Groundwater Yield Research Articles

Response to Pumping of Wells in Carbonate and Karst Aquifers and Effect on the Assessment of Sustainable Well Yield: Some Examples from Southern Italy

Carbonate and karst aquifers are of great importance for human water supplies, for supporting aquatic habitats and providing ecosystem services. Optimizing the groundwater withdrawals is therefore essential for obtaining the maximum flow rate for human purposes while minimizing the negative effects on the environment. In particular, when the abstraction of groundwater occurs through wells, the problem of defining the sustainable yield arises. This study analyzes pumping tests conducted in carbonate and karst aquifers in southern Italy to derive indications for defining the sustainable yield of yields. The four examined cases concern the Mesozoic–Cenozoic platform and transition pelagic carbonate rocks characterized by different degree of fracturing and karstification and hosting a carbonate aquifer with variable average groundwater yields. The analysis compared drawdown–time trends and their derivatives for 35 pumping tests with theoretical curves to identify the flow dimension. Parameters useful for examining the well yields were then determined. The results show that the response to the pumping of the investigated aquifers is very variable, both among the different sites and within the same site. Well yields are very different due to aquifer heterogeneity, local hydrostratigraphy and structural setting, and position of the pumping center within the groundwater flow system. To determine the operational pumping rate for a well in this environment, this study emphasizes the importance of analyzing drawdown trends over time to correctly predict the well’s long-term response to pumping. Specifically, when pumping induces a steady-state drawdown response, the focus for defining the sustainable abstraction shifts to the basin or aquifer scale. Conversely, when a transient drawdown response to pumping results, the well’s capacity to capture groundwater becomes the primary factor for well yield and its sustainability.

GROUNDWATER QUALITY INFLUENCING THE POTATO TUBER YIELD IN DOABA REGION OF PUNJAB, INDIA

Groundwater as a source of irrigation is extensively practiced in the Doaba region of Punjab, alongside high inputs such as chemical fertilizers and pesticides. These inputs pose dual threats to the deterioration and deepening of groundwater. Therefore, a survey-based investigation was conducted in the region, involving the collection of groundwater samples, their physico-chemical analysis, and the assessment of harvested potato tuber yields. The data analysis revealed that farmers are extracting groundwater from borewells at a depth of 254.0 feet on average, with a delivery depth of 145.67 feet. The analytical results indicated that all the collected groundwater samples were suitable for irrigation purposes. Furthermore, there was a significantly positive correlation between tuber yield and nitrate content of groundwater. Thus, it is crucial to consider the contribution of nitrate from groundwater when recommending nitrogen usage.

Observational evidence for groundwater influence on crop yields in the United States

As climate change shifts crop exposure to dry and wet extremes, a better understanding of factors governing crop response is needed. Recent studies identified shallow groundwater-groundwater within or near the crop rooting zone-as influential, yet existing evidence is largely based on theoretical crop model simulations, indirect or static groundwater data, or small-scale field studies. Here, we use observational satellite yield data and dynamic water table simulations from 1999 to 2018 to provide field-scale evidence for shallow groundwater effects on maize yields across the United States Corn Belt. We identify three lines of evidence supporting groundwater influence: 1) crop model simulations better match observed yields after improvements in groundwater representation; 2) machine learning analysis of observed yields and modeled groundwater levels reveals a subsidy zone between 1.1 and 2.5 m depths, with yield penalties at shallower depths and no effect at deeper depths; and 3) locations with groundwater typically in the subsidy zone display higher yield stability across time. We estimate an average 3.4% yield increase when groundwater levels are at optimum depth, and this effect roughly doubles in dry conditions. Groundwater yield subsidies occur ~35% of years on average across locations, with 75% of the region benefitting in at least 10% of years. Overall, we estimate that groundwater-yield interactions had a net monetary contribution of approximately $10 billion from 1999 to 2018. This study provides empirical evidence for region-wide groundwater yield impacts and further underlines the need for better quantification of groundwater levels and their dynamic responses to short- and long-term weather conditions.

Reviewing the Assessment of Optimal Yield of Groundwater in Korea

Reviewing the Assessment of Optimal Yield of Groundwater in Korea

Integrating in-situ data and spatial decision support systems (SDSS) to identify groundwater potential sites in the Esan plateau, Nigeria

Establishing suitable groundwater resource areas is a challenging endeavour across the globe. However, novel spatial technologies have emerged as valuable tools for the effective strategy, management, and assessment of groundwater resources, especially in data-scarce emerging economies. The current study used spatial decision support systems (SDSS) for evaluating and defining groundwater potential sites (GPSs) in Nigeria's Edo central region to promote sustainable governance of groundwater. By merging multiple groundwater contributing theme layers, a leading-edge information-based multiparametric analytical hierarchy process (AHP) was applied to define the groundwater prospective areas. By systematically assigning weights to every subject-specific layer and feature, the subject matter layers of geology, geomorphology, drainage density, slope, soil properties, landuse/landcover, rainfall distribution, hydraulic conductivity, transmissivity, curvature, proximity to surface water bodies, and elevation were generated and used for groundwater potential map generation. Each thematic layer's weights were allocated and adjusted depending on their qualities and relevance to groundwater recharge. The multicollinearity (MC) analysis was used to evaluate the model's predictive capacity. Finally, groundwater potential sites were created by integrating the theme-specific maps with the weighted total overlay computation tool. The study area contained three separate groundwater potential sites: low, moderate, and high. According to the regional geographic distribution, the largest portion of the area (65%) fell within the moderately significant groundwater potential geographical area. The high and low GPSs, which both have a low curvature and a valley plain characteristic, account for 25% and 10%, respectively, of the entire area. The outcomes were contrasted with the yield of groundwater from boreholes gathered in the study region. The validation analysis found an acceptable 88.89% similarity. This highlights the potential for the groundwater map's significant prediction. Therefore, the applied approach is a viable choice for the advancement of groundwater in the central Edo region and with comparable geology all over the globe.

Groundwater Exploration using Geoelectric Technique in Oru-Ijebu, South-West Nigeria

Forty Vertical Electrical Soundings (VES) were carried out using Allied Ohmega resistivity meter with schlumberger configuration in parts of Oru-Ijebu to determine the necessary geoelectrical parameters for delineating the aquiferous zones. Four to five distinct geoelectric layers were delineated from the survey area except for VESORU21 which exhibited six geoelectric layers namely the top soil, clayey sand/laterite, clay and granite gneiss. The first layer serves as the topsoil with high variable resistivity ranging from 11.2Ωm (VESORU7) to 153.8Ωm (VESORU25) with their corresponding thickness of 0.9m to 3.8m respectively. The thickness of the entire top soil of the investigated area ranges from 0.4m to 3.8m. The second layer is composed of sand, clay sand, laterite and partly sandy clay. The resistivity of clay/clayey sand overburden varying from 16.2Ωm with a thickness of 8.7m in VESORU17 and 484.3Ωm with a thickness of 3m VESORU6. The highest resistivity exhibited by the second layer is 974 Ωm in VESORU30 while its lowest resistivity is 21.9Ωm in VESORU34. The resistivity of the third layer which stands as a weathered lithology ranges from 17.2Ωm with a thickness of 10.3m at VESORU7 to 233.2Ωm at VESORU23 whose thickness is indeterminate due to current termination in the field to 196 Ωm; typically diagnostic of clay/clayey sand horizon except beneath VESORU1, VESORU2, VESORU11, VESORU30, VESORU32, VESORU34, and VESORU36 where the inferred lithology is sandstone, fresh basement and partly sandy-clay. The fourth and fifth layers are composed of fresh basement formation notably granite-gneiss rocks with resistivity values ranging from 88.5Ωm VESORU20 to 384Ωm in VESORU15. The maximum aquifer thickness is encountered beneath VESORU25. The weathered layer for the study area is thick enough for groundwater accumulation making it a very prolific one. VESORU1, VESORU2 and VESORU23 are marked by a low groundwater yield due to the dip and the thickness.

Mapping of Aquifer Characteristics and Reservoir Protective Capacity Variation in Obafemi-Owode Local Government Area, Ogun State South-West Nigeria

Variation of Aquifer potential characteristics and its impacts on the groundwater subsurface protection of the aquiferous zone using electrical resistivity method was carried out at Obafemi-Owode Local Government Area, Ogun State South-West Nigeria with the principal purpose of assessing and rating aquifer protective capacity of the overburden units in the area. Twenty seven (27) vertical electrical sounding (VES) were conducted using Schlumberger configuration with the maximum electrode spacing of 100m at each point using Allied OMHEGA Resistivity meter. The data were interpreted using partial curve matching techniques and computer iteration program using WINRESIST. Parameters such as aquifer resistivity, aquifer thickness, overburden thickness, bedrock resistivity, reflection coefficient and longitudinal unit conductance were calculated and used for evaluating the groundwater yields and vulnerability of the aquiferous zone to contaminant seepages. The range of reflection coefficient is found to be between 0.02 and 0.98 while that of the protective capacity is between 0.00135 and 0.510. Groundwater potentials of the area were categorized as being high (overburden thickness 13m and reflection coefficient less than 0.8); medium (overburden thickness 13m and with reflection coefficient 0.8) and low (overburden thickness < 13m and reflection coefficient. Also, the study area shows a very poor, poor, and moderate protective capacity rating. Seven (7) VES stations have very poor protective capacity, eighteen (18) VES stations shows poor protective capacity and only two (2) VES stations shows a moderate protective capacity rating. Since the illustration the longitudinal conductance revealed the impermeability of the confining layers which is generally ˂ 1.0 Siemens; values ˃1.0 Siemens which indicates zones in which the confined aquifer is subject to protection by the overlying formation materials; these revelations in the study area were possible indications that the groundwater quality status may have been impaired which necessitated the urgent need for the groundwater to be randomly...

Groundwater abstraction and woodland mortality: Lessons from Namibia

In response to escalating worldwide groundwater dependence amid climate change, accurate estimation of sustainable groundwater yield becomes crucial. This study investigated the impact of groundwater abstraction on tree mortality in Namibia. We compared tree mortality around production boreholes with monitoring boreholes and we correlated groundwater decline rates with tree mortality, establishing a model from which we derived a groundwater decline rate range limit. Ana tree mortality was significantly higher (P = 0.01) around production boreholes (13.3%) than around monitoring boreholes (0%). In the dammed Swakop River, Ana tree mortality correlated with decline rates (rS = 0.64, P < 0.01). The study suggests that decline rates of above 0.2–0.23 cm day−1 may cause elevated mortality (3–7%) and should not be sustained for extended periods. Rates exceeding 0.5 cm day−1 should be avoided, while monitoring is recommended for rates between 0.23 and 0.5 cm day−1. Woodlands in rivers with altered flood frequencies may be more sensitive to groundwater abstraction than previously thought. The study's methods offer a universal framework for refining sustainable yield calculations worldwide.

Hydro-Economic Approach for Quantifying Well Performance Thresholds and Recoverable Groundwater Yields in Texas

Groundwater overdraft may increase the depth of the potentiometric surface, or depth-to-water, over time; reducing potentiometric head available to support well operation and increasing the cost of pumping. These hydro-economic impacts create well failure thresholds. Understanding these impacts and thresholds is a critical issue for groundwater management but tools to assess them are not widely available or established. Therefore, an analytical model developed in this study quantifies changes in well performance with depth-to-water, calculates well failure thresholds, and estimates feasible storage yields for variable uses, wells, and aquifers. The model is developed and tested using both a single well and a regional analysis of the Carrizo-Wilcox Aquifer in Texas, U.S.A., where a contemporary groundwater dataset is available and management is depth-to-water-based. Results reveal how storage conditions drive well performance and suggest that performance in shallow and unconfined settings may be more limited by operational thresholds than affordability thresholds, while performance in deep and confined settings may be inversely limited. At the tested parameters for a single well, failure to account for drawdown would overestimate operationally feasible yields by 98% – 108% and economically feasible yields by 24%. The model could directly support manager, stakeholder, and policymaker consideration of desired future conditions.

3D electrical resistivity survey for reduction of groundwater drilling uncertainties in a clay-rich environment

Drilling for groundwater is expensive and challenging. It is even more challenging to find a location that will result in a high-yield well in heterogeneous environments. To tackle the heterogeneity issue, geophysical surveys can help in mapping the subsurface structure and delineating the drilling trajectory. The current study displays the effectiveness of 3D electrical resistivity tomography (ERT) to locate a permeable groundwater zone within a highly heterogeneous and clayey subsurface. Ground truthing the acquired geophysical data with in-situ sampling helps ensure accuracy in classifying groundwater zones in the final inverted 3D data set while also delineating boundaries between permeable groundwater zones and less permeable clayey structures. In-situ samples of groundwater and soil were used to measure the saturated region's resistivity in the laboratory using a column setup. Clay zones in the data set are classified from the nearby well data at similar depth ranges and from very low resistivity values from ERT data and laboratory measurements. The results display highly differentiating resistivity zones that are attributed to the scattered clay lenses (low resistivity) in conjunction with the freshwater zone (high resistivity). The distinction between clayey and nonclayey bodies is important to better inform drilling locations for optimal groundwater yield. This study concludes that with the aid of low-cost geophysical surveys and minimal in-situ sampling data correlations, permeable groundwater boundaries and clay lens volumes can be identified easily.

Multi-criteria groundwater potential zonation using GIS-based fuzzified AHP: Case study of Ondo metropolis Southwestern Nigeria

The study utilized the fuzzy analytical hierarchical process (F-AHP) in the multicriteria decision analysis of seven important hydrogeologic parameters associated with groundwater potentiality/yield. The purpose was to develop groundwater potential map using groundwater potential index values (GWPIV) for Ondo metropolis, Southwestern Nigeria. The hydrogeologic parameters were prioritize and assigned different weights hierarchically according to their level of importance using F-AHP, as aquifer layer thickness (0.05), aquifer layer resistivity (0.04), overburden thickness (0.12), transverse resistance (0.18), transmissivity (0.32), coefficient of anisotropy (0.25), and formation factor (0.03). From regional perspective, based on drainage basin, and river network, the region was categorized to be of low/moderate groundwater yield, with moderate to high flow connectivity. The higher and lower elevations are generally remarkable in the northern and southern areas respectively, hence possibility of movement of water towards the southern part with the northern forming the watershed. Furthermore, the longitudinal unit conductance recorded regional average value of 1.168, while 1.20, 1.16, and 1.10 were recorded for granite, gneiss and migmatite, which suggests moderate vulnerability to contamination. The average values recorded for overburden thickness, hydraulic conductivity, transmissivity, transverse resistance, formation factor, coefficient of anisotropy, fracture contrast, and reflection coefficient are 22.5 m, 0.33 m/d, 5.56 m2/d, 4966 ohm-m2, 2.42, 1.17, 15.3, and 0.66 respectively. The water table aquifer and the fractured basement are the major water bearing units in the area; while the geological units showed overlapping hydrogeologic properties. The obtained GWPIV ranged from 1.21 to 3.55 with regional average of 1.86, suggesting a moderate potential. Nevertheless, the southern part showed more propensity/yield than the northern area. The study showed the importance of geospatial mapping technique, involving fuzzy analytical hierarchical process, in groundwater evaluation, as it was able to solve and obtain different hydrogeological parameters, which were integrated to prioritize and define the area's groundwater prolificacy for the purpose of improving, expanding, and management of the existing water scheme in the study area.

Regional- to district-scale controls on thermal springs occurrence in South Africa: Insights from investigations of their spatial distribution and their spatial relationships with geological features

In the study presented here, the spatial distribution of thermal springs in South Africa was investigated using point distribution analysis, fractal analysis and Fry analysis, and the thermal springs’ spatial relationships with high-heat-producing granitoids (HHPGs), groundwater yield, and structural lineaments were investigated using distance distribution analysis. The purpose of these spatial investigations was to explore the regional- to district-scale geological controls on thermal springs occurrence in South Africa. The results show that regional- to district-scale geological controls on thermal springs occurrence in South Africa involve the presence of or proximity to HHPGs (as heat source control), groundwater yield of ∼2 L/s (as water source control) and intersections of structural lineaments with particular trends (as pathways control). In southern and eastern South Africa, the pathways controls are, respectively, intersections of ENE-trending lineaments with NNW- and NW-trending lineaments and intersections of ENE- and WNW-trending lineaments. This spatial information comprises a conceptual model that can be used as a framework for regional- to district-scale predictive modeling and mapping of the prospectivity (or likelihood) of areas where geothermal resources potentially exist in South Africa.

Direct Detection of Groundwater Accumulation Zones in Saprock Aquifers in Tectono-Thermal Environments

Some vertical electrical sounding (VES) data from tectono-thermal environments usually plot anomalously on a VES curve, thereby distorting the curve trend at the points of their occurrence. These datasets usually plot noisily in the form of a sudden rise and drop in electrical resistivity values. They constitute abnormal datasets that are usually deleted to recover trends and consequently develop confidence in both the datasets and the modelling and interpretational processes. This study was conducted to assess their origin and consequently gain an understanding of their contributions to groundwater accumulation and transmission in saprock aquifers. The results, supported by co-located drilling and pumping test data, show that these datasets are indicators of subsurface conditions where high-resistivity unconformal structures directly overlie saturated (low-resistivity) porous media, provided that the resistivity of the first breakout point is less than those from subsequent points. Remote sensing data reveal that these types of curves are common in hard rock and metasedimentary environments. Borehole groundwater yields can also be assessed qualitatively from the number and trend of breakoff points. The integrity of the breakoff points must be affirmed by using more sensitive equipment for data acquisition and repeating the measuring process using different potential electrode separations and—where possible—VES profile orientation.

Study on potential groundwater yield zone in sandstone aquifer based on a dual dynamic variable weight model: A case study in Shuangma Coal Mine of Ordos Basin

Accurate and effective assessment of groundwater potential in aquifers hundreds of meters deep remains a major challenge in mining and environmental protection. We analyzed the interaction mechanism of hydrogeological parameters, quantified it and incorporated it into the variable weight model (VWM) for secondary optimization, and constructed a dual dynamic variable weight model (PE-HVWM) that varies with multi-parameter entanglement and single-parameter state values to characterize the groundwater potential. Then, the pumping test data measured at the mining site were used to compare and analyze the results of different model predictions, and the optimized model was validated and tested using the Receiver Operating Curve (ROC) method and sensitivity analysis, which showed that the PE-HVWM method has a fairly high accuracy in groundwater potential prediction (AUC = 0.874). The PE-HVWM model can visualize the intrinsic correlation between hydrogeological parameters, and can respond sensitively to sudden changes in the state value of a hydrogeological parameter in the aquifer, and output groundwater potential results that are more in line with the actual situation after self-balancing by linking other parameters.

Integrated electrical resistivity methods for evaluation of fracture terrain groundwater potentials, case study of indurated shale of Lower Benue trough, Southeastern Nigeria

The incessant borehole failure in the Abakaliki area suggests that the application of vertical electrical sounding (VES) in prospecting for groundwater within the fractured terrain is relatively inefficient. Therefore, this research aimed at using integrated resistivity methods (azimuthal resistivity survey (ARS) and VES) to defined the structures and porosity parameters in the area to overcome the lapses experienced in applying VES method alone. The data acquisition was done along four azimuthal angles (0°,45°, 90°, and 135°), adopting the Wenner electrode array expanded symmetrically about the center point in increments of 5, 7, 10, 14, 20, 28, 40, and 50 m, whereas VES data was acquired using routine Schlumberger array and the resistivity of the subsurface was recorded using resistivity meter. The data was processed with IPI2WIN™, INTERPEX™, GRAPHER™, and SURFER™, and interpretated with respect to the geology of the area. The data delineated the fractures based on mean resistivity contrast. The fractures strike within the area are NW-SE, NE-SW and N–S, E-W (37.07%, 33.33%, 18.52%, and 11.11% respectively). The interconnectivity of the fractures was portrayed in some locations and they define the permeability of the area, coefficient of anisotropy, transmissivity, and longitudinal conductance defines the groundwater possible yield. The coefficient of anisotropy ranges from 1.05 to 9.54, and fracture porosity extends from 0.0006 to 1.95, with an average of 0.34. The transmissivity of groundwater in the area support withdrawal of marginal regional importance. Therefore, groundwater yield and recharge in the area is contingent on the variability and interconnectivity of the subsurface fractures, the number of existing boreholes being recharged by this fracture, and the baseflow dynamics and dipping angle of the major fracture at the borehole site.

Quantitative prediction of the impact of deep extremely thick coal seam mining on groundwater

Reasonable exploitation and utilization of groundwater near coal mines in arid areas are of great significance to regional ecological and geological environment protection and sustainable mining of coal resources. It is a challenge to accurately predict the impact of deep coal mining on groundwater resources before mining. Adopting a coal mine in Inner Mongolia, China, as a case study, first, a well-fitted GA-BP neural network model was established to predict the height of the water-conducting fracture zone (WCFZ). The prediction results of WCFZ were verified by in-situ measured data of optical fiber and cable sensing systems. In Chinese coal mines, hydrogeological research generally lags behind geological exploration. Therefore, in the context of limited hydrogeological data, a variable weight model (VWM) for evaluating the potential groundwater yield of the objective aquifer (OAPGY) was established considering geological survey data before mining. Then, drilling pumping test data was used to verify the OAPGY predictions. Finally, groundwater resource protection measures were proposed according to the zoning results. The research results could provide a reference and basis for sustainable utilization of groundwater and reducing the impact of coal mining on groundwater resources.

Hydrogeological characterization of the Complex Terminal aquifer using geoelectrical investigation in the arid environment of Chetma-Biskra (South-East of Algeria)

As a transition hydrogeological area, Biskra (Algeria) holds large groundwater resources in deeply buried aquifers such as the Complex Terminal. Due to a growing demand of drinking water supply and irrigation combined to low recharge, this arid region is facing an acute shortage of water and hence, the need for groundwater investigation. We used an integrated approach including geophysical investigation correlated to the geological and hydrogeological context in the Chetma area. The results highlight a deep structural form with significant hydrogeological features. In fact, two resistant limestone anticlines called Droh corresponding to a piezometric dome and a syncline filled with conductive deposit materials were identified. The Maastrichtian formation, consisting of fractured limestone, about 200 to 350 m thick, together with Lower Eocene marl limestone and limestone form a complex aquifer. At more than 400 m depth, boreholes capturing Maastrichtian limestone offer a high yield ranging from 25 to 90 L/s. Moreover, groundwater yield provides an average of 40 L/s at 300 m of depth. In contrast, synform geometries with high clay and marl content offer a weak groundwater yield. We confirmed the occurence of fractured aquifers which could constitute potentially groundwater production zones. This study provides new insights to enhance groundwater pumping for domestic and irrigation purposes for 2030.

AQUIFER SYSTEMS CHARACTERIZATION FOR GROUNDWATER MANAGEMENT IN ILE-OLUJI, SOUTHWESTERN NIGERIA, USING MCDA GIS-BASED AHP

Multicriteria decision analysis for groundwater potential mapping utilizing analytical hierarchical process of six hydrogeologic parameters including aquifer layer thickness, aquifer layer resistivity, overburden thickness, transverse resistance, transmissivity, and coefficient of anisotropy; in relation to groundwater yield was carried out in Ile Oluji, Southwestern Nigeria. The aim was to develop groundwater potential map using calculated groundwater potential index values (GWPIV). The obtained GWPIV which ranged from 1.53 (granite) – 3.50 (migmatite) with an average of 2.18 suggestive of moderate groundwater potential (90 % of the study area). The low potential zone (10 %) are observed sporadically in the central and northwestern parts. All the geological units recorded overlapping hydrogeologic properties. The longitudinal unit conductance recorded regional average of 0.219876 mhos. Therefore the protective capacity of groundwater system in the study area is weak, and relatively less-weaker in granite environment; and in northwestern and central parts. Nevertheless, the water table aquifer (accounts for 80%) and the fracture basement (constitutes 20%, frequently occurring in gneissic environment) are the water bearing units, with average overburden thickness in migmatite, granite, and gneiss 24.3 m, 24.5 m, and 27.9 m respectively. The average coefficient of anisotropy (1.12); hydraulic conductivity (0.37 m/d), transmissivity 6.86 m2/d (migmatite: 7.17 m2/d, granite: 7.14 m2/d, and gneiss: 6.02 m2/d). Hence gneissic offered both thick weathered layer and fractured aquifer. Empirical model for plot of formation factor and hydraulic conductivity in migmatite, granite, and gneiss, showed positive correlations in descending order as: granite (0.3778), migmatite (0.1057), and gneiss (0.0641).

Rainwater Harvesting through Point Recharge Method for Efficient Recharge of Tube Wells for Sustainable Management of Groundwater Resources in Karnataka

Water is a precious natural resource for sustaining life, agriculture and environment. The dependability on groundwater has reached high in all time in recent decades due to reasons such as unreliable supplies from surface water due to vagaries of monsoon, increase in demand for domestic, agricultural and other purposes. Karnataka is largely dependent on groundwater to meet industrial, municipal, domestic and irrigation needs. So, Rainwater harvesting (RWH) forms an important component for development and management of water resources for domestic, agricultural, municipal and industrial uses. Management of scanty rain fall by rain water harvesting, Augmentation of depleting natural resources of water (deeper ground water table) and Management of poor-quality ground water and scope for conjunctive/domestic use is need of the hour. With increase in withdrawal of ground water, ground water (GW) table is declining at a rapid pace with an urgent need to recharge GW in addition to dilute poor quality ground water. Double ring technique of Groundwater Recharge consists of filtering the water at different layers using gradation materials generally the pebbles of different size with synthetic material wrapped around the casing pipe. By harvesting rain water and recharging into point recharge soaking infiltration gallery established at Irrigation Water Management Research Centre, (IWMRC) Belavatagi Tq: Navalagund has shown encouraging results as far as water quality, discharge and water table are concerned. The results of assessment of influence of ground water recharge through rainwater harvesting on ground water yield (lps), quality (dS/m) and fluctuations (feet bgl) during the year 2020, have shown that around 3.35 lakhs liters of water could be collected from rain water harvesting during the year 2020. Also, from point recharge through 7 recharge events (rain fall events from July to October 2020), it was observed that the considerable rise in the water table from more than 100 feet below ground level to around 22 feet below ground level, drastic reduction in groundwater salinity i.e. electrical conductivity (EC) of ground water from more than 10 dS/m to an average (EC) of 1.32 dS/m and tube well yield has significantly increased from 0.4 lps to around 2.4 lps. Therefore, Artificial recharge techniques through rainwater harvesting can be a better strategic approach to combat the emerging problems of water scarcity especially over exploitation of ground water and its quality deterioration.

Delineation of groundwater potential zones using remotely sensed data and GIS-based analytical hierarchy process: Insights from the Geba river basin in Tigray, Northern Ethiopia

Study regionThe study was undertaken in the Geba Drainage Basin, major tributary of the Tekeze Drainage Basin in Northern Ethiopia. Study focusThe objective of this study is to identify the groundwater potential zones of Northern Ethiopia's Geba Drainage Basin. Nine groundwater indicators were used as inputs, including lithology, geomorphology, lineament density, drainage density, slope, elevation, land use and land cover, rainfall, and soil. According to their relative influence on groundwater potentiality, the thematic layers and their classes were assigned appropriate weights based on Saaty's 1–9 judgment scale. The assigned weights were then normalized using an Eigen vector-based Analytical Hierarchy process. By superimposing all the normalized layers in the GIS environment, a groundwater potential map was developed. New hydrological insights for the regionFive distinct groundwater potential zones—very good, good, moderate, poor, and very poor were found in the study area. The areal distribution showed that majority of the area (45%) fell within the poor groundwater potential zone. The groundwater potential zones of moderate, very poor, good, and very good cover approximately 27%, 12%, 10%, and 6% of the total area, respectively. The results were compared to the groundwater yield of boreholes collected from the study area. The validation analysis revealed a 72% similarity, which is representative. The employed method is therefore a reasonable option for groundwater development in the Geba Drainage Basin.