Estimating Groundwater Recharge Research Articles

A Stochastic Collocation Method for Simulating Groundwater Recharge

We propose a stochastic collocation method based on sparse tensor product spaces to efficiently estimate groundwater recharge. The spatial variability of hydraulic conductivity of soil usually leads to the uncertainty of groundwater recharge. Thus hydraulic conductivity in this research is treated as random variable following the log-normal distribution. Different soil columns are designed by varying the deployment of loam and clay loam. It is shown that the sparse grid collocation model produces very accurate results at lower computational cost compared to traditional Monte Carlo simulations. In addition, illustrative examples demonstrate that both the thickness and the deployment of clay layers have no obvious impact on the groundwater recharge amount under the soil depth of 3m in the specific example of Raoyang.

Measurement and modelling of evapotranspiration in three fynbos vegetation types

Many studies have investigated the water relations of indigenous plants in the fynbos shrublands of the Cape, South Africa. These have mainly focused on understanding the mechanisms by which individual plant species respond to droughts, the frequency and severity of which is expected to increase due to climate change. However, comparatively little information exists on the dynamics of water use by indigenous plants in the region, and, in particular, how water use varies seasonally and between sites. In this study we determined water use by 3 fynbos vegetation types growing at 4 different sites, namely: (i) lowland Atlantis Sand Plain fynbos growing on deep sandy soils, (ii) Kogelberg Sandstone fynbos growing in a riparian zone on deep alluvial soils, (iii) dryland Kogelberg Sandstone fynbos growing on shallow sandy soils at a montane site, and (iv) alluvial Swartland fynbos growing in clayey soils. Evapotranspiration (ET) was quantified at each site during specific periods using a boundary layer scintillometer and energy balance system. A simple dual source model in which the stand ET was calculated as the algebraic sum of outputs from soil evaporation and transpiration sub-models was used to scale up the ET measurements to annual values. The data showed large differences in ET depending on site characteristics and on plant attributes. Dense stands of riparian Sandstone Fynbos had an annual ET of 1 460 mm which exceeded the reference ET of 1 346 mm. Dryland Sandstone Fynbos used only 551 mm of water per year while the Sand Plain Fynbos’ annual ET was 1 031 mm, which was similar to the reference ET of 1 059 mm. We conclude that some indigenous plant species use large volumes of water which should be accounted for in, e.g., groundwater recharge estimates, and calculations of incremental water gains after clearing alien invasive plants, among other applications. Keywords : Evapotranspiration, fynbos, scintillometer, Western Cape

Comparative estimation of the potential groundwater recharge in Al Zerba catchment of Aleppo basin, Syria

Since groundwater is an integral component of natural hydrologic systems, an estimation of groundwater recharge is required to understand the changes in the temporal water budget and groundwater flow system. The rate of groundwater recharge varies widely in space and time particularly in arid to semiarid regions, and it is rather difficult to measure recharge directly. The aim of this study was to assess the natural groundwater recharge in Al Zerba catchment and the interaction between the surface and groundwater. The catchment is classified as an arid to semiarid climate with an aridity index of 0.25 to 0.3 and long-term average annual precipitation ranging from 300 to 350 mm. Delineation of the catchment boundary was carried out using spatial interpolation of elevation data extracted from the digital elevation model. The effects of vegetation and abstraction from pumping wells on the groundwater table were investigated. Furthermore, groundwater recharge was estimated based on water budget, water table fluctuation analysis by using rainfall infiltration breakthrough, and soil water balance using hydrologic evaluation of landfill performance model (HELP3). The results show that groundwater pumping leads negative impact to long-term decrease in groundwater levels, particularly in the dry season, while no significant effects of vegetation on groundwater were observed. Moreover, the result showed an average annual groundwater recharge ranging from 20 to 35 mm/a (about 10 to 15 % of the precipitation period 2001–2010), concentrated in the north and southwestern regions (outcrops of permeable/coarse-grained limestone and a major fault zone).

GIS-Based Water Budget Framework for High-Resolution Groundwater Recharge Estimation of Large-Scale Humid Regions

Groundwater recharge plays a vital role in replenishing aquifers, which impacts on groundwater resources availability. This paper develops a geographic information system (GIS)-based water budget framework in conjunction with a hydrologic model to derive high-resolution spatial-temporal distribution of groundwater recharge for the Southern Hills aquifer system, southwestern Mississippi, and southeastern Louisiana, United States. The framework includes parallel programming to distribute the large amount of software runs to a cluster of supercomputers to expedite computation time. Under the parallel computation, the hydrologic models are calibrated by the USGS WaterWatch runoff dataset and verified by the moderate resolution imaging spectroradiometer (MODIS) evapotranspiration dataset. A map of recharge time lag is derived to understand travel time of infiltrated precipitation reaching the last soil layer. A recharge index map is derived to quantify the percentage of precipitation that becomes groundwater recharge. The results show that the mean annual recharge rate was estimated 47.5 mm/year which was 3.1% of the mean annual precipitation on the area of the Southern Hills aquifer system. High recharge rate was estimated at the outcrops of Miocene deposits in southwestern Mississippi, which are the recharge zones of the deep sands in southeastern Louisiana. This paper successfully demonstrated the applicability of the framework to groundwater recharge estimation on large-scale humid areas.

Three criteria reliability analyses for groundwater recharge estimations

There is a broad variety of methods to estimate groundwater recharge, but tools to assess the reliability of particular methods are not available. This paper introduces three distinct criteria to assess the reliability of recharge: applicability of the method used, availability of reliable data, and spatial coverage. Weightings of each criterion are assigned using key attributes present to total attributes required under each criterion. A reliability assessment was applied to two point-recharge and two diffuse-recharge dominated groundwater basins in South Australia. We show that the use of groundwater age based on chlorofluorocarbon and the conventional chloride mass balance method gives unreliable estimates of recharge in karstic aquifers, primarily due to inappropriate assumptions concerning the nature of recharge in these systems. Among the methods evaluated, watertable fluctuation, numerical groundwater modelling, Darcy flow calculation and the water budget method are applied to both point and diffuse recharge dominant groundwater basins. The reliability of these methods depends primarily on the quality of data and spatial coverage of the basin. Once the reliability level is known, water resources planners and managers assess the level of risk to aquifers, the environment, and the socio-economic development required for sustainable management of groundwater.

Data requirements for using combined conductivity mass balance and recursive digital filter method to estimate groundwater recharge in a small watershed, New Brunswick, Canada

Summary Estimation of baseflow and groundwater recharge rates is important for hydrological analysis and modelling. A new approach which combines recursive digital filter (RDF) model with conductivity mass balance (CMB) method was considered to be reliable for baseflow separation because the combined method takes advantages of the reduced data requirement for RDF method and the reliability of CMB method. However, it is not clear what the minimum data requirements for producing acceptable estimates of the RDF model parameters are. In this study, 19-year record of stream discharge and water conductivity collected from the Black Brook Watershed (BBW), NB, Canada were used to test the combined baseflow separation method and assess the variability of parameters in the model over seasons. The data requirements and potential bias in estimated baseflow index (BFI) were evaluated using conductivity data for different seasons and/or resampled data segments at various sampling durations. Results indicated that the data collected during ground-frozen season are more suitable to estimate baseflow conductivity ( C bf ) and data during snow-melting period are more suitable to estimate runoff conductivity ( C ro ). Relative errors of baseflow estimation were inversely proportional to the number of conductivity data records. A minimum of six-month discharge and conductivity data is required to obtain reliable parameters for current method with acceptable errors. We further found that the average annual recharge rate for the BBW was 322 mm in the past twenty years.

Estimation of groundwater recharge in weathered basement aquifers, southern Zimbabwe; a geochemical approach

Geochemical techniques have been used to estimate groundwater recharge and its spatial variability in basement terrain in a semi-arid area of southern Zimbabwe. Recharge rates estimated by chloride mass balance have been determined in the Romwe catchment, a small (4.6km2) headwater catchment underlain by banded gneisses, with good hydrological and geological control. The results support the findings from piezometric monitoring that there are significant differences in hydrogeological properties of weathered basement derived from different primary lithologies. Annual recharge estimates for shallow weathered aquifers derived from melanocratic bedrock (dominated by pyroxene gneiss), 22mm, and leucocratic felsic bedrock, 6.7mm, are 3.7% and 1.1% respectively of the long-term mean annual rainfall. The significant uncertainties associated with the chloride mass balance recharge estimates are discussed. Groundwater derived from each lithology generally has a distinctive geochemistry (Na/Cl, K/Na, Mg/Ca, Na/Cl, B, Ba). The information from the Romwe catchment control area was then scaled up using information from remote sensing images (which defined areas of dark and light soils above the banded gneiss) to confirm the higher recharge rates in the melanocratic lithology in the unexplored Greater Romwe (225km2) area. It is concluded that properly calibrated, remote sensing images could be further regionalized to site groundwater sources in basement terrain, providing a relatively inexpensive development tool.

Evaluation of the atmospheric chloride deposition in the Danube hydrological zone of Bulgaria

Estimation of the long-term groundwater recharge based on the chloride mass balance method is easy for practical applications. This method is reliable only if the atmospheric chloride deposition is known. The direct measuring of this deposition is difficult and time consuming. In this study, the chloride deposition at the catchment scale is assessed based on the export of chloride with river waters (including baseflow), as the net groundwater recharge in the studied catchments is usually low, and its contribution to the exports of salts is insignificant. For the purpose of this study, a 25-year-long time series of discharge and chloride content (from 1951 to 1975) is processed, as the quality of river waters for this period is considered natural and unaffected by human activity in the studied catchments. The obtained value of the atmospheric chloride deposition for North Bulgaria is in the range of 2.5–2.8 g/m2/a based on representative stations. This is the first estimate of the atmospheric chloride deposition in the country, which may be used for assessment of the long-term groundwater recharge in North Bulgaria.

Evaluation of groundwater recharge estimates in a partially metamorphosed sedimentary basin in a tropical environment: application of natural tracers.

This study tests the representativeness of groundwater recharge estimates through the chloride mass balance (CMB) method in a tropical environment. The representativeness of recharge estimates using this methodology is tested using evaporation estimates from isotope data, the general spatial distribution of the potential field, and the topographical variations in the area. This study suggests that annual groundwater recharge rates in the area ranges between 0.9% and 21% of annual precipitation. These estimates are consistent with evaporation rates computed from stable isotope data of groundwater and surface water in the Voltaian Basin. Moreover, estimates of groundwater recharge through numerical model calibration in other parts of the terrain appear to be consistent with the current data in this study. A spatial distribution of groundwater recharge in the area based on the estimated data takes a pattern akin to the spatial pattern of distribution of the hydraulic head, the local topography, and geology of the terrain. This suggests that the estimates at least qualitatively predicts the local recharge and discharge locations in the terrain.

Development of Rainfall Recharge Model for Natural Groundwater Recharge Estimation in Godagari Upazila of Rajshahi District, Bangladesh

Estimation and forecast of groundwater recharge and capacity of aquifer are essential issues in effective groundwater resource management in Bangladesh. Godagari Upazilla is located in High Barind Tract situated in the northwestern part of Bangladesh. A typical dry climate with comparatively high temperature prevails in this Barind area. It is particularly significant in regions with large demands for groundwater supplies to meet irrigation needs, where such resources are the key to economic growth. However, the rate of aquifer recharge is one of the most complicated factors to assess in the evaluation of groundwater resources. Assessment of recharge, by whatever method, is normally subject to large uncertainties and errors. In this paper, an attempt has been taken to develop a rainfall recharge model by non-linear regression technique to determine groundwater recharge using only annual rainfall data in Godagari Upazilla based upon groundwater balance study carried out for a number of years. It was also proven that the developed model provided an accurate estimation for similar projects

Comparative performance of soil water balance models in computing semi-arid aquifer recharge

Estimating groundwater recharge is essential to ensure the sustainable use of groundwater resources, particularly in arid and semi-arid regions. Soil water balances have been frequently advocated as valuable tools to estimate groundwater recharge. This article compares the performance of three soil water balance models (Hydrobal, Visual Balan v2.0 and Thornthwaite) in the Ventós-Castellar aquifer, Spain. The models were used to simulate wet and dry years. Recharge estimates were transformed into water table fluctuations by means of a lumped groundwater model. These, in turn, were calibrated against piezometric data. Overall, the Hydrobal model shows the best fit between observed and calculated levels (r2 = 0.84), highlighting the role of soil moisture and vegetation in recharge processes.Editor D. Koutsoyiannis; Associate editor X. ChenCitation Touhami, I., et al., 2014. Comparative performance of soil water balance models in computing semi-arid aquifer recharge. Hydrological Sciences Journal, 59 (1), 193–203.

A distributed water balance approach to groundwater recharge estimation for Jeju volcanic island, Korea

Groundwater is a major source of water use in Jeju volcanic island of Korea. Due to highly permeable surface conditions, the island does not have any perennial streams or rivers. Therefore, accurate estimation of groundwater recharge and understanding groundwater system are critical to make a reliable water budget in the island. A distributed quasi steady state water balance model, WetSpass (Water and Energy Transfer between Soil, Plants and Atmosphere under quasi Steady State) was adopted to estimate spatially-varying groundwater recharge considering soil type, land use, topography, and groundwater depth. The results from the study using weather data from October 2006 to September 2007 indicated that the eastern and northern parts of the island showed relatively higher rate of recharge as compared with the western region. A total of 69% of recharge occurred in the middle of the Island where topographic elevation is greater than 200 m from the mean sea level. The total amount of recharge was 1,935.6 million tons, 41.8% of the total precipitation. The higher rate of recharge was observed in the watersheds where forest and bare soil as land uses, and sandy loam and clay loam as soil types are dominant. The total runoff was 1,142.7 million tons (24.7%) and the total evapotranspiration was 1,555.7 million tons (33.5%). The zonal hydraulic conductivities estimated with groundwater flow modeling and parameter estimation process showed a wide range of values from 1.2 m/d to 5,380 m/d. The results of groundwater flow modeling indicated that the crest of groundwater table is off-centered from the peak of Mt. Halla toward south.

Multi-response calibration of a conceptual hydrological model in the semiarid catchment of Wadi al Arab, Jordan

A key factor for sustainable management of groundwater systems is the accurate estimation of groundwater recharge. Hydrological models are common tools for such estimations and widely used. As such models need to be calibrated against measured values, the absence of adequate data can be problematic. We present a nested multi-response calibration approach for a semi-distributed hydrological model in the semi-arid catchment of Wadi al Arab in Jordan, with sparsely available runoff data. The basic idea of the calibration approach is to use diverse observations in a nested strategy, in which sub-parts of the model are calibrated to various observation data types in a consecutive manner. First, the available different data sources have to be screened for information content of processes, e.g. if data sources contain information on mean values, spatial or temporal variability etc. for the entire catchment or only sub-catchments. In a second step, the information content has to be mapped to relevant model components, which represent these processes. Then the data source is used to calibrate the respective subset of model parameters, while the remaining model parameters remain unchanged. This mapping is repeated for other available data sources. In that study the gauged spring discharge (GSD) method, flash flood observations and data from the chloride mass balance (CMB) are used to derive plausible parameter ranges for the conceptual hydrological model J2000g. The water table fluctuation (WTF) method is used to validate the model. Results from modelling using a priori parameter values from literature as a benchmark are compared. The estimated recharge rates of the calibrated model deviate less than ±10% from the estimates derived from WTF method. Larger differences are visible in the years with high uncertainties in rainfall input data. The performance of the calibrated model during validation produces better results than applying the model with only a priori parameter values. The model with a priori parameter values from literature tends to overestimate recharge rates with up to 30%, particular in the wet winter of 1991/1992. An overestimation of groundwater recharge and hence available water resources clearly endangers reliable water resource managing in water scarce region. The proposed nested multi-response approach may help to better predict water resources despite data scarcity.

Evaluation of Groundwater Resources of an Alluvial Pluvial Fan in Hebei Province, China Using Hydrological Budget Method

Estimating groundwater recharge and groundwater discharge are key components in determining the sustainable utilization of groundwater resources. Infiltration recharge by rainfall and irrigation water recharge are the main supply of groundwater in the study area. In this paper, based on the hydrological budget method, we analyzed, the utilization of groundwater resources, calculated, the recharge and excretion of groundwater in the study area from 1995 to 2012, and finally, pointed out the groundwater level is mainly affected by the irrigation water. Therefore, readjustment of the structure of plant is to ensure the ecological environment, utilize rationally the groundwater resources and achieve the goal of sustainable use of groundwater resources.

Estimation and condition of groundwater recharge in semiarid zone: example from the Ksour Ridge, NW Algeria

In a recharge area characterized by a semiarid or arid climate and a low annual rainfall, aquifers can be hardly recharged adequately, as it was demonstrated by classical monthly hydrological balance computations. The methodology proposed in this work relies on spatial and temporal interpolation of scarce climatic data. This methodology can be used to determine the recharge flow of aquifers in these zones. The AinSefra’s syncline (Western Saharan Atlas, Southwest Algeria) includes the sandstone aquifers of Continental Intercalary and the Plio-Quaternary layers. It forms an excellent example for this application. Three years with different annual rainfalls are chosen in this application: 1983 as dry year, 2006 as average year, and 2008 as humid one. This application requires information about the soil nature, the surface, and the altitude of the recharge areas. The rainfall and the recharge flow of aquifers indicate that the principal recharge areas are the Jurassic outcrops in the humid years when the annual rainfall exceeds 300 mm.

Development of a national groundwater recharge map for the Republic of Ireland

A groundwater recharge map has been created for the Republic of Ireland. This provides important baseline information for multiple purposes: aquifer water balance assessments using simple lumped models or distributed numerical groundwater models; assessment of the impact of groundwater abstractions as required under the European Water Framework Directive; and delineation of source protection zones. The groundwater recharge map is derived from existing hydrogeological and meteorological spatial datasets. The main hydrogeological controls on groundwater recharge include the permeability and thickness of superficial deposits (mainly tills in Ireland), the presence of saturated soils, and the ability of the underlying aquifer to accept percolating waters. Combinations of these factors are assessed, and a ‘recharge coefficient’ is established for different hydrogeological scenarios. To produce the groundwater recharge map, the geographic information system layer containing the recharge coefficients is multiplied by the effective rainfall. The recharge map is finally modified to take into account areas where the natural recharge capacity of the underlying aquifer is less than the estimated groundwater recharge potential. Originally drafted in 2005, the present map includes refined recharge coefficient estimates, improved representation of wet soils over gravel aquifers, and a full national coverage of full subsoil permeability and groundwater vulnerability mapping. There are a number of assumptions made in creating the groundwater recharge map (notably, only direct (diffuse) recharge is taken into account) and there are limitations of precision associated with the input datasets. For reasons of scale and generalization to a national coverage, the map is useful for giving regional estimates of recharge but these, in many cases, will need to be refined by site-specific studies.

지하수위 변동법에 의한 함양량 산정: 하천-대수층 상호작용의 영향

The water-table fluctuation (WTF) method has been often used for estimating groundwater recharge by analysis of waterlevel measurements in observation wells. An important assumption inherent in the method is that the water level rise is solely caused by precipitation recharge. For the observation wells located near a stream, however, the water-level can be highly affected by the stream level fluctuations as well as precipitation recharge. Therefore, in applying the WTF method, there should be consideration regarding the effect of stream-aquifer interactions. Analysis of water-level hydrographs from the National Groundwater Monitoring Wells of Korea showed that they could be classified into three different types depending on their responses to either precipitation recharge or stream level fluctuations. A simple groundwater flow model was used to analyze the errors of the WTF method, which were associated with stream-aquifer interactions. Not surprisingly, the model showed that the WTF method could greatly overestimate recharge, when it was used for the observation wells of which the water-level was affected by streams. Therefore, in Korea, where most groundwater hydrographs are acquired from wells nearby a stream, more caution is demanded in applying the WTF method.

Quantitative estimation of groundwater recharge ratio along the riparian of the Yellow River

Quantitative estimation of groundwater recharge is crucial for limited water resources management. A combination of isotopic and chemical indicators has been used to evaluate the relationship between surface water, groundwater, and rainfall around the riparian of the Yellow River in the North China Plain (NCP). The ion molar ratio of sodium to chloride in surface- and groundwater is 0.6 and 0.9, respectively, indicating cation exchange of Ca(2+) and/or Mg(2+) for Na(+) in groundwater. The δD and δ(18)O values in rainfall varied from -64.4 to -33.4‰ and from -8.39 to -4.49‰. The groundwater samples have δD values in the range of -68.7 to -58.0‰ and δ(18)O from -9.29 to -6.85‰. The δ(18)O and δD in surface water varied from -8.51 to -7.23‰ and from -64.42 to -53.73‰. The average values of both δD and δ(18)O from surface water are 3.92‰ and 0.57‰, respectively, higher compared to groundwater. Isotopic composition indicated that the groundwater in the riparian area of the Yellow River was influenced by heavy rainfall events and seepage of surface water. The mass balance was applied for the first time to estimate the amount of recharge, which is probably 6% and 94% of the rainfall and surface water, respectively.

Onset of deep drainage and salt mobilization following forest clearing and cultivation in the Chaco plains (Argentina)

moisture content and 94% lower chloride stocks compared to dry forest (0.05 6 0.04 kg/m 2 versus 0.77 6 0.4 kg/m 2 ). Estimates of groundwater recharge based on the displacement of chloride peaks suggested values of 27–87 mm yr � 1 for agricultural soybean stands, and 10.4 mm yr � 1 for pastures. While hydrological shifts in the regional groundwater system are poorly monitored and understood, our findings show that it is potentially sensitive to land use changes and to salinization processes.

Using Domestic Well Records to Determine Fractured Bedrock Watersheds and Recharge Rates

This study presents an approach for delineating groundwater basins and estimating rates of recharge to fractured crystalline bedrock. It entailed the use of completion report data (boring logs) from 2500 domestic wells in bedrock from the Coventry Quadrangle, which is located in northeastern Connecticut and characterized by metamorphic gneiss and schist. Completion report data were digitized and imported into ArcGIS(®) for data analysis. The data were processed to delineate groundwater drainage basins for the fractured rock based on flow conditions and to estimate groundwater recharge to the bedrock. Results indicate that drainage basins derived from surface topography, in general, may not correspond with bedrock drainage basins due to scale. Estimates of recharge to the bedrock for the study area indicate that only a small fraction of the precipitation or the amount of water that enters the overburden recharges the rock. The approach presented here can be a useful method for water resource-related assessments that involve fractured rock aquifers.