Search Results (193)

Managed aquifer recharge (MAR) is a complex and hidden process of storing surplus water under the ground surface and extracting it as, when and where needed. Evaluation of the success of any MAR project is challenging due to uncertainty in estimating the hydrogeological characteristics of the subsurface media. This paper demonstrates the use of a groundwater model (MODFLOW) to evaluate a new, large-scale regional MAR project in the agricultural heartland in Punjab, Pakistan. In this MAR project, flood waters have been diverted to the bed of an abandoned canal, where 144 recharge wells (the wells for accelerating the recharge into the aquifer) have been constructed to accelerate the recharge to the aquifer. The model was calibrated for a period of five years from October 2015 to June 2020 on a monthly stress period and the resulting water levels were simulated till 2035. The water balance components and future response of the aquifer to different scenarios up to 2035 including with and without MAR situations are presented. The model simulations showed that MAR can contribute to the replenishment of the aquifer and its potential for the case study site to contribute significantly to the management of groundwater and to enhance supplies for intensive agriculture. It was further established that MODFLOW can help in the evaluation of effectiveness of a MAR scheme. This study is unique as it evaluates a significantly large MAR project in an area where this practice has not been developed for improving groundwater access for large scale irrigation. The model provides guidelines for decision makers in the region as well as for the global community and livelihood benefits for rural communities. Full article

Groundwater storage refers to the water stored in the pore spaces of underground aquifers, which has been increasingly affected by both climate change and anthropogenic activities in recent decades. Therefore, monitoring their changes and the factors that affect it is of great importance. Although the influence of natural factors on groundwater is well-recognized, the impact of human activities, despite being a major contributor to its change, has been less explored due to the challenges in measuring such effects. To address this gap, our study employed an integrated approach using remote sensing and the Google Earth Engine (GEE) cloud-free platform to analyze the effects of various anthropogenic factors such as built-up areas, cropland, and surface water on groundwater storage in the Lake Urmia Basin (LUB), Iran. Key anthropogenic variables and groundwater data were pre-processed and analyzed in GEE for the period from 2000 to 2022. The processes linking these variables to groundwater storage were considered. Built-up area expansion often increases groundwater extraction and reduces recharge due to impervious surfaces. Cropland growth raises irrigation demand, especially in semi-arid areas like the LUB, leading to higher groundwater use. In contrast, surface water bodies can supplement water supply or enhance recharge. The results were then exported to XLSTAT software2019, and statistical analysis was conducted using the Mann–Kendall (MK) non-parametric trend test on the variables to investigate their potential relationships with groundwater storage. In this study, groundwater storage refers to variations in groundwater storage anomalies, estimated using outputs from the Global Land Data Assimilation System (GLDAS) model. Specifically, these anomalies are derived as the residual component of the terrestrial water budget, after accounting for soil moisture, snow water equivalent, and canopy water storage. The results revealed a strong negative correlation between built-up areas and groundwater storage, with a correlation coefficient of −1.00. Similarly, a notable negative correlation was found between the cropland area and groundwater storage (correlation coefficient: −0.85). Conversely, surface water availability showed a strong positive correlation with groundwater storage, with a correlation coefficient of 0.87, highlighting the direct impact of surface water reduction on groundwater storage. Furthermore, our findings demonstrated a reduction of 168.21 mm (millimeters) in groundwater storage from 2003 to 2022. GLDAS represents storage components, including groundwater storage, in units of water depth (mm) over each grid cell, employing a unit-area, mass balance approach. Although storage is conceptually a volumetric quantity, expressing it as depth allows for spatial comparison and enables conversion to volume by multiplying by the corresponding surface area. Full article

This study presents a robust methodology for the indirect estimation of groundwater abstraction for irrigation at the scale of individual wells, addressing a key gap in data-scarce agricultural settings. The approach combines NDVI time series, crop water requirement modelling, and spatial analysis of irrigation systems within a GIS environment. A soil water balance model was applied to Homogeneous Units of Analysis, and irrigation requirements were estimated using an ensemble approach accounting for key sources of uncertainty related to phenology detection, soil moisture at sowing (%SAW), and irrigation system efficiency. A spatial linkage algorithm was developed to associate individual wells with the irrigated areas they supply. Sensitivity analysis demonstrated that 10% increases in %SAW resulted in abstraction reductions of up to 1.98%, while 10% increases in irrigation efficiency reduced abstractions by an average of 6.48%. These findings support the inclusion of both parameters in the ensemble, generating eight abstraction estimates per well. Values ranged from 33,000 to 115,000 m³ for the 2023 season. Validation against flowmeter data confirmed the method’s reliability, with an R² of 0.918 and an RMSE equivalent to 9.3% of the mean observations. This approach offers an accurate, spatially explicit estimation of groundwater abstractions without requiring direct metering and offers a transferable, cost-effective tool to improve groundwater accounting and governance in regions with limited monitoring infrastructure. Full article

In the context of progressing climate change and the increasing frequency of extreme weather events, there is a growing need for effective strategies to mitigate their impacts. One such strategy involves the implementation of tools aimed at sustainable rainfall management at the site of precipitation. This study focuses on assessing the state of the water environment as a prerequisite for introducing sustainable Managed Aquifer Recharge (MAR) practices in urban areas. The research was conducted in the historic district of Warsaw, Poland. A comprehensive methodological approach was employed, including field and laboratory measurements of soil moisture and electrical conductivity (EC), vadose zone hydraulic conductivity, spring discharge rates, and analytical calculations based on climatic data. These were supplemented by groundwater flow modeling to estimate infiltration rates. The study showed that the infiltration rate in the aquifer is low—only 4.4% of the average annual precipitation. This is primarily due to limited green space coverage and high surface runoff, as well as high potential evaporation rates and low soil permeability in the vadose zone. A positive water balance and infiltration were observed only in December and January, as indicated by increased soil moisture and decreased EC values. A multi-criteria spatial analysis identified priority zones for the installation of retention infrastructure aimed at enhancing effective infiltration and improving the urban water balance. These findings underscore the need for targeted interventions in urban water management to support climate resilience and sustainable development goals. Full article

Climate change, marked by decreasing rainfall and increasing extreme events, represents a major challenge for water resources, particularly in semi-arid regions. To estimate aquifer recharge, it is essential to assess the fraction of precipitation contributing to groundwater recharge and to implement a water balance model. However, the limited number of rainfall stations has led researchers to rely on satellite and reanalysis rainfall products. The accuracy of these datasets is essential for reliable hydrological modeling. In this study, we evaluated five rainfall products—CHIRPS, ERA5_Ag, CFSR, GPM, and PERSIANN-CDR—by comparing them to ground measurements from gauging stations in the central Haouz region of Marrakech. The evaluation was conducted at three temporal scales: daily, monthly, and annual. Statistical metrics, including RMSE, MAE, NSE, Bias, and Pearson correlation, as well as classification metrics (accuracy, F1 score, recall, precision, and Cohen’s Kappa), and wavelet analysis, were applied to assess the accuracy of the products. The results identified ERA5_Ag and GPM as the most accurate products in capturing rainfall events. Nevertheless, ERA5_Ag showed a high bias. After applying the quantile mapping method to correct the bias, the product exhibited greater accuracy. The corrected datasets from these two products will be used to estimate recharge over the last 30 years, contributing to the development of a hydrogeological model for groundwater dynamics. Full article

More than half of the cultivated land belongs to the Irrigation Association. Therefore, there have been no farmland consolidation, irrigation, and drainage projects. The cultivation in the non-irrigation area suffers from poor geographical conditions and a lack of water sources. A practical planning strategy is required for expanding irrigation services. The mountainous area of Nantou County, Taiwan, has 7477 ha of available land and 4656 ha of agricultural land outside the irrigation area. Rain and streams are the main water source. There are 82 ponds, 80% of which belong to the loam soil, and the rainfall from October to February is limited. The water requirement of crops is 1.5–3.1 mm/day. Wild streams, groundwater, and rainwater are the only potential water sources due to elevation and terrain. The potential runoff is estimated to be 0–0.927 cms (m³/s) when using the SCS-CN method. Water supply and demand from October to April are limited, and the rainfall comprises 22% of the total water supply. Large reservoirs and water storage towers are required for flooding and in dry seasons. To address water storage challenges and stabilize the balance between water supply and demand, it is essential to construct additional ponds. Full article

This study presents a novel approach that integrates the Kalman filter and genetic algorithms to obtain the hydraulic parameters of a confined aquifer with precision, eliminating noise that is not normally considered in traditional procedures; these parameters are necessary for the design of wells, the calculation of water balances and the numerical modeling of aquifers. The Theis solution for horizontal radial groundwater flow to an extraction well within a confined aquifer is implemented in the Kalman filter to calibrate the hydraulic transmissivity and the storage coefficient, minimizing the differences between drawdown estimates and the Theis solution by means of genetic algorithms. The estimate error variances provided by the method allowed for the quantification of an approximate average drawdown measurement error of 0.12 m and 0.02 m, respectively, during the execution of two pumping tests. Full article

This review examines state-of-the-art practices in water harvesting and groundwater recharge, emphasizing their crucial role in sustainable water resource management. Groundwater, a crucial resource for drinking and agricultural water, is facing depletion due to the combined effects of urbanization, climate change, and unregulated extraction. This paper provides a comprehensive overview of contemporary knowledge on water harvesting and recharge, using a systematic four-step methodology to identify and analyze relevant studies from databases like Google Scholar, Scopus, and ScienceDirect. It categorizes water harvesting techniques, such as rainwater, flood water, and groundwater harvesting, and evaluates their effectiveness in enhancing recharge. Both natural and artificial recharge methods are explored, highlighting their role in improving groundwater levels and water quality. This study also reviews recharge estimation techniques and their applicability across hydrogeological contexts. This paper promotes a balanced approach to address issues of water scarcity by integrating water harvesting into groundwater management strategies. This integration aims to build resilience against climate change-driven environmental damage. Recommendations are provided to enhance the sustainability of these practices, with a particular focus on arid and semi-arid regions where water demand is rising. Overall, this study underscores the significance of water harvesting and recharge in promoting long-term resource sustainability. Full article

Evaluating the performance of irrigation water use is essential for efficient and sustainable water resource management. However, existing approaches often lack systematic quantification of irrigation water consumption and fail to differentiate between the use of precipitation and anthropogenic appropriation of water flows. Building on the green–blue water concept, consumptive water use, assumed equal to actual evapotranspiration (ET_a), was partitioned into green ET (GET) and blue ET (BET) using remote sensing data and the Budyko hypothesis. A novel BET metric of consumptive irrigation water use was developed and applied to the irrigated lands in northwest China to evaluate the performance of irrigation from 2001 to 2021. The results showed that in terms of total available water resources (precipitation + gross irrigation water (GIW)) compared to irrigation water demand, estimated as reference evapotranspiration (ET₀), Ningxia has sufficient water supply to meet irrigation demand, while the Hexi Corridor faces increasing risks of unsustainable water use. The Hetao irrigation scheme has shifted from a fragile supply–demand balance to a situation where water demand far exceeds availability. In Xinjiang, the balance between water supply and demand is tight. Furthermore, when considering the available water (GIW) relative to the net irrigation water demand (ET₀-GET), the Hexi Corridor faces significant water deficits, and Ningxia and Xinjiang are close to meeting local irrigation water demands by relying on current water availability and efficient irrigation practices. It is noteworthy that the BET remains lower than the GIW in northwest China (excluding the Hexi Corridor in recent years). The ratio of the BET to GIW is an estimate of the scheme irrigation efficiency, which was equal to 0.54 for all irrigation schemes taken together. In addition, the irrigation water use efficiency, estimated as the ratio of BET to net irrigation water, was evaluated in detail, and it was found that in the last 10 years the irrigation water use efficiency improved in Ningxia, the Hetao irrigation scheme, and Xinjiang. However, the Hexi Corridor continues to face severe net irrigation water deficits, suggesting the likelihood of groundwater use to sustain irrigated agriculture. BET innovatively separates consumptive use of precipitation (green water) and consumptive use of irrigation (blue water), a critical advancement beyond conventional approaches’ estimates that merge these distinct hydrological components to help quantifying water use efficiency. Full article

The accurate knowledge of groundwater availability and its variations is crucial for sustainable groundwater management; in this framework, the water balance is a useful tool to assess the availability of water resources. Currently, the management authority needs a more precise evaluation of groundwater availability to face the rising freshwater demand. In this work, water balance has been determined for the main aquifers in the central Apennines (Italy)—over 2000 km² wide—and the calculated outflow was compared with springs’ discharge from the data. Inflow data were collected over a 6-year period, from 2018 to 2023, considering both rainfall and snow; the contribution of the snow melting has often been omitted or rarely considered as immediate liquid contribution in the previous works, where usually only liquid inflows from rain have been considered. The snow contribution has been properly evaluated from a recent network of snow gauges and included in the total precipitation for more accurate results. Indeed, for each aquifer, monthly inflow datasets from rain gauges have been interpolated inside the structure using the equations obtained from regression lines and then used for a water balance assessment. An initial comparison of water balances, estimated with and without snow data, demonstrates that neglecting the snow contribution can lead to an underestimation of infiltration values. A comparison between calculated outflows including the snow melt and the measured springs’ discharge has shown a good correspondence for each investigated aquifer. Full article

Groundwater systems are important for maintaining ecological balance and ensuring water supplies. However, under the combined pressures of shifting climate patterns and human activities, their responses to extreme events have become increasingly complex. As China’s largest freshwater lake, Poyang Lake supports critical water resources, ecological health, and climate adaptation efforts. Yet, the relationship between groundwater storage (GWS) and extreme hydrological events in this region remains insufficiently studied, hindering effective water management. This study investigates the GWS response to extreme events by downscaling Gravity Recovery and Climate Experiment (GRACE) data and validating it with five years of observed daily groundwater levels. Using GRACE, the Global Land Data Assimilation System (GLDAS), and ERA5 data, a convolutional neural network (CNN)–attention mechanism (A)–long short-term memory (LSTM) model was selected to downscale with high resolution (0.1° × 0.1°) and estimate recovery times for GWS to return to baseline. Our analysis revealed seasonal GWS fluctuations that are in phase with precipitation, evapotranspiration, and groundwater runoff. Recovery durations for extreme flood (2020) and drought (2022) events ranged from 0.8 to 3.1 months and 0.2 to 4.8 months, respectively. A strong correlation was observed between groundwater and meteorological droughts, while the correlation with agricultural drought was significantly weaker. These results indicate that precipitation and groundwater runoff are more sensitive to extreme events than evapotranspiration in influencing GWS changes. These findings highlight the significant sensitivity of precipitation and runoff to GWS, despite improved management efforts. Full article

In response to the escalating frequency and severity of wildfires, this study carried out a preliminary assessment of their impact on groundwater systems by simulating post-fire effects on groundwater recharge. The study focuses on the El Sutó spring area in Santa Cruz, Bolivia, a region that is susceptible to water scarcity and frequent wildfires. The United States Geological Survey (USGS) Soil-Water-Balance model version 2.0 was utilized, adjusting soil texture and infiltration capacity parameters to reflect the changes induced by wildfire events. The findings indicated a significant decrease in groundwater recharge following a hypothetical high-severity wildfire, with an average reduction of approximately 39.5% in the first year post-fire. A partial recovery was modeled thereafter, resulting in an estimated long-term average reduction of 10%. Based on these results, the El Sutó spring was provisionally classified as having high vulnerability shortly after a wildfire and moderate vulnerability in the extended period. Building on these model-based impacts, a preliminary Fire-Related Forest Recharge Impact Score (FRIS) was proposed. This index is grounded in soil properties and recharge dynamics and is designed to assess hydrological vulnerability after wildfires in dry tropical forests. Although these findings remain exploratory, they offer a predictive framework intended to guide future studies and inform strategies for managing wildfire impacts on groundwater resources. Full article

The estimation of water requirements constitutes a critical prerequisite for delineating water scarcity hotspots and mitigating intersectoral competition, particularly in endorheic basins in arid or semi-arid regions where hydrological closure exacerbates resource allocation conflicts. Under conditions of water scarcity, water supplied locally by precipitation and shallow groundwater bodies should be taken into account to estimate the net water requirements to be met with water conveyed from off-site sources. This concept is embodied in the distinction of blue ET (BET) and green ET (GET). In this study, the Budyko hypothesis (BH) method was optimized to partition the total ET into GET and BET during 2001–2018 in the Heihe River Basin. In this region, a better knowledge of net water requirements is even more important due to water allocation policies which reduced water supply to irrigated lands in the last 15 years. This study proposes a modified BH method based on a new vegetation-specific parameter (${\omega }_v$) which was optimized for different vegetation types using precipitation and actual ET data obtained from remote sensing observations. The results show that the BH method partitioned GET and BET reasonably well, with a percent bias of 23.8% and 37.4% and a root mean square error of 84.8 mm/a and 113.6 mm/a, respectively, when compared with reported data, which are superior to that of the precipitation deficit and soil water balance methods. A sensitivity experiment showed that the BH method exhibits a low sensitivity to uncertainties of input data. The results documented differences in the contribution of GET and BET to total ET across different land cover types in the Heihe River Basin. As expected, rainfed forest and grassland ecosystems are predominantly governed by GET, with 81.3% and 87.2% of total ET, respectively. In contrast, croplands and shrublands are primarily regulated by BET, with contributions of 61.5% and 84.3% to total ET. The improved BH method developed in this study paves the way for further analyses of the net water requirements in arid and semi-arid regions. Full article

This study investigates the complex interaction of biophysical and meteorological factors that drive evapotranspiration (ET) in saline environments. Leveraging a total of 182 cloud-free Landsat 5/8 time-series data from 1988 to 2019, we employed the Surface Energy Balance System (SEBS) model to quantify ET and investigate its relationships with soil salinity, vegetation cover, groundwater depth, and landscape metrics. We validated the predicted ET at two experimental sites using ET observation calculated by a water balance model. The result shows an R² of 0.78 and RMSE of 0.91 mm for the SEBS predicted ET, indicating high accuracy of the ET estimation. We detected abandoned saline farmland patches across Hetao and extracted the normalized difference vegetation index (NDVI), salinization index (SI), and the predicted ET for analysis. The results indicate that ET is negatively correlated with SI with a Pearson correlation coefficient (r) up to −0.7, while ET is positively correlated with NDVI (r = 0.4). In addition, we designed a control-variable experiment in the Yichang subdistrict to investigate the effects of groundwater depth, land aggregation index, soil salinity index, and the area of abandoned saline farmland patches on ET. The results indicate that increased NDVI could significantly enhance ET, while smaller saline farmland patches exhibited greater sensitivity to groundwater recharge, with higher averaged ET than larger patches. Moreover, we analyzed factor importance using Lasso regression and Random Forest (RF) regression. The result shows that the ranking of the importance of the features is consistent for both methods and for all the features, with NDVI being the most important (with an RF importance score of 0.4), followed by groundwater table depth (GWTD), and the influence of the surface area of abandoned saline farmland being the weakest. We found that smaller patches of abandoned saline farmland were more sensitive to changes in groundwater levels induced by nearby irrigation, affecting their averaged ET more dynamically than larger patches. Decreasing patch size over time indicates ongoing changes in land management and ecological conditions. This study, through a multifactor analysis of ET in abandoned saline farmland and its intrinsic factors, provides a reference for evaluating the dry drainage efficiency of abandoned saline farmland in a dry drainage system. Full article

Waterholes in semi-arid environment are sections of rivers that fill during high river flows or floods and keep water once flow ceases. They are essential water sources for rive ecosystems. Some waterholes remain even during prolonged droughts. The resilience of ecosystems in these environments depends on the persistence of the waterholes. While most semi-arid, ephemeral river systems are disconnected from regional groundwater and losing in most parts there may be some sections that can be connected to localised groundwater or parafluvial areas. To assess the persistence of waterholes the groundwater contribution to the water balance needs to be addressed. This study assesses groundwater connectivity to waterholes in a part of the Murray-Darling Basin, one of the largest watersheds in the world, using environmental tracers radon and stable isotopes. Approximately 100 samples were collected from 27 waterholes along the Narran, Calgoa, Barwon and Darling rivers, as well as 8 groundwater bore samples. The assessment of groundwater connectivity or the lack of is necessary from water balance modelling and estimation of persistence of these waterholes. As expected, the results indicate consistently low radon concentrations in the waterholes and very small deviation in stable isotopes ${\delta }^{18}$O and ${\delta }^2$H. In general, most of these waterholes are losing water to groundwater, indicated by low salinity (EC values) and low radon concentrations. While radon concentrations are small in most cases and indicative of little groundwater contributions, some variability can be assigned to bank return and parafluvial flow. It indicates that these contributions may have implications for waterhole persistence in ephemeral streams. The study demonstrates that in some cases local bank return flow or parafluvial flow may contribute to waterhole persistence. Full article