Average Groundwater Recharge Research Articles

Potential groundwater recharge from deep drainage of irrigation water.

Knowledge of soil water dynamics in the deep vadose zone provides valuable information on the temporal and spatial variability of groundwater recharge. However, semi-arid climate can complicate how the input of water, such as irrigation, can contribute to potential groundwater recharge. This study assessed the recharge rates and their timing under irrigated cropland from a semi-arid region of northern Iran. A deep drainage (10m) experiment was performed and in situ soil water content was measured to analyze the soil water dynamics and model hydraulic parameters using HYSDRUS-1D. The best parameters selected from inverse parameter optimization were used to calibrate model and estimate the long-term (20-year) average groundwater recharge and the influence of the root zone, unsaturated zone and the time scale on the recharge processes. The simulated annual flux ranged from 24mm to 268mm (mean of 110mm) at 2-m depth and ranged between 26mm to 207mm (mean of 95mm) at the 10-m depth. High fluxes, observed between December and April, may be the result of greater precipitation combined with the irrigation return flow. The May-October period showed a gradual decrease in flux at the depth of 2m. At the depth of 10m, the flux showed some continuity (base flux) during the long-term recharge simulation. In total, 12.7% of the input water contributed to the recharge of the groundwater. The annual soil water fluxes were almost similar irrespective of depth below the root zone and the flux rates did not show any clear relation between the different components of the water budget at any depth. This approach improved our understanding of the recharge process in the deep vadose zone in a semiarid region and can help for the development of effective management of groundwater resources.

Climate Change Impact on Groundwater Recharge of Umm ER Raduma Unconfined Aquifer Western Desert, Iraq

The impact of future climate change on groundwater resources is significant, especially for arid and semi-arid areas such as the Middle East. In this study, the effect of climate change on groundwater recharge in the Umm er Radhuma unconfined aquifer in the Western Desert, Iraq was simulated using a modelling approach (WetSpass). Climate variables predicted for the period 2020 to 2099, were generated from the Hadley Center for Climate Prediction and Research (HadCM3), these appropriate for the most important developments in emission scenarios A2 and B2, in seven selected meteorology stations throughout the study area. The results indicated an increase in annual precipitation and in average temperature for the two selected scenarios. For the study region, precipitation is predicted to increase by 5.4% and 3.19%, for A2 and B2 scenarios, respectively. Consequently, the annual average groundwater recharge is expected to decrease by 16% for both scenarios in the next century.

Characterization of groundwater –surface water interactions using high resolution integrated 3D hydrological model in semiarid urban watershed of Niamey, Niger

This study investigates groundwater-surface water interactions using an equivalent porous medium approach in a data scarce and semi-arid hydrogeological watershed located south-west Niger. A large scale fully-integrated hydrologic model was built and calibrated using HydroGeoSphere with a sequential approach of increasing levels of temporal resolution: 1) steady state average conditions; 2) dynamic equilibrium with repeating monthly normal forcing data; and 3) fully transient conditions. This approach provided a useful and straightforward method for reducing the calibration effort of the large-scale fully-integrated hydrologic model. River-aquifer exchange flux dynamics, water balance components for different land use classes, as well as basin average groundwater recharge were computed from the model. Simulation results show that exchange flux between groundwater and surface water are important processes in the basin, with the Niger River acting primarily as a gaining stream, with local losing zones. Ephemeral streams constitute important focused groundwater recharge areas, while ponds exhibit either groundwater discharge behavior, or a recharge zone profile depending on local topography. The basin average water balance highlights the importance of plant transpiration (58% of total rainfall) over surface evaporation (8%), with groundwater recharge of up to 5% of total rainfall. Overland flow and infiltration account for 11% and 16% of the total annual rainfall respectively, and groundwater discharge to the river is 2% of the total rainfall.

Characterisation of groundwater flow and recharge in crystalline basement rocks in the Talensi District, Northern Ghana

A numerical groundwater flow model, calibrated under equilibrium conditions to characterise the spatial variation of key hydraulic parameters and groundwater flow pattern in a crystalline aquifer in the Upper East Region of Ghana has been developed. The development of groundwater flow model was to provide the baseline information to assist in assessing the impacts of population growth and climate change scenarios on large scale development of groundwater resources for various uses. The results revealed an apparent dominant northeast–southwest flow pattern influenced mainly by the hydraulic conductivity field, with estimated values ranging between 0.001 and 58 m/day, and local flow systems which are controlled mainly by local variations in the topography in the area. The estimated average groundwater recharge from the calibrated model and chloride mass balance technique: 2.00% and 2.07% of the annual precipitation respectively has a direct positive correlation with elevation. The low recharge rate is evident in the high evaporation rates as revealed by stable isotope (δ2H and δ1⁸O) analysis of sampled water sources. The study also reveals the aquifer is being partly recharged by the White Volta River. This gives an indication that the area holds good groundwater fortunes for potential commercial groundwater development as predicted by scenario analysis which suggests that the aquifer can sustain increased abstractions by more than 100% of the current rate provided the current recharge rate is maintained. However, for the aquifer to sustain large scale abstractions beyond 100% of the current rate under conditions of reduced vertical recharge by more than 40% of the current rate, deliberate efforts would have to be made to enhance artificial vertical recharge to augment the natural recharge.

Water resource assessment, gaps, and constraints of vegetable production in Robit and Dangishta watersheds, Upper Blue Nile Basin, Ethiopia

The vast majority of farmers in sub-Saharan Africa depend on rainfed agriculture for food production and livelihood. Various factors including but not limited to rainfall variability, land degradation, and low soil fertility constrain agricultural productivity in the region. The objectives of this study were to 1) estimate the water resources potential to sustain small-scale irrigation (SSI) in Ethiopia during the dry season so as to expand food supply by growing vegetables, and 2) understand the gaps and constraints of vegetable production. The case studies were conducted in the Robit and Dangishta watersheds of the Upper Blue Nile Basin, Ethiopia. To document farmers’ cropping practices, field-level data were collected from 36 households who had been cultivating tomato (Solanum lycopersicum L.) and onion (Allium cepa L.) during the dry season (November – April). Two components of the Integrated Decision Support System (IDSS) - the Soil and Water Assessment Tool (SWAT) and Agricultural Policy Environmental eXtender (APEX) – were respectively used to assess impacts of SSI at the watershed and field-scale levels. Results suggest that there is a substantial amount of surface runoff and shallow groundwater recharge at the watershed scale. The field-scale analysis in the Robit watershed indicated that optimal tomato yield could be obtained with 500 mm of water and 200 to 250 kg/ha of urea applied with 50 kg/ha of diammonium phosphate (DAP). In Dangishta, optimum onion yield can be obtained with 400 mm of water and 120 to 180 kg/ha of urea applied with 50 kg/ha of DAP. The field-scale simulation indicated that the average shallow groundwater recharge (after accounting for other groundwater users such as household and livestock use) was not sufficient to meet tomato and onion water demand in the dry season (October to April). The field-scale analysis also indicated that soil evaporation attributed a significant proportion of evapotranspiration (60% for onion and 40% for tomato). Use of mulching or other soil and water conservation interventions could optimize irrigation water for vegetable production by reducing soil evaporation and thereby increasing water availability in the crop root zone.

Combining remotely sensed actual evapotranspiration and GIS analysis for groundwater level modeling

This paper describes a combination of large-scale spatially remote-sensed actual evapotranspiration and geographical information systems of surface runoff to estimate groundwater recharge potential, by water balance, to model groundwater level. We selected an area nearby the city of Aguas de Santa Barbara, central-western part of Sao Paulo State, Brazil to be analyzed between 2014 and 2018, during recent El Nino-Southern Oscillation most active period (2016/2017) and verify its posteriori effects on vegetation (until early 2018). The Simple Algorithm for Evapotranspiration Retrieving (SAFER), with biweekly MODIS and seasonal Sentinel-2 imagery, and the rational method for runoff modeling were applied, which was applied in a daily-basis hydrological model, which is the main novelty of this report. The average annual groundwater recharge potential for each of the land uses (pasture, sugarcane crop, silviculture, and forest) varied between 15 and 50% of the rainfall. Silviculture showed higher evapotranspirations rates than forest and sugarcane crops. Groundwater levels measured at 46 monitoring wells were analyzed to obtain enough data to create the hydrographs required for the validation. 36 shallow wells (which reached depths smaller than 3 m) had the best results (R2 > 0.92), where the root mean squared absolute error (RMSE) term appeared to be less than 20% of the mean groundwater level, indicating that it has a faster response to remote-sensed actual evapotranspiration and that the water balance is sufficiently understood for policy and decision making. The results of this study lead to the conclusion that including spatiotemporal thermal and soil moisture conditions by remote-sensing tools in the evapotranspiration account improved the modeling of groundwater levels for shallow wells at daily basis.

Prediction of nitrate accumulation and leaching beneath groundwater irrigated corn fields in the Upper Platte basin under a future climate scenario

Understanding the impacts of future climate change on soil hydrological processes and solute transport is crucial to develop appropriate strategies to minimize the adverse impacts of agricultural activities on groundwater quality. To evaluate the direct effects of climate change on the transport and accumulation of nitrate-N, we developed an integrated modeling framework combining climatic change, nitrate-N infiltration in the unsaturated zone, and groundwater level fluctuations. The study was based on a center-pivot irrigated corn field at the Nebraska Management Systems Evaluation Area (MSEA) site. Future groundwater recharge (GR) and actual evapotranspiration (ETa) rates were predicted via an inverse vadose zone modeling approach by using climatic data generated by the Weather Research and Forecasting (WRF) climate model under the RCP 8.5 scenario, which was downscaled from the global CCSM4 model to a resolution of 24 km by 24 km. A groundwater flow model was first calibrated on the basis of historical groundwater table measurements and then applied to predict the future groundwater table in 2057–2060. Finally, the predicted future GR rate, ETa rate, and groundwater level, together with future precipitation data from the WRF climate model, were used in a three-dimensional (3D) model to predict nitrate-N concentrations in the subsurface (saturated and unsaturated parts) from 2057 to 2060. The future GR was predicted to decrease in the study area, as compared with the average GR data from the literature. Correspondingly, the groundwater level was predicted to decrease (30 to 60 cm) over the 5 years of simulation in the future. The nitrate-N mass in the simulation domain was predicted to increase but at a slower rate than in the past. Sensitivity analysis indicated that the accumulation of nitrate-N is sensitive to groundwater table elevation changes and irrigation rates.

Dominant Influencing Factors of Groundwater Recharge Spatial Patterns in Ergene River Catchment, Turkey

Groundwater is of great significance in sustaining life on planet earth. The reliable estimation of groundwater recharge is the key understanding the groundwater reservoir and forecasting its potential accessibility. The main objective of this study was to assess the groundwater recharge and its controlling factors at the Ergene river catchment. A grid-based water balance model was adopted to determine the spatially distributed long-term groundwater recharge and other water budget components, relying upon the hydro-climatic variables, land-use, soil, geology, and relief of the investigated area. The model calculations were performed for the hydrological reference horizon of 20 years at a spatial resolution of 100 × 100 m. The base flow index (BFI) separation concept was applied to split up the simulated total runoff into groundwater recharge and direct runoff. Subsequently, the statistical methods of Pearson product–moment correlation and principal component analysis (PCA) were combined for identifying the dominant catchment and meteorological factors influencing the recharge. The average groundwater recharge over the investigated area amounts to 95 mm/year. The model validation and statistical analysis indicate that the difference between simulated and observed total runoff and recharge values is generally under 20% and no significant inconsistency was observed. PCA indicated that recharge is controlled, in order of significance, by land-use, soil, and climate variables. The findings of this research highlight the key role of spatial variables in recharge determination. In addition, the generated outputs may contribute to groundwater resource management in the Ergene river catchment.

Determining Regional-Scale Groundwater Recharge with GRACE and GLDAS

Groundwater recharge (GR) is a key component of regional and global water cycles and is a critical flux for water resource management. However, recharge estimates are difficult to obtain at regional scales due to the lack of an accurate measurement method. Here, we estimate GR using Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) data. The regional-scale GR rate is calculated based on the groundwater storage fluctuation, which is, in turn, calculated from the difference between GRACE and root zone soil water storage from GLDAS data. We estimated GR in the Ordos Basin of the Chinese Loess Plateau from 2002 to 2012. There was no obvious long-term trend in GR, but the annual recharge varies greatly from 30.8 to 66.5 mm year−1, 42% of which can be explained by the variability in the annual precipitation. The average GR rate over the 11-year period from GRACE data was 48.3 mm year−1, which did not differ significantly from the long-term average recharge estimate of 39.9 mm year−1 from the environmental tracer methods and one-dimensional models. Moreover, the standard deviation of the 11-year average GR is 16.0 mm year−1, with a coefficient of variation (CV) of 33.1%, which is, in most cases, comparable to or smaller than estimates from other GR methods. The improved method could provide critically needed, regional-scale GR estimates for groundwater management and may eventually lead to a sustainable use of groundwater resources.

Assessment of artificial groundwater recharge potential through estimation of permeability values from infiltration and aquifer tests in unconsolidated alluvial formations in coastal areas.

Twenty infiltration tests and 12 pumping tests were carried out in Wadi Baysh in southwestern Saudi Arabia. The objective of the study was to assess the soil and aquifer permeability from the point of view of artificial groundwater recharge. Infiltration tests showed that the soil permeability values ranged from 0.58 to 37.15m/day and showed good recharge potential. The analysis of the pumping tests showed that the aquifer permeability values ranged from 2.6 to 57.4m/day and were approximately within the same range as those obtained from infiltration tests. Monitoring of groundwater levels in a few wells before and 1month after a heavy rainfall event in August 2016 shows an average increase of 2.25m in the groundwater levels which substantiates the recharge rates obtained from infiltration and pumping tests. Average annual groundwater recharge for the area calculated from water table fluctuation method is 72.08mm/year indicating that the lower reaches of Wadi Baysh catchment has good potential for groundwater recharge and if managed properly can help in tackling the problem of groundwater depletion due to excessive pumping.

Estimation of groundwater recharge using GIS-based WetSpass model for Birki watershed, the eastern zone of Tigray, Northern Ethiopia

This research aimed to use WetSpass model to estimate long-term average annual and seasonal groundwater recharge for Birki watershed (45 km2) in northern Ethiopia using long-term (10 years) hydro-meteorological and biophysical (soil, land use, topography, slope and groundwater depth) data of the watershed. Both primary and secondary input data were collected using field survey and disk-based data collection methods. The model was used to understand the groundwater recharge potential of the given area for wise utilization, proper management and future planning of the water resource. The results showed that, summer (rainy season) recharge ranges from 0 to 41.09 mm/year with mean value of 24.1 mm/year (96.5%), winter (dry season) recharge ranges from 0 to 1.9 mm/year with mean value of 0.8 mm/year (3.5%) and yearly recharge ranges from 0 to 42.6 mm/year with mean value of 24.9 mm/year. Ten years of mean annual precipitation 573 mm contributed to 7.4% as recharge to the groundwater, 7.1% of surface runoff and 85.5% lost as evapotranspiration. Annually, 1.1205 million m3 water recharges into the groundwater table as recharge from the precipitation for the entire watershed area. Annually on average 0.17 m3/d/ha groundwater can be extracted safely without depleting the groundwater. Understanding the groundwater recharge of the Birki watershed is important for management, proper utilization and future planning of water resources for sustainable management. It is also good baseline information for water resource experts and policymakers of the region for further investigation of water resources, design, and developmental activities and for planning purpose.

Hydrologic impacts of drought-adaptive agricultural water management in a semi-arid river basin: Case of Rincon Valley, New Mexico

This paper examines the coupled effects of weather condition, crop coverage change, and regional water management (i.e., releases from Caballo Reservoir) on hydrologic characteristics of Rincon Valley (2466 km2), a semi-arid agricultural area in New Mexico, U.S.A., using Soil and Water Assessment Tool (SWAT). The model simulates the vertical water budget and horizontal water transfers during the period 1994–2013, incorporating irrigation of fourteen crops in normal (2008) and dry (2011) years to evaluate the hydrologic impacts of cropping change as a drought-adaptive water management strategy. It was calibrated (2000–2002) and validated (2003–2005) using daily-observed streamflow data. Furthermore, evapotranspiration, diversion and irrigation water volume were verified for the period of 2000–2005 using monthly crop irrigation requirement data and canal discharge data. Results demonstrate the significant role of surface water infiltration, providing approximately 18% of the average annual groundwater recharge during the irrigation season. Watershed scale evapotranspiration (ET) and return flows for the irrigation season were estimated to be 23% and 1% higher than those for the non-irrigation season, respectively. For irrigation units, the ratio of ET to combined precipitation and irrigation water for the dry year was 5% higher than the normal year whereas surface runoff, soil water storage, and groundwater recharge were 7%, 17%, and 39% lower than the normal year, respectively. High groundwater recharge occurs in the hydrologic response units (HRU) where corn and cotton are planted on silty clay loam soil. The Alfalfa acreage (i.e., the largest water user) was reduced by 15% while the cotton acreage was increased by 13% in order to adapt to lower water availability during the dry year. Quantitative understanding of the hydrologic fluxes in the Rincon Valley’s irrigated agricultural area illuminates adaptive land and water management to buffer the adverse impacts of prolonged droughts.

Multi-Dimensional Evaluation of Simulated Small-Scale Irrigation Intervention: A Case Study in Dimbasinia Watershed, Ghana

This paper studied the impacts of small-scale irrigation (SSI) interventions on environmental sustainability, agricultural production, and socio-economics using an Integrated Decision Support System (IDSS). The IDSS is comprised of a suite of models, namely the Soil and Water Assessment Tool (SWAT), Agricultural Policy/Environmental eXtender (APEX), and Farm Income and Nutrition Simulator (FARMSIM). The IDSS was applied in Dimbasinia watershed in northern Ghana using irrigation water from shallow groundwater. The watershed has a modest amount of shallow groundwater resources. However, the average annual irrigation water requirement exceeded the average annual shallow groundwater recharge. It was found that the current crop yield in Dimbasinia watershed was only ~40% of the potential crop production. This is mainly related to climate variability, low soil fertility, and land-management practices. For example, application of 50 kg/ha urea and 50 kg/ha DAP doubled maize and sorghum yield from the current farmers’ practices. Better income was obtained when irrigated vegetables/fodder were cultivated in rotation with sorghum as compared to in rotation with maize. Investment in solar pumps paid better dividends and also supplied clean energy. The socio-economic analysis indicated that having irrigated dry season vegetables will improve household nutrition. Since shallow groundwater recharge alone may not provide sufficient water for irrigation in a sustainable manner, surface water may be stored using water-harvesting structures to supplement the groundwater for irrigation. Integrated use of the water resources will also reduce depletion of the shallow groundwater aquifer. We conclude that IDSS is a promising tool to study gaps and constraints as well as upscaling of SSI.

Analysis and numerical modelling of large-scale controls on aquifer structure and hydrogeological properties in the African basement (Benin, West Africa)

Abstract The metamorphic basement units of the Upper Ouémé watershed in Benin have been investigated to identify the structural controls on aquifer properties, groundwater flow and water balance at large scale. Spatial analysis of borehole and hydrogeophysical data suggests that large-scale weathering profiles, aquifer transmissivity and storage properties are better correlated to a palaeo-weathering surface. Multi-model analysis, combined with assessment of nine transient numerical groundwater models against observations, suggests the best conceptualizations are those where hydraulic conductivity and specific yield are distributed within a weathered zone determined through interpolation of weathered zone thickness. When compared to previous studies, the general groundwater balance of simulated models suggests the groundwater system contributes, on average, 49.8 m 3 s −1 to the river flow (mostly during the rainy season). The same volumetric flow would be lost to groundwater evapo-transpiration and deep/lateral drainage of the catchment. Borehole abstraction (about 7.5 m 3 s −1 ) represents only 6% of the average groundwater recharge and 1% of the average rainfall. This suggests that despite relatively low borehole productivity, the basement aquifer system still has an important unused potential for rural to mid-scale water supply and that, at present, the main external drivers for groundwater resource sustainability are changes in climate and land use.

Modelling Vadose Zone Processes for Assessing Groundwater Recharge in Semi-Arid Region

Normally groundwater recharge is estimated using methods based on water balance, water table fluctuations, fixed factor of annual rainfall and tracer movement. In many of these methods water stored in the vadose zone and evapotranspiration are not accounted properly. These factors control groundwater recharge to a large extent, particularly in arid and semi-arid regions which are normally characterized by a deep water table, thick vadose zone and high evapotranspiration. In this study, HYDRUS-1D and MODFLOW models were used to assess the recharge flux and groundwater recharge in an area under a semi-arid region giving due consideration to important vadose zone processes. Cumulative recharge flux at water table in various sub-areas varied from 20.01 cm to 23.43 cm (29.26% to 34.26% of the monsoon rainfall). The average groundwater recharge was 22.2%. Total surface runoff in various sub-areas varied from 3.39 cm to 14.36 cm (5% to 21% of the monsoon rainfall). Evapotranspiration was found to be a major recharge controlling factor. Reference evapotranspiration varied from 37.19 cm to 45 cm (54% to 66% of the monsoon rainfall). Natural recharge under the prevailing pumping rate and pumping schedule was 23.3% of the monsoon rainfall. Simulation results revealed that if all the surface runoff is retained in the area, water table will rise by 1.46 m.

Hydrologic performance of bioretention in an expressway service area.

Bioretention can be an effective measure for stormwater treatment. However, there is a lack of systematic analysis of the impact of bioretention design parameters on hydrologic performance. Herein, SWMM and RECARGA models were applied to generate the typical annual rainfall runoff and simulate the water balance of the bioretention system in an expressway service area. The purpose of the investigation was to identify key design parameters for the bioretention system and delineate the priorities in developing the design. Results showed that the average groundwater recharge ratios for bioretention basins with and without an underdrain were 58.29% and 92.27%, respectively, the average overflow ratios were 4.13% and 4.19%, the average evapotranspiration ratios were 4.48% and 4.47%, and the average outflow ratio for bioretention with an underdrain was 33.94%. The ratio of the bioretention area to drainage area, and the saturated infiltration rates of planting soil and native soil were the main factors influencing water balance, while the underdrain diameter and gravel layer depth exerted little effect. Based on the impact analysis, multivariate nonlinear regression models of runoff reduction rate for two types of bioretention basin were established, which both exhibited high determination coefficients and acceptable Nash-Sutcliffe coefficients.

Understanding surface water–groundwater interactions for managing large irrigation schemes in the multi-country Fergana valley, Central Asia

Traditionally, surface water supplies are the sole sources to satisfy crop water requirements in large irrigation schemes such as those in the Fergana Valley, Central Asia. Recent studies indicate that 23–30% of these requirements are met from shallow groundwater, but this is not usually quantified. To manage favorable groundwater levels – i.e., without increasing soil salinity and nutrient leaching and reducing crop yields – information on, and quantification of, groundwater recharge and discharge rates at large spatial and temporal scales, as well as understanding their mechanisms of interaction, is indispensable. With the aim to quantify groundwater recharge, discharge and their interaction, a conceptual water balance model at a scale of a Water Consumers’ Association was established on a monthly basis for a 10-year period. Average groundwater recharge was estimated as 780 ± 75.7 mm, representing 62% of surface water supplies. The highest average annual recharge (930 mm) driven by excessive precipitation and water supply was in 2010 and the lowest (667–726 mm) was in years of lower water availability: 2006–2008 and 2012. The net groundwater recharge was 82.4 ± 79 mm, and determined the groundwater level fluctuations. The highest positive net groundwater recharge rate (247 mm) and the shallowest groundwater level (123 cm) also occurred in 2010. The negative net recharge in 2006 (–11 mm), 2008 (–41 mm) and 2012 (–5 mm) indicated deeper groundwater levels during these periods. The groundwater recharge values were excessively high even for this large irrigation scheme. To save limited freshwater resources, groundwater discharge should be reduced, with one option being to reduce excessive drainage outflow.

WetSpass-Based Study of the Effects of Urbanization on the Water Balance Components at Regional and Quadrat Scales in Beijing, China

China is the largest country in terms of population and its booming urbanization has exerted negative effects on ground-surface hydrological processes at different spatial scales, land-use types, and water balance, such as surface runoff, groundwater recharge, and evapotranspiration. However, it is not yet well understood as to how the modifications of the spatial patterns of landscapes affect the water balance on a regional scale. In this study, the water and energy transfer among soil, plants, and atmosphere (WetSpass) model was applied to evaluate the urbanization effects on the water balance on a regional scale by using Beijing as the case city for this current study. The relationships among impervious surfaces, landscape pattern indices, and water balance components were also quantified. Results indicated built-up land in 2012 was 673 km2 larger than it in 2000, mostly converted from croplands. WetSpass model also indicated the variation rates of annual average surface runoff, evapotranspiration and groundwater recharge were 7%, 0.4% and −2% in the whole Beijing area, while they reached 52%, 6% and −24% in the urban area of Beijing from 2000 to 2012, respectively. At a city scale, four districts—Dongcheng, Xicheng, Chaoyang, and Haidian—were characterized by higher impervious percentage, as reflected by lower groundwater recharge and higher surface runoff than other districts. At quadrat scale, however, groundwater recharge (surface runoff) was negatively (positively) correlated with impervious percentages. For landscape indices, the Aggregation Index was positively correlated with surface runoff and negatively correlated with groundwater recharge while Patch Density Index, Splitting Index, Patch Richness Density Index, and Shannon’s Diversity Index presented opposite relationships. The results of this study can help to develop human knowledge about the impacts of urbanization on hydrological cycles on a regional scale.

Effects of irrigation on groundwater recharge under deep buried depth condition

In this paper the dynamic changes of the groundwater levels and soil moisture were studied to realize the groundwater recharge. The irrigation recharge coefficient was calculated based on groundwater level and soil moisture and verified by the numerical model with MODFLOW. The average groundwater recharge coefficient was 0.0875 the whole year. With the deep groundwater level in Jinghuiqu Irrigation district the results from changes of groundwater showed that the time of recharge was longer. The soil moisture had a similar trend with the groundwater level. Overexploitation without recharge of groundwater led the decreasing of groundwater level. The research may provide as a reference to increasing the surface water irrigation for development of groundwater ecological environment of the district.

Evaluating the impact of artificial groundwater recharge structures using geo-spatial techniques in the hard-rock terrain of Rajasthan, India

Groundwater levels in hard-rock areas in India have shown very large declines in the recent past. The situation is becoming more critical due to a paucity of rainfall, limited surface water resources and an increasing pattern of groundwater extraction in these areas. Consequently, the Ground Water Department with the aid of World Bank has implemented the water structuring programme to mitigate groundwater scarcity and to develop a viable solution for sustainable development in the region. The present study has been undertaken to assess the impact of artificial groundwater recharge structures in the hard-rock area of Rajasthan, India. In this study groundwater level data (pre-monsoon and post-monsoon) of 85 dug-wells are used, spread over an area of 413.59 km2. The weathered and fractured gneissic basement rocks act as major aquifer in the area. Spatial maps for pre- and post-monsoon groundwater levels were prepared using the kriging interpolation technique with best fitted semi-variogram models (Spherical, Exponential and Gaussian). The groundwater recharge is calculated spatially using the water level fluctuation method. The entire study period (2004–2011) is divided into pre- (2004–2008) and post-intervention (2009–2011) periods. Based on the identical nature of total monsoon rainfall, two combinations of average (2007 and 2009) and more than average (2006 and 2010) rainfall years are selected from the pre- and post-intervention periods for further comparisons. All of the water harvesting structures are grouped into the following categories: as anicuts (masonry overflow structure); percolation tanks; subsurface barriers; and renovation of earthen ponds/nadis. A buffer of 100 m around the intervention site is taken for assessing the influence of these structures on groundwater recharge. The relationship between the monsoon rainfall and groundwater recharge is fitted by power and exponential functions for the periods of 2004–2008 and 2008–2011 with R 2 values of 0.95 and 0.98, respectively. The average groundwater recharge is found to be 18% of total monsoon rainfall prior to intervention and it became 28% during the post-intervention period. About 70.9% (293.43 km2) of the area during average rainfall and more than 95% (396.26 km2) of the area during above-average rainfalls show an increase in groundwater recharge after construction of water harvesting structures. The groundwater recharge pattern indicates a positive impact within the vicinity of intervention sites during both average and above-average rainfall. The anicuts are found to be the most effective recharge structures during periods of above-average rainfall, while subsurface barriers are responded well during average rainfall periods. In the hard-rock terrain, water harvesting structures produce significant increases in groundwater recharge. The geo-spatial techniques that are used are effective for evaluating the response of different artificial groundwater recharge techniques.