Increased Groundwater Recharge Research Articles

Variations in water-balance components and carbon stocks in poplar plantations with differing water inputs over a whole rotation: implications for sustainable forest management under climate change

Understanding the long-term variations of stand water balance and carbon stocks under different water inputs is crucial for sustainable forest management under climate change. However, due to the lack of in-situ data, how forest plantations respond to variation in water inputs during stand development remains poorly understood. We varied water inputs with distinct irrigation amounts and measured the water-balance components, carbon stock growth, and water productivity during a whole rotation (2015–2019) in poplar plantations. Furthermore, in 2020, soil water contents in our stand and an adjacent 37-year-old poplar plantation were measured. Under rainfed conditions, soil water storage of different layers decreased greatly year by year, especially at the 2–3 m depth, such that transpiration was curtailed in 2019, a dry year. By 2019, the 0–2 m depth layer became periodically dried, and the 2–3 m was persistently dried, which was further confirmed by observations in 2020. Additionally, serious soil desiccation occurred throughout the 0–6 m soil depth in the 37-year-old poplar stand. Increasing the water inputs avoided stand water stress and decreased the drying rate of the deep soil. Furthermore, the highest water inputs treatment brought great increases in groundwater recharge, carbon stock growth, and water productivity. This treatment also led to 67% higher soil water storage in the 0–1 m soil layer and 23% higher soil water storage in the 1–6 m layer by the end of 2019, as compared to the rainfed treatment. However, these advantages were small or disappeared if the water inputs were insufficient. Our findings will be helpful to predict water relations and facilitate sustainable forest management under climate change in water-limited regions.

THE USE OF GIS FOR MANAGED AQUIFER RECHARGE (MAR) SITE SELECTION IN WADI ARABA - JORDAN

Ponte Academic JournalJul 2022, Volume 78, Issue 7 THE USE OF GIS FOR MANAGED AQUIFER RECHARGE (MAR) SITE SELECTION IN WADI ARABA - JORDANAuthor(s): Ala' Hamed Alelaimat ,Ismail Yusoff, Tham Fatt Ng, Yahya A Majali, Mohd Khairul Nizar ShamsuddinJ. Ponte - Jul 2022 - Volume 78 - Issue 7 doi: 10.21506/j.ponte.2022.7.8 Abstract:Jordan is considered as one of the ten most waterscarce countries in the world, but the country facing challenges in its water sector, Groundwater is the most important source of water in Jordan, it provides more than half of the total water demand, Some of Jordan groundwater resources are presently exploited at maximum capacity and in some cases more than safe yield. To meet this challenge, we should search for practical solutions that increase groundwater recharge, naturally or artificially. This study aims to select suitable sites for Managed Aquifer Recharge (MAR) through GIS techniques, the selected criteria choosing based on Rainfall, Slope, Geological formations, Land Use, Soil texture and Depth to water table, and assigned weightages and ranks, these layers have been integrated into GIS software for generating MAR suitability map of Wadi Araba. The area falls into five categories of (MAR) potential zones i.e., very good, good, moderate, low, and very low depending on the likelihood of (MAR) suitable locations. Based on this study, it is found that 16.7% with an area of 1473.7 km2 and 30.15% with 2649.5 km2 area are under the very good and good category of (MAR) suitability respectively. An area of 1779.3 km2 represents 20.24% is found under the moderate category whereas 1944.24 km2 and 890.94 km2 equals 32.82% of Wadi Araba area falls under the low and very low category of (MAR) suitability respectively. Download full text:Check if you have access through your login credentials or your institution Username Password

Ensuring the Long-Term Provision of Heathland Ecosystem Services—The Importance of a Functional Perspective in Management Decision Frameworks

The ecosystem services framework can be used as a way of balancing economic, ecological and societal drivers in land management decision-making processes. As heathland management is typically linked directly to services, the aim of this study was to quantify trade-offs related to the effects of five common heathland management measures (grazing, mowing, burning, choppering, and sod-cutting) using quantitative data from empirical studies within a northwestern heathland in Germany. Besides important services (groundwater recharge and quality, carbon stocks and appreciation by the general public) we included ecosystem functions (balances of nitrogen, phosphorus and major cations) and the net cost of management implementation as trade-off components. We found that all management practices have advantages and disadvantages leading to unavoidable trade-offs. The effect of a management practice on the trade-off components was often closely related to the amount of biomass and/or soil removed during a management cycle (Rannual). Choppering and sod-cutting (large Rannual by involving soil removal) were very good at maintaining a low N system whilst concurrently increasing groundwater recharge, albeit at the cost of all other components considered. If the aim is to preserve heathlands and their associated ecosystem services in the long-term this trade-off is inevitable, as currently only these high-intensity measures are capable of removing enough nitrogen from the system to prevent the transition to non-heather dominated habitat types. Our study, therefore, shows that in order to maintain structural integrity and thereby the service potential a habitat provides, management decision frameworks may need to prioritize ecosystem functioning over ecosystem services. Burning and mowing (low Rannual) were best at retaining phosphorus, cations and carbon and had the lowest costs. Grazing (intermediate Rannual) provided the highest relative benefit in terms of groundwater quality and appreciation. Together these results can help identify management combinations in both space and time, which will be more beneficial for functions and services than management practices considered in isolation. Furthermore, our study assists in recognizing key areas of action for the development of novel management practices and can help raise awareness of the diversity of rare species and potential benefits to people that protected cultural landscapes provide.

Quantifying the impact of urban runoff injection on groundwater Enhancement in a semi-arid environment using SWMM and MOFLOW Model

<p>In the urban area, surface runoff can be utilized effectively to improve groundwater table through rainwater harvesting. The main aims of this study were to:1) investigate the potential of the surface runoff to inject into Urmia aquifer and increase groundwater recharge of this aquifer using SWMM - MOFLOW Model, 2) to investigate the quality of the urban runoff for aquifer recharge, and 3) to investigate the feasibility and effeteness of the artificial recharge via injection wells in a semi-arid area. Urmia city with an area of 930 Km2 is located at the West of the Urmia Lake in the North-West of Iran. The study aquifer has a negative groundwater budget, while some of the sub basin in the study watershed is prone to flood in the falling season. In this study, based on the location of surcharged channels, the quantity of rechargeable surface runoff to inject into the aquifer was estimated via SWMM model. Calibrated MODFLOW model was applied to predict the potential effects of the injectable water runoff on the groundwater surface. Estimated runoff by SWMM model was used as the input of the MODFLOW model. The quantity of the heavy metals (Fe2+, Zn2+, Mn2+, Pb and Cu2+) TDS and pH were measured to control runoff quality. According to the results, 1.12 million cubic meters (MCM) per year of runoff can be injected to the aquifer via 9 designed injection wells. This amount is equivalent to the annual loss of the aquifer (about 20 centimeters per year) that can ensure the stability of the aquifer in the injection area.</p>

Integrating magnetic susceptibility, hydrogeochemical, and isotopic data to assess the seawater invasion in coastal aquifers of Digha, West Bengal, India.

Seawater intrusion in coastal aquifers is a major concern due to geogenic and anthropogenic activities leading to declining groundwater quality. The present study focuses on deciphering the sea water intruded zones and its extent in the Quaternary alluvial aquifer system in the coastal belt of Digha, West Bengal, India. In this study, 36 groundwater samples were collected during pre-monsoon (2020). Subsequently, an integrated approach of hydrogeological, hydrogeochemistry, bulk magnetic susceptibility, isotopic, multivariate statistical, and geochemical modeling is adopted. Spatial distribution maps of hydrological parameters (salinity, conductivity, TDS) and major ion concentration (Na+, K+, Ca2+, Mg2+, Cl-, SO42-, F-, and Br-) suggest that the northern, south-west, and eastern parts of the study area are largely affected by saltwater intrusion and are corroborated with seawater mixing index (SMI). Based on sodium adsorption ratio (SAR), sodium percentage (Na%), and Permeability index (PI) distribution maps, the same locations are identified under critical condition for the suitability of groundwater for irrigation. The order of concentration of cations and anions in the water samples are Na+ > Ca2+ > Mg2+ > K+ and HCO3- > SO4- > Cl- > Br- > F- respectively. Piper diagram shows three principal hydrochemical water types with water composition changes from fresh (86%) to saline water mix (14%). The hydrochemical facies evolution diagram depicts 81% of water samples are in the freshening phase, and 19% are in the intrusion phase. The various bivariate plots revealed that ion exchange, reverse ion exchange, silicate weathering, seawater mixing, and anthropogenic inputs are the governing factors that control groundwater evolution. R-mode factor analysis, principal component analysis (PCA), and agglomerative hierarchical cluster (AHC) also indicate the influence on groundwater from seawater mixing and/or seawater intrusion. The superlativeness of bulk magnetic susceptibility (χ) analysis of water samples in delineating seawater intruded zones is elaborated. Saturation index (SI) shows that groundwater is saturated (> 0) with calcite, dolomite, and aragonite, plausibly due to seawater ingression. Stable isotopic analysis of δ2H (- 53.979 to - 16.9578‰) and δ18O (- 7.00183 to - 1.37 ‰) suggests precipitation recharge/paleo-water at some locations and evaporation enrichment of groundwater. It is recommended to increase groundwater recharge, reduce groundwater extraction at critically affected locations, and have regular monitoring and management to control seawater intrusion.

The impact of geomorphology on groundwater recharge in a semi-arid mountainous area

The impact of geomorphological structures on rainwater infiltration and groundwater recharge in the mountainous terrain of a semi-arid region was studied in the southern part of the Judean Western Mountain Aquifer (WMA) in Israel and the Palestinian Authority. The study was conducted in two main typical geomorphological landscape units which include exposed rock outcrops on the hillslope, and human-made agricultural soil terraces in a first-order stream channel. We measured rainwater infiltration through the unsaturated zone in the two geomorphological setups using vadose zone monitoring systems (VMS), that enabled continuous tracking of rainwater percolation and tracer transport through the unsaturated zone with respect to the rain patterns.The results from three years of continuous monitoring of water percolation through the unsaturated zone indicated a quick and intense percolation pattern in the rocky terrain compared to that measured in the deep soil of the terrace. The precipitation patterns, as reflected from the rain distribution and intensities, appeared to have a significant impact on deep water percolation and ultimately on groundwater recharge. In the rocky terrain, rain events of high intensity, even during drought years of low cumulative precipitation, resulted in deep water infiltration, which ultimately turned into groundwater recharge. On the other hand, infiltration through deep soils, as prevailed in terraces, valleys, and high plains, was found to be very limited, subjected to intense evaporation and ultimately result by reduced groundwater recharge. It appears that the value of annual cumulative precipitation is of a lower importance to groundwater recharge while high rain intensity is the most dominant factor responsible for deep water infiltration.Tracer migration patterns in the unsaturated zone revealed that precipitation on the rock outcrops promotes the generation of local runoff that rapidly drains into the subsurface through infiltration hot spots. It has been observed that these hot spots are often marked by prickly burnet shrubs (Sarcopoterium spinosum), which thrive year-round on the water abundancy in the soil pockets beneath the impervious rock on land surface. An important outcome of this study is the suggested strong coupling between geomorphological features and groundwater recharge. Application of variable infiltration functions to the different geomorphological characteristics of each terrain may improve groundwater recharge models. Climate changes in recent years, expected to lead to decreased annual precipitations and increased evaporation in parallel with an increase in rainfall intensities in the semi-arid mountainous areas of the eastern Mediterranean. Yet according to our results, the expected increase in rain intensity may actually result in an increase in groundwater recharge.

Building resilient agricultural system through groundwater management interventions in degraded landscapes of Bundelkhand region, Central India

Study regionThe study was carried out at community scale watershed in one of the fragile ecologies of Central India. Study focusThis paper quantifies the impact of rainwater management (RWM) interventions on major water balance components, irrigation use, crop intensification and energy consumption and their interrelationships. New hydrological insights for the regionRWM interventions harvested additional 35 mm of surface runoff in various masonry structures and facilitated groundwater recharge from 720 mm rainfall received. The net groundwater recharge during monsoon season was estimated 75−80 mm; out of this, 25 % (15−20 mm) was used in kharif and 75 % (50−60 mm) in rabi season. Groundwater recharge largely took place in wet and normal years due to RWM interventions, which supported for meeting freshwater demand in recurring dry years. Increased groundwater recharge helped to enhance cropping intensity from 120 % to 180 % by converting significant fallow lands into productive cultivation. The time required to refill dug wells decreased by 50 % with every one meter increment in hydraulic head. Therefore, well recovery period reduced minimum by 50 % after the project interventions. The study shows a huge untapped potential for sustainable crop intensification by adopting science-based natural resource management approach in fragile eco regions of the semi-arid tropics.

Midchannel islands in lowland river corridors and their impacts on flow structure and morphology:A numerical based conceptual analysis

Midchannel islands (MCIs) are influential geomorphic units in regulating morphological and ecological dynamics in sand-dominated rivers. The primary objectives of the study were to understand a) the relationship between morphometric characteristics of the basin and the occurrence location of the MCIs, b) the role of MCIs on the hydraulic gradient and the other hydraulic variables along the reach, and c) the influence of island growth process on hydrodynamics in the wake and contraction regions. Spatial distributions of MCIs depending on the morphometric features of the three characteristic basins were considered. While the basin-scale analysis was conducted using GIS-based data, the reach and individual scale analyses were performed based on a Reynolds-averaged Navier–Stokes (RANS) model. Uniform circular cylinder and island geometries were exposed to identical flow conditions. The expansion of these island geometries was mimicked both in rectangular and trapezoidal cross-sections. The variation of water surface slope and bottom shear stress variables, which greatly trigger the intensive bilateral interaction between hydrological-morphological-ecological elements in river corridors, depending on the growth of the island, was determined. The role of imposed island geometry on the secondary flow structure within the downstream cross-section of the island and streamwise velocity fluctuations in contraction regions were analyzed. The basin-scale analysis showed that with decreasing basin slopes, the family of islands emerged at a longer distance to the basin outlet. It was also seen that MCIs location is closer to the basin outlet forbasins with a lower aspect ratio. Besides, asymmetrical large-scale counter-rotating streamwise vortices were detected behind the MCIs based on numerical simulations. GIS-based data showed that this coherent flow structure brought about channel adjustments in downstream of the island. In addition to morphological consequences, it was hypothesized that this alteration in the flow structure due to MCI has potential impacts on riverine ecology. These impacts are increase in groundwater recharge, vertical exchange of surface–subsurface water, local heterogeneity in sediment characteristics (i.e., convenient fish spawning areas), and enlargement in the hyporheic zone.

Quantifying the effects of urban green space on water partitioning and ages using an isotope-based ecohydrological model

Abstract. The acceleration of urbanization requires sustainable, adaptive management strategies for land and water use in cities. Although the effects of buildings and sealed surfaces on urban runoff generation and local climate are well known, much less is known about the role of water partitioning in urban green spaces. In particular, little is quantitatively known about how different vegetation types of urban green spaces (lawns, parks, woodland, etc.) regulate partitioning of precipitation into evaporation, transpiration and groundwater recharge and how this partitioning is affected by sealed surfaces. Here, we integrated field observations with advanced, isotope-based ecohydrological modelling at a plot-scale site in Berlin, Germany. Soil moisture and sap flow, together with stable isotopes in precipitation, soil water and groundwater recharge, were measured over the course of one growing season under three generic types of urban green space: trees, shrub and grass. Additionally, an eddy flux tower at the site continuously collected hydroclimate data. These data have been used as input and for calibration of the process-based ecohydrological model EcH2O-iso. The model tracks stable isotope ratios and water ages in various stores (e.g. soils and groundwater) and fluxes (evaporation, transpiration and recharge). Green water fluxes in evapotranspiration increased in the order shrub (381±1mm)<grass(434±21mm)<trees(489±30 mm), mainly driven by higher interception and transpiration. Similarly, ages of stored water and fluxes were generally older under trees than shrub or grass. The model also showed how the interface between sealed surfaces and green space creates edge effects in the form of “infiltration hotspots”. These can both enhance evapotranspiration and increase groundwater recharge. For example, in our model, transpiration from trees increased by ∼ 50 % when run-on from an adjacent sealed surface was present and led to groundwater recharge even during the growing season, which was not the case under trees without run-on. The results form an important basis for future upscaling studies by showing that vegetation management needs to be considered within sustainable water and land use planning in urban areas to build resilience in cities to climatic and other environmental change.

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

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

Evaluation of Climate Change Impact on Groundwater Recharge in Groundwater Regions in Taiwan

Climate change can directly or indirectly influence groundwater resources. The mechanisms of this influence are complex and not easily quantified. Understanding the effect of climate change on groundwater systems can help governments adopt suitable strategies for water resources. The baseflow concept can be used to relate climate conditions to groundwater systems for assessing the climate change impact on groundwater resources. This study applies the stable baseflow concept to the estimation of the groundwater recharge in ten groundwater regions in Taiwan, under historical and climate scenario conditions. The recharge rates at the main river gauge stations in the groundwater regions were assessed using historical data. Regression equations between rainfall and groundwater recharge quantities were developed for the ten groundwater regions. The assessment results can be used for recharge evaluation in Taiwan. The climate change estimation results show that climate change would increase groundwater recharge by 32.6% or decrease it by 28.9% on average under the climate scenarios, with respect to the baseline quantity in Taiwan. The impact of climate change on groundwater systems may be positive. This study proposes a method for assessing the impact of climate change on groundwater systems. The assessment results provide important information for strategy development in groundwater resources management.

Stormwater harvesting in ephemeral streams: how to bypass clogging and unsaturated layers

To cope with water scarcity in drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration. These stormwater harvesting systems are often accompanied by high evaporation rates and hygiene problems. This is commonly a consequence of low infiltration rates, which are caused by clogging layers that form on top of the soil profile and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using analytical equations, numerical models, and sensitivity analyses. Dams built in the channel of ephemeral streams (wadis) are selected as a study case to construct the numerical simulations. The modelling demonstrated that vadose-zone wells and infiltration trenches contribute to effective bypassing of the clogging layer. By implementing these solutions, recharge begins 2250–8100% faster than via infiltration from the bed surface of the wadi reservoir. The sensitivity analysis showed that the recharge rates are especially responsive to well length and trench depth. In terms of recharge quantity, the well had the best performance; it can infiltrate up to 1642% more water than the reservoir, and between 336 and 825% more than the trench. Moreover, the well can yield the highest cumulative recharge per dollar and high recharge rates when there are limitations to the available area. The methods investigated here significantly increased recharge rates, providing practical solutions to enhance aquifer water storage in drylands.

Impact of Rainwater Harvesting on Hydrological Processes in a Fragile Watershed of South Asia.

Agricultural water management (AWM) interventions play an important role in ensuring sustainable food production and mitigating climate risks. This study was carried out in a watershed located in a low rainfall (400-600 mm) region of western India. The Soil and Water Assessment Tool model was calibrated using surface runoff, soil loss, and reservoir storage levels, between the year 2000 and 2006. The investigation indicated that the various AWM interventions increased groundwater recharge from 30 mm/year to 80 mm/year and reduced surface runoff from 250 mm/year to 100 mm/year. The intervention structures were refilled two to three times during the monsoon season depending on rainfall intensity and duration. The interventions have the advantage of building a resilient system by enhancing groundwater availability even in dry years, stimulating crop intensification and protecting the landscape from severe erosion. The results indicate that soil erosion has been reduced by more than 75% compared to the nonintervention situation. Moreover, the AWM interventions led to the cultivation of 100-150 ha of fallow land with high-value crops (horticulture, vegetables, and fodder). Household income increased by several folds compared to the nonintervention situation. The study showed about 50% reduction in downstream water availability, which could be a major concern. However, there are a number of ecosystem trade-offs such as improved base flow to the stream and reduction in soil loss that should be considered. The study is of great importance to stakeholders to decide on the optimal design for AWM interventions to achieve sustainable development goals.

Regional groundwater flow and karst evolution\u2013theoretical approach and example from Switzerland

In regional scale aquifers in the Rhine Valley and Tabular Jura east of Basel (Switzerland), the groundwater circulation was investigated using regional-scale geological and hydraulic 3D models. The main aquifers in the area comprise the Quaternary aquifer of unconsolidated gravel deposits along the River Rhine and its tributaries, as well as the regional scale karst aquifer within the Upper Muschelkalk. Land subsidence, a process likely associated with salt solution mining, indicates further subordinate groundwater bearing segments and complex groundwater interactions along fault zones. In the aquifer systems we investigated, regional-scale groundwater circulation was simulated and visualized in relation to the geological settings. Lithostratigraphic units and fault structures were parameterized and analyzed, including the sensitivity of hydraulic properties and boundaries. Scenario calculations were used to investigate the sensitivity that the aquifer systems had to hydraulic parameter changes during Quaternary aggradation and degradation in the main valley. Those calculations were also done for base-level changes in the Rivers Rhine and Birs. For this purpose, this study considered probable historic base-levels before river regulation occurred, and before river dams and power plants were constructed. We also focused on scenarios considering increased groundwater recharge rates, e.g. due to exceptional long-lasting precipitation, or heavy rainfall events in the catchment area. Our results indicate that increased groundwater recharge rates in the catchment areas during such events (or periods) are associated with orders of magnitude increases of regional inflow into the Upper Muschelkalk karst aquifer. Furthermore, the groundwater fluctuations and groundwater saturated regions within the karst aquifer shift to places where high densities of sinkholes are documented. When the surface water base-levels adapt to probable historic levels, it leads to increased hydraulic gradients (i.e. local lowering of the groundwater level by up to 7 m). Those increased gradients are associated with increased groundwater flow within some aquifer regions that are particularly prone to karst development.

Regional-Scale Model Analysis of Climate Changes Impact on the Water Budget of the Critical Zone and Groundwater Recharge in the European Part of Russia

Groundwater recharge by precipitation is the main source of groundwater resources, which are widely used in the European part of Russia (ER). The main goal of the presented studies is to analyze the effect of observed climate changes on the processes of groundwater recharge. For this purpose analysis of long-term meteorological data as well as water budget and groundwater recharge simulation were used. First, meteorological data of 22 weather stations, located from south (Lat 46°) to north (Lat 66°) of ER for historical (1965–1988) and modern (1989–2018) periods were compared to investigate the observed latitudinal changes in annual and seasonal averages of precipitation, wind speed, air temperature, and humidity. Second, water budget in critical zone was simulated, using codes SURFBAL and HYDRUS-1D. SURFBAL generates upper boundary conditions for unsaturated flow modelling with HYDRUS-1D, taking into account snow accumulation and melting as well as topsoil freezing, which are important processes that affect runoff generation and the infiltration of meltwater. Water budget and groundwater recharge simulations based on long-term meteorological data and soil and vegetation parameters, typical for the investigated region. The simulation results for the historical and modern periods were compared to find out the impact of climate change on the average annual and seasonal averages of surface runoff, evapotranspiration, and groundwater recharge, as well as to assess latitudinal differences in water budget changes. The results of the simulation showed, that despite a significant increase in air temperature, groundwater recharge in the southern regions did not change, but even increased up to 50–60 mm/year in the central and northern regions of ER. There are two main reasons for this. First, the observed increase in air temperature is compensated by a decrease in wind speed, so there was no significant increase in evapotranspiration in the modern period. Also, the observed increase in air temperature and precipitation in winter is the main reason for the increase in groundwater recharge, since these climate changes lead to an increase in water infiltration into the soil in the cold period, when there is no evapotranspiration.

Impacts of afforestation on groundwater resource: a case study for Upper Yazoo River watershed, Mississippi, USA

ABSTRACT Groundwater resource overdraft is a serious water resource concern worldwide. Although afforestation has been recognized as conserving water resources, improving water quality and mitigating river flood, the role it plays with groundwater resources is not fully investigated. Here we applied the US Geological Survey’s Mississippi Embayment Regional Aquifer Study (MERAS) model to estimate impacts of afforestation in croplands on groundwater resource availability in the Upper Yazoo River Watershed (a humid subtropical climate), Mississippi, USA. Simulations showed that the average groundwater level had declined 1.2 m in the croplands over a 20-year period from 1987 to 2007, whereas the average groundwater level had declined only 0.13 m after afforestation for the same simulation period and occurred mainly due to no groundwater pumping and a slight increase in groundwater recharge. Our study implies that afforestation on low-productive croplands in a humid subtropical region could be an alternative to mitigate groundwater depletion.

Effect of various combinations of aperture diameter and pattern on concrete paver block

In the heavy Rainfall areas water – logging on roads is the main cause for the early damage of roads, which requires frequent maintenance. In the permeable concrete block pavement (PCBP), through joints water is percolated with that reducing storm water runoff, urban heat island effects, and increasing groundwater recharge. To increase the rate of infiltration in PCBPs, concrete paver block (CPB) with an aperture was developed. To study the effect of aperture, an experimental program was conducted on CPBs with different combinations of aperture diameter and pattern, by keeping aperture area as constant. These blocks were tested for compressive strength, split tensile strength and water absorption. In CPBs, for different combinations of aperture diameter and pattern, there was no significant change in compressive strength and water absorption values. Split tensile strength of CPBs was impacted adversely with increase in the number of apertures, to improve this property appropriate aperture pattern should be adopted.

Climate change effects on groundwater recharge and temperatures in Swiss alluvial aquifers

Climate change will have both quantitative and qualitative effects on groundwater resources. These impacts differ for aquifers in solid and unconsolidated rock, in urban or rural locations, and in the principal processes of groundwater recharge.Having knowledge about the intrinsic key parameters (aquifer geometries, storage properties, groundwater renewal rates, residence times, etc.), the principal groundwater recharge processes, and the temperature imprinting makes it possible to compare and forecast the sensitivity of individual aquifers to climate change.The sensitivity of future groundwater temperature development for selected climate projections was qualitatively investigated for representative Swiss unconsolidated rock groundwater resources in the Central Plateau as well as the Jura and Alpine region.For non-urban and rural areas, climate change is expected to have a strong overall impact on groundwater temperatures. In urban areas, however, direct anthropogenic influences are likely to dominate. Increased thermal subsurface use and waste heat from underground structures, as well as adaptation strategies to mitigate global warming, increase groundwater temperatures. Likewise, measurements for the city of Basel show that groundwater temperatures increased by an average of 3.0 ± 0.7 °C in the period from 1993 to 2016, and that they can exceed 18 °C, especially in densely urbanized areas. Similarly, regarding shallow aquifers with low groundwater saturated zone thicknesses, such as in Davos (Canton Grisons), groundwater temperatures will strongly be influenced by changes in groundwater recharge regimes. In contrast, groundwater temperature changes within deep aquifers with large groundwater saturated zone thicknesses, such as in Biel/Bienne (Canton Bern), or in some cases in aquifers with large distances from the land surface to the groundwater table and extended unsaturated zones, such as in Winterthur (Canton Zurich), are strongly attenuated and can only be expected over long time periods.In the context of the presented research we hypothesized that quantitative groundwater recharge and the associated temperature imprinting of aquifers is primarily determined by infiltrating surface waters (i.e. “river-fed aquifers”). We show that seasonal shifts in groundwater recharge processes could be an important factor affecting future groundwater temperatures. Moreover, the interaction with surface waters and increased groundwater recharge during high runoff periods are likely to strongly influence groundwater temperatures. Accordingly, for the “business as usual” climate change scenario and for the end of the century, a shift in precipitation and river flood events from summer to winter months could be accompanied by an increase in groundwater recharge in comparatively cool seasons, which would be accompanied by a tendency to “cool down” groundwater resources.

Field investigation of the groundwater contribution to baseflow in an urban stream from a Quaternary aquifer with a leaky base

AbstractGroundwater contributions to baseflow in Minnehaha Creek, a creek located in a highly developed watershed in the Minneapolis‐St. Paul metropolitan area, from the watershed's Quaternary aquifer were quantified as part of an effort to manage low flow conditions in the creek. Considerable uncertainty exists with any single method used to quantify groundwater contributions to baseflow; therefore, a “weight of evidence” approach in which methods spanning multiple spatial scales was utilized. Analyses conducted at the watershed‐scale (streamflow separation and stable isotope analyses) were corroborated with site‐scale measurements (piezometer, seepage meter, and streambed temperature profiles) over a multi‐year period to understand processes and conditions controlling connectivity between the stream, its shallow aquifer system and other flow sources. In the case of Minnehaha Creek, groundwater discharge was found to range from 6.2 to 23 mm year−1, which represented only 5 to 11% of annual streamflow during the study period. From the weight of evidence, it is conjectured that regional‐scale hydrogeological conditions control groundwater discharge in Minnehaha Creek. Implications of these results with regard to possible augmentation of baseflow by increasing groundwater recharge with infiltration of stormwater are discussed.

Spatio-temporal Variability and Climate Change Impact on the Crop Water Requirement of Pigeonpea (Cajanus cajan) - A Case Study, North-Eastern Karnataka, India

Background: Global climate change and its impact on crop water requirement have widely discussed in recent years. In the present century, climate change had become a significant concern and atmospheric temperature is the dominant climatic factor that indicates the changes in both regional and global scales. This study was undertaken to evaluate the trend and predict the changes in crop water requirement under various climate change scenarios. Methods: The statistical nonparametric Mann-Kendall test and Sen’s slope used to identify trend in the data series. In this study ArcGIS V. xx software used for investigating spatial patterns in data. CROPWAT-8.0 model used for calculation of crop water requirement under various climate change scenarios. Total six climate change scenarios were considered for assessment.Result: The crop water requirement (ETc) of pigeonpea estimated and exhibited an increasing trend and a decreasing trend in study area in the past 35 years. The spatial distribution maps reveal that the distribution of ETc is found an increasing trend in all the scenarios to reference ETc. An increasing trend of ETc of pigeon pea was observed in all the places under various climate change scenarios. It was suggested to promote rainwater harvesting, soil and water conservation and increase ground water recharge in the study area to minimize the risk of yield reduction due to the availability of minimum water under changing climatic condition.