Affect Groundwater Recharge Research Articles

Groundwater Recharge Potential Index and artificial groundwater recharge in the alluvial soils of the middle Ganga Basin

Recent studies prove the faster depletion of groundwater is a cause of concern in the middle Ganga basin. Most of the groundwater-related studies in the middle Ganga basin deal with groundwater levels and quality aspects. The past studies on groundwater potential are confined to arid and humid zones of India, which leaves ample space for semi-humid to semi-arid, frost-prone, and alluvial region. The basin has alluvial soil due to sediments deposited by the river Ganga. In this study, eight thematic maps were prepared for the assessment of the groundwater recharge potential. These maps are; rainfall, geomorphology, slope, drainage density, lineament density, lithology, Land Use/Land Cover (LULC), and Groundwater Fluctuation (GWF). The weighted overlay of these thematic maps gave the Groundwater Recharge Potential Zone (GWRPZ) map representing the spatial variation of the Groundwater Recharge Potential Index (GWRPI) in the basin, whose value varies from 0.071 to 0.309. A total of 92 artificial groundwater recharge sites have been identified using specialized GIS processes taking into account stream network. The Analytic Hierarchy Process (AHP) based weights classification offers a robust framework for prioritizing and understanding the relative significance of factors affecting groundwater recharge. Alluvial soils are capable of holding large amount of water, and are overlaid by large aquifers. A large number of wells and tube wells have led to the over-extraction of groundwater in the region. This is the reason of the study being carried out despite being a region infested with large aquifers.

Hydrogeomorphology and recharge mechanism of a coastal aquifer in tectonic-controlled watersheds: A multi-proxy approach based on remote sensing and environmental isotopes

Coastal aquifers worldwide can be considered an essential water source required for preservation of the coastal ecosystems. However, these aquifers are vulnerable to seawater intrusions and over-pumping due to their proximity to the sea and human activities, respectively. Therefore, the investigation of recharge mechanism has special importance in the regions of tectonic rift activities where they exhibit complex geological structures and hydrogeological characteristics. In the current research, an integrated approach of remote sensing and environmental isotopes together with field investigation and subsurface datasets (aeromagnetic, gravity and well logs) are employed to identify the nature and factors affecting groundwater recharge of the Miocene coastal aquifer along the Red Sea-Gulf of Suez western margin (continental rift basin). The research findings reveal that: (1) The coastal Miocene aquifer consists of both clastic (sandstone, sand and gravels) and carbonate rocks (limestone and dolomite) with subsurface thickness ranges between 100 and 200 m. (2) Its groundwater shows contrast salinity values (expressed by total dissolved solids, TDS) between 2755 and 10,996 mg/l, due to the variation in recharge rates and the lithologic dissimilarity of the water bearing formations. (3) The environmental isotopes indicate that the Miocene groundwater has a mixed isotopic signature between modern meteoric (rainfall) and fossil waters. (4) The isotopic data of the Miocene aquifer and the enriched Gulf of Suez verifies that no seawater intrusions are affecting this aquifer with existing hydraulic barriers (clogged/sealed faults or impermeable massive blocks). (5) The hydrogeomorphological investigations, aeromagnetic and gravity data reveal an existence of two morphotectonic depressions (water collectors) which have paleo and recent recharge opportunities for the subsurface sedimentary layers (2–4 km thick). From the applied viewpoint, these two depressions have potential prospects for future groundwater exploration, which has significant impact on food security and land reclamation.

Discrepancy and estimates of groundwater recharge under different land use types on the Loess Plateau

Study regionThe Dongzhi tableland on the loess plateau, China. Study focusThis study investigates how various land use types on the Loess Plateau affect groundwater recharge using the chloride mass balance method (CMB). By integrating data from Cl–, NO3/Cl–, and stable isotopes (δ18O and δ2H), the research develops a new approach to estimate the average ion concentration rates in soil profiles. This methodology provides a nuanced understanding of how precipitation infiltration recharges groundwater under different land use scenarios and the impact of land use changes on these processes. New hydrological insights for the regionThe research findings highlight significant variations in groundwater recharge rates among different land uses. Grasslands show the highest recharge rate at 26 mm/yr, followed by forests at 23 mm/yr, while shrublands have the lowest at 5 mm/yr. Agricultural lands have moderate recharge rates ranging from 14 to 16 mm/yr. Transitioning from agricultural land to other land uses like shrublands and forests results in dramatic changes in recharge rates, with decreases and increases in recharge of 72% and 61%, respectively. These insights are crucial for developing strategic land-use planning to optimize groundwater recharge and enhance water security on the Loess Plateau. The study emphasizes the need for policies that balance hydrological science and land management to sustain both human livelihoods and ecological continuity.

Towards Sustainable Water Solutions: Investigating Groundwater Possibility in Dindori District of Madhya Pradesh, India

Groundwater is a crucial resource, as approximately 45% of irrigation and around 80% of domestic water needs in India are fulfilled by groundwater reservoirs. Therefore, it is essential to determine where the probability of groundwater availability is high and where it is low. In areas with low probability, there is a need for the rapid development of recharge structures. GIS and remote sensing technology is a crucial tool for obtaining information about availability of ground water potential as well as finding suitable site for recharge structures. The investigation will involve geological surveys to understand the hydrogeological characteristics of the region, including aquifer properties, recharge mechanisms, and groundwater quality. Additionally, environmental impact assessments will be conducted to evaluate the sustainability of groundwater extraction and its potential implications on the surrounding ecosystems. Furthermore, socio-economic analyses will explore the existing water usage patterns, community needs, and stakeholders' perspectives to develop inclusive and equitable groundwater management plans.
 "This study focuses on the Dindori district in Madhya Pradesh, India. There are different factors affecting groundwater recharge, including topography, slope, land use and land cover, drainage density, geology, soil distribution, rainfall, lineament, etc. Satellite images provide information about land use/land cover, geomorphology, and DEM delineate slope, drainage, and lineament. They are classified into different classes and assigned weights. ArcGIS software was used for data integration and weighted overlay analysis to create a groundwater potential map for the Dindori district. The groundwater potential map is categorized into five classes: 'Excellent' (0.01%), 'Good' (9.78%), 'Moderate' (70.04%), 'Poor' (19.97%), and 'Very Poor/Nil' (0.17%)."

Response of Evapotranspiration, Photosynthetic Characteristics and Yield of Soybeans to Groundwater Depth

To clarify the physiological mechanism of different groundwater depths affecting soybean evapotranspiration, photosynthetic characteristics and yield, a field experiment with four groundwater depth levels (1 m (D1), 2 m (D2), 3 m (D3) and 4 m (D4)) was conducted through the groundwater simulation system in 2021 and 2022. In this study, a quantitative analysis was conducted on the groundwater recharge and irrigation water demand and evapotranspiration (ET) of soybean fields with different treatments, and the effects of different treatments on soybean leaf area index (LAI), chlorophyll content index (SPAD), intercepted photosynthetic active radiation (IPAR), photosynthetic gas exchange parameters, dry matter accumulation (DMA) and yield were explored. The results showed the following: (1) Groundwater depth affected soybean ET and the source of ET. With the increase in groundwater depth, groundwater recharge and its contribution to ET gradually decreased, but the amount of irrigation required gradually increased, resulting in the ET as D1 > D4 > D2 > D3. (2) Soybean LAI, SPAD and IPAR were significantly affected by the different groundwater depths, of which the D1 treatment always maintained the maximum, followed by the D4 treatment, and the D3 treatment was the minimum. The photosynthetic gas exchange parameters under different treatments changed synergistically, showing significant differences in the flowering and podding stages, notably D1 > D4 > D2 > D3. Soybean DMA and yield first decreased and then increased with the increase in groundwater depth, and the average DMA and yield under the D1 treatment increased by 27.71%, 46.80% and 22.82% and 20.29%, 29.91% and 12.83% in the two years, respectively, compared to the D2, D3 and D4 treatments. (3) The structural equation model demonstrated that the groundwater depth indirectly affected the growth of soybean leaf area by affecting groundwater recharge, which in turn regulated soybean ET and photosynthetic capacity and ultimately affected DMA and yield. The above results showed that in the case of shallow groundwater depth (D1), the largest groundwater recharge promoted the growth of soybean leaf area and chlorophyll synthesis and increased the absorption and utilization of solar radiation. And it improved the leaf stomata conditions, accelerated the gas exchange between the plant and atmosphere, enhanced the photosynthetic production capacity and ET and achieved maximum DMA and yield. Soybean leaf growth and photosynthesis diminish with the increase in groundwater depth. In the case of deep groundwater depth (D4), the maximum irrigation improved the growth and photosynthetic performance of soybean leaves, which was favorable to ET, and ultimately led to increases in DMA and yield.

Limpopo National Park (Mozambico): groundwater assessment as a tool for a sustainable management of the area

This paper deals with updated results coming from hydrogeological studies carried on the framework of the SECOSUD Phase II, called “Conservation and equitable use of biological diversity in the SADC region (Southern African Development Community), a project supported by the Italian Ministry of Foreign Affairs in the SADC, whose focus area includes South Africa Development Countries. The main goal of the SECOSUD Phase II Project is the definition and implementation of scenarios for sustainable development, aimed at an equitable conservation of biodiversity resources and, as a consequence of this target, the hydrogeological characterization, with the groundwater recharge assessment, of this area and its buffer zone. Limpopo National Park is one of the jewels in the crown of Mozambique’s protected areas. As a matter of fact, sustaining the conservation of biodiversity, due to its complexity and multiple drivers, which stress it, is on first a matter of water environment assessment, as most ecosystems are highly dependent on the hydrological cycle and groundwater availability. After gathering regional and local geological data, which let us set up a detailed geological map of the area under study, pointing out the main outcropping geological units, with their main hydrogeological properties, the methodological approach adopted has been to assess the potential infiltration, applying the Inverse Hydrogeological Budget Technique, performed for the focus area. Because of the lack of meteorological data referred to Limpopo National Park, it has been applied a spatial distribution of precipitation measurements, collected in many gauge stations, located in the Kruger National Park during the last 54 years, which represent an interesting rainfall historical series. The target of the study has been to assess a trend of meteorological data with the aim of understanding how precipitations could affect groundwater recharge, and their influence on groundwater availability. The estimation of groundwater recharge is the tool for suggesting better water management in the area, aimed to preserve as much biodiversity as people living in the buffer zone.

The Assessment of the Groundwater Quality in the Coastal Aquifers of the Essaouira Basin, Southwestern Morocco, Using Hydrogeochemistry and Isotopic Signatures

Because of anthropogenic activity and seawater intrusion, coastal aquifers worldwide frequently face a threat to their water supply due to salinization. This paper investigates the assessment of the groundwater quality in coastal aquifers of the Hauturivien aquifer in the Essaouira basin. In this study, 56 groundwater samples collected from the Hauturivian aquifer across four campaigns in 2017, 2018, 2019, and 2020 were subjected to multivariate analyses involving principal component analysis (PCA) and cluster analysis (CA) using SPSS software. Among the three main water types, the mixed Ca-Mg-Cl classification was predominant in the investigated aquifer. In addition to the natural processes (such as the water–rock interaction, ion exchange, dissolution/precipitation dynamics, and evaporation) that govern groundwater quality, current land use practices have increased salinization in this poorly drained semi-arid area. Based on assessments using Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI), the water quality is suitable for human consumption, but its use for irrigation is limited to crops that can tolerate high salt levels. The stable isotopes (δ2H and δ18O) of groundwater demonstrated that local precipitation is the primary recharge source. Nonetheless, the evaporation process, influenced by various geological conditions, affects groundwater recharge, regardless of the topographical differences in the study area.

Identification and mapping of potential recharge in the Middle Seybouse sub-catchment of the Guelma region (North East of Algeria): contribution of remote sensing, multi-criteria analysis, ROC-Curve and GIS

Due to the rapid population increase in the Middle Seybouse sub-catchment area in North-East Algeria, the intense agricultural practices, and the industrial development, precious water resources proven to be significantly challenged in their sustainable exploitation both in terms of quantity and quality. The aim of this study is to identify the most suitable areas for groundwater recharge in the Middle Seybouse sub-catchment, over about 770.91 km², using remote sensing data and Geographical Information Systems (GIS). Six factors are recognized to positively affect groundwater recharge: rainfall, land cover, topography, drainage density, lineament density, and lithology. According to their level of involvement in the recharge process, these parameters have been reclassified and then evaluated using the multi-criteria analysis known as “Analytical Hierarchy Process” (AHP). A potential recharge map of the study area was produced showing that 60% of this area, located in the southern and central parts of the catchment, has a high to very high potential. ROC (receiver operating characteristic) curve is used to validate the resulting groundwater potential recharge map using the existing wells in the study area.

Assessment of Aquifer Recharge Potential Using Remote Sensing, GIS and the Analytical Hierarchy Process (AHP) Combined with Hydrochemical and Isotope Data (Tamassari Basin, Burkina Faso)

In the Tamassari basin, the agricultural population is highly dependent on groundwater resources for its socioeconomic development. However, the decrease in rainfall in the region since the late 1960s and the demographic pressure on the land are significantly affecting groundwater recharge. In order to exploit this groundwater sustainably, it is necessary to identify potential recharge areas for a better capitalisation of this resource. The objective of this study is to map the recharge potential of the existing aquifers making use of remote sensing and GIS techniques and to make a validation based on chloride and tritium contents in the borehole water. The processing carried out on the Landsat 5 and Landsat 8 images combined with a digital elevation model (ALOS PALSAR), highlight the lithological, linear and topographical characteristics of the study area. In addition, various supervised classification algorithms were used to produce the most accurate land use map. Field campaigns were conducted to validate the thematic maps resulting from the geospatial data processing and to collect water samples for hydrochemical (chloride) and isotopic analysis (tritium). The analytical hierarchy process (AHP) was used to derive recharge factors weights. The resulting recharge map shows a perfect agreement between the recharge classes derived from spatial modelling and the tritium isotope analyses. This was not the case with the chloride contents, which showed a dispersion over all the recharge areas.

Quantifying the City-Scale Impacts of Impervious Surfaces on Groundwater Recharge Potential: An Urban Application of WRF–Hydro

Decades of urbanization have created sprawling, complex, and vulnerable cities, half of which are located in water-scarce areas. With the looming effects of climate change, including increasing droughts and water shortages, there is an urgent need to better understand how urbanization impacts the water cycle at city scale. Impervious surfaces disrupt the natural flow of water, affecting groundwater recharge in water-scarce cities, such as Los Angeles, looking to harness local water resources. In the face of growing water demand, informing on opportunities to maximize potential groundwater recharge can help increase cities’ resilience. WRF–Hydro, a physics-based hydrological modeling system, capable of resolving atmospheric, land surface, and hydrological processes at city scale, is adapted to represent urban impervious surfaces. The modified model is used to assess the hydrological implications of historical urbanization. Pre- and post-urban scenarios are used to quantify the impacts of impervious surfaces on the local water budget. Our results show that urbanization in LA has vastly decreased the potential for groundwater recharge, with up to half of the water inflow being redirected from infiltration in highly urbanized watersheds, while doubling surface runoff’s share of the city’s water budget, from ~15% to 30%. This study not only sheds light on the role of imperviousness on groundwater recharge in water-scarce cities, but also offers a robust and transferable tool for the management of urban land and water resources.

Functional fluvial landforms of the Pantanal: Hydrologic trends and responses to climate changes

Large-scale fluvial landforms emerge from iterative processes that sculpt Earth's surface. Tectonics, climate variability and erosion are major recurrent processes reshaping fluvial landforms ending up in self-affine patterns. In the case of the Pantanal, the largest wetland in South America, its depositional tract can be subdivided as fluvial megafans, interfans and the main trunk system. Here we provide an outlook of their origins by means of self-affine landforms and on the feedback of climate changes over landform functionalities. Climate variability modulates the magnitude of interannual fluvial discharge and sediment load from highlands to plains, affects groundwater recharge, as well as the subsidence and generation of accommodation in the depositional tract through river avulsion. Scenarios are envisaged by analyzing long-term summer rainfall intensity and the number of dry days in autumn/winter over the Upper Paraguay River Basin, and annual flood peaks measured at fluvial gauge stations in the Paraguay River at Ladário (Brazil) and Asunción (Paraguay). The frequency distributions of the annual flood peaks are found unimodal for Asunción and bimodal for Ladário, which suggests an unknown water supply at Asunción, likely from Pilcomayo River and Pantanal's groundwater. The latter might play a delayed role on Pantanal's hydrologic functioning at 20–40 years timescales. Besides the Paraguay River flood peaks, summer rainfall intensity and the number of dry days in autumn/winter are quasi-periodic at interannual and decadal scales. Cross-correlations analyses indicate a long-range memory between river floods and rainfall intensity, and 15–20 years lag between river floods and the number of dry days in drought seasons. Trends analysis suggests that summer rainfall intensity and the number of dry days in autumn/winter have been consistently increasing by about 0.6 mm/day/decade and 1 day/decade, respectively. Therefore, magnifications of fluvial discharge and sediment load at wet seasons and water deficits at drought seasons are anticipated. Such a scenario indicates extreme dry cycles over all self-affine functional landforms, particularly on abandoned lobes relying exclusively on rainwater, whereas extremes of rainfall intensity at rivers headwaters may amplify the risks of large-scale avulsions at active lobes of the fluvial megafans. In contrast, active lobes of megafans, interfans and the main trunk river system emerge as hotpots for wildlife refuge and ecosystem services.

Glacial Melt in the Canadian Rockies and Potential Effects on Groundwater in the Plains Region

The prevailing concern in the Western Canadian Plains is that glaciers from the eastern Canadian Rocky Mountains (CRM) are losing mass, thus affecting groundwater recharge in the Plains. The generally accepted hypothesis is that those glaciers are the geological source of groundwater for aquifers located in the Plains. The aquifers located in this region, close to the eastern part of the Rockies, represent a major source of water for the local population. It is believed that aquifer recharge originates as infiltration from snowmelt and ice in the Front Ranges of the eastern Rockies. A growing concern relates to the significant glacier melt estimated from glacier mass balances, which indicate that glaciers and ice fields have experienced considerable mass losses over the last 15 years, between 1 and 5 km3 per year, thus reducing recharge. However, deep groundwater flow under melting glacier conditions in mountainous regions is poorly understood. In this study, three 2D numerical hydrogeological models are built in order to simulate the groundwater flow under the glaciers from the Main and Front Ranges of the CRM and the Plains in the province of Alberta, Canada. Numerical results and a sensitivity analysis indicate that up to three different regional groundwater-flow systems are present in the region. These systems reveal the time- and space-scales associated with the combination of a mountainous region, foothills, Plains, and deep geological conditions. Based on the current knowledge of the hydrogeology of the study area and numerical modelling results, it is highly unlikely that the melting of glaciers affects groundwater in the Plains in the immediate future. The contribution of glacier water in the eastern part of the Rockies is time-dependent with delayed groundwater flows of 1000s of years in the Front ranges, 1000s to 100,000s of years in the foothills and Foreland; and 100,000s to millions of years to the Plains, at the regional scale.

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

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

Quantifying Groundwater Resources for Municipal Water Use in a Data-Scarce Region

Groundwater is a major source of drinking water worldwide, often considered more reliable than surface water and more accessible. Nowadays, there is wide recognition by the scientific community that groundwater resources are under threat from overexploitation and pollution. Furthermore, frequent and prolonged drought periods due to climate change can seriously affect groundwater recharge. For an appropriate and sustainable management of water systems supplied by springs and/or groundwater withdrawn from aquifers through drilling wells or drainage galleries, the need arises to properly quantify groundwater resources availability, mainly at the monthly scale, as groundwater recharge is influenced by seasonality, especially in the Mediterranean areas. Such evaluation is particularly important for ungauged groundwater bodies. This is the case of the aquifer supplying the Santissima Aqueduct, the oldest water supply infrastructure of the city of Messina in Sicily (Southern Italy), whose groundwater flows are measured only occasionally through spring water sampling at the water abstraction plants. Moreover, these plants are barely maintained because they are difficult to reach. In this study, groundwater recharge assessment for the Santissima Aqueduct is carried out through a GIS-based inverse hydrogeological balance methodology. Although this approach was originally designed to assess aquifer recharge at the annual scale, wherever a model conceptualization of the groundwater system was hindered by the lack of data, in the present study some changes are proposed to adjust the model to the monthly scale. In particular, the procedure for evapotranspiration assessment is based on the Global Aridity Index within the Budyko framework. The application of the proposed methodology shows satisfactory results, suggesting that it can be successfully applied for groundwater resources estimation in a context where monthly information is relevant for water resources planning and management.

Impacts of Climate Change on Groundwater Availability and Spring Flows: Observations from the Highly Productive Medicine Lake Highlands/Fall River Springs Aquifer System

AbstractMedicine Lake Highlands/Fall River Springs Aquifer System, located in northeastern California, is home to some of the largest first‐order springs in the United States. This work assesses the likely effects of projected climate change on spring flow. Four anticipated climate futures (GFDL A2, GFDL B1, CCSM4 rcp 8.5, CNRM rcp 8.5) for California, which predict a range of conditions (generally warming and transitioning from snow to rain with variable amounts of total precipitation), are postulated to affect groundwater recharge primarily by changing evapotranspiration. The linkages between climate variables and spring flow are evaluated using a water balance model that represents the physics of evapotranspiration and recharge, the Basin Characterization Model. Three of the four climate scenarios (GFDL A2, GFDL B1, CCSM4 rcp 8.5) project that by the year 2100, groundwater recharge (and consequently decreased spring flow) will decrease by 27%, 21%, and 9%, respectively. The fourth scenario (CNRM rcp 8.5) showed an increase in recharge of 32% due to a significant increase in precipitation (27%). Evapotranspiration increases due to a shift in the type of precipitation and a longer growing season. While the likelihood of each scenario is outside the scope of this work, unless total precipitation increases dramatically in the future, increased temperatures and decreasing precipitation will likely result in reduced spring flows, along with warmer water temperatures in downstream habitats.

Climate change and groundwater resources availability in the Great Limpopo National Park (Mozambique): the current state of knowledge

This work outlines a comprehensive study of groundwater resources supply in Mozambique’s Great Limpopo National Park buffer zone in Southern Africa. To protect biological diversity and the water resources supply of dispersed communities of the buffer zone is a crucial problem to fix people in the region and, in the meantime, to boost the development of the Limpopo National Park. This work shows the current state of knowledge about this topic and try to point out some suggestions on technical solutions. Some previous studies concluded that two different main factors make a complex water supply in this area: (i) the rainwater distribution, it is hard to transform the rainwater into groundwater resources available for exploitation, and (ii) the common groundwater resources, rich in elements such as Boron (B), Mercury (Hg), Uranium (U), Zinc (Zn) and Lead (Pb). The occurrence of these elements is linked to the presence of groundwater with long residence times, unsafe for people’s health. The methodological approach adopted has been to assess the potential infiltration, applying the inverse hydrogeological budget technique, starting from the main outcropping geological units, in the study area. Due to the lack of meteorological data referred to Limpopo National Park, the gauge stations located in the Kruger National Park during the last 64 years have been, on the whole, considered. The target of the study has been to assess the trend of meteorological data and understand how precipitations could affect groundwater recharge and their availability. Without a strategy of biodiversity conservation and sustainable water resources management, they cannot be reached and guaranteed healthy conditions for local dispersed communities. A hydrogeoethical responsible approach is essential to protect biological diversity and hydrosocial cycle framework with integrative ecosystem services and nature-based solutions.

Hydraulic redistribution by deeply rooted grasses and its ecohydrologic implications in the southern Great Plains of North America

AbstractPerennial bioenergy crops with deep (>1 m) rooting systems, such as switchgrass (Panicum virgatum L.), are hypothesized to increase carbon storage in deep soil. Deeply rooted plants may also affect soil hydrology by accessing deep soil water for transpiration, which can affect soil water content and infiltration in deep soil layers, thereby affecting groundwater recharge. Using stable H and O isotope (δ2H and δ18O) and 3H values, we studied the soil water conditions at 20–30 cm intervals to depths of 2.4–3.6 m in paired fields of switchgrass and shallow rooted crops at three sites in the southern Great Plains of North America. We found that soil under switchgrass had consistently higher soil water content than nearby soil under shallow‐rooted annual crops by a margin of 15%–100%. Soil water content and isotopic depth profiles indicated that hydraulic redistribution of deep soil water by switchgrass roots explained these observed soil water differences. To our knowledge, these are the first observations of hydraulic redistribution in deeply rooted grasses, and complement earlier observations of dynamic soil water fluxes under shallow‐rooted grasses. Hydraulic redistribution by switchgrass may be a strategy for drought avoidance, wherein the plant may actively prevent water limitation. This raises the possibility that deeply rooted grasses may be used to passively subsidize soil water to more shallow‐rooted species in inter‐cropping arrangements.

Land‐use comparison of depression‐focussed groundwater recharge in the Canadian prairies

AbstractIn the cold semiarid Canadian prairies, groundwater recharge is focussed under numerous topographic depressions, in which snowmelt runoff converges. Agricultural land uses on the uplands surrounding the depressions affect snow accumulation, snowmelt infiltration, evapotranspiration (ET) and soil moisture dynamics, thereby influencing snowmelt runoff and depression‐focussed recharge. The objective of this study is to compare the differences in hydrological processes under two common land uses in the Canadian prairies, namely grazed grass and annual crop, and examine how they affect groundwater recharge. A short‐term (3 years) paired catchment study was used for detailed observation of hydrological processes in two depressions, supplemented by a longer‐term (17 years) data set covering a larger scale to quantify the differences in snowmelt runoff between the two land uses. Compared to the grazed grassland, the cropland had a shorter and more intense period of ET, and root water uptake restricted to the shallower (top 0–80 cm) soil zone. The amount of snowmelt runoff was greater in the grazed grassland primarily due to a higher amount of snow accumulation, which was dictated by differences in topography. This finding was contrary to previous studies in the Canadian prairies that indicated substantially smaller snowmelt runoff in ungrazed grassland, but was consistent with the larger‐scale remote sensing results, which showed only a marginal difference between grazed grasslands and croplands. Groundwater recharge rates were estimated using the chloride mass balance method for the present condition using “modern” pore water containing tritium. The rates were similar between the grazed grassland and croplands, implying similarity in snowmelt runoff characteristics. These results suggest that groundwater recharge will continue to be focussed under depressions in the future, though the amount and seasonality of recharge may be influenced by warmer winters.

Future changes in snowpack will impact seasonal runoff and low flows in Czechia

Study RegionCentral Europe, Czechia. Study FocusMountains are referred to as “water towers” because they substantially affect the hydrology of downstream areas. However, snow storages will decrease in the future due to the increase in air temperature which will affect streamflow regime. Main objectives of this study were 1) to simulate the future changes in snow for a large set of mountain catchments in Czechia, reflecting a wide range of climate projections and 2) to analyse how the snow changes will affect groundwater recharge, streamflow seasonality and low flows in the future. New Hydrological InsightsThe future hydrological projections showed a decrease in annual maximum SWE by 30 %–70 % in the study area until the end of the 21st century. Additionally, snowmelt was found to occur on average 3–4 weeks earlier. The results showed the large variability between individual climate chains and indicated that the increase in air temperature causing the decrease in snowfall might be partly compensated by the increase in winter precipitation. Changes in snowpack will cause the highest streamflow during melting season to occur one month earlier, in addition to lower spring runoff volumes due to lower snowmelt inputs. The future climate projections leading to overall dry conditions in summer are associated with both the lowest summer precipitation and seasonal snowpack. The expected lower snow storages might therefore contribute to more extreme low flow periods.

Modeling the impact of spatiotemporal vegetation dynamics on groundwater recharge

Climate change affects the growth of vegetation and its physiological states such as leaf area index (LAI), which in turn can affect groundwater recharge because of changes in evapotranspiration (ET). Presently, most recharge modeling studies over-simplify transient vegetation conditions and the potential corresponding impact on recharge by using climatological values of vegetation parameters such as LAI. Our study uses the Community Land Model (CLMv4.5) to investigate the sensitivity of recharge to interannual varying vegetation in Minnesota (USA) across different climate, hydrogeology, and ecoregions at a 25 km spatial resolution and for the period of 2000–2015. The Ensemble Kalman Filter (EnKF) was used to calibrate soil and runoff parameters to statewide water table depth observations. Results of the study indicate that although year-to-year varying vegetation does not affect long-term climatological recharge estimates, it can drive disproportionately large variability in annual and seasonal recharge. Comparing simulations with dynamic and climatological vegetation inputs, the average magnitude difference (root mean square difference, RMSD) for recharge was 21.1% in response to only a 4% difference in LAI inputs. Regression analysis revealed that the combination of local hydrogeology and vegetation-type affects the magnitude of recharge response to LAI and ET changes. We also found cross-ecoregion dominance of temperature rather than precipitation controlling LAI anomalies and resulting recharge variability, with springtime temperature being the primary factor because of its impact on leaf-out conditions. Drier western Minnesota showed higher relative LAI differences as well as higher spring time and relative annual recharge compared to the wetter eastern part of the state, indicating higher vulnerability of the water-limited region to changing vegetation and climatic conditions. Our study shows that models can underestimate or overestimate annual and seasonal recharge if vegetation dynamics are neglected, demonstrating the need to incorporate transient vegetation conditions when assessing the impact of future climate change on recharge.