Distribution Of Recharge Research Articles

Determining recharge distribution in fractured carbonate aquifers in central Italy using environmental isotopes: snowpack cover as an indicator for future availability of groundwater resources

Environmental isotopes were used to determine the source and to understand the physical–chemical processes involved in groundwater movement along a flowpath. This study applies groundwater stable isotopes to assess snow-cover influence on the recharge processes of some regional carbonate aquifers of central Italy. Starting with extensively investigated aquifers, 17 springs were selected and sampled (June–October 2016) for isotope analyses. The δ18O–δD results follow the local meteoric water line; the low mismatch between the 2016 sampling surveys suggests that those springs are not influenced by seasonal variability. Nevertheless, the average elevations of recharge areas calculated using the vertical isotope gradient were higher compared to those obtained with hypsographic profiles. This means that the relevant contribution to recharge comes from higher elevation areas; hence, snowpack coverage and snowpack persistence over time on recharge areas were analysed using satellite images. Four different relationships between the snowpack characteristics and the elevation of recharge areas have been identified. These offer relevant information about the different degrees of dependence of the regional aquifers of central Italy on the recharge due to high-elevation subbasins where the snowpack cover is significant. A possible correlation emerges between computed isotope recharge elevation and mean snow cover elevation, revealing how snowmelt is a primary source for aquifer recharge. Consequently, to evaluate the risk of groundwater resource depletion in a climate-change scenario, there is discussion on how a potential snow-cover reduction would affect the recharge rate of mountainous aquifers.

Spatiotemporal evaluation of future groundwater recharge in arid and semi-arid regions under climate change scenarios

ABSTRACT In this study, the Hydrologic Evaluation of Landfill Performance (HELP3.8D) model was developed to evaluate the spatiotemporal distribution of potential groundwater recharge (GWR) in Tasuj aquifer, northwestern Iran. High-resolution future climatic data from second-generation Canadian Earth System Model (CanESM2) general circulation models (GCMs) was produced under different scenarios of Representative Concentration Pathways (RCP2.6, RCP4.5, and RCP8.5). The analysis of climate parameters demonstrated that under RCP2.6, climatic variation will be substantially similar to that of the observed period (1961–2005), while moderate and severe droughts are anticipated under scenarios RCP4.5 and RCP8.5, respectively, over 2017–2030. The projection results showed that GWR will be altered by climate change, on average, from 31 mm/year at baseline to 32 (+3%), 28.5 (−8%) and 11.5 (−63%) mm/year under the RCP2.6, RCP4.5 and RCP8.5 scenarios, respectively. This approach can be easily replicated by other researchers and could be beneficial for monitoring water security and managing groundwater resources in other catchment areas.

Recharge assessment of the Gran Sasso aquifer (Central Italy): Time-variable infiltration and influence of snow cover extension

Study regionCarbonate karstified aquifers represent one of the most important groundwater reservoirs for both drinking purposes and environmental preservation. Currently, the recharge–discharge equilibrium in these aquifers is at risk of depletion from withdrawal increases and global change effects. Based on these factors, detailed analyses of recharge distribution over the last 20 years (2001–2020), both in terms of rainfall and snow melting contributions, have been carried out for the Gran Sasso regional aquifer (Central Italy). Study focusUsing the same input data, water budgets at different time scales were calculated using the Turc, Thornthwaite and APLIS methods. In addition, simplified future scenarios considering the real risk of climate change effects have been implemented by applying an increase in temperature and a shortage of snow coverage periods. New hydrological insightsThe obtained aquifer recharge values are similar and a significant contribution to recharge from snowmelt has also been highlighted. The measured spring discharge values are higher with respect to the calculated recharge, especially in drought periods, underlining the resilience of groundwater resources in the Gran Sasso aquifer; these values are also confirmed by the different responses of spring discharge to recharge variations. A significant decrease in recharge and consequently in baseflow discharge is conceivable for future scenarios, revealing that immediate optimization measures are required to correct groundwater resources management and to avoid potential emergency conditions.

Spatial distribution of groundwater recharge, based on regionalised soil moisture models in Wadi Natuf karst aquifers, Palestine

Abstract. While groundwater recharge is considered fundamental to hydrogeological insights and basin management and studies on its temporal variability are in great number, much less attention has been paid to its spatial distribution, by comparison. And in ungauged catchments it has rarely been quantified, especially on the catchment scale. For the first time, this study attempts such analysis, in a previously ungauged basin. Our work is based on the results of field data (as published in Messerschmid et al., 2020) of several soil moisture stations, which represent five geological formations of karst rock in Wadi Natuf, a semi-arid to sub-humid Mediterranean catchment in the occupied Palestinian West Bank. For that purpose, recharge was conceptualised as deep percolation from soil moisture under saturation excess conditions, which had been modelled parsimoniously and separately with different formation-specific recharge rates. For the regionalisation, inductive methods of empirical field measurements and observations were combined with deductive approaches of extrapolation, based on a new basin classification framework (BCF) for Wadi Natuf, thus following the recommendations for hydrological Prediction in Ungauged Basins (PUB), by the International Association of Hydrological Sciences (IAHS). Our results show an average annual recharge estimation in Wadi Natuf catchment (103 km2), ranging from 235 to 274 mm (24 to 28×106 m3) per year, equivalent to recharge coefficients (RCs) of 39 %–46 % of average annual precipitation (over a 7-year observation period but representative of long-term conditions as well). Formation-specific RC values, derived from empirical parsimonious soil moisture models, were regionalised and their spatial distribution was assessed and quantified on the catchment scale. Thus, for the first time, a fully distributed recharge model in a hitherto entirely ungauged (and karstic) aquifer basin was created that drew on empirical methods and direct approaches. This was done by a novel combination of existing methods and by creating a unified conceptual basin classification framework for different sets of physical basin features. This new regionalisation method is also applicable in many comparable sedimentary basins in the Mediterranean and worldwide.

Spatial-Temporal Water Balance Components Estimation Using Integrated GIS-Based Wetspass-M Model in Moulouya Basin, Morocco

The Moulouya basin in Morocco is one of many river basins around the world that are regulated with physical flow control, a range of regulations and storage structures. The water budget of the basin is unbalanced; the available water resources are insufficient for agricultural productivity, nature conservation and ecosystem services. This study evaluates spatial and temporal distributions of actual evapotranspiration, groundwater recharge and surface runoff for the period 2000–2020 using the WetSpass-M model in the Moulouya basin, Morocco. The WetSpass-M model’s input data are created in grid maps with the ArcGIS tool. They include monthly meteorological parameters (e.g., temperature, wind speed, rainfall,), soil map, land cover, topography, slope and groundwater depth. A good correlation has been observed between the simulated groundwater recharge and base flow, with the value of R2 = 0.98. The long-term spatial and temporal average annual precipitation of 298 mm is distributed as 45 mm (15.1%) groundwater recharge and 44 mm (14.8%) surface runoff, while 209 mm (70.1%) is lost through evapotranspiration. The simulated results showed that the average groundwater recharge of 15.1 mm (30%) falls during the summer and spring seasons, while the remaining 29.5 mm (70%) occurs during the winter and autumn seasons. Annually, 2430 million m3 of water recharges to the groundwater system from the rainfall for the entire basin. The study’s findings would help local stakeholders and policymakers in developing sustainable and effective management of available surface water and groundwater resources in the Moulouya basin.

Assessment of the spatial-temporal distribution of groundwater recharge in data-scarce large-scale African river basin.

The systematic assessment of spatial and temporal distribution of groundwater recharge (GWR) is crucial for the sustainable management of the water resources systems, especially in large-scale river basins. This helps in identifying critical zones in which GWR largely varies and thus leads to negative consequences. However, such analyses might not be possible when the models require detailed hydro-climate and hydrogeological data in data-scarce regions. Hence, this calls for alternate suitable modeling approaches that are applicable with the limited data and, however, includes the detailed assessment of the spatial-temporal distribution of different water balance components especially the GWR component. This paper aimed at investigating the spatial and temporal distribution of the GWR at monthly, seasonal and annual scales using the WetSpass-M physically distributed hydrological model, which is not requiring the detailed catchment information. In addition, the study conducted the sensitivity analysis of model parameters to assess the significant variation of GWR. The large-scale river basins such as the Omo river basin, Ethiopia, were chosen to demonstrate the potential of the WetSpass-M model under limited data conditions. From the modeling results, it was found that the maximum average monthly GWR of 13.4 mm occurs in July. The estimated average seasonal GWR is 32.5 mm/yr and 47.6 mm/yr in the summer and winter seasons, respectively. Further, it was found that GWR is highly sensitive to the parameter such as average rainfall intensity factor.

Modelling of Irrigation Return Flow in Unconfined Aquifer of Dharoi Command in Mehsana District of Gujarat, India

Surface water flow and subsurface flow have traditionally been investigated separately and simulators have been developed over the years, to model each of these systems. Growing interest in conjunctive water management, and need for simulations of surface/subsurface flow and their interactions has lead to the linking of models of the respective domains. This study from Dharoi command area, using MODFLOW, showed pertaining to the second layer of the calibrated model. The first layer is a thin soil cover layer of about 3 m uniform thickness. Top layer is kept under unconfined water table condition, where as the next layer is given the scope of transforming between water table to confined state and vice versa depending upon the fluctuation of the computed water level with respect to the bottom boundary of the top layer. No recharge and discharge options other than a single boundary condition of average May water level in the extreme north-east grid has been allowed. This calibration is based upon matching the observed and computed average gradient of the water table (hydraulic gradient) and nothing to do with matching the point to point values of the observation wells as that could lead to misappropriation in respect of hydrologic condition. Over all gradient of the water table in the area of interest is computed as 0.23 m per km in comparison to an observed hydraulic gradient of 0.3 m per km. The rivers such as Sabarmati downstream of Dharoi dam and up to Bijapur, Rupen and Pushpawati are activated in the transient run. Conductance value is considered as 0.0001 m/sec for all the rivers. proximity of the second layer under unconfined state. Comparisons of water levels in selected locations. Overall match between the trends and the point values indicate that the calibrated model transient run can be considered as base case and various options can be studied with this model. Visual MODFLOW is very effective to know the present scenario of ground water flow, water level of aquifer, wells, also point values indicate that the calibrated model transient run can be considered as base case and various options can be studied with this model. Visual MODFLOW is very effective to know the present scenario of ground water flow, water level of aquifer, wells, also distribution of spatial recharge, specific yield distribution. It gives very close result to the observed value.

Modelling of potential groundwater artificial recharge in the transboundary Algero‐Tunisian Basin (Tebessa‐Gafsa): The application of stable isotopes and hydroinformatics tools*

AbstractWater resource overuse is a considerable challenge in areas with diverse activities and mixed climate. An area with deteriorated water quality (salinity higher than 5 g/L), typical of the transboundary Algero‐Tunisian area of the Tebessa‐Gafsa Basin in North Africa, was selected to investigate the spatial distribution of groundwater recharge and the water resources management. Several data including soil type, hydrogeologic characteristics, geomorphologic parameters, and climatic settings were used. Seasonal and early groundwater recharge and evapotranspiration were evaluated by applying the physical WetSpass model (Water and Energy Transfer between Soil, Plants, and Atmosphere Under quasi‐Steady State) model‐based geographic information system during 44 years. Results indicate spatio‐temporal changes in the recharge values. The highest values (13.3 mm) were recorded to the north of the study area during the wet season, while the lowest values, which reached −0.5 mm, were recorded to the south during the dry season. The recharge period of these transboundary aquifers, dated using isotopic tools (3H, 2H, and 18O), coincides with the Late Pleistocene and the Early Holocene humid periods. This Pleistocene and Holocene period could be responsible for the groundwater recharge in the Middle East and North Africa regions. Then, management and geovalorization of unconventional water processes promoting better water resource use have been proposed by applying artificial groundwater recharge.

Hummock-scale controls on groundwater recharge rates and the potential for developing local groundwater flow systems in water-limited environments

We use two-dimensional numerical models to identify controls on groundwater recharge, water table dynamics, and the sink-source function of fine-textured hummocks in water-limited environments. A silty clay loam hummock with aspen forest cover in the sub-humid Boreal Plains region of Canada is used to develop a conceptual model and calibrate a variably-saturated flow model to better investigate the dynamics of recharge, water table position, and lateral flow between the forested hummock and adjacent peatland. Scenario testing (achieved by raising and lowering the hydraulic conductivity by an order of magnitude and altering the hummock height and length) provides further understanding of the controls that hydraulic conductivity and hummock morphometry exert on recharge and forestland-peatland interactions. We find that the hydraulic conductivity of the glacial till has the largest control over recharge, followed by the hummock height and length and, lastly, annual atmospheric fluxes. Hummocks with higher hydraulic conductivity or long morphometric profiles are most often sinks of water as they promote increased root-water uptake, while taller hummocks with lower hydraulic conductivity tend to act as hydrologic sources for adjacent wetlands. The magnitude of annual recharge and water table elevation are poorly correlated with annual atmospheric fluxes due to the strong effects of multi-year storage deficits or surpluses; however, they are appreciably affected by decadal wet-dry cycles typical of the Boreal Plains climate. Additionally, we show that both distance along a hummock and elevation are key factors in controlling the spatial distribution of recharge at a single hummock. It is common to conceptualize the water table as a shallow and subdued replica of surface topography, where water flows from topographic highs (i.e., forestlands) to topographic lows (i.e., peatlands) in humid environments; however, as we show here, recharge rates, water table elevation, and the sink-source function of a forested hummock in water-limited environments is highly variable in time and space, and strongly dependent on both the hydrogeological and morphometric properties of the hummock.

Processes explaining the origin and evolution of groundwater composition in the Andean Precordillera and Altiplano of the Tarapacá Region of northern Chile

In the arid area of northern Chile, groundwater resources in the Andean formations are essential for native populations, ecological services, mining, and other human activities. Validated conceptual hydrogeological models are required for current and future water and land management. This work aims to explain the processes controlling the origin and distribution of recharge and groundwater composition in the Andean Precordillera and Altiplano of the Tarapacá Region of northern Chile, using major solutes in spring, river, and well water, and the stable and radioactive isotopes of water oxygen, hydrogen, and dissolved inorganic carbon. The waters are mainly of the Na-Ca-SO4 type. Processes controlling the chemical evolution of waters are atmospheric dust contribution, evapo-concentration, and enhanced volcanic rock weathering, as well as halite dissolution in some locations. The isotopic composition of Precordillera eastern flank water samples follows an evaporation line, while those in the western flank, in the Altiplano, follow a line that is parallel to the local meteoric line, suggesting unsaturated zone evaporation processes of infiltrated rainfall. δ13CDIC contents (-2 to -27‰) indicate mixing processes, volcanic CO2 in the Altiplano, and calcite dissolution in some sectors. In the western depression, the only recharge is due to water infiltration in creek channels. In the highland areas, 5–25% of precipitation produces recharge. The estimated groundwater renewal time in the Precordillera was 3–14 kyr. The piezometric elevation in the Precordillera due to low-permeability intrusive rocks and local recharge prevents the east-west groundwater transfer from the Altiplano to the western depression and explains why the volcanic CO2 in the Altiplano basins is not observed on the western flank. These results provide new insights for the evolution of water quality in volcanic aquifers in arid environments and provide considerations for estimating groundwater residence times using radiocarbon in areas influenced by volcanic CO2.

Numerical Modeling as an Effective tool for Artificial Groundwater Recharge Assessment

Quantification of distribution of groundwater recharge in spatial and temporal scale is a precondition for operating groundwater system effectively. Groundwater in aquifers depends on rainfall-recharge and percolation from water storages. Groundwater extraction at rates higher than its recharge rates, results in receding water tables at alarming rate. The study is to assess groundwater recharge capability of various structures in the Cuddalore aquifer, Tamil Nadu, India. The groundwater flow model was developed using MODFLOW, a finite-difference model with the support of GMS graphical user interface. Calibration, validation and the χ 2 test proved that there is no significant difference amid observed heads and modeled heads. Modelling results indicate that artificial recharge could augment groundwater levels in the area by 2 m.

Groundwater recharge to a structurally complex aquifer system on the island of Tobago (Republic of Trinidad and Tobago)

Trinidad and Tobago is a developing two-island nation in the Lesser Antilles of the Caribbean. Tobago is the smaller island and has small highly heterogeneous aquifers composed of igneous and metamorphic crystalline rock with strong structural controls on the spatial distribution of permeability. Hydrogeologic analyses of the water budget and groundwater production suggest that portions of the island are underlain by prolific fractured-rock aquifer systems. This study quantifies the amount and spatial distribution of recharge, as well as the fraction of recharge captured by groundwater pumping, using historical data, new field data, remote sensing data, multiple storage quantification methods and stable isotope analysis. Despite extensive freshwater withdrawals, groundwater production reaches only ~10% of annual groundwater recharge. Groundwater capture zones are created using a first-order hydrologic balance approach and with backward particle tracking in a steady-state groundwater model. Both approaches to generating capture zones suggest that many wells capture water from outside their topographic watershed. The location of sustainable, high yield, fresh potable groundwater wells less than 1 km from the coast, that have fractured bedrock intakes well below sea level, supports the concept of a rigorous and active groundwater flow system. Understanding the hydrogeology of small bedrock island aquifers is critical to evaluating groundwater resources, especially in the Caribbean where there is strong seasonality in precipitation, finite surface-water storage and increases in potable water demand.

Estimating the Temporal Distribution of Groundwater Recharge by Using the Transient Water Table Fluctuation Method and Watershed Hydrologic Model

HighlightsThe transient water table fluctuation method (TWTFM) is revisited.A novel application of linking SWAT model and TWTFM is suggested.A method is proposed to estimate daily groundwater recharge distribution.The method is demonstrated for the Jeju Island in Korea.Abstract. Estimating groundwater recharge remains a difficult but necessary task as part of managing available groundwater supplies. For example, the average groundwater recharge rate of Jeju Island is 54%, which is considerably higher than the inland recharge rate (~15%) in Korea. Although groundwater is the main water source of this and many other islands, quantifying temporal groundwater recharge for water resources planning remains difficult. To estimate groundwater recharge based on rainfall, a simple and straightforward method is proposed that uses an application of the Transient Water Table Fluctuation Method (TWTFM) linked with the Soil and Water Assessment Tool (SWAT). By using the computed annual percolation from the SWAT as input, two parameters (reaction factor and specific yield) could be estimated by assuming that the sum of daily recharge via the TWTFM was approximately equal to the annual percolation near the water table. This methodology was applied to the Hancheon watershed of Jeju Island, South Korea. Runoff time series data for two years (2009 and 2010) were used to calibrate SWAT and another two years of data were used to validate computed discharges from SWAT. For the calibration of the combined SWAT and TWTFM model, groundwater level data from 2009 and 2010 were used, and then data from 2011 and 2012 were used to predict groundwater recharge using the calibrated TWTFM parameters. The proposed methodology can be used as an efficient tool for estimating the temporal distribution of groundwater recharge using only groundwater data and the annual percolation rate. This methodology can be beneficial for regions where the vadose zone depth is deeply formed and temporal recharge predictions are essential for water management. Keywords: Reaction factor, Specific yield, SWAT, Transient water table fluctuation method (TWTFM).

Potential and net recharge assessment in paddy dominated Hirakud irrigation command of eastern India using water balance and geospatial approaches

Spatially distributed potential and net recharge rates were assessed in the paddy dominated Hirakud command area (Eastern India) at 100 m grid resolution using surface water balance and Water Table Fluctuation (WTF) methods, respectively, for the period 2001–05. Net recharge estimated using the WTF method corresponding to observation well locations was further interpolated using kriging technique available in the ArcGIS software. Net recharge to potential recharge ratios (%) were also assessed spatially. Water balance components (i) runoff was estimated using the Natural Resources Conservation Service-Curve Number (NRCS-CN) method (ii) reference evapotranspiration by (Hargreaves and Samani, Applied Engineering Agriculture ASABE 1:96–99, 1985)), crop evapotranspiration by (Allen et al., Crop evapotranspiration: Guidelines for computing crop water requirements, FAO Irrigation and Drainage, Food and Agriculture Organization, Rome, Italy, 1998) and evaporation from uncultivated lands by Ritchie (1972) approaches, and (iii) canal seepage using simple canal flow model. Annual groundwater draft during Kharif and Rabi was found to be 144.41 and 112.49 ha-m, respectively. Nearly, 90% of the study area contributed runoff in the range of 200–400 mm during the years 2002–03, 2003–04, and 2004–05. The estimated seepage losses vary between 5 and 15% of irrigation depth for all distributaries. Potential groundwater recharge during wet, normal, and dry years ranges between 650 and 1033 mm, and equivalent to 67%, 78%, and 60% of annual rainfall, respectively. Net recharge ranges between 8 and 11% of the annual rainfall. Mean ratio between net recharge to potential recharge is nearly 30%, indicating that nearly 70% of potential recharge is accounted as outflow from the study area. Parmanpur distributary canal located at the centre of the study area that exhibited higher potential recharge can be scheduled at the end to avoid water logging problem. Further, extraction of groundwater during non-monsoon period for irrigation purpose not only helps in controlling waterlogging but also helps in maintaining stable groundwater level. Overall, spatio-temporal distribution of recharge in the command area indicated that the irrigation demands during non-monsoon season can be met through sustainable management of underexploited groundwater resources. Such an integrated management of surface and groundwater can help in improving water use efficiencies as well as agricultural productivity.

Modeling the Matrix-Conduit Exchanges in Both the Epikarst and the Transmission Zone of Karst Systems

Usual conceptual models of karst hydrodynamics highlight the important role of unsaturated subsystems in recharge repartition. However, few of them have been compared with scarce suitable physically-based numerical models. Hybrid models that couple single continuum medium with discrete features promise an improved consideration of karst specificities. Here we evaluate their capability to properly reproduce interactions between a vertical conduit and the surrounding unsaturated matrix. We simulate the response of such a configuration to a single recharge event for various sets of parameters. We show the ability of hybrid models to reproduce the most significant behaviors described in the literature, i.e., transient storage and distribution of recharge, flow concentration towards conduits in the epikarst, and matrix-conduit exchanges varying in time and space. In addition to the explicit conduits, simulating variably saturated flows with the Richards equation and distinguishing the epikarst and the transmission zone are key elements to reproduce most processes. The contrasts between subsystems necessary to observe desired behaviors have been quantified. They are reinforced by the varying matrix saturation that causes realistic competition between matrix and explicit conduits. The study also highlights the need to deepen knowledge of the scaled medium properties we need to know to apply such models to actual cases.

Surface water – Groundwater Coupled Modelling for Watershed Water Resources Sustainability Assessment

There are limited studies in Cisangkuy Watershed which shows the water resources availability and variability with respect to changing climates and land use. Uncertainties due to climate change and population growth have created a critical water resources situation for Cisangkuy Watershed. These uncertainties come from undescribed quantification of surface water – groundwater interaction. Investigating spatio-temporal variability of recharge-discharge is a critical initial step for water-resource management. The main objective of this study is to set up a physically-based spatially distributed SWAT and MODFLOW for the analysis of the different hydrological and hydrogeological component. The objectives to be achieved include 1) identifying the characteristics and distribution of river stream recharge -discharge 2) assessing surface water and groundwater quantity. The result shows that calibrated SWAT-MODFLOW model can represent surface water – groundwater interaction in Cisangkuy Watershed spatio-temporally. Baseflow from aquifer discharge is main factor that give contribution to river discharge in study area, so we can conclude that Cisangkuy Watershed has a good potential of water resources on the low area, but also has high potential of disaster due to groundwater like flood and landslide.This study is expected to develop water resources management in Indonesia. So that water resources sustainability can be analyzed from the aspect of the quantity of surface water and groundwater.

Assessment of Groundwater Recharge in Agro-Urban Watersheds Using Integrated SWAT-MODFLOW Model

Numerical models are employed widely to evaluate the hydrological components of a watershed but, traditionally, watershed models simplify either surface or subsurface flow module. In this setup, as a bridge between groundwater and surface water regimes, aquifer recharge is the most affected segment of the water balance. Since the watershed processes are increasingly changed, the need for a comprehensive model with detailed conceptualizing capacity of both groundwater and surface water flow systems is growing. This work focuses on the spatiotemporal groundwater recharge assessment in gauged and ungauged agro-urban watersheds in South Korea using the updated SWAT-MODFLOW model, which integrates the Soil and Water Assessment Tool (SWAT2012) and Newton–Raphson formulation for Modular Finite Difference Groundwater Flow (MODFLOW-NWT) in a single executable code. Before coupling, the setup, calibration, and verification of each model were performed separately. After integration, irrigation pumps and drain cells mapping to SWAT auto-irrigation and subbasins were initiated. Automatic calibration techniques were used for SWAT and MODFLOW-NWT models, but a manual calibration was used for the integrated model. A physical similarity approach was applied to transfer parameters to the ungauged watershed. Statistical model performance indicators revealed that the low streamflow estimation was improved in SWAT-MODFLOW. The spatiotemporal aquifer recharge distribution from both the stream seepage and precipitation showed a substantial change, and most of the aquifer recharge occurs in July–September. The areal annual average recharge reaches about 18% of the precipitation. Low-lying areas receive higher recharge consistently throughout a year. Overall, SWAT-MODFLOW exhibited reasonable versatility in evaluating watershed processes and produced valuable results with reasonable accuracy. The results can be an important input for policymakers in the development of sustainable groundwater protection and abstraction strategies for the region.

Shallow aquifer groundwater dynamics due to land use/cover change in highly urbanized basin: The case of Kathmandu Valley

Study regionKathmandu Valley, Nepal. Study focusIn the context of rapid urbanization in Kathmandu Valley (KV), this study quantifies spatial distribution of recharge and changes in drawdown under pumping rate and land use/cover change scenarios. Both scenarios are incorporated in a groundwater flow model in MODFLOW. New hydrological insights for this regionCurrent groundwater recharge rate is spatially distributed across the basin in a range of 95.3–85.3 % of precipitation in dry season and 48−38% of precipitation in wet season as per recharge area distributions. This results in groundwater recharge of 1.052 MCM and 1.949 MCM in dry and wet seasons respectively. In the case of increase in both pumping rate and encroachment of recharge areas (due to land use/cover change) and only encroachment of recharge areas, drawdown is projected to change respectively by −5.25 m in dry season and −7.39 m in wet season and −1.09 m in dry season and -3.63 m in wet season in 2050. The central urban, northern foothills, and southern parts are projected to observe more draw down. Meanwhile, the boundary forest area has the potential to increase the water table in the future.

Application of Hydrogeological Mapping and Geospatial Analysis to Determine Recharge and Discharge Areas in Sumowono Groundwater Basin

Sumowono groundwater basin is locating at Semarang Regency, Temanggung Regency, and some part in Kendal Regency. Increasing population growth in the Sumowono groundwater basin area is the cause of increasing water demand. This study aims to determine groundwater utility by the community, the value of each determinant parameters of the recharge area, and the distribution of recharge and discharge areas. The research methods were hydrogeological mapping and geospatial analysis, which includes combining several geological and hydrogeological parameters, namely hydraulic conductivity, precipitation, soil cover, slope, water table depth, and electrical conductivity (EC). Based on the result of the hydrogeological mapping, groundwater is mainly used for irrigation, fisheries, industry and domestic purposes. The soil covers consist of sandy clay and clay sand. The slope has a value of 0°-40°. Rainfall has a range 2, 500-3, 200 mm/year, depth of water table is up to 20 m below ground surface. The hydraulic conductivity values are 3.1 m/day (tuffaceous sandstone), and 270 m/day (volcanic breccia) with the EC values is 36-550 µS/cm. Based on the results of the geospatial analysis, the recharge area is spreading in the south and the east, while the discharge area is located in the northern part of the study area.

Field-based estimation and modelling of distributed groundwater recharge in a Mediterranean karst catchment, Wadi Natuf, West Bank

Abstract. While groundwater recharge is one of the most prominently covered subjects in hydrogeology, the spatial distribution of recharge has been given relatively little attention, especially in semi-arid, karstic aquifers. Under conditions of highly diverse geology, relief, vegetation and land use, the complexity and variability of spatially distributed hydrological processes remains a challenge in many regions around the world. This is particularly true for hitherto ungauged basins, such as Wadi Natuf, a 103 km2 large karstic Eastern Mediterranean watershed in the Palestinian upstream mountain and recharge area of the Western Aquifer Basin (WAB), which is shared with Israel in the coastal plain. In this first in a series of two papers, distributed recharge is estimated and represented, based on 7 years of extensive field observations and measurements and based conceptually on observable physical landscape features such as geology, land use and land cover (LU/LC) and especially soil conditions. For the first time in the WAB, a forward calculated soil moisture and percolation model (SMSP) was set up with parameters directly gained from field observations. The model was parameterised in a strictly parsimonious manner, as a one-dimensional model (a.k.a. “tank”, bucket or box model). This is based on dominant hydrological processes, in particular saturation excess in the soil column, and identifying patterns of linkage between different landscape features. Average soil thickness was encountered at the range of decimetres, rarely above one metre. Both soil thickness and LU/LC features, such as terraced olive groves or forests as well as grassland or barren rock outcrops, were found to be highly formation specific. This linkage allowed us to further simplify the model and its requirements in a realistic manner for eight soil moisture stations, chosen at six different geological formations with typical soil and LU/LC representations. The main result of the model was the determination of formation-specific recharge coefficients, spatially ranging between 0 % and almost 60 % of annual rainfall or up to 300 mm a−1 in Wadi Natuf's climate. The karstified main aquifers showed recharge coefficients (RC) above 40 % and even the less prominent slightly aquitardal local aquifers reached RC values above 30 %. The model was separately tested on two conceptual levels: on the level of basin form (soil moisture) and basin response (signatures of peak recharge and local spring discharge events) under well-controlled conditions in isolated sub-catchments. In principle, our approach is applicable in many of the scarcely gauged karstic groundwater basins around the world with a highly diverse landscape and geology.