Estimating Groundwater Recharge Research Articles

Estimation of Spatial Groundwater Recharge Using WetSpass Model For east Wasit province ,Iraq

Groundwater is an important water source, especially in arid and semi-arid areas. Recharge is critical to managing and analyzing groundwater resources despite estimation difficulty due to temporal and spatial change. the study aim is to estimate annual groundwater recharge for the eastern Wasit Province, Iraq. Where suffers from a surface water shortage due to the region's high elevation above Tigris River water elevation by about 60 m. It is necessary to search for alternative water sources, such as groundwater use, especially with the increased demand for water in light of the growth of oil extraction in the region, where oil extraction requires a quantity of water three times the amount of oil extracted. The result shows the annual recharge calculated using the WetSpass model for the period (2014-2019) ranged from 0 to 65.176 mm/year at a rate of 27.117 mm/year and a standard deviation of 21.498. The simulation results reveal that the WetSpass model simulates the components of the hydrological water budget correctly. For managing and planning available water resources, a better grasp of the simulation of long-term average geographical distribution around the components of the water balance is beneficial.

Estimation of Spatial Groundwater Recharge Using WetSpass Model for East Wasit Province, Iraq

AbstractGroundwater is an important water source, especially in arid and semi-arid areas. Recharge is critical to managing and analyzing groundwater resources despite estimation difficulty due to temporal and spatial change. The study aim is to estimate annual groundwater recharge for the eastern Wasit Province part, Iraq. Where suffers from a surface water shortage due to the region's high elevation above Tigris River water elevation by about 60 m, it is necessary to search for alternative water sources, such as groundwater use. The spatially distributed WetSpass model was used to estimate the annual recharge. The inputs for the model were prepared using the ARC-GIS program, which includes the topography and slope grid, soil texture grid, land use, groundwater level grid, and meteorological data grids for the study area for the period (2014-2019). The result shows that the annual recharge calculated using the WetSpass model (2014-2019) varied of 0 to 65.176 mm/year at an average of 27.117 mm/year, about 10.8%, while the rate of the surface runoff was 5.2% and Evapotranspiration formed 83.33% of the annual rainfall rate of 251.192 mm. The simulation results reveal that the WetSpass model simulates the components of the hydrological water budget correctly. For managing and planning available water resources, a best grasp of the simulation of long-range average geographical distribution around the water balance components is beneficial.

The State-of-the-Art Estimation of Groundwater Recharge and Water Balance with a Special Emphasis on India: A Critical Review

Groundwater recharge estimation is essential for sustainable water management and water supply schemes. In this paper, we review groundwater recharge estimation techniques and identify the appropriate methods by considering India’s hydrological and climatic conditions. Significant components of recharge, factors affecting groundwater recharge, aquifer systems of India, and historical groundwater recharge estimation practices are reviewed. Currently used recharge estimation methods are assessed based on case studies. The most popular estimation methods are studied and compared based on their application in various regions. It is observed that the accuracy of the recharge estimates is largely influenced by false assumptions, the possibility of erroneous measurements, a potential lack of reliable data, and a variety of problems associated with parameter estimation. The suitability of different methods for a region is found to depend on time and space considerations, the objective of the study, hydrogeological condition, and availability of data. In Indian conditions, it is suggested to use water table fluctuation and water balance methods for the recharge estimation, provided that accurate water level measurements are assured.

CMBEAR: Python-Based Recharge Estimator Using the Chloride Mass Balance Method in Australia.

The chloride mass balance (CMB) method is widely used to estimate long-term rates of groundwater recharge. In regions where surface water runoff is negligible, recharge can be estimated using measurements of chloride concentrations of groundwater and precipitation, and an estimate of long-term average rainfall. This paper presents the Chloride Mass Balance Estimator of Australian Recharge (CMBEAR), a Jupyter (Python) Notebook that is set up to rapidly apply the CMB method using gridded maps of chloride deposition rates across the Australian continent. For an Australian context, the chloride deposition rate and rainfall maps have been provided. Thus, CMBEAR requires only a spreadsheet with the groundwater chloride concentration, the latitude and longitude of the sample location, and some simple user inputs. CMBEAR may be easily applied in other regions, providing that a gridded chloride deposition map is available. Recharge estimates from CMBEAR are compared against published applications of the CMB method. CMBEAR is also applied to a large dataset from the Northern Territory and is used to produce a gridded map of recharge for western Victoria. CMBEAR provides a reproducible and straightforward approach to apply the CMB method to estimate groundwater recharge.

Groundwater Recharge Assessment Using Multi Component Analysis: Case Study at the NW Edge of the Varaždin Alluvial Aquifer, Croatia

Exploring the interaction between precipitation, surface water, and groundwater has been a key subject of many studies dealing with water quality management. The Varaždin aquifer is an example of an area where high nitrate content in groundwater raised public concern, so it is important to understand the aquifer recharge for proper management and preservation of groundwater quality. The NW part of the Varaždin aquifer has been selected for study area, as precipitation, Drava River, accumulation lake, and groundwater interact in this area. In this study, groundwater and surface water levels, water temperature, water isotopes (2H and 18O), and chloride (Cl−) were monitored in precipitation, surface water, and groundwater during the four-year period to estimate groundwater recharge. Head contour maps were constructed based on the groundwater and surface water levels. The results show that aquifer is recharged from both Drava River and accumulation lake for all hydrological conditions–low, mean, and high groundwater levels. The monitoring results of water temperature, chloride content, and stable water isotopes were used as tracers, i.e. as an input to the mixing model for estimation of the contribution ratio from each recharge source. The calculation of mixing proportions showed that surface water is a key mechanism of groundwater recharge in the study area, with a contribution ratio ranging from 55% to 100% depending on the proximity of the observation well to surface water.

Estimation of groundwater recharge in a shallow sandy aquifer using unsaturated zone modeling and water table fluctuation method

Quantification of groundwater recharge is one of the most important issues in hydrogeology, especially in view of the ongoing changes in climate and land use. In this study, we use numerical models of 1D vertical flow in the vadose zone and the water table fluctuation (WTF) analysis to investigate local-scale recharge of a shallow sandy aquifer in the Brda outwash plain in northern Poland. We show that these two methods can be jointly used to improve confidence in recharge estimation. A set of preliminary numerical simulations based on soil water content measurements from 4 grassland and pine forest profiles provided a wide range of recharge estimates (263 mm to 839 mm for a 3-year period). Additional simulations were performed with the lower boundary condition specified as a functional relationship between the groundwater table elevation and the rate of groundwater outflow from the vertical profile (horizontal drains boundary condition). In this way, we could reproduce the water table fluctuations resulting from recharge and lateral discharge to nearby lakes. The agreement between simulated and observed groundwater levels differed depending on the specific set of parameters characterizing vadose zone flow, which allowed us to find the most representative parameter sets and refine the range of plausible recharge estimates (501 mm to 573 mm per 3 years). The recharge rates from WTF (410 mm to 606 mm per 3 years) were in good agreement with numerical simulations, providing that the effect of the natural recession of groundwater table due to lateral outflow was considered (master recession curve method). Our results show that: (i) the proposed approach combining 1D vadose zone modeling and WTF improves recharge estimation, (ii) multiple types of observations, including groundwater table positions, are needed to calibrate and validate vadose zone flow models, and (iii) extended periods of observations and simulations are necessary to capture year-to-year variability in the recharge rates.

Groundwater recharge rate estimation using remotely sensed and ground-based data: A method application in the mesoscale Thur catchment

Study regionThe mesoscale Thur catchment located in the north‐eastern part of Switzerland is a study site in which a range of hydrological research has been conducted. Study focusGroundwater recharge is challenging to quantify due to the complexity of hydrogeological processes and limited observations. Because of its spatiotemporal availability, remotely sensed data present an attractive water management tool. Its application in mesoscale catchments (10 – 104 km2) however, remains limited. This study investigated the use of satellite products used in conjunction with ground-based data to determine spatiotemporal variations in water available for groundwater recharge. Gridded components from readily available precipitation, evapotranspiration, and hydrological discharge data were used to generate spatiotemporal maps over a 20-year period. New hydrological insights for the regionClosure of the water balance found that monthly data displayed a moderate correlation, with improved correlations of obtained seasonal and annual intervals, suggesting that over the long-term the Thur catchment is in a steady state. Maps were generated and trends for the 20-year period assessed. Examination of the gridded water balance components for different hydrological years emphasized the limiting effect of precipitation on recharge. This study highlights the value of remotely sensed data in groundwater recharge estimates, but emphasises the importance of continued ground-based monitoring; the lack of which is a limiting factor in water management where mesoscale catchments are concerned.

Long-Term (44 Years) Regional Groundwater Recharge Estimation for Agricultural Sustainability

Long-Term (44 Years) Regional Groundwater Recharge Estimation for Agricultural Sustainability

Groundwater recharge estimation using empirical methods from rainfall and streamflow records

Study regionGumara and Ribb watersheds, Abbay Basin, Ethiopia. Study focusIn this paper, an attempt was made to estimate groundwater recharge from streamflow and rainfall records. The groundwater recharge was estimated by different empirical methods, including the water balance method. The Ribb and Gumara rivers streamflow data were collected from the Ministry of Water, Irrigation, and Electricity of Ethiopia for estimating groundwater recharge by using baseflow separation techniques. The climate data was obtained from the Amhara National Meteorology Agency for estimating rainfall recharge and water balance components. New hydrological insights for the regionGroundwater resource development needs the determination of groundwater recharge volume. The annual areal rainfall, reference evapotranspiration, and recharge from rainfall of the study area were estimated as 1399.8 mm, 1300.21 mm, and 253.70 mm, respectively. The evapotranspiration was determined using the Penman-Monteith method. The baseflow separation techniques of RORA, PART, WHAT, and RECESS were employed during this study. The recharge coefficient estimated from rainfall and streamflow data were found at 0.18 and 0.20 respectively, which indicated that the study area has high groundwater recharge volume which could be used for different groundwater development projects. This study provides evidence for the groundwater potential areas identified by using geospatial methods and groundwater development projects that can be practiced in the area.

Estimation of groundwater recharge using multiple climate models in Bayesian frameworks

AbstractGroundwater recharge plays a vital role in replenishing aquifers, sustaining demand, and reducing adverse effects (e.g. land subsidence). In order to manage climate change-induced effects on groundwater dynamics, climate models are increasingly being used to predict current and future recharges. Even though there has been a number of hydrological studies that have averaged climate models’ predictions in a Bayesian framework, few studies have been related to the groundwater recharge. In this study, groundwater recharge estimates from 10 regional climate models (RCMs) are averaged in 12 different Bayesian frameworks with variations of priors. A recession-curve-displacement method was used to compute recharge from measured streamflow data. Two basins of different sizes located in the same water resource region in the USA, the Cedar River Basin and the Rainy River Basin, are selected to illustrate the approach and conduct quantitative analysis. It has been shown that groundwater recharge prediction is affected by the Bayesian priors. The non-Empirical Bayes g-Local-based Bayesian priors result in posterior inclusion probability values that are consistent with the performance of the climate models outside the Bayesian framework. With the proper choice of priors, the Bayesian frameworks can produce good results of groundwater recharge with R2, percent bias error, and Willmott's index of agreement of >0.97, <2%, and >0.97, respectively, in the two basins. The Bayesian framework with an appropriate prior provides opportunity to estimate recharge from multiple climate models.

Quantitative estimation of groundwater recharge in the thick loess deposits using multiple environmental tracers and methods

Accurate estimation of groundwater recharge in regions with limited water and thick unsaturated zones is challenging because of the limited water flux. This study aims to employ multiple tracers and methods to investigate the mechanism of groundwater recharge in the thick loess deposits of China. We collected soil samples under different vegetation, unconfined groundwater, and precipitation to determine the water isotopes (δ2H, δ18O, and 3H), chloride (Cl-), nitrate (NO3–). Then, these tracers were employed to estimate recharge rates with methods considering the differences in shallow- and deep-rooted vegetation, as well as those in unsaturated and saturated zones. Results indicated that local precipitation predominantly recharges groundwater through matrix flow at a velocity of 14.5 cm year−1 with the residence time of > 200 years. The recharge rates range from 0 to 37 mm year−1, equivalent to 0–7% of annual average precipitation. However, the deep-rooted vegetation greatly reduced deep drainage compared with shallow-rooted vegetation, which will perturb the current hydraulic connectivity between unsaturated and saturated zones. The multiple tracers and methods can complement each other to enhance the understanding of groundwater recharge mechanisms. The indicated relationship between recharge form and land use suggests the urgency in developing strategies to balance the agroforestry system and water resource sustainability.

Evaluating the relationship between hydrological extremes and groundwater in Luvuvhu River Catchment, South Africa

Extreme hydrological events have been reported to be on an increase in terms of magnitude and frequency in southern Africa. Groundwater in this area plays a significant role in domestic water supply and agriculture. The aim of this study is to evaluate the relationship between groundwater levels and hydrological extremes in north-eastern South Africa. An index-based approach was used to determine the drought and flood events over the study period while the Water Table Fluctuation approach was used to determine groundwater recharge. Flow duration curves were further employed to determine the exceedance period of high and low flows in the study area. Mann-Kendall and Sequential Mann-Kendall were used to detect trends and the point of change. Both floods and drought were found to have occurred in the study area at different magnitudes, however both the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) found that majority of these were not categorized as mild to near normal conditions. Specific yield determined using the simple linear regression method ranged between 0.04 and 0.06. Groundwater recharge estimates ranged between 1.1 and 11.5 % of mean annual rainfall ranging between 167–1000 mm/a. About 60 % of the stations (i.e. rainfall, streamflow, and groundwater) show significantly decreasing trend. This therefore indicates that there is a decreasing trend in groundwater levels, streamflow, and rainfall over the study area. Based on the trend analysis findings, it suggests that extreme events in the catchment influences groundwater resources.

Estimating surface runoff and groundwater recharge in an urban catchment using a water balance approach

Land-use changes often have significant impact on the water cycle, including changing groundwater/surface-water interactions, modifying groundwater recharge zones, and increasing risk of contamination. Surface runoff in particular is significantly impacted by land cover. As surface runoff can act as a carrier for contaminants found at the surface, it is important to characterize runoff dynamics in anthropogenic environments. In this study, the relationship between surface runoff and groundwater recharge in urban areas is explored using a top-down water balance approach. Two empirical models were used to estimate runoff: (1) an updated, advanced method based on curve number, followed by (2) bivariate hydrograph separation. Modifications were added to each method in an attempt to better capture continuous soil-moisture processes and explicitly account for runoff from impervious surfaces. Differences between the resulting runoff estimates shed light on the complexity of the rainfall–runoff relationship, and highlight the importance of understanding soil-moisture dynamics and their control on hydro(geo)logical responses. These results were then used as input in a water balance to calculate groundwater recharge. Two approaches were used to assess the accuracy of these groundwater balance estimates: (1) comparison to calculations of groundwater recharge using the calibrated conceptual HBV Light model, and (2) comparison to groundwater recharge estimates from physically similar catchments in Switzerland that are found in the literature. In all cases, recharge is estimated at approximately 40–45% of annual precipitation. These conditions were found to closely echo those results from Swiss catchments of similar characteristics.

Impact of anthropogenic activities on river-aquifer exchange flux in an irrigation dominated Ganga river sub-basin

The easy accessibility of groundwater in the alluvial plains of the Kosi river basin has considerably altered the crop calendar and farmers’ irrigation response, especially in the dry years after 2004. The present study attempts to develop a framework for analyzing the spatio-temporal variation in the groundwater recharge/ extraction pattern as well as river and aquifer flux exchange due to increasing anthropogenic activities in the basin. The influence of anthropogenic activities over groundwater recharge/extraction statistics has been discussed in Laveti et al. (2021). The estimated groundwater recharge (Laveti et al., 2021) along with aquifer characteristics (hydraulic conductivity, porosity, and specific storage), and riverbed conductance were used as inputs to the groundwater flow transient model in the study. The model observed, an increasing groundwater dependency for agricultural activities, results in a continuous increase of flux from the river to the aquifer. Between 1997 and 2010, the river to aquifer flux increased by almost 1% of the average river discharge. This increase in river to aquifer flux exchange was evident, especially during the dry periods after 2004, which coincided with the government’s Million Shallow Tube Well Programme (MSTP) in the basin. The increasing trend of the river to aquifer flux transfer and the decreasing trend of the aquifer to river flux transfer observed in the Kosi basin can have disturbing long-term effects in terms of reduced river flow and river stage. Therefore, the concerned authorities and the stakeholders must take immediate notice of the observations.

An alternative method for groundwater recharge estimation in karst

Aquifers with time variant catchment boundaries, regional flows, and inflows from surface streams and accumulations are common in karst areas. Due to the lack of reliable methods for determination of water balance in the phreatic zone of such aquifers, groundwater recharge estimation is a challenge task. This paper introduces a new method for estimation of groundwater recharge in karst – the so-called partial correlation method (PCM). The basic hypothesis is that the groundwater recharge rates can be determined from the time series of precipitation, air temperature, relative humidity, and spring discharge, by using a partial cross-correlation function as objective function. Following this hypothesis, a simple conceptual model of water balance in the soil cover, epikarst and vadose zone is developed, and an objective function for estimation of the optimal value of parameter of this model is proposed. PCM is applied on the catchment of Žrnovnica Spring located in the Dinaric karst area of Croatia. The results of application are compared with the results of previous studies, as well as with the results obtained by five empirical models that have been used for estimation of groundwater recharge in the Mediterranean karst. The effective infiltration coefficients obtained by PCM for the Žrnovnica Spring are generally in accordance with the previously published ones.

Groundwater recharge and potential exploitation in the Densu basin, Southwestern Ghana

Recharge estimation is important to the effective development and management of groundwater resources, since it forms the basis for assigning abstraction rates. This study applied the water table fluctuation method and chloride mass balance approach to estimate groundwater recharge in the Densu basin, identified as the most problematic and vulnerable catchment in Ghana, using chloride and water level data from 10 monitoring wells. In general, the results revealed seasonal and spatial variation in groundwater recharge in the basin, with a north-south decreasing trend. The chloride mass balance approach and water level fluctuation method revealed average groundwater recharge of 70 mm and 62 mm/year respectively. With the total groundwater abstraction in the basin estimated to be only 8% of the annual recharge rate, the potential for groundwater use in the basin is great, granted adequate water quality assessment supports the useable quantity available in the basin.

Using bromide data tracer and HYDRUS‐1D to estimate groundwater recharge and evapotranspiration under film‐mulched drip irrigation in an arid Inland Basin, Northwest China

AbstractAccurate estimation of groundwater recharge (GR) and evapotranspiration (ET) are essential for sustainable management of groundwater resources, especially in arid and semi‐arid regions. In the Manas River Basin (MRB), water shortage is the main factor restricting sustainable development of irrigated agriculture, which relies heavily on groundwater. Film‐mulched drip irrigation significantly changes the pattern and dominant processes of water flow in the unsaturated zone, which increases the difficulty of GR and ET estimation. To better estimate GR and ET under film‐mulched drip irrigation in the MRB, bromide tracer tests and soil lithologic investigation were conducted at 12 representative sites. A one‐dimensional variably saturated flow model (HYDRUS‐1D) was calibrated at each site using soil evaporation data inferred from the bromide tracer tests. The results showed that average annual soil evaporation in uncultivated lands calculated from bromide trace tests was 25.55 mm. The annual GR ranged from 5.5 to 37.0 mm under film‐mulched drip irrigation. The annual ET ranged from 507.0 to 747.1 mm, with soil evaporation between 35.7 and 117.0 mm and transpiration between 460.9 and 642.3 mm. Soil evaporation represented 7% to 16% of the total ET and more than 70% of precipitation and irrigation water was used by cotton plants. Spatial variations of soil lithology, water table depth and initial soil water content led to the spatial differences of GR and ET in the MRB. Our study indicated that bromide tracer tests are useful for inferring ET in the arid and semi‐arid oases. The combination of bromide tracer tests and HYDRUS‐1D enhances reliability for estimation of GR and ET under film‐mulched drip irrigation in the MRB and shows promise for other similar arid inland basins around the world.

Integrated Hydrological Analysis of Little Akaki Watershed Using SWAT-MODFLOW, Ethiopia

In Ethiopia, groundwater is the main source of freshwater to support human consumption and socio-economic development. Little Akaki watershed is located in Upper Awash basin, known for its high annual rainfall and considered as the potential groundwater recharge zone. On the contrary, urbanization and industrial expansion are increasing at an alarming rate in the area. This became a concern threatening the groundwater resources’ sustainability. To address these challenges, integrated analysis of groundwater recharge and groundwater numerical simulations were made. For groundwater recharge estimation, SWAT model was used. The result indicated that recharge in the watershed mostly occurs from July to October with maximum values in August. On average, the estimated annual catchment recharge was 179 mm. For the numerical simulation and prediction of the groundwater flow system, MODFLOW 2005 was used. The model simulations indicated that the groundwater head converges towards the main river and, finally, to the outlet of the watershed. The study indicated areas of interactions between the river and groundwater. The scenario examination result reveals increasing the present pumping rate by over fifty percent (by 50%, 100%, and 200%) will surely cause visible groundwater head decline near the outlet of the watershed, and substantial river baseflow reduction. The recharge reduction scenario also indicates the huge risk of groundwater sustainability in the area.

Climate and land-use change impacts on spatiotemporal variations in groundwater recharge: A case study of the Bangkok Area, Thailand

Groundwater contributes to the socioeconomic development of the Thai capital Bangkok and its vicinity. However, groundwater resources are under immense pressure due to population growth, rapid urbanisation, overexploitation, and climate change. Therefore, evaluating the combined impact of climate change and land-use change on groundwater recharge can be useful for developing sound groundwater management systems. In this research, the future climate is projected using three Regional Climate Models (RCMs), namely ACCESS-CSIRO-CCAM, CNRM-CM5-CSIRO-CCAM, and MPI-ESM-LR-CSIRO-CCAM for three future periods: near future (2010–2039), mid future (2040–2069), and far future (2070–2099) under two Representative Concentration Pathway (RCP) scenarios 4.5 and 8.5 as suggested in the IPCC's Fifth Assessment Report. All RCMs project the temperature to rise incessantly, although future precipitation is predicted to fluctuate (increase and decrease) among the various RCMs and RCP scenarios. A Dyna-CLUE model is employed to analyse the future land-use change scenarios (low, medium, and high urbanisation), with the aim of expanding the built-up area and creating land-use maps covering the period to 2099. A hydrological model, WetSpass, is used to estimate groundwater recharge under future climate and land-use change. The findings reveal that groundwater recharge is expected to decrease in high and medium urbanisation areas, ranging from 5.84 to 20.91 mm/yr for the RCP 4.5 scenario and 4.07 to 18.72 mm/yr for RCP 8.5. In contrast, for the low urbanisation scenario, the model projects an increase in groundwater recharge ranging from 7.9 to 16.66 mm/yr for the RCP 4.5 scenario and 5.54 to 20.04 mm/yr for RCP 8.5.

Assessment of CHADFDM satellite‐based input dataset for the groundwater recharge estimation in arid and data scarce regions

AbstractAquifer natural recharge estimations are a prerequisite for understanding hydrologic systems and sustainable water resources management. As meteorological data series collection is difficult in arid and semiarid areas, satellite products have recently become an alternative for water resources studies. A daily groundwater recharge estimation in the NW part of the Lake Chad Basin, using a soil–plant‐atmosphere model (VisualBALAN), from ground‐ and satellite‐based meteorological input dataset for non‐irrigated and irrigated land and for the 2005–2014 period is presented. Average annual values were 284 mm and 30°C for precipitation and temperature in ground‐based gauge stations. For the satellite‐model‐based Lake Chad Basin Flood and Drought Monitor System platform (CHADFDM), average annual precipitation and temperature were 417 mm and 29°C, respectively. Uncertainties derived from satellite data measurement could account for the rainfall difference. The estimated mean annual aquifer recharge was always higher from satellite‐ than ground‐based data, with differences up to 46% for dryland and 23% in irrigated areas. Recharge response to rainfall events was very variable and results were very sensitive to: wilting point, field capacity and curve number for runoff estimation. Obtained results provide plausible recharge values beyond the uncertainty related to data input and modelling approach. This work prevents on the important deviations in recharge estimation from weighted‐ensemble satellite‐based data, informing in decision making to both stakeholders and policy makers.