Hard Rock Region Research Articles

Energy models in service of aquifer specific groundwater irrigation expansion in India

Abstract Pumping energy is a key component of the groundwater governance challenge, yet it is largely missing in the discourse on agricultural use of groundwater. A sub-category of literature studying groundwater-energy nexus tends to focus on groundwater depletion hotspots where entrenched interests and long-standing histories restrict the range of feasible energy pricing options. Using an agent based model, we estimate expected impacts of expanding groundwater irrigation under five different energy provision models in Odisha, an Indian state with among the lowest irrigation coverage, and therefore, free of path dependent policies. We find aquifer properties play a crucial role in mediating the groundwater-energy nexus. For this study region, on average, the maximum volume of water that can be pumped from a well of a specific depth in an alluvial aquifer is approximately 150 times the volume that can be pumped from a well in a hard-rock aquifer. Therefore, the risk of over-consumption and aquifer depletion is a far greater challenge in alluvial than hard-rock aquifers. Risks of groundwater consumption and depletion can be limited in hard-rock aquifers provided the number and depths of wells can be controlled. Capital subsidies for well construction could be an effective policy to increase irrigated area so long as economic incentives for digging deeper are not distorted. Our results imply that solar pumps are a relatively safe option for hard-rock regions where deep drawdowns naturally limit the extent of over-extraction. Solar pumps are also estimated to be among the most economical for expanding irrigation. Using a novel dataset comprising of biophysical and socioeconomic data, we find hard-rock regions to have limited irrigation coverage, high availability of annually replenishable groundwater, and high concentrations of marginalized farmers. Therefore, groundwater irrigation expansion in hard-rock areas could have dual benefits of ensuring future food security and targeting poverty reduction.

Demarcation of groundwater potential zones in Ponnai sub-basin, Southern India using remote sensing, GIS and fuzzy-AHP approaches

ABSTRACT Groundwater is an essential source for household, irrigation and industry needs. The amount of groundwater and its quality are rapidly declining because of urbanization and industrialization. Groundwater resources in hard rock regions should be handled properly to maximize their utilization. This work aims to demarcate the Groundwater Potential Zones (GWPZ) in a part of the Palar River Basin (Ponnai sub-basin) by combining Remote Sensing (RS), Geographic Information System (GIS) and Fuzzy-Analytical Hierarchy Process (FAHP). The factors which influence the groundwater like geology, land use/land cover (LULC), geomorphology, slope, soil, rainfall, lineament density (LD), drainage density (DD), normalized difference vegetation index (NDVI), topographic wetness index (TWI) and topographic position index (TPI) are considered for mapping of GWPZ. The weightage is allocated to these parameters on the basis of the FAHP technique and the obtained groundwater potential map was classified as, very poor (13.5%), poor (21.76%), moderate (31.5%), good (20.66%) and very good (8.54%). The GWPZ map was validated with the actual well yield of the Ponnai sub-basin. The research work will serve as a guideline for the effective use of groundwater and long-term sustainable management of the aquifer in the Ponnai sub-basin.

Hydrogeochemical and multivariate statistical approaches to investigate the characteristics of groundwater quality in fluoride-enriched hard rock region in Tirupathur district of Tamil Nadu, India.

Fluoride pollution is a major issue worldwide, posing health risks such as dental and skeletal fluorosis. This study was conducted in fluoride enrichment hard rock regions of Vaniyambadi and Ambur talks in Tirupathur district, Tamil Nadu. Four hundred eighty groundwater samples were collected from May 2021 to April 2022 and grouped as summer, southwest monsoon (SWM), northeast monsoon (NEM), and winter. Maximum concentration of fluoride was found to be 4mg/L in the summer season in Vellakuttai region of Vaniyambadi taluk. The study aims to investigate the hydrogeochemical process and mechanism influencing groundwater chemistry and it also provides the confirmation of exploratory data analysis in groundwater quality using structural equation modeling. The Piper and Gibbs diagrams illustrate the rock-water interaction and anthropogenic sources that contribute to the NaHCO3 and NaCl-type waters, respectively. Multivariate statistical analysis such as hierarchical cluster analysis (HCA), principal component analysis (PCA), multiple linear regression (MLR), and structural equation modeling (SEM) has been carried out to determine the groundwater quality. HCA manifests the nature and sources of groundwater, whereas PCA divides all the physicochemical parameters into two PC loadings, accounting for 97.46%, 99.46%, 99.18%, and 98.93% of cumulative % of variance during the summer, SWM, NEM, and winter seasons, respectively. PC1 has a higher loading factor to Cl, Ca, and Mg, whereas PC2 has a higher loading factor to Na, HCO3, SO4, and NO3. The results of the MLR model provide higher accuracy in detecting the contamination factors associated with the environment and natural rocks. SEM revealed the goodness-of-fit indices 0.993, 0.999, 1.000, and 0.999 in summer, SWM, NEM, and winter, respectively. Hence, this study provides insight view of variation of fluoride concentration in groundwater in different seasons and also mentions the factors that influence fluoride concentration in Vaniyambadi and Ambur taluk.

Ant Colony Based Artificial Neural Network for Predicting Spatial and Temporal Variation in Groundwater Quality

The quality of groundwater is of utmost importance, as it directly impacts human health and the environment. In major parts of the world, groundwater is the main source of drinking water, hence it is essential to periodically monitor its quality. Conventional water-quality monitoring techniques involve the periodical collection of water samples and subsequent analysis in the laboratory. This process is expensive, time-consuming and involves a lot of manual labor, whereas data-driven models based on artificial intelligence can offer an alternative and more efficient way to predict groundwater quality. In spite of the advantages of such models based on artificial neural network (ANN) and ant colony optimization (ACO), no studies have been carried out on the applications of these in the field of groundwater contamination. The aim of our study is to build an ant colony optimized neural network for predicting groundwater quality parameters. We have proposed ANN comprising of six hidden layers. The approach was validated using our groundwater quality dataset of a hard rock region located in the northern part of Karnataka, India. Groundwater samples were collected by us once every 4 months from March 2014 to October 2020 from 50 wells in this region. These samples were analyzed for the pH, electrical conductivity, Na+, Ca+, K+, Mg2+, HCO3−, F−, Cl− and U+. This temporal dataset was split for training, testing and validation of our model. Metrics such as R2 (Coefficient of Determination), RMSE (Root Mean Squared Error), NSE (Nash–Sutcliffe efficiencies) and MAE (Mean Absolute Error) were used to evaluate the prediction error and model performance. These performance evaluation metrics indicated the efficiency of our model in predicting the temporal variation in groundwater quality parameters. The method proposed can be used for prediction and it will aid in modifying or reducing the temporal frequency of sample collection to save time and cost. The study confirms that the combination of ANN with ACO is a promising tool to optimize weights while training the network, and for prediction of groundwater quality.

Intelligent Analysis of Construction Costs of Shield Tunneling in Complex Geological Conditions by Machine Learning Method

The estimation of construction costs for shield tunneling projects is typically based on a standard quota, which fails to consider the variation of geological parameters and often results in significant differences in unit cost. To address this issue, we propose a novel model based on a random forest machine learning procedure for analyzing the construction cost of shield tunnelling in complex geological conditions. We focus specifically on the unit consumption of grease, grouting, labor, water, and electricity. Using a dataset of geotechnical parameters and consumption quantities from a shield tunneling project, we employ KNN and correlation analysis to reduce the input dataset dimension from 17 to 6 for improved model accuracy and efficiency. Our proposed approach is applied to a shield tunneling project, with results showing that the compressive strength of geomaterial is the most influential parameter for grease, labor, water, and electricity, while it is the second most influential for grouting quantity. Based on these findings, we calculate the unit consumption and cost of the tunnelling project, which we classify into three geological categories: soil, soft rock, and hard rock. Comparing our results to the standard quota value, it is found that the unit cost of shield tunneling in soil is slightly lower (6%), while that in soft rock is very close to the standard value. However, the cost in the hard rock region is significantly greater (38%), which cannot be ignored in project budgeting. Ultimately, our results support the use of compressive strength as a classification index for shield tunneling in complex geological conditions, representing a valuable contribution to the field of tunneling cost prediction.

Performance Evaluation of RBF Wells with Special Reference to Water Quality Parameters in Hard Rock Region of Tungabhadra Catchment

Tungabhadra River is the chief source for drinking water and agriculture developments in Davangere and adjoining districts of Karnataka. It is reported that the water of Tungabhadra is getting polluted by the direct / indirect effluent discharges due to which people living on the river bank are facing the problem of drinking water. River Bank Filtration (RBF) wells which will naturally treat the polluted surface and ground water have been drilled in perpendicular to the river at a distance of 30m, 50m and 80m to understand the extent of treatment of RBF wells to provide clean and safe drinking water. The present study deals with the problems of water quality in a selected village (Somlapura) located in a hard rock terrain of river Tungabhadra, Karnataka, India. As a part of the investigation, water samples were collected from River Bank Filtration wells and adjoining river and aquifers were analyzed using standard methods. Outcomes of water quality presents that the concentrations of turbidity and total coliform were lesser in the RBF well water samples when compared to Tungabhadra River water samples. The water from RBF wells contained fresh water, which is highly mineralized and free from bacterial contamination relative to the water from river. However, groundwater of the adjoining aquifers showed wide variations in various physio-chemical parameters. From the analysis, unsafe levels of total coliforms (included E.coli and F. Coli) were detected in Tungabhadra River i.e., It varied between 1680 and 3179 MPN/100 ml. It is observed that the average removal efficiency of coliform bacteria from RBF well 1 & 2 was 99.84% and 99.82% respectively.

Exploration of groundwater potential zones mapping for hard rock region in the Jakham river basin using geospatial techniques and aquifer parameters

Geospatial techniques are useful to understand the groundwater resources assessment, development, and management. Groundwater mapping is essential to counter the excessive withdrawal of groundwater and fulfil the need of drinking, irrigation water in hard rock areas. Currently, the main problem is facing the groundwater level is decreasing due to less rainfall, climate changes and increasing demand, which is under in the hot zones. This results can be more useful for future challenges, sustainable development and demand to Jakham river basin. The main objective of this paper to demarcated the groundwater potential zones (GWPZ) using geospatial techniques for the hard rock region with the reference of aquifer parameters. In this paper, we have used to total eight thematic layers such as geomorphology, land use, soil, topographic elevation, slope, post-monsoon groundwater level (GWL), net recharge, and transmissivity, which are prepared from satellite data and field verification. All thematic layers were integrated for assigning the weights to demarcation of the groundwater potential zones in the RS and GIS environment. The selected thematic layers and features were assigned weightage and normalized by the analytic hierarchy process (AHP) technique. Finally, the thematic layers were systematically integrated using weighted overlay analysis within a GIS environment. We have classified into five GWPZ classes i.e. very high, high, moderate, low, and very low for basin area using GIS, and AHP methods. The study area result indicated that high and moderate zone, which is confined in the central part of the basin, covers 2.43 % and 43.88 % area, respectively. The low (49.21 %) and very low (4.25%) GW potential zone is under the confined aquifer in the high slope and rock outcrops formations near the basin boundary. The final GWPZ map was validated with groundwater level fluctuation data, which illustrates the accuracy of the adopted approach. This unique approach and conclusions of this work may also help to develop the framework and policies for swiftly analyzing groundwater recharge planning, development and locating the artificial recharge structures in the other semi-arid, arid and hard rock regions.

Water Security in South Asian Cities: A Review of Challenges and Opportunities

Achieving water security in South Asian cities will require a realistic and holistic understanding of the challenges that are growing in extent and severity. These challenges include the rapid rise in urban household water demand due to both overall population growth and increasing urbanization rate. Additionally, surface water supply in closed river basins is fully utilized, and there is little opportunity in these regions to increase the extraction of surface water to meet rising demands. Furthermore, groundwater extraction in most regions exceeds natural recharge rates, leading to rapidly falling annual water tables and seasonal depletion in hard rock regions and to gradually declining water tables requiring deeper wells and increased pumping effort in alluvial regions. Additionally, even in cities with abundant water resources, poorer segments of the population often face economic water scarcity and lack the means to access it. Nevertheless, there are important potential engineering opportunities for achieving water security in South Asian cities. Much withdrawn water is lost due to urban water distribution inefficiency, and a range of proven techniques exist to improve distribution. Metering of urban water can lead to structural improvements of management and billing, though the water needs of the poorest city residents must be ensured. Industrial water-use efficiency can be significantly improved in manufacturing and electricity generation. The quantities of wastewater generated in South Asia are large, thus treating and reusing this water for other purposes is a strong lever in enhancing local water security. There is limited potential for rooftop rainwater harvesting and storage, though capture-enhanced groundwater recharge can be important in some areas. Some individual inter-basin transfer projects may prove worthwhile, but very-large-scale projects are unlikely to contribute practically to urban water security. Overall, the water challenges facing South Asian cities are complex, and although no single intervention can definitively solve growing problems, numerous actions can be taken on many fronts to improve water security.

Impact of monsoon shower on the hydrogeochemistry of groundwater along the lithological contact: a case study from South India

Groundwater chemistry is mainly governed by lithological variations, space and resident time. In addition, hydrogeochemical characteristics of groundwater in the lithological contact zones are too complex. Hence, Cretaceous–Tertiary (KT) boundary from Ariyalur district, Tamilnadu, India, was selected for this study to identify the hydrogeochemistry of groundwater. This study includes 284 groundwater samples from four different seasons (pre-monsoon, post-monsoon, southwest monsoon and northeast monsoon). Groundwater samples were collected and analysed for major cations and anions, including physical parameters using standard procedures. High electrical conductivity (EC) showed the longer residence time of groundwater in hard rock region at the central and southern part of the study area. Ca2+, Na+, Cl− and HCO3− are the dominant ions in all the four seasons. The seasonal composition migration was observed from Na–Ca–Cl–HCO3 type to Na–Mg–Cl–HCO3 type, and Ca-HCO3 is the predominant water type in piper plot. Interpretation of data reveals that the groundwater quality was unsuitable for domestic and irrigation purposes during pre- and southwest monsoon seasons. Rock–water interaction and dissolution of minerals are the main sources of groundwater chemistry. Agriculture activities during monsoonal seasons also play a role in controlling the hydrogeochemistry of groundwater in this region.

Determining the Hydrological Behaviour of Catchment Based on Quantitative Morphometric Analysis in the Hard Rock Area of Nand Samand Catchment, Rajasthan, India

India’s water resources are under tremendous pressure due to elevated demand for various purposes. The over-exploitation of these valuable resources has resulted in an imbalance in the watershed ecology. The application of spatial analysis tools in studying the morphological behaviour of watersheds has increased in recent decades worldwide due to the accessibility of the geospatial database. A morphometric analysis of a river basin is vital to determine the hydrological behaviour to develop effective management. Under the current study, morphological behaviour of Nand Samand catchment in the hard rock region was evaluated employing remote sensing (RS) and geographical information system (GIS) tools. The Nand Samand catchment (Rajasthan State, India) has an area of 865.18 km2 with the highest and lowest elevations of 1318 m and 570 m above mean sea level, respectively. This study utilises a 30 m high-spatial-resolution ASTER imagery digital elevation model for delineating the catchment. The drainage network is assessed using a GIS method, and morphometric parameters like linear, areal, and relief aspects were calculated. Results were obtained for parameters viz., basin length of 82.66 km, constant channel maintenance equal to 0.68 km, stream frequency of 2.11 km−2, drainage density of 1.48 km−1, and length overflow of 0.34 km. Form factor of 0.13, and the circulatory ratio of 0.28 showed that an elongated shape characterises the study area. The results would help understand the relationship between hydrological variables and geomorphological parameters for better decision-making. The techniques used could effectively help to perform better drainage basin and channel network morphometric analyses. The found morphometric characteristics will be helpful in understanding the Nand Samand catchment and similar areas in India in order to better guide the decision-makers in providing adequate policy to the development of the region.

Characterization of groundwater potential zones in water-scarce hardrock regions using data driven model

Characterization of groundwater potential zones in water-scarce hardrock regions using data driven model

Estimating Water Flux in a Granitic Aquifer from Temperate Profile Measurements in Borewells of a Hard Rock Region, India

Abstract Electrical conductivity (EC) and temperature logging were carried out in twenty-five borewells/piezometers in a hard rock region of Telangana, India at an interval of 1 and 2 m right from the water table till the bottom of the borewell to study the fracture zones at different depths and to recognize temperature variation with depths. The temperature and EC profiles of the groundwater were recorded at regular intervals along the depths of the borewells, the sensitivity of the sensor of the logger being limited to 0.1 K. An attempt was made to calculate the vertical component of the water flux in 25 borewells using the temperature profile measurements in these borewells by applying the heat convection and conduction equation and taking into account the volumetric heat capacity of water and the thermal conductivity of rocks (in the present study, granite). The temperature data was first linearly fitted. The dispersion that would exist in thermal conductivity under the assumption as uniform flux for 22 of the borewell’s is unlikely, and data was fitted to the exponential trend of the temperature profile, considered to a non-zero water flux. This approach resulted in a comparatively better fit than the linear variation. Thus the water flux was calculated for 22 sites using the exponential variation relationship. It was found that the water flux ranges from 4 to 30 mm/year, which shows significant large variation from one location to other. It was also observed using the temperature measurements at the surface (from the temperature recorded at the meteorological station) that the temperature at depths is not affected by the variations at the surface, which confirms the reliability of vertical velocity/flow rate determination.

Hydrological subsurface investigation using geophysical electrical and magnetic methods in and around Valliyar river basin, India

The focus of the present study is to identify potential groundwater zones using resistivity Schlumberger array and magnetic method for mapping hidden lineaments in and around the Valliyar river basin situated in the tail of Southern India. Estimation by 2-D radial power spectrum indicates that the maximum depth at which the magnetic source is present is about 700 m to 800 m. In case of shallow depth magnetic source rock, it is about 40 m to 45 m. The results of magnetic data have revealed the presence of a major magnetic lineament trending in NW to SE direction. The electrical resistivity survey in our study area gives information on sub-surface layers like the weathered zone, aquifer resistivity and aquifer thickness. The locations corresponding to ves-35, ves-40, and ves-47 have weathered and fracture layers having a thickness greater than 20 m, situated in the magnetic major lineament trend. Regarding master curves for layer analysis, H and HA type curves are generally observed in the hard rock region. The interpretation of results from the present study endorses that the coastal region of the study area has good groundwater potential.

Modelling the hydrological interactions between a fissured granite aquifer and a valley mire in the Massif Central, France

Abstract. We developed a high-resolution MIKE SHE/MIKE 11 model of a 231.3 ha headwater catchment in the granitic uplands of the French Massif Central to estimate the contribution of groundwater upwelling to the water balance of the Dauges mire, an acidic valley mire of international importance for nature conservation. We estimated that groundwater upwelling from the underlying weathered granite formations – mostly an approximately 55 m deep fissured zone – provides 27.1 % of total long-term inflows to the mire. This contribution increases to 37.2 % in September when total inflows are small. Overland boundary inflow accounts for an average of 40.2 % of total inflows. However, most of this originates from groundwater seepage through mineral soils along the mire margins or in small non-channelised valleys upslope of the mire. A sensitivity analysis showed that model performance in terms of the simulation of mire groundwater levels was most sensitive to parameters describing the mineral soils and weathered granite formations rather than the overlying peat layer. Variation partitioning demonstrated that groundwater upwelling was the most important factor driving simulated monthly groundwater table depth within the mire. Sustained groundwater upwelling maintains the mire water table close to or at ground level for most of the year. As a result, precipitation and overland boundary inflows quickly leave the wetland as saturation-excess runoff. There was close agreement between the observed distribution of mire habitats and areas where the simulated long-term groundwater seepage rate was larger than zero in September. Our results demonstrate that, contrary to the assumed small contribution of groundwater to the hydrology of hard-rock regions, groundwater upwelling from underlying weathered formations can be a quantitatively important and functionally critical element of the water balance of valley mires in granitic headwater catchments. These results have important legal and management implications.

Interaction of cutting disc with heterogeneous ground

AbstractIn this contribution, the peridynamic theory [1] is utilized to analyze the interaction of cutting disc of a Tunnel Boring Machine (TBM) with mixed (heterogeneous) ground conditions. Peridynamic formulations, in contrast to classical continuum theory, do not contain spatial derivatives [1,2], which makes it a preferable tool for modeling phenomena involving discontinuities, such as complex fracture and fragmentation processes [3]. The model was initially used to simulate a full‐scale Linear Cutting Machine (LCM) test for various penetration levels [4]. The cutting forces obtained were in agreement with the experiment [5]. Excavation process in mixed ground conditions is analyzed using simulations in which a cutting disc moves from a soft ground (soil, weathered rock or soft rock) region into a hard rock region. There is a sudden increase in the force on the cutting disc as it moves from a soft to hard ground, this abnormal peak in force is further investigated with respect to various tool penetrations.

Targeting groundwater potential zones using Electrical resistivity and GIS techniques in Kadavanar Sub-basin, South India

Geographical Information System techniques are widely used to determine suitable sites for groundwater recharge through artificial recharge techniques. The present research work is to identify suitable locations for constructing artificial recharge structures in the Kadavanar Sub-basin, South India. People in the Sub-basin mainly depend on the groundwater resources for drinking and irrigation purposes. Groundwater resources are often overexploited in many parts of this Sub-basin to meet the water demand leading to groundwater consumption. A lot of surfaces and sub-surface information and criteria are required for mapping the groundwater recharge zone. This is where the geographic information system [GIS] provides the right impetus besides the groundwater prospective zone to harness multilayered spatial data so that multi-criteria analysis is possible. This analysis integrates historic rainfall data analysis, groundwater level fluctuation, stream network, aquifer thickness, land use/land cover and basin slope. Drainage map, slope map and land use/land cover maps were prepared from satellite imageries. Vertical electrical sounding (VES) geophysical survey with Schlumberger electrode configuration was also conducted in the basin at 50 locations to map the aquifer thickness. Spatial variation maps for groundwater level and aquifer thickness were generated using GIS. Weighted aggregation method was used in this study to obtain groundwater recharge maps. Finally, multi-criteria analysis has been carried out to identify and assess the potential sites for groundwater recharge according to the associated weightages. It is established that GIS is best suited for the mapping of groundwater recharge zones. A similar study can be extended to any other hard-rock region facing water crises.

Delineation of Potential Groundwater Zones Using Shear Wave Velocity in Eastern Deccan Volcanic Province, India

A comprehensive study based on Multichannel Analysis of Surface Waves (MASW), a near-surface geophysical technique, was carried out for the first time in the Mandla Lobe of the Eastern Deccan Volcanic Province. The study was conducted to demarcate fractures, which are essential for finding potential groundwater zones in the hard rock region and for the delineation of shallow subsurface geological features in terms of shear wave velocity. The MASW surveys were carried out at different selected locations in the study area to delineate fractures in the basaltic terrain covered with thin weathering and alluvium cover. These basalts are mainly comprised of massive, vesicular and amygdaloidal varieties and interpreted as different basaltic flows of Mandla, Dhuma and Pipardahi formations. The shear wave velocity sections divulge the layered nature of the basalt sequences. In some of the massive flows, there are low-velocity vertical zones that can be deduced to be either vertical columnar joints or fracture zones, and the low-velocity weathered flows can be the good groundwater reservoirs. The shear wave velocities Vs obtained are in the range from 300 to 2500 m/s at different locations, and the thicknesses of flows are varied in the MASW sections. The obtained shear wave data are compared with the borehole data, and the results are well correlated. The study clearly differentiates the variations within basaltic formations, which are interpreted as potential groundwater zones.

A GIS-based evaluation of hydrochemical characterisation of groundwater in hard rock region, South Tamil Nadu, India

Groundwater is a major source for domestic and agricultural uses in Natham Taluk, Dindigul district, Tamil Nadu, India. The intention of this study is to determine the quality of groundwater for domestic and irrigation purposes in the hard rock region. Totally, 37 samples were collected and analysed for physical parameters that are pH, EC, TDS, TH, major cations and anions. Piper diagram shows that Ca-HCO3 and mixed Ca-Mg-Cl is the most prominent type of water. Gibbs diagram reveals that the higher concentrations of magnesium, sodium and potassium ions are accredited to geological sources such as rock-water interaction, ion exchange process and evaporation that are the major factors affecting the nature of groundwater. In view of irrigation indices, most of the sample locations are fit for irrigation use except magnesium hazard value. Additional statistical analysis, such as correlation and principal component analysis, was calculated using SPSS software. All results are indicated; weathering, rock-water interactions and anthropogenic activities are a significant factor that alters the existence of groundwater in the research area.

Delineation of groundwater potential zone using analytical hierarchy process and GIS for Gundihalla watershed, Karnataka, India

Remote sensing (RS) and geographical information system (GIS) have a wide range of applications in groundwater assessment, exploration, and resource management. Several other types of research targeting the water quality assessment in the study area have been done. However, the present work is the first attempt to delineate the groundwater potential zone using a different approach. This paper finds the way to identify the groundwater potential zone for Gundihalla watershed located in the hard rock region of Bellary district in Karnataka state. Various thematic layers such as geomorphology, lithology, land use and land cover (LULC), soil, drainage density, lineament density, rainfall, and slope were prepared for the study area. The various sub-criteria of each thematic layer were ranked based on their influence in the groundwater recharge, and each thematic layer was given a weightage, derived from the analytical hierarchy process (AHP). The overall groundwater potential map for the study areas is obtained by performing a weighted overlay analysis of all the thematic layers. The resultant groundwater potential zone (GWPZ) map is further categorized into five different groundwater potential: very good (76%) good (23.70%), moderate (23.30%), poor (18%), and very poor (16.40%). The obtained results were validated using groundwater fluctuation data for pre- and post-monsoon periods. The validation holds well for the methodology adopted. Thus, the results were utilized for carrying out water management through artificial recharge and further exploration approaches.

Managed Aquifer Recharge at a Farm Level: Evaluating the Performance of Direct Well Recharge Structures

A field study evaluated the performance of direct well recharge structures (DWRS) in order to harvest and filter farm runoff and its discharge into open dug wells to augment groundwater recharge. This was undertaken between 2016 and 2018 using a total of 11 wells in the Dharta watershed, situated in a semi-arid hardrock region of Udaipur district, Rajasthan, India. The depth to water level in each DWRS well was monitored weekly for 1 to 3 years before and after the DWRS was established, and water samples were taken for water quality analysis (pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, fluoride, and Escherichia coli) before and during the monsoon period. For each DWRS well, two control wells in close proximity were also monitored and sampled. Five of the DWRS established in 2018 also had flow meters installed in order to measure discharge from the filter to the well. The volume of water recharged through DWRS into individual wells during the 2018 monsoon ranged from 2 to 176 m3 per well. Although the mean rise in water levels over the monsoon was higher in DWRS wells than in nearby control wells, the difference was not significant. Values of pH, EC, TDS, and F decreased in DWRS and control wells as each monsoon progressed, whereas the turbidity of wells with DWRS increased slightly. There was no significant difference between DWRS and control wells for pH, EC/TDS, turbidity, or fluoride. The presence of E. coli in DWRS wells was higher than in control wells, however, E. coli exceeded drinking water guidelines in all sampled wells. On the basis of this study, it is recommended that rural runoff should not be admitted to wells that are used for, or close to, wells used for drinking water supplies, even though salinity and fluoride concentrations may be reduced. For this study, none of the 11 DWRS wells produced sufficient additional recharge to potentially increase dry season irrigation supplies to justify expenditure on DWRS. This even applies to the DWRS well adjacent to a small ephemeral stream that had a significantly larger catchment area than those drawing on farmers’ fields alone. An important and unexpected finding of this study was that no sampled open dug well met drinking water standards. This has led to a shift in local priorities to implement well-head water quality protection measures for wells used for drinking water supplies. It is recommended that parapet walls be built around the perimeter of such dug wells, as well as having covers be installed.