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Special Issue "Modeling of Water Systems"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Water Resources Management and Governance".

Deadline for manuscript submissions: closed (30 April 2017)

Special Issue Editors

Guest Editor
Prof. Dr. Gordon Huang

University of Regina, Faculty of Engineering and Applied Science, Regina, Canada
Website | E-Mail
Phone: 1-306-585-4095
Interests: Waste management, site remediation, and risk assessment, Simulation and optimization of hydrological and environmental systems, Modeling of energy and environmental management systems, Climate modeling, impact assessment, and adaptation planning
Guest Editor
Dr. Yurui Fan

Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, SK S4S 0A2, Canada
E-Mail
Interests: water resources; hydrology; modeling; management; optimization

Special Issue Information

Dear Colleagues,

For decades, water deterioration and resource-shortage problems have led to a variety of adverse impacts on socioeconomic development and human life. Challenges of water problems adhering to the principle of sustainable development have been of significant concerns to many researchers and decision makers. These issues are highly complicated, involving a large number of social, economic, environmental, technical, and political factors, coupled with complex spatial variability and a cascading effect. Such complexities force researchers to develop more robust mathematical methods and tools to analyze the relevant information, simulate the related processes, implement mitigation strategies, assess the potential impacts/risks, and generate sound decision alternatives.

This Special Issue on Modeling of Water Systems aims to explore new mathematical techniques to aid decision makers in mitigating water problems. Many questions will be addressed, such as: what are the new techniques in modelling water systems? How do we generate sound water management strategies in consideration of climate change and socio-economic development? Are there appropriate approaches to reflect the extensive uncertainties in the process of modeling water regime and optimizing water management strategies? In addition, case studies associated with a variety of water management issues will be included.

Dr. Gordon Huang
Dr. Yurui Fan
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • water pollution
  • water resources
  • simulation and optimization
  • risk analysis and management
  • decision making

Published Papers (32 papers)

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Research

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Open AccessArticle Application of a Double-Sided Chance-Constrained Integer Linear Program for Optimization of the Incremental Value of Ecosystem Services in Jilin Province, China
Water 2017, 9(8), 629; https://doi.org/10.3390/w9080629
Received: 27 June 2017 / Revised: 13 August 2017 / Accepted: 16 August 2017 / Published: 22 August 2017
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Abstract
The Interconnected River System Network Project (IRSNP) is a significant water supply engineering project, which is capable of effectively utilizing flood resources to generate ecological value, by connecting 198 lakes and ponds in western Jilin, northeast China. In this article, an optimization research [...] Read more.
The Interconnected River System Network Project (IRSNP) is a significant water supply engineering project, which is capable of effectively utilizing flood resources to generate ecological value, by connecting 198 lakes and ponds in western Jilin, northeast China. In this article, an optimization research approach has been proposed to maximize the incremental value of IRSNP ecosystem services. A double-sided chance-constrained integer linear program (DCCILP) method has been proposed to support the optimization, which can deal with uncertainties presented as integers or random parameters that appear on both sides of the decision variable at the same time. The optimal scheme indicates that after rational optimization, the total incremental value of ecosystem services from the interconnected river system network project increased 22.25%, providing an increase in benefits of 3.26 × 109 ¥ compared to the original scheme. Most of the functional area is swamp wetland, which provides the greatest ecological benefits. Adjustment services increased obviously, implying that the optimization scheme prioritizes ecological benefits rather than supply and production services. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Chance-Constrained Dynamic Programming for Multiple Water Resources Allocation Management Associated with Risk-Aversion Analysis: A Case Study of Beijing, China
Water 2017, 9(8), 596; https://doi.org/10.3390/w9080596
Received: 29 April 2017 / Revised: 8 July 2017 / Accepted: 3 August 2017 / Published: 11 August 2017
Cited by 2 | PDF Full-text (1752 KB) | HTML Full-text | XML Full-text
Abstract
Water shortage and water pollution have become major problems hindering socio-economic development. Due to the scarcity of water resources, the conflict between water supply and demand is becoming more and more prominent, especially in urban areas. In order to ensure the safety of [...] Read more.
Water shortage and water pollution have become major problems hindering socio-economic development. Due to the scarcity of water resources, the conflict between water supply and demand is becoming more and more prominent, especially in urban areas. In order to ensure the safety of urban water supply, many cities have begun to build reservoirs. However, few previous studies have focused on the optimal allocation of water resources considering storage reservoirs. In this study, a multi-water resources and multiple users chance-constrained dynamic programming (MMCDP) model has been developed for water resources allocation in Beijing, China, which introduces reservoir and chance-constrained programming into the dynamic programming decision-making framework. The proposed model can distribute water to different departments according to their respective demands in different periods. Specifically, under the objective of maximal benefits, the water allocation planning and the amount of water stored in a reservoir for each season under different feasibility degrees (violating constraints or available water resources situations) can be obtained. At the same time, the model can be helpful for decision-makers to identify the uncertainty of water-allocation schemes and make a desired compromise between the satisfaction degree of the economic benefits and the feasibility degree of constraints. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle A Stepwise-Cluster Inference Model for Phenanthrene Immobilization at the Aqueous/Modified Palygorskite Interface
Water 2017, 9(8), 590; https://doi.org/10.3390/w9080590
Received: 29 April 2017 / Revised: 17 July 2017 / Accepted: 3 August 2017 / Published: 8 August 2017
PDF Full-text (1640 KB) | HTML Full-text | XML Full-text
Abstract
A stepwise-cluster inference (SI) model was established through introducing stepwise-cluster analysis (SCA) into the phenanthrene immobilization process at the aqueous/modified palygorskite interface. SCA has the advantages of tackling the nonlinear relationships among environmental factors and the phenanthrene sorption amount in the immobilization process. [...] Read more.
A stepwise-cluster inference (SI) model was established through introducing stepwise-cluster analysis (SCA) into the phenanthrene immobilization process at the aqueous/modified palygorskite interface. SCA has the advantages of tackling the nonlinear relationships among environmental factors and the phenanthrene sorption amount in the immobilization process. The essence of SCA is to form a tree-based classification on a series of cutting or mergence procedures under given statistical criteria. The results indicated that SI could help develop a statistical relationship between environmental variables and the phenanthrene sorption amount, where discrete and nonlinear complexities exist. During the experiment, data were randomly sampled 10 times for model calibration and verification. The R2 (close to one) and root mean squared error (RMSE) (close to zero) values guaranteed the prediction accuracy of the model. Compared to other statistical methods, the calculation of R2 and RMSEs showed that SI was more straightforward for describing the nonlinear relationships and precisely fitting and predicting the immobilization of phenanthrene. Through the calculation of the input effects on the output in the SI model, the influence of environmental factors on phenanthrene immobilization were ranged in descending order as: initial phenanthrene concentration, ionic strength, pH, added humic acid dose, and temperature. It is revealed that SCA can be used to map the nonlinear and discrete relationships and elucidate the transport patterns of phenanthrene at the aqueous/modified palygorskite interface. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle An Optimization Model for Waste Load Allocation under Water Carrying Capacity Improvement Management, A Case Study of the Yitong River, Northeast China
Water 2017, 9(8), 573; https://doi.org/10.3390/w9080573
Received: 27 June 2017 / Revised: 27 July 2017 / Accepted: 27 July 2017 / Published: 1 August 2017
Cited by 1 | PDF Full-text (2162 KB) | HTML Full-text | XML Full-text
Abstract
In this study, a two-stage stochastic programming (TSP) model was developed for supporting regional waste load(chemical oxygen demand (COD)and NH3-N) allocation in four main pollution departments (industry, municipal, livestock breeding, and agriculture), constrained by the water carrying capacity, which can be [...] Read more.
In this study, a two-stage stochastic programming (TSP) model was developed for supporting regional waste load(chemical oxygen demand (COD)and NH3-N) allocation in four main pollution departments (industry, municipal, livestock breeding, and agriculture), constrained by the water carrying capacity, which can be improved by ecological restoration engineering, in the nine function zones of the Yitong River. A number of scenarios corresponding to different stream flow levels were examined. The results revealed that the carrying capacity of COD and NH3-N has a similar tendency with a positive correlation to stream flow levels. The allocation amount of each pollutant for the four departments was obtained differently in each zone, and ecological restoration engineering solutions were obtained for different zones to improve the carrying capacity of the pollutants in order to meet the permitted emission allocation and water qualities. The results are helpful in establishing a rational discharge permit system of each pollution unit under water quality targets, and provide a basis for production plans of these pollution units. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle A Hybrid Model for Forecasting Groundwater Levels Based on Fuzzy C-Mean Clustering and Singular Spectrum Analysis
Water 2017, 9(7), 541; https://doi.org/10.3390/w9070541
Received: 27 April 2017 / Revised: 11 July 2017 / Accepted: 15 July 2017 / Published: 19 July 2017
Cited by 2 | PDF Full-text (3148 KB) | HTML Full-text | XML Full-text
Abstract
Having the ability to forecast groundwater levels is very significant because of their vital role in basic functions related to efficiency and the sustainability of water supplies. The uncertainty which dominates our understanding of the functioning of water supply systems is of great [...] Read more.
Having the ability to forecast groundwater levels is very significant because of their vital role in basic functions related to efficiency and the sustainability of water supplies. The uncertainty which dominates our understanding of the functioning of water supply systems is of great significance and arises as a consequence of the time-unbalanced water consumption rate and the deterioration of the recharge conditions of captured aquifers. The aim of this paper is to present a hybrid model based on fuzzy C-mean clustering and singular spectrum analysis to forecast the weekly values of the groundwater level of a groundwater source. This hybrid model demonstrates how the fuzzy C-mean can be used to transform the sequence of the observed data into a sequence of fuzzy states, serving as a basis for the forecasting of future states by singular spectrum analysis. In this way, the forecasting efficiency is improved, because we predict the interval rather than the crisp value where the level will be. It gives much more flexibility to the engineers when managing and planning sustainable water supplies. A model is tested by using the observed weekly time series of the groundwater source, located near the town of Čačak in south-western Serbia. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle An Integrated Method for Interval Multi-Objective Planning of a Water Resource System in the Eastern Part of Handan
Water 2017, 9(7), 528; https://doi.org/10.3390/w9070528
Received: 9 May 2017 / Revised: 28 June 2017 / Accepted: 12 July 2017 / Published: 16 July 2017
Cited by 1 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
In this study, an integrated solving method is proposed for interval multi-objective planning. The proposed method is based on fuzzy linear programming and an interactive two-step method. It cannot only provide objectively optimal values for multiple objectives at the same time, but also [...] Read more.
In this study, an integrated solving method is proposed for interval multi-objective planning. The proposed method is based on fuzzy linear programming and an interactive two-step method. It cannot only provide objectively optimal values for multiple objectives at the same time, but also effectively offer a globally optimal interval solution. Meanwhile, the degree of satisfaction related to different objective functions would be obtained. Then, the integrated solving method for interval multi-objective planning is applied to a case study of planning multi-water resources joint scheduling under uncertainty in the eastern part of Handan, China. The solutions obtained are useful for decision makers in easing the contradiction between supply of multi-water resources and demand from different water users. Moreover, it can provide the optimal comprehensive benefits of economy, society, and the environment. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Factor Analysis and Estimation Model of Water Consumption of Government Institutions in Taiwan
Water 2017, 9(7), 492; https://doi.org/10.3390/w9070492
Received: 8 April 2017 / Revised: 24 June 2017 / Accepted: 3 July 2017 / Published: 5 July 2017
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Abstract
Models for adequately estimating water consumption in Taiwanese government institutions were developed to assist the government to more accurately predict and account for their water needs. A correlation coefficient matrix of associated factors was constructed based on records per unit of water consumption, [...] Read more.
Models for adequately estimating water consumption in Taiwanese government institutions were developed to assist the government to more accurately predict and account for their water needs. A correlation coefficient matrix of associated factors was constructed based on records per unit of water consumption, describing the impact of various water consumption factors. To understand and quantify the effect of the impact factors, linear and nonlinear regression models, as well as an artificial neural network model were adopted. To account for data variability, the data used for modelling were either fully or partially adopted. For partial adoption, the quartile method was employed to remove any outliers. Analysis of the factors affecting water consumption revealed that the building floor area and number of personnel in an organization had the largest impact on estimated consumption, followed by the number of residential personnel. As the coefficient of variation for the green irrigated area and number of consulting personnel was low, the total area and the total number personnel of water consumption decreased the effectiveness of the model. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Agricultural Water Productivity Oriented Water Resources Allocation Based on the Coordination of Multiple Factors
Water 2017, 9(7), 490; https://doi.org/10.3390/w9070490
Received: 28 March 2017 / Revised: 12 June 2017 / Accepted: 20 June 2017 / Published: 5 July 2017
Cited by 9 | PDF Full-text (2896 KB) | HTML Full-text | XML Full-text
Abstract
Agricultural water productivity (AWP), which is associated with multiple factors, is an important index for measuring the effectiveness of agricultural water management. The purpose of this study is to promote AWP through optimally allocating limited agricultural water resources with the coordination of related [...] Read more.
Agricultural water productivity (AWP), which is associated with multiple factors, is an important index for measuring the effectiveness of agricultural water management. The purpose of this study is to promote AWP through optimally allocating limited agricultural water resources with the coordination of related elements. Firstly, the coordination effects of multiple factors related to AWP are quantified as relative optimum membership degrees based on the fuzzy optimum selecting theory. Secondly, based on the relative optimum membership degrees for various crops, a linear fractional programming model is established to maximize AWP in agricultural water resources allocation. Thirdly, the impacts of the allocation schemes on the development of social-economy and ecological environment are discussed using the multi-dimensional regulation theory. The developed integrated system has advantages in increasing agricultural water productivity through the coordination of multiple factors with aspects of economy, society and resources. Moreover, the system is capable of screening schemes considering harmonious development of resources, economy, society and ecology based on optimization results, providing decision makers with more sustainable schemes for irrigation water allocation. The integrated system including the aforementioned three parts is applied to a real-world case study in China to demonstrate its feasibility and applicability. Different water allocation schemes for various crops under different scenarios were obtained. The average value of AWP is 1.85 kg/m3, which is 0.31 kg/m3 higher than the current value of AWP. An optimum scheme with 1.1405 × 108 m3 of water being allocated was also selected due to its highest level of coordination for resources, economy, society and ecology. The developed system can provide an effective method for AWP promotion. The obtained results can help local decision makers adjust water resources allocation schemes. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Optimal Use of Agricultural Water and Land Resources through Reconfiguring Crop Planting Structure under Socioeconomic and Ecological Objectives
Water 2017, 9(7), 488; https://doi.org/10.3390/w9070488
Received: 5 May 2017 / Revised: 28 June 2017 / Accepted: 29 June 2017 / Published: 4 July 2017
Cited by 13 | PDF Full-text (2065 KB) | HTML Full-text | XML Full-text
Abstract
Many economic, social and ecological problems can be attributed to the scarcity and mismanagement of water and land resources. In this study, a multi-objective fuzzy–robust programming (MOFRP) method was developed for supporting the optimal use of land and water resources in agriculture. MOFRP [...] Read more.
Many economic, social and ecological problems can be attributed to the scarcity and mismanagement of water and land resources. In this study, a multi-objective fuzzy–robust programming (MOFRP) method was developed for supporting the optimal use of land and water resources in agriculture. MOFRP improved existing methods through taking ecological services of crop cultivation into account. It was also capable of reflecting fuzziness in preferences, priorities and parameters that were largely neglected in previous agricultural decision making. This method was applied to address a case in arid northwestern China. Optimal plans of crop cultivation reconfiguration were generated for sustaining local development under economic, ecological and social objectives as well as physical restraints in water and land resources. Compared to the status quo, the optimized plan would increase economic and ecological benefits by 12.2% and 18.8%, respectively. The efficiency of irrigation water could also be enhanced with the economic and ecological benefits per unit water being raised and the water consumption per unit land being reduced. The comparisons of the MOFRP model to four alternatives validated that it was capable of achieving satisfactory benefits and reducing system-violation risks without neglecting valuable uncertain information and ecological services of crops. The proposed method was also applicable to other multi-objective management problems under uncertainty without loss of generality. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessFeature PaperArticle Effects of the Food-to-Microorganism (F/M) Ratio on N2O Emissions in Aerobic Granular Sludge Sequencing Batch Airlift Reactors
Water 2017, 9(7), 477; https://doi.org/10.3390/w9070477
Received: 30 April 2017 / Revised: 11 June 2017 / Accepted: 22 June 2017 / Published: 29 June 2017
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Abstract
The present study investigated the effect of the food-to-microorganism (F/M) ratio on nitrous oxide (N2O) emissions in aerobic granular sludge sequencing batch airlift reactors. Three identical sequencing batch airlift reactors were fed with sodium acetate-based wastewater at different chemical oxygen demand [...] Read more.
The present study investigated the effect of the food-to-microorganism (F/M) ratio on nitrous oxide (N2O) emissions in aerobic granular sludge sequencing batch airlift reactors. Three identical sequencing batch airlift reactors were fed with sodium acetate-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.2 to 0.67 g COD/g SS. The results indicated that N2O emissions increased with an increase of the F/M ratio. N2O emissions at the high F/M ratio of 0.67 g COD/g SS were the highest (4.4 ± 0.94 mg/d). The main source of the high N2O emissions at the F/M ratio of 0.67 g COD/g SS was nitrifier denitrification, rather than heterotrophic denitrification, confirmed by the qPCR (quantitative real-time PCR) results. The heterotrophic denitrification was destroyed by the DO (dissolved oxygen) diffusing into the sludge particles with porous structures. This study offers theoretical support to study the N2O emissions in aerobic granular sludge, and can provide guidance for conducting risk assessment and enhancing our ability to predict N2O production in aerobic granular sludge at different F/M ratios. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Early Warning and Forecasting System of Water Quality Safety for Drinking Water Source Areas in Three Gorges Reservoir Area, China
Water 2017, 9(7), 465; https://doi.org/10.3390/w9070465
Received: 7 April 2017 / Revised: 17 June 2017 / Accepted: 22 June 2017 / Published: 28 June 2017
Cited by 1 | PDF Full-text (5370 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, the effects of water pollution accidents on water quality safety and regional residents’ living have attracted worldwide attention. Therefore, the objective of this research is to propose an early warning and forecasting model and develop a visual system of water quality safety [...] Read more.
Nowadays, the effects of water pollution accidents on water quality safety and regional residents’ living have attracted worldwide attention. Therefore, the objective of this research is to propose an early warning and forecasting model and develop a visual system of water quality safety for drinking water source areas in the Three Gorges Reservoir Area under accident conditions. Based on an Instantaneous Point Source Two-dimensional Water Quality Model and the security requirements of water quality, an early warning and forecasting model was presented, and then the system was advanced by a MATLAB platform. In addition, a hypothetical case was also carried out for the Fenghuangshan drinking water source area. Within 0.040 h to 0.096 h after the accident, the water quality could meet the standard, and the warning level was primary and intermediate, sequentially. From 0.096 h to 11.960 h after the accident, the pollutant concentration exceeded the standard, under which conditions advanced warning started. Then the intermediate and primary warnings restarted in sequence until the pollutant concentration decreased to the background value. Therefore, the proposed model could accurately predict the spatial-temporal change trend of pollutant concentration, and the developed system could efficiently realize early warnings and the forecasting of water quality safety. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Urban Flood Simulation Using MODCEL—An Alternative Quasi-2D Conceptual Model
Water 2017, 9(6), 445; https://doi.org/10.3390/w9060445
Received: 24 March 2017 / Revised: 11 June 2017 / Accepted: 13 June 2017 / Published: 21 June 2017
Cited by 4 | PDF Full-text (15533 KB) | HTML Full-text | XML Full-text
Abstract
Urban flood modelling has been evolving in recent years, due to computational facilities as well as to the possibility of obtaining detailed terrain data. Flood control techniques have also been evolving to integrate both urban flood and urban planning issues. Land use control [...] Read more.
Urban flood modelling has been evolving in recent years, due to computational facilities as well as to the possibility of obtaining detailed terrain data. Flood control techniques have also been evolving to integrate both urban flood and urban planning issues. Land use control and flow generation concerns, as well as a set of possible distributed measures favouring storage and infiltration over the watershed, also gained importance in flood control projects, reinforcing the need to model the entire basin space. However, the use of 2D equations with highly detailed digital elevation models do not guarantee good results by their own. Urban geometry, including buildings shapes, walls, earth fills, and other structures may cause significant interference on flood paths. In this context, this paper presents an alternative urban flood model, focusing on the system behaviour and its conceptual interpretation. Urban Flood Cell Model-MODCEL is a hydrological-hydrodynamic model proposed to represent a complex flow network, with a set of relatively simple information, using average values to represent urban landscape through the flow-cell concept. In this work, to illustrate model capabilities, MODCEL is benchmarked in a test proposed by the British Environmental Agency. Then, its capability to represent storm drains is verified using measured data and a comparison with Storm Water Management Model (SWMM). Finally, it is applied in a lowland area of the Venetian continental plains, representing floods in a complex setup at the city of Noale and in its surroundings. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Evaluation of Groundwater Remediation Technologies Based on Fuzzy Multi-Criteria Decision Analysis Approaches
Water 2017, 9(6), 443; https://doi.org/10.3390/w9060443
Received: 30 March 2017 / Revised: 13 June 2017 / Accepted: 15 June 2017 / Published: 20 June 2017
Cited by 2 | PDF Full-text (1634 KB) | HTML Full-text | XML Full-text
Abstract
Petroleum is an essential resource for the development of society and its production is huge. There is a great risk of leakage of oil during production, refining, and transportation. After entering the environment, the oil pollutants will be a great threat to the [...] Read more.
Petroleum is an essential resource for the development of society and its production is huge. There is a great risk of leakage of oil during production, refining, and transportation. After entering the environment, the oil pollutants will be a great threat to the environment and may endanger human health. Therefore, it is very important to remediate oil pollution in the subsurface. However, it is necessary to choose the appropriate remediation technology. In this paper, 18 technologies are evaluated through constructing a parameter matrix with each technology and seven performance indicators, and a comprehensive analysis model is presented. In this model, four MCDA methods are used. They are SWA (Simple Weighted Addition Method), WP (Weighted Product Method), CGT (Cooperative Game Theory), and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution). Mean ranking and Borda ranking methods are used to integrate the results of SWA, WP, CGT, and TOPSIS. Then two selection priorities of each method (mean ranking and Borda ranking) are obtained. The model is proposed to help decide the best choice of remediation technologies. It can effectively reduce contingency, subjectivity, one-sidedness of the traditional methods and provide scientific reference for effective decision-making. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessFeature PaperArticle Allelopathy Inhibitory Effects of Hydrodictyon reticulatum on Chlorella pyrenoidosa under Co-Culture and Liquor-Cultured Conditions
Water 2017, 9(6), 416; https://doi.org/10.3390/w9060416
Received: 8 March 2017 / Revised: 26 May 2017 / Accepted: 7 June 2017 / Published: 9 June 2017
Cited by 1 | PDF Full-text (3316 KB) | HTML Full-text | XML Full-text
Abstract
Eutrophication has become increasingly serious in recent years, which severely impairs the aquatic ecosystem. Applying environmentally-friendly methods to effectively control the growth of algae and avoid eutrophication has been proved to be a promising way. Thus, the potential of Hydrodictyon reticulatum on eutrophication [...] Read more.
Eutrophication has become increasingly serious in recent years, which severely impairs the aquatic ecosystem. Applying environmentally-friendly methods to effectively control the growth of algae and avoid eutrophication has been proved to be a promising way. Thus, the potential of Hydrodictyon reticulatum on eutrophication control was studied in this research. The allelopathy inhibitory effects of H. reticulatum on the growth of Chlorella pyrenoidosa were investigated under both co-culture and liquor-cultured conditions. The biomass and chlorophyll a content of C. pyrenoidosa were determined with time during the experimental period. Nitrogen and phosphorus removal capacities of H. reticulatum were also examined. Results showed that the growth of C. pyrenoidosa was obviously inhibited under both co-culture and liquor-cultured conditions, and the “Hormesis effect” was patently observed. The strength of allelopathy inhibitory effect depended on the relative biomass between H. reticulatum and C. pyrenoidosa. The allelopathy inhibitory effect of H. reticulatum on C. pyrenoidosa under co-culture condition was stronger than that under liquor-cultured condition. The decrease speeds of nitrogen and phosphorus concentrations were in direct proportion to the concentration of H. reticulatum. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Inexact Two-Stage Stochastic Programming for Water Resources Allocation under Considering Demand Uncertainties and Response—A Case Study of Tianjin, China
Water 2017, 9(6), 414; https://doi.org/10.3390/w9060414
Received: 25 April 2017 / Revised: 25 May 2017 / Accepted: 2 June 2017 / Published: 9 June 2017
Cited by 7 | PDF Full-text (1215 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, an inexact two-stage stochastic programming model was developed for supporting regional water resource allocation management under uncertainties. The proposed model is an integrated framework of interval parameter programming and two-stage stochastic programming, which can tackle uncertain parameters expressed as interval [...] Read more.
In this paper, an inexact two-stage stochastic programming model was developed for supporting regional water resource allocation management under uncertainties. The proposed model is an integrated framework of interval parameter programming and two-stage stochastic programming, which can tackle uncertain parameters expressed as interval values with probability distribution information. The proposed model was successfully applied to a typical heavy industrial city suffering water shortage in the east of China, Tianjin. The uncertainties of future water demand were taken into account through generating a set of representative scenarios. The results indicated that different scenarios would affect the water distribution patterns, water shortages, total benefits and system cost. The results revealed that the transferred water from Luan River and Changjiang River would still be the main water resource for each water user. Besides, nearly all water demand in planning horizon would be guaranteed through the reasonable dispatch except under high demand level scenario, in which a small proportion of water requirement in agricultural, municipal and environmental sectors would not be satisfied. The developed method could be used by environmental managers to identify the optimal water supply plan from multiple sources to different end-user sectors under system uncertainties. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Modelling of Violent Water Wave Propagation and Impact by Incompressible SPH with First-Order Consistent Kernel Interpolation Scheme
Water 2017, 9(6), 400; https://doi.org/10.3390/w9060400
Received: 30 April 2017 / Revised: 27 May 2017 / Accepted: 31 May 2017 / Published: 4 June 2017
Cited by 7 | PDF Full-text (6107 KB) | HTML Full-text | XML Full-text
Abstract
The Smoothed Particle Hydrodynamics (SPH) method has proven to have great potential in dealing with the wave–structure interactions since it can deal with the large amplitude and breaking waves and easily captures the free surface. The paper will adopt an incompressible SPH (ISPH) [...] Read more.
The Smoothed Particle Hydrodynamics (SPH) method has proven to have great potential in dealing with the wave–structure interactions since it can deal with the large amplitude and breaking waves and easily captures the free surface. The paper will adopt an incompressible SPH (ISPH) approach to simulate the wave propagation and impact, in which the fluid pressure is solved using a pressure Poisson equation and thus more stable and accurate pressure fields can be obtained. The focus of the study is on comparing three different pressure gradient calculation models in SPH and proposing the most efficient first-order consistent kernel interpolation (C1_KI) numerical scheme for modelling violent wave impact. The improvement of the model is validated by the benchmark dam break flows and laboratory wave propagation and impact experiments. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Flood Simulations and Uncertainty Analysis for the Pearl River Basin Using the Coupled Land Surface and Hydrological Model System
Water 2017, 9(6), 391; https://doi.org/10.3390/w9060391
Received: 23 March 2017 / Revised: 24 May 2017 / Accepted: 28 May 2017 / Published: 1 June 2017
Cited by 4 | PDF Full-text (3086 KB) | HTML Full-text | XML Full-text
Abstract
The performances of hydrological simulations for the Pearl River Basin in China were analysed using the Coupled Land Surface and Hydrological Model System (CLHMS). Three datasets, including East Asia (EA), high-resolution gauge satellite-merged China Merged Precipitation Analysis (CMPA)-Daily, and the Asian Precipitation Highly-Resolved [...] Read more.
The performances of hydrological simulations for the Pearl River Basin in China were analysed using the Coupled Land Surface and Hydrological Model System (CLHMS). Three datasets, including East Asia (EA), high-resolution gauge satellite-merged China Merged Precipitation Analysis (CMPA)-Daily, and the Asian Precipitation Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE) daily precipitation were used to drive the CLHMS model to simulate daily hydrological processes from 1998 to 2006. The results indicate that the precipitation data was the most important source of uncertainty in the hydrological simulation. The simulated streamflow driven by the CMPA-Daily agreed well with observations, with a Pearson correlation coefficient (PMC) greater than 0.70 and an index of agreement (IOA) similarity coefficient greater than 0.82 at Liuzhou, Shijiao, and Wuzhou Stations. Comparison of the Nash-Sutcliffe efficiency coefficient (NSE) shows that the peak flow simulation ability of CLHMS driven with the CMPA-Daily rainfall is relatively superior to that with the EA and APHRODITE datasets. The simulation results for the high-flow periods in 1998 and 2005 indicate that the CLHMS is promising for its future application in the flood simulation and prediction. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle SWE-SPHysics Simulation of Dam Break Flows at South-Gate Gorges Reservoir
Water 2017, 9(6), 387; https://doi.org/10.3390/w9060387
Received: 7 April 2017 / Revised: 19 May 2017 / Accepted: 28 May 2017 / Published: 31 May 2017
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Abstract
This paper applied a Smoothed Particle Hydrodynamics (SPH) approach to solve Shallow Water Equations (SWEs) to study practical dam-break flows. The computational program is based on the open source code SWE-SPHysics, where a Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) reconstruction method is [...] Read more.
This paper applied a Smoothed Particle Hydrodynamics (SPH) approach to solve Shallow Water Equations (SWEs) to study practical dam-break flows. The computational program is based on the open source code SWE-SPHysics, where a Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) reconstruction method is used to improve the Riemann solution with Lax-Friedrichs flux. A virtual boundary particle method is applied to treat the solid boundary. The model is first tested on two benchmark collapses of water columns with the existence of downstream obstacle. Subsequently the model is applied to forecast a prototype dam-break flood, which might occur in South-Gate Gorges Reservoir area of Qinghai Province, China. It shows that the SWE-SPH modeling approach could provide a promising simulation tool for practical dam-break flows in engineering scale. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessFeature PaperArticle Optimising Fuzzy Neural Network Architecture for Dissolved Oxygen Prediction and Risk Analysis
Water 2017, 9(6), 381; https://doi.org/10.3390/w9060381
Received: 30 March 2017 / Revised: 17 May 2017 / Accepted: 24 May 2017 / Published: 28 May 2017
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Abstract
A fuzzy neural network method is proposed to predict minimum daily dissolved oxygen concentration in the Bow River, in Calgary, Canada. Owing to the highly complex and uncertain physical system, a data-driven and fuzzy number based approach is preferred over traditional approaches. The [...] Read more.
A fuzzy neural network method is proposed to predict minimum daily dissolved oxygen concentration in the Bow River, in Calgary, Canada. Owing to the highly complex and uncertain physical system, a data-driven and fuzzy number based approach is preferred over traditional approaches. The inputs to the model are abiotic factors, namely water temperature and flow rate. An approach to select the optimum architecture of the neural network is proposed. The total uncertainty of the system is captured in the fuzzy numbers weights and biases of the neural network. Model predictions are compared to the traditional, non-fuzzy approach, which shows that the proposed method captures more low DO events. Model output is then used to quantify the risk of low DO for different conditions. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle A Stochastic Multi-Objective Chance-Constrained Programming Model for Water Supply Management in Xiaoqing River Watershed
Water 2017, 9(6), 378; https://doi.org/10.3390/w9060378
Received: 23 March 2017 / Revised: 24 May 2017 / Accepted: 24 May 2017 / Published: 27 May 2017
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Abstract
In this paper, a stochastic multi-objective chance-constrained programming model (SMOCCP) was developed for tackling the water supply management problem. Two objectives were included in this model, which are the minimization of leakage loss amounts and total system cost, respectively. The traditional SCCP model [...] Read more.
In this paper, a stochastic multi-objective chance-constrained programming model (SMOCCP) was developed for tackling the water supply management problem. Two objectives were included in this model, which are the minimization of leakage loss amounts and total system cost, respectively. The traditional SCCP model required the random variables to be expressed in the normal distributions, although their statistical characteristics were suitably reflected by other forms. The SMOCCP model allows the random variables to be expressed in log-normal distributions, rather than general normal form. Possible solution deviation caused by irrational parameter assumption was avoided and the feasibility and accuracy of generated solutions were ensured. The water supply system in the Xiaoqing River watershed was used as a study case for demonstration. Under the context of various weight combinations and probabilistic levels, many types of solutions are obtained, which are expressed as a series of transferred amounts from water sources to treated plants, from treated plants to reservoirs, as well as from reservoirs to tributaries. It is concluded that the SMOCCP model could reflect the sketch of the studied region and generate desired water supply schemes under complex uncertainties. The successful application of the proposed model is expected to be a good example for water resource management in other watersheds. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Study of the Removal of Aniline from Wastewater via MEUF Using Mixed Surfactants
Water 2017, 9(6), 365; https://doi.org/10.3390/w9060365
Received: 15 April 2017 / Revised: 10 May 2017 / Accepted: 19 May 2017 / Published: 23 May 2017
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Abstract
In this paper, the anionic surfactant sodium dodecyl sulfate (SDS) and the bio-surfactant rhamnolipid are mixed to achieve micellar-enhanced ultrafiltration, and the associated aniline removal efficiency is investigated. The impacts of five factors, including the mixing ratio of the SDS concentration to the [...] Read more.
In this paper, the anionic surfactant sodium dodecyl sulfate (SDS) and the bio-surfactant rhamnolipid are mixed to achieve micellar-enhanced ultrafiltration, and the associated aniline removal efficiency is investigated. The impacts of five factors, including the mixing ratio of the SDS concentration to the rhamnolipid concentration, the pH, the salinity, the operating pressure, and the aniline concentration in the feed solution, on the aniline rejection and the membrane permeation flux are explored. The aniline rejection mechanism of the rhamnolipid mixture surfactant is analyzed. This study shows that the effect of these factors on the aniline rejection is in the order of pH > mixing ratio > operating pressure > aniline concentration > salinity; the factors that affect the membrane permeation flux are in the order of mixing ratio > operating pressure > salinity > pH > aniline concentration. Under the optimal test conditions (i.e., SDS:rhamnolipid = 8:2, pH = 5, salinity = 250 mmol/L, operating pressure = 3.5 bar, aniline concentration = 1.5 mM), the verification test results showed an aniline rejection of 78.36%. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessFeature PaperArticle A Semi-Infinite Interval-Stochastic Risk Management Model for River Water Pollution Control under Uncertainty
Water 2017, 9(5), 351; https://doi.org/10.3390/w9050351
Received: 14 March 2017 / Revised: 20 April 2017 / Accepted: 12 May 2017 / Published: 18 May 2017
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Abstract
In this study, a semi-infinite interval-stochastic risk management (SIRM) model is developed for river water pollution control, where various policy scenarios are explored in response to economic penalties due to randomness and functional intervals. SIRM can also control the variability of the recourse [...] Read more.
In this study, a semi-infinite interval-stochastic risk management (SIRM) model is developed for river water pollution control, where various policy scenarios are explored in response to economic penalties due to randomness and functional intervals. SIRM can also control the variability of the recourse cost as well as capture the notion of risk in stochastic programming. Then, the SIRM model is applied to water pollution control of the Xiangxihe watershed. Tradeoffs between risks and benefits are evaluated, indicating any change in the targeted benefit and risk level would yield varied expected benefits. Results disclose that the uncertainty of system components and risk preference of decision makers have significant effects on the watershed's production generation pattern and pollutant control schemes as well as system benefit. Decision makers with risk-aversive attitude would accept a lower system benefit (with lower production level and pollutant discharge); a policy based on risk-neutral attitude would lead to a higher system benefit (with higher production level and pollutant discharge). The findings can facilitate the decision makers in identifying desired product generation plans in association with financial risk minimization and pollution mitigation. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Fuzzy Comprehensive Assessment Method Based on the Entropy Weight Method and Its Application in the Water Environmental Safety Evaluation of the Heshangshan Drinking Water Source Area, Three Gorges Reservoir Area, China
Water 2017, 9(5), 329; https://doi.org/10.3390/w9050329
Received: 14 March 2017 / Revised: 4 May 2017 / Accepted: 4 May 2017 / Published: 6 May 2017
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Abstract
The safety of drinking water from source areas is an important issue, and the fuzzy comprehensive assessment method is a useful evaluation approach. However, it has limitations due to its complicated calculation, as well as the effects of subjective factors on the results. [...] Read more.
The safety of drinking water from source areas is an important issue, and the fuzzy comprehensive assessment method is a useful evaluation approach. However, it has limitations due to its complicated calculation, as well as the effects of subjective factors on the results. The objective of the research is to develop an effective method with more objective results for tackling water environmental evaluation problems in drinking water source areas. In this study, a new method— i.e., the fuzzy comprehensive assessment method based on the entropy weight method—was proposed; a water environmental safety evaluation index system was built, and then the water environmental safety of the Heshangshan drinking water source area was evaluated. The results indicated that the water environment of the study area was substantially safe. Furthermore, water-saving measurements should be taken, the industrial structure should be optimized, investment in environmental protection should be increased, and the utilization ratio of water resources should be improved. It can be concluded that the proposed approaches were feasible and reasonable. It is the first attempt to develop such an evaluation method and index system for water environmental safety evaluation, which can provide references and decision support for the related researchers and managers. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle A Multi-Objective Chance-Constrained Programming Approach for Uncertainty-Based Optimal Nutrients Load Reduction at the Watershed Scale
Water 2017, 9(5), 322; https://doi.org/10.3390/w9050322
Received: 1 March 2017 / Revised: 8 April 2017 / Accepted: 27 April 2017 / Published: 3 May 2017
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Abstract
A multi-objective chance-constrained programming integrated with Genetic Algorithm and robustness evaluation methods was proposed to weigh the conflict between system investment against risk for watershed load reduction, which was firstly applied to nutrient load reduction in the Lake Qilu watershed of the Yunnan [...] Read more.
A multi-objective chance-constrained programming integrated with Genetic Algorithm and robustness evaluation methods was proposed to weigh the conflict between system investment against risk for watershed load reduction, which was firstly applied to nutrient load reduction in the Lake Qilu watershed of the Yunnan Plateau, China. Eight sets of Pareto solutions were acceptable for both system investment and probability of constraint satisfaction, which were selected from 23 sets of Pareto solutions out of 120 solution sets. Decision-makers can select optimal decisions from the solutions above in accordance with the actual conditions of different sub-watersheds under various engineering measures. The relationship between system investment and risk demonstrated that system investment increased rapidly when the probability level of constraint satisfaction was higher than 0.9, but it reduced significantly if appropriate risk was permitted. Evaluation of robustness of the optimal scheme indicated that the Pareto solution obtained from the model provided the ideal option, since the solutions were always on the Pareto frontier under various distributions and mean values of the random parameters. The application of the multi-objective chance-constrained programming to optimize the reduction of watershed nutrient loads in Lake Qilu indicated that it is also applicable to other environmental problems or study areas that contain uncertainties. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Effects of Precipitation and Topography on Total Phosphorus Loss from Purple Soil
Water 2017, 9(5), 315; https://doi.org/10.3390/w9050315
Received: 7 April 2017 / Revised: 25 April 2017 / Accepted: 27 April 2017 / Published: 28 April 2017
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Abstract
The Sichuan Basin is the main agricultural production area of the upper reaches of the Yangtze River and is also an extremely important ecological area because it is rich in biodiversity and has complex and diverse landscape types. The dominant soil type, purple [...] Read more.
The Sichuan Basin is the main agricultural production area of the upper reaches of the Yangtze River and is also an extremely important ecological area because it is rich in biodiversity and has complex and diverse landscape types. The dominant soil type, purple soil, is prone to rapid soil erosion and weathering processes because it is shallow and rich in phosphorus and other nutrients. Field experiments were conducted to reveal the effects of precipitation and topography characteristics on nonpoint source pollutants from purple soil. The results showed that total phosphorus (TP) load and TP concentration both increased with increasing rainfall amount, and there was an initial time of runoff and sediment yield before runoff generation. Moreover, the TP load generally increased with precipitation intensity as setting a coincident value of rainfall amount; however, the difference between TP load at 30 and 60 mm/h was minimal as was the difference between 90 and 120 mm/h. Similarly, TP concentration increased with increasing precipitation intensity. In terms of topographical conditions, TP load increased with increasing gradient, but began to decline when the gradient was about 20°, which indicates that 20° is the critical gradient for TP loss. There was a significant positive correlation between gradient and TP concentration when the gradient was <15°, whereas the increase in TP concentration slowed as the gradient increased. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Numerical Simulation of Soil Evaporation with Sand Mulching and Inclusion
Water 2017, 9(4), 294; https://doi.org/10.3390/w9040294
Received: 20 March 2017 / Revised: 12 April 2017 / Accepted: 18 April 2017 / Published: 22 April 2017
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Abstract
A model of unsaturated soil-water movement using a prediction model of basic physical soil properties for calculating correlation functions was developed using VADOSE/W. The reliability of the model was assessed by comparing the results with those of a soil-column test. Coefficients of determination, [...] Read more.
A model of unsaturated soil-water movement using a prediction model of basic physical soil properties for calculating correlation functions was developed using VADOSE/W. The reliability of the model was assessed by comparing the results with those of a soil-column test. Coefficients of determination, R2, between the simulated and the measured daily evaporation for sand-mulch thicknesses of 0 (control, CK), 1.7, 3.6 and 5.7 cm were 0.8270, 0.8214, 0.8589 and 0.9851, respectively. R2, between the simulated and measured cumulative evaporation for mulch thicknesses of 0, 1.7, 3.6 and 5.7 cm were 0.9755, 0.9994, 0.9997 and 0.9983, respectively. The fits were, thus, good, verifying the reliability of the model. The program accurately predicted the distribution of cumulative evaporation and volumetric water content during evaporation from a soil column with mulch thicknesses of 1, 1.3, 1.5, 1.7, 2, 3, 5 cm and depths of sand inclusion thick of 0, 5, 10 and 15 cm for 20 days. Cumulative evaporation of sand inclusion was lower than in CK. Cumulative evaporation was independent of the mulch thickness and depended only on the depth of the inclusion: the deeper the inclusion, the higher the evaporation. The best mulch thickness was 5 cm, and the best inclusion depth was 5 cm. This study offers a new method to study the evaporation process with sand mulching and inclusion, which can provide guidance for improving the utilization efficiency of soil water. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Possibilities of Using Low Quality Digital Elevation Models of Floodplains in Hydraulic Numerical Models
Water 2017, 9(4), 283; https://doi.org/10.3390/w9040283
Received: 29 December 2016 / Revised: 23 March 2017 / Accepted: 13 April 2017 / Published: 21 April 2017
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Abstract
The paper presents a method for the correction of low quality DEMs, based on aerial photographs, for use in 2D flood modeling. The proposed method was developed and tested on the example of the floodplain of the Warta River, which is the third [...] Read more.
The paper presents a method for the correction of low quality DEMs, based on aerial photographs, for use in 2D flood modeling. The proposed method was developed and tested on the example of the floodplain of the Warta River, which is the third biggest river in Poland. The correction of DEM is based on a series of a small number of measurements using GPS-RTK, which enable calculations of the global statistics like mean error (ME), root mean square error (RMSE) and standard deviation (SD). The impact of DEM accuracy was estimated by using a 2D numerical model. The calculated values of flow velocities, inundation area and volume of floodplain for each tested DEM were compared. The analyses indicate that, after the correction procedure, the predictions of corrected DEM based on poor quality data is in good quantitative and qualitative agreement with the referenced LIDAR DEM. The proposed method may be applied in the areas for which high resolution DEMs based on LIDAR data are not available. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Applications of Coupled Explicit–Implicit Solution of SWEs for Unsteady Flow in Yangtze River
Water 2017, 9(3), 91; https://doi.org/10.3390/w9030091
Received: 26 December 2016 / Revised: 15 February 2017 / Accepted: 20 February 2017 / Published: 23 February 2017
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Abstract
In engineering practice, the unsteady flows generated from the operation of hydropower station in the upstream region could significantly change the navigation system of waterways located in the middle-lower reaches of the river. In order to study the complex propagation, convergence and superposition [...] Read more.
In engineering practice, the unsteady flows generated from the operation of hydropower station in the upstream region could significantly change the navigation system of waterways located in the middle-lower reaches of the river. In order to study the complex propagation, convergence and superposition characteristics of unsteady flows in a long channel with flow confluence, a numerical model based on the coupling of implicit and explicit solution algorithms of Shallow Water Equations (SWEs) has been applied to two large rivers in the reach of Yangtze River, China, which covers the distance from Yibin to Chongqing located upstream side of the Three Gorges Dam. The accuracy of numerical model has been validated by both the steady and unsteady flows using the prototype hydrological data. It is found that the unsteady flows show much more complex water level and discharge behaviors than the steady ones. The studied unsteady flows arising from the water regulation of two upstream hydropower stations could influence the region as far as Zhutuo hydrologic station, which is close to the city of Chongqing. Meanwhile, the computed stage–discharge rating curves at all observation stations demonstrate multi-value loop patterns because of the presence of additional water surface gradient. The present numerical model proves to be robust for simulating complex flows in very long engineering rivers up to 400 km. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle SPH Simulations of Solute Transport in Flows with Steep Velocity and Concentration Gradients
Water 2017, 9(2), 132; https://doi.org/10.3390/w9020132
Received: 7 December 2016 / Revised: 6 February 2017 / Accepted: 14 February 2017 / Published: 17 February 2017
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Abstract
In this study, a meshless particle method, smoothed particle hydrodynamics (SPH), is adopted to solve the shallow water equations (SWEs) and the advection diffusion equations (ADEs) for simulating solute transport processes under 1D/2D conditions with steep gradients. A new SPH-SWEs-ADEs model is herein [...] Read more.
In this study, a meshless particle method, smoothed particle hydrodynamics (SPH), is adopted to solve the shallow water equations (SWEs) and the advection diffusion equations (ADEs) for simulating solute transport processes under 1D/2D conditions with steep gradients. A new SPH-SWEs-ADEs model is herein developed to focus on the numerical performance of solute transport in flows with steep velocity and concentration gradients, since the traditional mesh-based methods have numerical difficulties on solving such steep velocity/concentration gradient flows. The present model is validated by six benchmark study cases, including three steep concentration gradient cases and three coupled steep concentration/velocity gradient cases. The comparison between the simulated results and the exact solutions for the former three cases shows that complete mass concentration conservation in pure advection-dominated flows is preserved. The numerical oscillation in concentration and the negative concentration resulted from the discretization of the advection term of ADEs can be totally avoided. The other three cases confirm that this model can also well capture coupled steep gradients of velocities and concentrations. It is demonstrated that the presented solver is an effective and reliable tool to investigate solute transports in complex flows incorporating steep velocity gradients. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Hydrologic Response of Climate Change in the Source Region of the Yangtze River, Based on Water Balance Analysis
Water 2017, 9(2), 115; https://doi.org/10.3390/w9020115
Received: 5 December 2016 / Revised: 25 January 2017 / Accepted: 8 February 2017 / Published: 13 February 2017
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Abstract
Due to the large amount of water resources stored in glaciers, permafrost, and lakes, the source region of the Yangtze River (SRYR) is of great importance for the overall basin water flow. For this purpose, a state of art review and calculations were [...] Read more.
Due to the large amount of water resources stored in glaciers, permafrost, and lakes, the source region of the Yangtze River (SRYR) is of great importance for the overall basin water flow. For this purpose, a state of art review and calculations were made for the period 1957–2013 using observed hydrological and meteorological data with a water balance approach. Actual evapotranspiration was calculated and validated by empirical formulas. Water storage change analysis was conducted with uncertainty boundaries using a 10-year moving window. Results show that temperature, precipitation, and actual evapotranspiration in the SRYR increased by 0.34 °C, 11.4 mm, and 7.6 mm per decade, respectively (significant at 0.05 probability level). Runoff appears to have increased at a rate of 3.3 mm per decade. The SRYR water storage in total has not changed significantly during the period, although the moving average is mostly below zero. Based on the water balance equation, the increase in calculated evapotranspiration is mainly due to the significantly increasing temperature. This in combination with increasing precipitation leads to a relatively stable water storage during the study period. Correlation analyses show that precipitation dominates runoff during the warm season (May to October), while temperature anomalies dominate the runoff during the cold season (November to April). The influence of temperature on runoff seems to enhance during the winter period. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessArticle Influence of Rack Slope and Approaching Conditions in Bottom Intake Systems
Water 2017, 9(1), 65; https://doi.org/10.3390/w9010065
Received: 7 December 2016 / Revised: 12 January 2017 / Accepted: 16 January 2017 / Published: 21 January 2017
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Abstract
The study analyzes the flow over bottom racks made of longitudinal T-shaped bars. A clear water flow is considered in a laboratory flume. Free surface profiles, wetted rack lengths, and discharge coefficients are measured, changing parameters such as longitudinal slope, void ratio, and [...] Read more.
The study analyzes the flow over bottom racks made of longitudinal T-shaped bars. A clear water flow is considered in a laboratory flume. Free surface profiles, wetted rack lengths, and discharge coefficients are measured, changing parameters such as longitudinal slope, void ratio, and approaching flow. The present work complements existing experimental studies, considering the influence of the approaching flow conditions. The velocity field measured with Particle Image Velocimetry (PIV) technique and the pressure field with Pitot tubes are quantified. Numerical simulations (CFD) are used to complement laboratory data. The energy head along the rack is calculated and compared with the hypothesis of horizontal energy level with minimum energy at the beginning of the rack. A discharge coefficient adjustment that considers the slope, the void ratio, and the position along the rack is proposed and presented with the results of other works. Theoretical proposals to calculate the pressure field along the flow are compared with measurements in the laboratory. The relation between the static pressure head in the space of bars and the discharge coefficient is used as an alternative method to define the discharge. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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Open AccessReview Modeling Biofilms in Water Systems with New Variables: A Review
Water 2017, 9(7), 462; https://doi.org/10.3390/w9070462
Received: 30 April 2017 / Revised: 8 June 2017 / Accepted: 23 June 2017 / Published: 4 July 2017
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Abstract
In nature, microorganisms mainly live in biofilms rather than planktonically to defend against various environmental stimuli. Understanding and predicting the dynamics and mechanisms of biofilms is of grand importance to human life. Besides experimental approaches, modeling provides a powerful tool to describe biofilms [...] Read more.
In nature, microorganisms mainly live in biofilms rather than planktonically to defend against various environmental stimuli. Understanding and predicting the dynamics and mechanisms of biofilms is of grand importance to human life. Besides experimental approaches, modeling provides a powerful tool to describe biofilms mathematically, and the in silico simulation offers a deep insight into the underlying functional machineries of biofilms. In this review, we briefly summarized the main advances in biofilm modeling, including the 1D model, multidimensional model, as well as the incorporation of extracellular polymeric substance and quorum sensing signals. Specifically, we focus on recent experimental advances in biofilms, which may challenge the current modeling systems via newly discovered properties and novel participants in natural water systems. We hope this article could build a bridge between in silico modeling and new experimental discoveries, and, in particular, we wish to attract more attention to biofilm-related-environmental issues at various scales. Full article
(This article belongs to the Special Issue Modeling of Water Systems)
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