, whilst clarifying the effects of regulation versus climate at the sub-basin scale. Full article

(This article belongs to the Special Issue Past and Future Trends and Variability in Hydro-Climatic Processes)

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25 pages, 3337 KiB

Open AccessEditor’s ChoiceArticle

A Comparative Assessment of Hydrological Models in the Upper Cauvery Catchment

by Robyn Horan, R Gowri, Pawan S. Wable, Helen Baron, Virginie D. J. Keller, Kaushal K. Garg, Pradeep P. Mujumdar, Helen Houghton-Carr and Gwyn Rees

Water 2021, 13(2), 151; https://doi.org/10.3390/w13020151 - 11 Jan 2021

Cited by 21 | Viewed by 5294

Abstract

This paper presents a comparison of the predictive capability of three hydrological models, and a mean ensemble of these models, in a heavily influenced catchment in Peninsular India: GWAVA (Global Water AVailability Assessment) model, SWAT (Soil Water Assessment Tool) and VIC (Variable Infiltration [...] Read more.

This paper presents a comparison of the predictive capability of three hydrological models, and a mean ensemble of these models, in a heavily influenced catchment in Peninsular India: GWAVA (Global Water AVailability Assessment) model, SWAT (Soil Water Assessment Tool) and VIC (Variable Infiltration Capacity) model. The performance of the three models and their ensemble were investigated in five sub-catchments in the upstream reaches of the Cauvery river catchment. Model performances for monthly streamflow simulations from 1983–2005 were analysed using Nash-Sutcliffe efficiency, Kling-Gupta efficiency and percent bias. The predictive capability for each model was compared, and the ability to accurately represent key catchment hydrological processes is discussed. This highlighted the importance of an accurate spatial representation of precipitation for input into hydrological models, and that comprehensive reservoir functionality is paramount to obtaining good results in this region. The performance of the mean ensemble was analysed to determine whether the application of a multi-model ensemble approach can be useful in overcoming the uncertainties associated with individual models. It was demonstrated that the ensemble mean has a better predictive ability in catchments with reservoirs than the individual models, with Nash-Sutcliffe values between 0.49 and 0.92. Therefore, utilising multiple models could be a suitable methodology to offset uncertainty in input data and poor reservoir operation functionality within individual models. Full article

(This article belongs to the Special Issue Modelling Hydrologic Response of Non-homogeneous Catchments)

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16 pages, 4799 KiB

Open AccessEditor’s ChoiceArticle

A Study on Interaction between Overfall Types and Scour at Bridge Piers with a Moving-Bed Experiment

by Wei-Lin Lee, Chih-Wei Lu and Chin-Kun Huang

Water 2021, 13(2), 152; https://doi.org/10.3390/w13020152 - 11 Jan 2021

Cited by 7 | Viewed by 3041

Abstract

River slopes can be changed due to an extreme event, e.g., a large-scale earthquake. This can uplift a riverbed greatly and thereby change the behavior of the river flow into a free or submerged overfall. Corresponding damage, including extreme erosion, on bridge piers [...] Read more.

River slopes can be changed due to an extreme event, e.g., a large-scale earthquake. This can uplift a riverbed greatly and thereby change the behavior of the river flow into a free or submerged overfall. Corresponding damage, including extreme erosion, on bridge piers located in the river can take place due to the aforementioned flow conditions. A reconstructed bridge pier in the same location would also experience a similar impact if the flow condition is not changed. It is important to identify these phenomena and research the mechanism in the interaction between overfall types and scour at bridge piers. Therefore, this paper is aimed at studying a mechanism of free and submerged overfall flow impacts on bridge piers with different distances by a series of moving-bed experiments. The experiment results showed clearly that bridge pier protection requires attention particularly when the pier is located in the maximum scour hole induced by the submerged overfall due to the z directional flow eddies. In many other cases, such as when the location of the bridge pier was at the upstream slope of a scour hole induced by a flow drop, a deposition mound could be observed at the back of the pier. This indicates that, while a pier is at this location, an additional protection takes place on the bridge pier. Full article

(This article belongs to the Special Issue Soil–Water Conservation, Erosion, and Landslide)

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29 pages, 18838 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Deterministic Analysis and Uncertainty Analysis of Ensemble Forecasting Model Based on Variational Mode Decomposition for Estimation of Monthly Groundwater Level

by Min Wu, Qi Feng, Xiaohu Wen, Zhenliang Yin, Linshan Yang and Danrui Sheng

Water 2021, 13(2), 139; https://doi.org/10.3390/w13020139 - 9 Jan 2021

Cited by 22 | Viewed by 4591

Abstract

Precise multi-time scales prediction of groundwater level is essential for water resources planning and management. However, credible and reliable predicting results are hard to achieve even to extensively applied artificial intelligence (AI) models considering the uncontrollable error, indefinite inputs and unneglectable uncertainty during [...] Read more.

Precise multi-time scales prediction of groundwater level is essential for water resources planning and management. However, credible and reliable predicting results are hard to achieve even to extensively applied artificial intelligence (AI) models considering the uncontrollable error, indefinite inputs and unneglectable uncertainty during the modelling process. The AI model ensembled with the data pretreatment technique, the input selection method, or uncertainty analysis has been successfully used to tackle this issue, whereas studies about the comprehensive deterministic and uncertainty analysis of hybrid models in groundwater level forecast are rarely reported. In this study, a novel hybrid predictive model combining the variational mode decomposition (VMD) data pretreatment technique, Boruta input selection method, bootstrap based uncertainty analysis, and the extreme learning machine (ELM) model named VBELM was developed for 1-, 2- and 3-month ahead groundwater level prediction in a typical arid oasis area of northwestern China. The historical observed monthly groundwater level, precipitation and temperature data were used as inputs to train and test the model. Specifically, the VMD was used to decompose all the input-outputs into a set of intrinsic mode functions (IMFs), the Boruta method was applied to determine input variables, and the ELM was employed to forecast the value of each IMF. In order to ascertain the efficiency of the proposed VBELM model, the performance of the coupled model (VELM) hybridizing VMD with ELM algorithm and the single ELM model were estimated in comparison. The results indicate that the VBELM performed best, while the single ELM model performed the worst among the three models. Furthermore, the VBELM model presented lower uncertainty than the VELM model with more observed groundwater level values falling inside the confidence interval. In summary, the VBELM model demonstrated an excellent performance for both certainty and uncertainty analyses, and can serve as an effective tool for multi-scale groundwater level forecasting. Full article

(This article belongs to the Section Hydrology)

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16 pages, 3045 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of 220 Years of Floodplain Population Dynamics in the US at Different Spatial Scales

by Firoza Akhter, Maurizio Mazzoleni and Luigia Brandimarte

Water 2021, 13(2), 141; https://doi.org/10.3390/w13020141 - 9 Jan 2021

Cited by 13 | Viewed by 3589

Abstract

In this study, we explore the long-term trends of floodplain population dynamics at different spatial scales in the contiguous United States (U.S.). We exploit different types of datasets from 1790–2010—i.e., decadal spatial distribution for the population density in the US, global floodplains dataset, [...] Read more.

In this study, we explore the long-term trends of floodplain population dynamics at different spatial scales in the contiguous United States (U.S.). We exploit different types of datasets from 1790–2010—i.e., decadal spatial distribution for the population density in the US, global floodplains dataset, large-scale data of flood occurrence and damage, and structural and nonstructural flood protection measures for the US. At the national level, we found that the population initially settled down within the floodplains and then spread across its territory over time. At the state level, we observed that flood damages and national protection measures might have contributed to a learning effect, which in turn, shaped the floodplain population dynamics over time. Finally, at the county level, other socio-economic factors such as local flood insurances, economic activities, and socio-political context may predominantly influence the dynamics. Our study shows that different influencing factors affect floodplain population dynamics at different spatial scales. These facts are crucial for a reliable development and implementation of flood risk management planning. Full article

(This article belongs to the Special Issue Flood Risk in the Anthropocene)

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19 pages, 8417 KiB

Open AccessEditor’s ChoiceArticle

Soil Moisture Retrieval during the Wheat Growth Cycle Using SAR and Optical Satellite Data

by Min Zhang, Fengkai Lang and Nanshan Zheng

Water 2021, 13(2), 135; https://doi.org/10.3390/w13020135 - 8 Jan 2021

Cited by 15 | Viewed by 3274

Abstract

The objective of this paper is to propose a combined approach for the high-precision mapping of soil moisture during the wheat growth cycle based on synthetic aperture radar (SAR) (Radarsat-2) and optical satellite data (Landsat-8). For this purpose, the influence of vegetation was [...] Read more.

The objective of this paper is to propose a combined approach for the high-precision mapping of soil moisture during the wheat growth cycle based on synthetic aperture radar (SAR) (Radarsat-2) and optical satellite data (Landsat-8). For this purpose, the influence of vegetation was removed from the total backscatter by using the modified water cloud model (MWCM), which takes the vegetation fraction (

f_{v e g}

) into account. The VV/VH polarization radar backscattering coefficients database was established by a numerical simulation based on the advanced integrated equation model (AIEM) and the cross-polarized ratio of the Oh model. Then the empirical relationship between the bare soil backscattering coefficient and both the soil moisture and the surface roughness was developed by regression analysis. The surface roughness in this paper was described by using the effective roughness parameter and the combined roughness form. The experimental results revealed that using effective roughness as the model input instead of in-situ measured roughness can obtain soil moisture with high accuracy and effectively avoid the uncertainty of roughness measurement. The accuracy of soil moisture inversion could be improved by introducing vegetation fraction on the basis of the water cloud model (WCM). There was a good correlation between the estimated soil moisture and the observed values, with a root mean square error (RMSE) of about 4.14% and the coefficient of determination (

R^{2}

) about 0.7390. Full article

(This article belongs to the Special Issue Applications of Remote Sensing in Agricultural Water Management)

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15 pages, 6847 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

A Green Roof Case Study in the Urban Context of Milan: Integrating the Residential and Cultivation Functions for Sustainable Development

by Giulia Procaccini and Carol Monticelli

Water 2021, 13(2), 137; https://doi.org/10.3390/w13020137 - 8 Jan 2021

Cited by 3 | Viewed by 5565

Abstract

Green roofs are increasing in popularity because of both their pleasant appearance and their positive effects for the urban ecosystems and the building indoor climatic conditions. Though this technology has already been applied all over the world, it is still commonly considered of [...] Read more.

Green roofs are increasing in popularity because of both their pleasant appearance and their positive effects for the urban ecosystems and the building indoor climatic conditions. Though this technology has already been applied all over the world, it is still commonly considered of difficult application and management. Easy and fast approaches for green roofs must therefore be examined and encouraged in order to increase their number to counterbalance urban overheating. This thesis case study aimed to represent a prototype of a green roof integrated with a residential function in order to achieve an easy management of the cultivation area. The project was designed in terms of sustainability and was analyzed for its social, environmental and economic impacts, pointing out the numerous benefits that can be derived by the combination and juxtaposition of humans and native plants. The proposed solution is favorable in terms of a sustainable development: it aspires to be reproduced and extensively applied to other facilities of a city as a solution for the overheating and overpopulation of contemporary cities. Full article

(This article belongs to the Special Issue Green Roofing with Native Species: Enhance Water Use and Sustainability)

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27 pages, 6564 KiB

Open AccessEditor’s ChoiceArticle

Impact of Climate Change on Precipitation Extremes over Ho Chi Minh City, Vietnam

by Dao Nguyen Khoi, Nguyen Trong Quan, Pham Thi Thao Nhi and Van Thinh Nguyen

Water 2021, 13(2), 120; https://doi.org/10.3390/w13020120 - 7 Jan 2021

Cited by 14 | Viewed by 6659

Abstract

In the context of climate change, the impact of hydro-meteorological extremes, such as floods and droughts, has become one of the most severe issues for the governors of mega-cities. The main purpose of this study is to assess the spatiotemporal changes in extreme [...] Read more.

In the context of climate change, the impact of hydro-meteorological extremes, such as floods and droughts, has become one of the most severe issues for the governors of mega-cities. The main purpose of this study is to assess the spatiotemporal changes in extreme precipitation indices over Ho Chi Minh City, Vietnam, between the near (2021–2050) and intermediate (2051–2080) future periods with respect to the baseline period (1980–2009). The historical extreme indices were calculated through observed daily rainfall data at 11 selected meteorological stations across the study area. The future extreme indices were projected based on a stochastic weather generator, the Long Ashton Research Station Weather Generator (LARS-WG), which incorporates climate projections from the Coupled Model Intercomparison Project 5 (CMIP5) ensemble. Eight extreme precipitation indices, such as the consecutive dry days (CDDs), consecutive wet days (CWDs), number of very heavy precipitation days (R20mm), number of extremely heavy precipitation days (R25mm), maximum 1 d precipitation amount (RX1day), maximum 5 d precipitation amount (RX5day), very wet days (R95p), and simple daily intensity index (SDII) were selected to evaluate the multi-model ensemble mean changes of extreme indices in terms of intensity, duration, and frequency. The statistical significance, stability, and averaged magnitude of trends in these changes, thereby, were computed by the Mann-Kendall statistical techniques and Sen’s estimator, and applied to each extreme index. The results indicated a general increasing trend in most extreme indices for the future periods. In comparison with the near future period (2021–2050), the extreme intensity and frequency indices in the intermediate future period (2051–2080) present more statistically significant trends and higher growing rates. Furthermore, an increase in most extreme indices mainly occurs in some parts of the central and southern regions, while a decrease in those indices is often projected in the north of the study area. Full article

(This article belongs to the Special Issue Hydrological Extremes in a Warming Climate: Nonstationarity, Uncertainties and Impacts)

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27 pages, 1021 KiB

Open AccessEditor’s ChoiceArticle

A Robust Neutrosophic Modeling and Optimization Approach for Integrated Energy-Food-Water Security Nexus Management under Uncertainty

by Firoz Ahmad, Shafiq Ahmad, Mazen Zaindin and Ahmad Yusuf Adhami

Water 2021, 13(2), 121; https://doi.org/10.3390/w13020121 - 7 Jan 2021

Cited by 21 | Viewed by 3814

Abstract

Natural resources are a boon for human beings, and their conservation for future uses is indispensable. Most importantly, energy-food-water security (EFWS) nexus management is the utmost need of our time. An effective managerial policy for the current distribution and conservation to meet future [...] Read more.

Natural resources are a boon for human beings, and their conservation for future uses is indispensable. Most importantly, energy-food-water security (EFWS) nexus management is the utmost need of our time. An effective managerial policy for the current distribution and conservation to meet future demand is necessary and challenging. Thus, this paper investigates an interconnected and dynamic EFWS nexus optimization model by considering the socio-economic and environmental objectives with the optimal energy supply, electricity conversion, food production, water resources allocation, and CO

_{2}

emissions control in the multi-period time horizons. Due to real-life complexity, various parameters are taken as intuitionistic fuzzy numbers. A novel method called interactive neutrosophic programming approach (INPA) is suggested to solve the EFWS nexus model. To verify and validate the proposed EFWS model, a synthetic computational study is performed. The obtained solution results are compared with other optimization approaches, and the outcomes are also evaluated with significant practical implications. The study reveals that the food production processes require more water resources than electricity production, although recycled water has not been used for food production purposes. The use of a coal-fired plant is not a prominent electricity conversion source. However, natural gas power plants’ service is also optimally executed with a marginal rate of production. Finally, conclusions and future research are addressed. This current study emphasizes how the proposed EFWS nexus model would be reliable and beneficial in real-world applications and help policy-makers identify, modify, and implement the optimal EFWS nexus policy and strategies for the future conservation of these resources. Full article

(This article belongs to the Special Issue The Water-Energy-Food Nexus: Sustainable Development)

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28 pages, 2215 KiB

Open AccessEditor’s ChoiceReview

Multi-Criteria Decision-Making Methods to Address Water Allocation Problems: A Systematic Review

by Sintayehu Legesse Gebre, Dirk Cattrysse and Jos Van Orshoven

Water 2021, 13(2), 125; https://doi.org/10.3390/w13020125 - 7 Jan 2021

Cited by 69 | Viewed by 10612

Abstract

The water allocation problem is complex and requires a combination of regulations, policies, and mechanisms to support water management to minimize the risk of shortage among competing users. This paper compiles the application of multi-criteria decision-making (MCDM) related to water allocation. In this [...] Read more.

The water allocation problem is complex and requires a combination of regulations, policies, and mechanisms to support water management to minimize the risk of shortage among competing users. This paper compiles the application of multi-criteria decision-making (MCDM) related to water allocation. In this regard, this paper aims to identify and to discern the pattern, distribution of study regions, water problem classifications, and decision techniques application for a specific water allocation problem. We applied a systematic literature review study from 2000 to 2019 by using four literature databases (Web of Science, Scopus, Science Direct, and Google Scholar). From 109 papers, 49 publications have been identified and information extracted. This study reveals that in the past two decades the application of MCDM in the area of water allocation has increased particularly after 2014. Around 65% and 12% of study papers were conducted in Asia and Europe, respectively. Water shortage, water use management, and water quality were consecutively the most top-ranked discussed water problems. NSGA II (non-dominated sorting genetic algorithm), GA (genetic algorithm), and LP (linear programming) are the more often applied decision methods to solve water allocation problems. The key findings of this study provide guidelines for future research studies. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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11 pages, 1154 KiB

Open AccessEditor’s ChoiceArticle

Valuation of Drought Information: Understanding the Value of the US Drought Monitor in Land Management

by Tingting Liu, Richard Krop, Tonya Haigh, Kelly Helm Smith and Mark Svoboda

Water 2021, 13(2), 112; https://doi.org/10.3390/w13020112 - 6 Jan 2021

Cited by 7 | Viewed by 2902

Abstract

Droughts affect recreation and tourism, grazing, forests, and timber, and can have important indirect effects for the ecosystems and species that rely on water. Despite its importance, the effect of drought in the land management sector is less understood than in other water-intensive [...] Read more.

Droughts affect recreation and tourism, grazing, forests, and timber, and can have important indirect effects for the ecosystems and species that rely on water. Despite its importance, the effect of drought in the land management sector is less understood than in other water-intensive sectors, such as agriculture and public water supplies. This study presents the first-ever estimates of the economic valuation of the information provided by the U.S. Drought Monitor using the avoided cost method. These estimates are based on the time and labor saved by using the U.S. Drought Monitor rather than compiling drought-related information from other sources, or using other sources for tracking/monitoring droughts, communicating drought conditions, and dealing with drought-related issues. The results reflect rational behavior—the more time needed to compile or collect drought information provided by the U.S. Drought Monitor, the higher the dollar value in avoided cost. This dollar amount also varies by institution and organization, which indicates respondents from different organizations value the information from the U.S. Drought Monitor differently. For example, compared to the state offices, the field offices in the Bureau of Land Management value more of the information provided by the U.S. Drought Monitor. These estimates can be used to estimate the societal benefits and help policy makers evaluate the U.S. Drought Monitor in different sectors. Full article

(This article belongs to the Section Hydrology)

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18 pages, 12783 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Integrated Low-Cost Approach for Measuring the State of Conservation of Agricultural Terraces in Tuscany, Italy

by Martina Cambi, Yamuna Giambastiani, Francesca Giannetti, Elena Nuti, Andrea Dani and Federico Preti

Water 2021, 13(2), 113; https://doi.org/10.3390/w13020113 - 6 Jan 2021

Cited by 9 | Viewed by 3692

Abstract

Agricultural terraces are an important element of the Italian landscape. However, abandonment of agricultural areas and increase in the frequency of destructive rainfall events has made it mandatory to increase conservation efforts of terraces to reduce hydrological risks. This requires the development of [...] Read more.

Agricultural terraces are an important element of the Italian landscape. However, abandonment of agricultural areas and increase in the frequency of destructive rainfall events has made it mandatory to increase conservation efforts of terraces to reduce hydrological risks. This requires the development of new approaches capable of identifying and mapping failed or prone-to-fail terraces over large areas. The present work focuses on the development of a more cost-effective alternative, to help public administrators and private land owners to identify fragile areas that may be subject to failure due to the abandonment of terracing systems. We developed a simple field protocol to acquire quantitative measurements of the degree of damage—dry stone wall deformation—and establish a damage classification system. This new methodology is tested at two different sites in Tuscany, central Italy. The processing is based on existing DTMs derived from Airborne Laser Scanner (ALS) data and open source software. The main GIS modules adopted are flow accumulation and water discharge, processed with GRASS GIS. Results show that the damage degree and terrace wall deformation are correlated with flow accumulation even if other factors other than those analyzed can contribute to influence the instability of dry stone walls. These tools are useful for local land management and conservation efforts. Full article

(This article belongs to the Special Issue Terraced Landscapes and Hydrological-Geological Hazards)

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25 pages, 5349 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Investigating the Effects of Agricultural Water Management in a Mediterranean Coastal Aquifer under Current and Projected Climate Conditions

by Vassilios Pisinaras, Charalampos Paraskevas and Andreas Panagopoulos

Water 2021, 13(1), 108; https://doi.org/10.3390/w13010108 - 5 Jan 2021

Cited by 18 | Viewed by 5464

Abstract

Coastal delta plains are areas with high agricultural potential for the Mediterranean region because of their high soil fertility, but they also constitute fragile systems in terms of water resources management because of the interaction of underlying aquifers with the sea. Such a [...] Read more.

Coastal delta plains are areas with high agricultural potential for the Mediterranean region because of their high soil fertility, but they also constitute fragile systems in terms of water resources management because of the interaction of underlying aquifers with the sea. Such a case is the Pinios River delta plain located in central Greece, which also constitutes a significant ecosystem. Soil and Water Assessment Tool (SWAT) and SEAWAT models were combined in order to simulate the impact of current water resources management practices in main groundwater budget components and groundwater salinization of the shallow aquifer developed in the area. Moreover, potential climate change impact was investigated using climate data from Regional Climate Model for two projected periods (2021–2050 and 2071–2100) and two sea level rise scenarios (increase by 0.5 and 1 m). Modeling results are providing significant insight: although the contribution of the river to groundwater inflows is significant, direct groundwater recharge from precipitation was found to be higher, while capillary rise constitutes a major part of groundwater outflows from the aquifer. Moreover, during the simulation period, groundwater flow from the aquifer to the sea were found to be higher than the inflows of seawater to the aquifer. Regarding climate change impact assessment, the results indicate that the variability in groundwater recharge posed by the high variability of precipitation during the projected periods is increasing the aquifer’s deterioration potential of both its quantity and quality status, the latter expressed by the increased groundwater Cl⁻ concentration. This evidence becomes more significant because of the limited groundwater storage capacity of the aquifer. Concerning sea level rise, it was found to be less significant in terms of groundwater salinization impact compared to the decrease in groundwater recharge and increase in crop water needs. Full article

(This article belongs to the Special Issue Geo-Environmental Approaches for the Analysis and Assessment of Groundwater Resources at Catchment-Scale)

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15 pages, 3252 KiB

Open AccessEditor’s ChoiceArticle

Magnesium as Environmental Tracer for Karst Spring Baseflow/Overflow Assessment—A Case Study of the Pertuso Karst Spring (Latium Region, Italy)

by Francesco Maria De Filippi, Silvia Iacurto, Gerardo Grelle and Giuseppe Sappa

Water 2021, 13(1), 93; https://doi.org/10.3390/w13010093 - 4 Jan 2021

Cited by 12 | Viewed by 4215

Abstract

Following a previous research carried out on the same site, this paper presents the update of the Mg²⁺ based method for the estimation of Pertuso Spring discharge, located in Central Italy. New collected data confirmed the validity of the proposed model and [...] Read more.

Following a previous research carried out on the same site, this paper presents the update of the Mg²⁺ based method for the estimation of Pertuso Spring discharge, located in Central Italy. New collected data confirmed the validity of the proposed model and the conservative behaviour of Mg²⁺ for groundwater related to the Pertuso Spring aquifer. Further analysis allowed to obtain a local linear relationship between magnesium concentration and total spring discharge (including exploitation rate), regardless of the mixing model proposed with the Aniene River. As regards two samples which fall out of the linear relationship and could have been detected as “outliers”, more in-depth data processing and sensitivity analyses revealed that the lowering in magnesium, at equal discharges, is determined by the appearance of the quick-flow component, less mineralized and related to storm events. Results showed that under specific conditions, related to the absence or presence of previous intense rainfall events, Mg²⁺ could be effectively a useful tracer for separating spring conduit flow (overflow) from diffuse flow (baseflow) within the karst aquifer. Full article

(This article belongs to the Special Issue Recent Advances in Karstic Hydrogeology)

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19 pages, 3929 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Are Biocrusts and Xerophytic Vegetation a Viable Green Roof Typology in a Mediterranean Climate? A Comparison between Differently Vegetated Green Roofs in Water Runoff and Water Quality

by Bernardo Rocha, Teresa A. Paço, Ana Catarina Luz, Paulo Palha, Sarah Milliken, Benzion Kotzen, Cristina Branquinho, Pedro Pinho and Ricardo Cruz de Carvalho

Water 2021, 13(1), 94; https://doi.org/10.3390/w13010094 - 4 Jan 2021

Cited by 19 | Viewed by 4375

Abstract

Green roofs can be an innovative and effective way of mitigating the environmental impact of urbanization by providing several important ecosystem services. However, it is known that the performance of green roofs varies depending on the type of vegetation and, in drier climates, [...] Read more.

Green roofs can be an innovative and effective way of mitigating the environmental impact of urbanization by providing several important ecosystem services. However, it is known that the performance of green roofs varies depending on the type of vegetation and, in drier climates, without resorting to irrigation, these are limited to xerophytic plant species and biocrusts. The aim of this research was therefore to compare differently vegetated green roofs planted with this type of vegetation. A particular focus was their ability to hold water during intense stormwater events and also the quality of the harvested rainwater. Six test beds with different vegetation compositions were used on the roof of a building in Lisbon. Regarding stormwater retention, the results varied depending on the composition of the vegetation and the season. As for water quality, almost all the parameters tested were higher than the Drinking Water Directive from the European Union (EU) and Word Health Organization (WHO) guidelines for drinking-water quality standards for potable water. Based on our results, biocrusts and xerophytic vegetation are a viable green roof typology for slowing runoff during stormwater events. Full article

(This article belongs to the Special Issue Green Roofing with Native Species: Enhance Water Use and Sustainability)

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16 pages, 4688 KiB

Open AccessEditor’s ChoiceArticle

Effects of Different Normalization, Aggregation, and Classification Methods on the Construction of Flood Vulnerability Indexes

by Luana Lavagnoli Moreira, Mariana Madruga de Brito and Masato Kobiyama

Water 2021, 13(1), 98; https://doi.org/10.3390/w13010098 - 4 Jan 2021

Cited by 53 | Viewed by 5911

Abstract

Index-based approaches are widely employed for measuring flood vulnerability. Nevertheless, the uncertainties in the index construction are rarely considered. Here, we conducted a sensitivity analysis of a flood vulnerability index in the Maquiné Basin, Southern Brazil, considering distinct normalization, aggregation, classification methods, and [...] Read more.

Index-based approaches are widely employed for measuring flood vulnerability. Nevertheless, the uncertainties in the index construction are rarely considered. Here, we conducted a sensitivity analysis of a flood vulnerability index in the Maquiné Basin, Southern Brazil, considering distinct normalization, aggregation, classification methods, and their effects on the model outputs. The robustness of the results was investigated by considering Spearman’s correlations, the shift in the vulnerability rank, and spatial analysis of different normalization techniques (min-max, z-scores, distance to target, and raking) and aggregation methods (linear and geometric). The final outputs were classified into vulnerability classes using natural breaks, equal interval, quantiles, and standard deviation methods. The performance of each classification method was evaluated by spatial analysis and the Akaike’s information criterion (AIC). The results presented low sensitivity regarding the normalization step. Conversely, the geometric aggregation method produced substantial differences on the spatial vulnerability and tended to underestimate the vulnerability where indicators with low values compensated for high values. Additionally, the classification of the vulnerability into different classes led to overly sensitive outputs. Thus, given the AIC performance, the natural breaks method was most suitable. The obtained results can support decision-makers in reducing uncertainty and increasing the quality of flood vulnerability assessments. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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28 pages, 11445 KiB

Open AccessEditor’s ChoiceReview

Modeling Surface Processes on Debris-Covered Glaciers: A Review with Reference to the High Mountain Asia

by Da Huo, Zhaohui Chi and Andong Ma

Water 2021, 13(1), 101; https://doi.org/10.3390/w13010101 - 4 Jan 2021

Cited by 9 | Viewed by 4609

Abstract

Surface processes on debris-covered glaciers are governed by a variety of controlling factors including climate, debris load, water bodies, and topography. Currently, we have not achieved a general consensus on the role of supraglacial processes in regulating climate–glacier sensitivity in High Mountain Asia, [...] Read more.

Surface processes on debris-covered glaciers are governed by a variety of controlling factors including climate, debris load, water bodies, and topography. Currently, we have not achieved a general consensus on the role of supraglacial processes in regulating climate–glacier sensitivity in High Mountain Asia, which is mainly due to a lack of an integrated understanding of glacier surface dynamics as a function of debris properties, mass movement, and ponding. Therefore, further investigations on supraglacial processes is needed in order to provide more accurate assessments of the hydrological cycle, water resources, and natural hazards in the region. Given the scarcity of long-term in situ data and the difficulty of conducting fieldwork on these glaciers, many numerical models have been developed by recent studies. This review summarizes our current knowledge of surface processes on debris-covered glaciers with an emphasis on the related modeling efforts. We present an integrated view on how numerical modeling provide insights into glacier surface ablation, supraglacial debris transport, morphological variation, pond dynamics, and ice-cliff evolution. We also highlight the remote sensing approaches that facilitate modeling, and discuss the limitations of existing models regarding their capabilities to address coupled processes on debris-covered glaciers and suggest research directions. Full article

(This article belongs to the Section Hydrology)

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19 pages, 10720 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Flood Mapping Proposal in Small Watersheds: A Case Study of the Rebollos and Miranda Ephemeral Streams (Cartagena, Spain)

by Valentina Betancourt-Suárez, Estela García-Botella and Alfredo Ramon-Morte

Water 2021, 13(1), 102; https://doi.org/10.3390/w13010102 - 4 Jan 2021

Cited by 10 | Viewed by 4239

Abstract

Anthropogenic landscape changes cause significant disturbances to fluvial system dynamics and such is the case of the watersheds studied near the Spanish Mediterranean coast (Cartagena). Economic growth resulted in the addition of external water resources from the Tajo River (1979) as part of [...] Read more.

Anthropogenic landscape changes cause significant disturbances to fluvial system dynamics and such is the case of the watersheds studied near the Spanish Mediterranean coast (Cartagena). Economic growth resulted in the addition of external water resources from the Tajo River (1979) as part of the National Water Plan (1933). Irrigation water has caused the water table to rise since 1979. Furthermore, water resources have boosted urban touristic expansion, industrial estates, and road infrastructures. This study presents a diagnosis of the official flood hazard maps by applying remote sensing techniques that enable the identification of (i) areas flooded during recent events; and (ii) the possible effects of anthropogenic actions on fluvial processes affecting flooding (land use and land cover change—LULCC). The flooded areas were identified from a multispectral satellite image taken by a sensor on Sentinel-2. A multi-temporal analysis of aerial photographs (1929, 1956, 1981, 2009, and 2017) showing the fluvial and anthropic environment at a detailed scale (1:25,000) was used to define the fluvial geomorphology and the main anthropic alterations on the Rebollos ephemeral stream. Official inputs from geographical information repositories about land use were also gathered (LULC). The result was compared to the official flood hazard maps (SNCZI) and this revealed floodable areas that had not been previously mapped because official maps rely only on the hydraulic method. Finally, all the recent changes that will have increased the disastrous consequences of flooding have been detected, analyzed, and mapped for the study area. Full article

(This article belongs to the Special Issue Water Economics and Water Distribution Management)

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17 pages, 7309 KiB

Open AccessEditor’s ChoiceArticle

Assessment of the Dissimilarities of EDI and SPI Measures for Drought Determination in South Africa

by Omolola M. Adisa, Muthoni Masinde and Joel O. Botai

Water 2021, 13(1), 82; https://doi.org/10.3390/w13010082 - 1 Jan 2021

Cited by 14 | Viewed by 4897

Abstract

This study examines the (dis)similarity of two commonly used indices Standardized Precipitation Index (SPI) computed over accumulation periods 1-month, 3-month, 6-month, and 12-month (hereafter SPI-1, SPI-3, SPI-6, and SPI-12, respectively) and Effective Drought Index (EDI). The analysis is based on two drought monitoring [...] Read more.

This study examines the (dis)similarity of two commonly used indices Standardized Precipitation Index (SPI) computed over accumulation periods 1-month, 3-month, 6-month, and 12-month (hereafter SPI-1, SPI-3, SPI-6, and SPI-12, respectively) and Effective Drought Index (EDI). The analysis is based on two drought monitoring indicators (derived from SPI and EDI), namely, the Drought Duration (DD) and Drought Severity (DS) across the 93 South African Weather Service’s delineated rainfall districts over South Africa from 1980 to 2019. In the study, the Pearson correlation coefficient dissimilarity and periodogram dissimilarity estimates were used. The results indicate a positive correlation for the Pearson correlation coefficient dissimilarity and a positive value for periodogram of dissimilarity in both the DD and DS. With the Pearson correlation coefficient dissimilarity, the study demonstrates that the values of the SPI-1/EDI pair and the SPI-3/EDI pair exhibit the highest similar values for DD, while the SPI-6/EDI pair shows the highest similar values for DS. Moreover, dissimilarities are more obvious in SPI-12/EDI pair for DD and DS. When a periodogram of dissimilarity is used, the values of the SPI-1/EDI pair and SPI-6/EDI pair exhibit the highest similar values for DD, while SPI-1/EDI displayed the highest similar values for DS. Overall, the two measures show that the highest similarity is obtained in the SPI-1/EDI pair for DS. The results obtainable in this study contribute towards an in-depth knowledge of deviation between the EDI and SPI values for South Africa, depicting that these two drought indices values are replaceable in some rainfall districts of South Africa for drought monitoring and prediction, and this is a step towards the selection of the appropriate drought indices. Full article

(This article belongs to the Section Hydrology)

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