Groundwater Recharge Structures Research Articles

Assessing Suitable Groundwater Recharge Locations and Structures Using GIS Technique in a Semi-Arid Region

Abstract: Groundwater management is the continuous research problem in semi-arid regions of India especially in Telangana State. The observed phenomenon can be ascribed to a combination of climatic factors, such as erratic rainfall and soaring temperatures, along with human factors like large-scale cultivation of paddy crops using traditional methods and the extensive drilling of numerous bore wells. Few parts of Nalgonda revenue division in Telangana State are experiencing such conditions which pulled for the augmentation of groundwater resource by suggesting suitable artificial groundwater recharge structures by adopting geographical information system technique and Central Ground Water Board guidelines. Nala bunds, check dams and water absorption trenches are the appropriate recharge structures for the study area that were identified using drainage network, lineaments, slope and land use land cover. In conclusion, this study has proven the reliability of GIS technique when followed with proper guidelines is effective in finding the suitable groundwater recharge structures.

Hypsometric Analysis of WRC-1 Watershed, Chargarh River Basin, Central India: A Remote Sensing and GIS Approach

Hypsometric analysis is a valuable tool for determining the tectonic evolution of a river basin and the erosion susceptibility. It is also important for integrated watershed management, which include selecting suitable locations for groundwater recharge structures and for conservation of soil and water. This type of study can analyze the relationship between horizontal cross sectional area and the altitude of the watershed. It evaluates the hypsometric curve and hypsometric integral, as generated for the WRC-1 watershed, Chargarh river basin through remote sensing and GIS technique. In the present case, hypsometric analysis was carried out using Survey of India topographic maps, Arc map-10.2 software and SRTM-DEM. The hypsometric integral is calculated using mean elevation minus minimum elevation, divided by relief. The hypsometric curve, with a value of 0.69 for the hypsometric integral clearly indicates an inequilibrium stage (youthful stage) of geomorphic development, which is highly susceptible to erosion. These interpretations can further utilize appropriate measures of soil and water conservation for long-term development within the WRC-1 watershed.

Delineation of suitable sites for groundwater recharge based on groundwater potential with RS, GIS, and AHP approach for Mand catchment of Mahanadi Basin

Groundwater management requires a systematic approach since it is crucial to the long-term viability of livelihoods and regional economies all over the world. There is insufficient groundwater management and difficulties in storage plans as a result of increased population, fast urbanisation, and climate change, as well as unpredictability in rainfall frequency and intensity. Groundwater exploration using remote sensing (RS) data and geographic information system (GIS) has become a breakthrough in groundwater research, assisting in the assessment, monitoring, and conservation of groundwater resources. The study region is the Mand catchment of the Mahanadi basin, covering 5332.07 km2 and is located between 21°42′15.525″N and 23°4′19.746″N latitude and 82°50′54.503″E and 83°36′1.295″E longitude in Chhattisgarh, India. The research comprises the generation of thematic maps, delineation of groundwater potential zones and the recommendation of structures for efficiently and successfully recharging groundwater utilising RS and GIS. Groundwater Potential Zones (GPZs) were identified with nine thematic layers using RS, GIS, and the Multi-Criteria Decision Analysis (MCDA) method. Satty's Analytic Hierarchy Process (AHP) was used to rank the nine parameters that were chosen. The generated GPZs map indicated regions with very low, low to medium, medium to high, and very high groundwater potential encompassing 962.44 km2, 2019.92 km2, 969.19 km2, and 1380.42 km2 of the study region, respectively. The GPZs map was found to be very accurate when compared with the groundwater fluctuation map, and it is used to manage groundwater resources in the Mand catchment. The runoff of the study area can be accommodated by the computing subsurface storage capacity, which will raise groundwater levels in the low and low to medium GPZs. According to the study results, various groundwater recharge structures such as farm ponds, check dams and percolation tanks were suggested in appropriate locations of the Mand catchment to boost groundwater conditions and meet the shortage of water resources in agriculture and domestic use. This study demonstrates that the integration of GIS can provide an efficient and effective platform for convergent analysis of various data sets for groundwater management and planning.

Hydrological Inferences of Morphometric Parameters for Management of River Sub-basin in Semi-arid Tropics of India using Geospatial Technique

The runoff and sediment produced from a river basin due to effective precipitation depends on the characteristics of its catchment. The catchment characteristic is site-specific and varies from basin to basin. It depends upon the topographic characteristics, climatic parameters, soil properties, geology, and human-induced activities of the catchment. Knowledge of these factors is essential for sustainable management of natural resources, i.e. soil and water and site-specific conservation measures of the basin or watershed. Morphometric parameters of the basin truly reflect the combination of all characteristics, and this is one of the major indicators for the hydrological behaviour of any watershed or catchment. For the present study, Pairi River sub-basin, situated between 81°51'58.7"- 82°26'16.04" E longitude to 19°55'51.9"- 20°55'6.9" N latitude, has been considered for the morphometric analysis using geospatial technique . Results of morphometric analysis revealed that the Pairi sub-basin has seventh order drainage network with a dendritic pattern. The dendritic drainage pattern of the subbasin shows that the basin has homogeneous lithology and a lack of structural control. The drainage density and stream frequency indicates that the sub-basin has a gentle slope and good permeability of sub-surface material. So, this sub-basin is suitable for constructing artificial groundwater recharge structures to improve the groundwater resource. The length of overland flow revealed that surface runoff may reach the stream more quickly within the sub-basin. The bifurcation ratio varies different successive stream orders. The mean bifurcation ratio is low, indicating that the geologic structure does not distort the drainage pattern and produces low to moderate peak flow in the subbasin. The shape parameters such as form factor, circulatory ratioand elongation ratio indicate that the sub-basin is elongated in shape, high infiltration capacity, and flatter hydrograph with low to moderate runoff. This study can be useful for developing and managing natural resources of the Pairi sub-basin, like site-specific soil and water conservation measures such as check dam, percolation tank, water harvesting structure and development and management of groundwater, etc

Determination of potential recharge zones and its validation against groundwater quality parameters through the application of GIS and remote sensing techniques in uMhlathuze catchment, KwaZulu-Natal, South Africa

Urbanization has accelerated changes in the quantity and stability of the water resources in the uMhlathuze watershed of KwaZulu-Natal. This study applied the use of GIS and remote sensing to demarcate groundwater potential recharge zones in the uMhlathuze catchment using AHP approach and Catastrophe theory by assigning weights to 10 parameters with their sub-criteria and the results were validated against groundwater quality data. It was discovered that 22.92% and 26.38% of the catchment is encompassed by ‘Low’ groundwater potential recharge zones, 0.37% and 0.08% by ‘Very low’ groundwater potential recharge zones, 9.42% and 10.26% by ‘Good’ groundwater potential recharge zones, 66.87% and 63.19% by ‘Moderate’, and 0.42% and 0.09% by ‘Very good’ for AHP and Catastrophe theory respectively. The resultant map demonstrated that recharge potential of groundwater is lowest in mountainous regions coupled with hard rock geology of low transmissivity, whereas the highest potential prevails in lower slopes and plains with more permeable soil. The findings of the validation revealed that the lowest and highest total dissolved solid, nitrate and groundwater level overlaps with the ‘Good and Very good’ and ‘Low and Very low’ groundwater potential recharge zones respectively. From the collective findings of this study, it is inferred that the convergence and use of GIS and remote sensing for delineating the groundwater potential recharge zones are effective. The study further recommends that this method can be applied in research/projects involving the implementation of artificial groundwater recharge structures for better groundwater planning and governance.

Water Demand and Supply Analysis using WEAP Model for Veda River Basin Madhya Pradesh (Nimar Region), India

Significant gaps exist in water management strategies implemented in the sub-basin of Narmada River, the Veda River Basin. Hence, the main goal of this study is to predict water demand and supply, recharge and draft with the use of the Water Evaluation and Planning System (WEAP) Model. The study area is watershed of the Veda River located in the Nimar region of Madhya Pradesh, and Middle Narmada River sub-basin of India. In this study, the WEAP model is used as a decision support system for watershed management. The WEAP model uses water balance approach for the generation of results, based on that 4 types of scenarios have been developed are high population growth, high industrial growth, rainwater harvesting, and water storage structures for future trends. The unmet water demands were simulated in all administrative blocks, catchments, and industries which amounting to 9.58´108 m3 in 2011 and 9.65´108 m3 in 2030. Results suggested that the addition of water storage structures as well as artificial groundwater recharge structures reduce the unmet water demand for domestic consumption and meet irrigation water requirements.
 HIGHLIGHTS
 
 Watershed management using a Decision Support System
 GIS and WEAP (Water Evaluation and Planning System) model used in order to find demand and supply of water
 Scenarios generated based on demand and supply analysis
 Analysis of scenarios and future suggestions
 
 GRAPHICAL ABSTRACT

Assessing the Groundwater Reserves of the Udaipur District, Aravalli Range, India, Using Geospatial Techniques

Population increase has placed ever-increasing demands on the available groundwater (GW) resources, particularly for intensive agricultural activities. In India, groundwater is the backbone of agriculture and drinking purposes. In the present study, an assessment of groundwater reserves was carried out in the Udaipur district, Aravalli range, India. It was observed that the principal aquifer for the availability of groundwater in the studied area is quartzite, phyllite, gneisses, schist, and dolomitic marble, which occur in unconfined to semi-confined zones. Furthermore, all primary chemical ingredients were found within the permissible limit, including granum. We also found that the average annual rainfall days in a year in the study area was 30 from 1957 to 2020, and it has been found that there are chances to receive surplus rainfall once in every five deficit rainfall years. Using integrated remote sensing, GIS, and a field-based spatial modeling approach, it was found that the dynamic GW reserves of the area are 637.42 mcm/annum, and the total groundwater draft is 639.67 mcm/annum. The deficit GW reserves are 2.25 mcm/annum from an average rainfall of 627 mm, hence the stage of groundwater development is 100.67% and categorized as over-exploited. However, as per the relationship between reserves and rainfall events, surplus reserves are available when rainfall exceeds 700 mm. We conclude that enough static GW reserves are available in the studied area to sustain the requirements of the drought period. For the long-term sustainability of groundwater use, controlling groundwater abstraction by optimizing its use, managing it properly through techniques such as sprinkler and drip irrigation, and achieving more crop-per-drop schemes, will go a long way to conserving this essential reserve, and create maximum groundwater recharge structures.

Investigation of groundwater recharge prospect and hydrological response of groundwater augmentation measures in Upper Kosi watershed, Kumaun Himalaya, India

The discharge pattern of springs in the Himalayan region is highly variable due to diverse lithology, complex hydro-geological formations and dynamic tectonic activities. Therefore, delineation of groundwater recharge potential zones is extremely essential for sustainability of groundwater resources in Himalayan region. Apart from delineating potential zone, it becomes more important to evaluate the identified recharge zones for their validity. The current study therefore, was aimed to delineate recharge potential zones that suggested the suitable sites where potential of recharging groundwater is more. Second objective of the study included evaluation of identified recharge sites/zone through implementation of groundwater recharge structures followed by monitoring discharge in Upper Kosi watershed in Uttarakhand, Kumaun Himalaya, India. Standard technique was established in order to detect potential recharge sites through allocating weightage as well as score to various controlling through multi-criteria decision-making approach in GIS domain. The results indicated that only 19.6% area in the Upper Kosi basin lied in good to excellent recharge potential. However, 31.7% and 15.2% area lied in fair and moderate recharge potential which was also considered as suitable for execution of artificial recharge structures. Moreover, a slow recession in discharge was observed from the treated micro-watershed as compared to the untreated one. This validates the legitimacy of the recharge zone(s) identified using the contended approach.

Rainfall variability analysis using Precipitation Concentration Index: a case study of the western agro-climatic zone of Punjab, India

Due to climate change, the rainfall pattern has changed, which ultimately either cause flood or drought in any region of the world. Hence, a rainfall variability analysis helps to manage the water resources better. Rainfall variability analysis of a long term at particular area reveals vital information about past and future climate. The study's objective was to analyse the rainfall variability and intensity of long term monthly rainfall data (1982–2018) using the Precipitation Concentration Index (PCI). Data was collected from Punjab Agricultural University, Regional Research Station, located at Bathinda, India. The PCI was calculated for the annual, winter, pre-monsoon, monsoon, post-monsoon season, and decadal scale. Results have outlined that PCIAnnual ranges from the lowest of 14.96 in 2006 to the highest of 43.82 in 2000, and the average of 37 years is 23.22. About ≈59.5% of the year PCIAnnual was characterised by Strong Irregularity of Precipitation Distribution (SIPD, PCIAnnual> 20), an indication of SIPD within the 37 years. While ≈2.7% of the year recorded annual value within the moderate irregular range (10<PCIAnuual<15), which indicates an irregular rainfall distribution (MIPD) and concentration across the months. Similarly, the precipitation concentration in China was also found strongly irregular in the western and northern parts of the northwest and the northern region of the Tibetan Plateau. The study recommends that the Bathinda Development Authority (BDA) may use and adopt these results and redevelop the existing groundwater recharge structures (pond) and artificial recharge structures.

GIS-based mapping of water-level fluctuations (WLF) and its impact on groundwater in an Agrarian District in Tamil Nadu, India

This study describes the results of groundwater table variation in Thanjavur District before and after the monsoon seasons. Groundwater-level data acquired by the field measurement and the elevation data have been obtained from the topographic survey. Groundwater is the major source for different sectors in this region, and the major portion was used for irrigation. The impacts of geology, soil types, topographic elevation, land-use changes were critically analyzed and identified that these factors are controlling the infiltration capacity. The maximum fluctuation in the water table was 2 m below the ground level; still, 50% of the study area is under threat of overexploitation. This is projecting to a severe shortage in water supply soon. Groundwater quality is threatening by the saline intrusion in the coastal region, and the irrigation return flows inland. The spatial variation maps were useful in visualizing the seasonal water level and fluctuation in Thanjavur. A proper monitoring system, efficient irrigation practices, and effective groundwater recharge structures are recommended.

Application of geospatial modeling in deciphering groundwater recharge site and structures in Paschim Medinipur district, India

Indiscriminate urbanization and population explosion have put tremendous stress on groundwater resource of Paschim Medinipur, an agriculture-dominated area. In this aspect delineation of potential groundwater recharge zones can play a crucial role in the long run. Initially, ten different influencing factors i.e., geology, geomorphology, rainfall, aquifer material, drainage density, soil type, lineament and fault density, slope, elevation and Land use land cover (LULC) are integrated into ArcGIS environment to generate the potential groundwater recharge zones (GWRZ) within the study area. The final GWRZ was categorized into three classes namely high, medium and low where about 33% (3152.46 sq. km) of the total area fall under high GWRZ, about 25% (2379.02 sq. km) is covered by medium GWRZ and low GWRZ covers about 39.96% (3743.16 sq. km) of the study area. Predicted model is validated with water table fluctuation data collected from 87 monitoring wells by implementing Success Rate Curve (SRC) and the Prediction Rate Curve (PRC) where an accuracy of 81% prediction is observed. The study of WTF trend for past 23 years using the multiplicative model of time series shows a significant declining trend in-depth to water-table. Based on the model outcome various recharge structures are recommended in the specific locations of the study area which may be further confirmed through field investigation before implementation. Outcomes of the present study can be a first-hand tool to the policymakers, planners and government officials for sustainable water resource management in the study area.

Planning rainwater conservation measures using geospatial and multi-criteria decision making tools.

The assessment of rainwater-harvesting demand (RWHD) map and the identification of appropriate priority-based locations for rainwater-harvesting (RWH) and groundwater recharge structures are very crucial for the water managers, particularly in irrigation commands. This study addresses this challenge by using multi-criteria decision-making (MCDM) and geospatial techniques to present a novel and robust approach for generating RWHD map and identifying sites/zones for distinct RWH and groundwater recharge on a priority basis. Primary thematic layers such as existing irrigation water supply, irrigation demand, and groundwater potential were considered in this study for delineating RWHD zones. Further, sites suitable for RWH and groundwater recharge were identified using soil, slope, drainage network, and lineament thematic layers of the study area and they were prioritized. Four zones of rainwater demand were identified for the prioritization of RWH and groundwater structures: (a) "low" rainwater-harvesting demand zone (covering 3% of the total study area), (b) "moderate" rainwater-harvesting demand zone (40%), (c) "high" rainwater-harvesting demand zone (42%), and (d) "very high" rainwater-harvesting demand zone (15%). Moreover, 46 sites for check dams and 145 suitable sites for percolation tanks were identified, together with 253ha area for groundwater recharge based on the priority of rainwater-harvesting demand. Integration of geospatial and MCDM techniques in conjunction with suitable thematic layers provides a helpful and realistic tool for large-scale planning and management of rainwater conservation measures.

Rainfall-surface runoff estimation for the Lower Bhavani basin in south India using SCS-CN model and geospatial techniques

Rainfall and surface runoff are the two most important components, which control the groundwater recharge of the basin. The long-term groundwater recharge of an aquifer gets affected by the population growth, irregular agriculture activities and industrialization. Hence, estimation of rainfall-surface runoff is very much essential for proper groundwater management practices. In the present study, Soil Conservation Service Curve Number (SCS-CN) model was employed in combination with geospatial techniques to estimate rainfall-surface runoff for the Lower Bhavani River basin in South India. To develop the SCS-CN model, rainfall data were obtained for 33 years (1983–2015) from 22 rain gauge stations spread over the basin. IRS LISS-IV satellite data of 5.8 m spatial resolution were used to analyze the land use/land cover (LU/LC) behavior. Based on the soil properties, four Hydrological Soil Groups (HSG) were identified in the basin which is most significant for surface runoff estimation. Curve Number (CN) values were obtained for various Antecedent Moisture Conditions (AMC) such as dry condition (AMC I), average condition (AMC II) and wet condition (AMC III). Spatial distribution of CN values was plotted using Geographical Information System (GIS) for the entire Lower Bhavani Basin to assess the surface runoff potential. The results indicate that the annual rainfall varies from 267 mm (2002) to 1528.6 mm (2005), and the annual surface runoff varies from 102.04 mm (1985) to 463.02 mm (2010). The SCS-CN model outputs predict that the average surface runoff of the basin is 211.99 mm, and the average surface runoff volume is 81,995,380 m3. The study also indicates that nearly 53% of the basin area is dominated by high to very high surface runoff potential. Finally, the output of surface runoff potential was validated with the Average Groundwater Level Fluctuation (AGLF) observed in 57 wells spread over the entire basin. The basin AGLF ranges from 2.32 to 21.72 m. The surface runoff potential categories are satisfactorily matching with the AGLF categories. Moderate surface runoff as well as moderate AGLF zones mostly occupy the central portion of the basin, which possess good groundwater potential. However, the high surface runoff zones in the basin lead more surface water flow into the river channels, which reduce the infiltration rate and decline the water table. This problem can be solved by constructing suitable artificial groundwater recharge structures across the river channels in the high surface runoff potential areas.

Morpho-lithostructural analysis of Ala River basin for flood risk assessment: geospatial techniques intervention

An integrated approach of morphometric and litho-structural studies for flood risk assessment of Ala River Basin (ARB) in Akure city, southwestern Nigeria aided by geospatial techniques was carried out. The Ala River Basin comprises of four sub-basins covering a total area of 427km2 with fourth stream order of dendritic and sub-trellis drainage patterns. The values obtained for the morphometric features such as Form Factor, Circularity Ratio, Elongation Ratio, Stream Frequency, and Relief Ratio and Compactness Coefficient for ARB revealed an elongated basin type, posing a great flood threat to the urban community. Drainage density for all the sub-basins is very low, typically a coarse type that supports ample time for overland flow. All the lithological units are characteristically impermeable with low lineaments density. Thinness of the soil profile, and frequency of stream flow showed good relation to low infiltration with attendant high runoff leading to flood events in the upstream section. Flood sub-basin wise prioritization was carried out by employing the result obtained from morphometric classification and structural analysis. Different weightages were assigned to the different morphometric and structural parameters for the four sub-basins based on flood potentials. Ala River sub-basins have been classified into three namely; high, moderate and low based on flood potentials. The sub-basin I and II located at the upstream section are highly vulnerable to floods, while sub-basin III and IV located at the downstream section are not presently vulnerable to flooding respectively. The flood water in the flood threatened sub-basins (I and II) can also be harvested through siting and construction of natural groundwater recharge structures such as check dams and contour bunds.

Mapping of Groundwater Recharge Potential Zones and Identification of Suitable Site-Specific Recharge Mechanisms in a Tropical River Basin

The increasing demands for the groundwater resources along with decreasing availability, especially in the hard-rock aquifers, call for sustainable groundwater management in India. The present study attempts to identify the potential zones for groundwater recharge, through water conservation measures, in a tropical river basin of Kerala (India), viz., Ithikkara River Basin. The approach enables us to locate the areas suitable for different groundwater recharge structures using remote sensing, geospatial data, and multi-influencing factor technique in the GIS environment. The geo-environmental variables used in the study are lithology, geomorphology, available space for recharge, slope angle, lineament density, soil texture, rainfall, percentage of sand fraction in soil, land use/land cover, and drainage density. The results indicate that lithology, available space for recharge and geomorphology, is the significant variables controlling the groundwater recharge of the study area. The estimated recharge potential zones of the basin are classified into four different classes based on their suitability for groundwater recharge, viz., very good, good, moderate, and least recharge potential zones. Roughly, 50% of the basin area belongs to very good and good recharge zones and is suitable for implementing various groundwater-recharging mechanisms. Based on the variability in the geo-environmental factors of the study area, different artificial groundwater recharge structures (i.e., rainwater infiltration pits, percolation ponds/trenches, injection wells/pond-cum-injection wells and check dams) are suggested using a rule-based approach. The results of the study will be beneficial to the formulation of sustainable groundwater management plans for the region.

Identification of Suitable Sites for Artificial Groundwater Recharge Structures in Semi-arid region of Anantapur District: AHP Approach

The conservation and sustainable advancement of soil and water assets is one of the fundamental standards for improvement of arid and semi-arid regions of India. The present study is underway to evaluate the Artificial Groundwater Recharge Zones (AGRZ) in the semi-arid region of Anantapur district, Andhra Pradesh, India using Remote Sensing (RS), Geographical Information System (GIS) and Analytical Hierarchy Process (AHP) technique. The comparative weights were assigned to different thematic layers with the help of the decision making tool of AHP. A set of eight thematic layers influence groundwater potential (GWP) is determined based on their corresponding weights, which depend on a Saaty’s 9 points scale. These weights are normalized using AHP technique to identify the AGRZs. Five AGRZs were recognized as very low, low, moderate, good and very good, depending on its suitability to identify the sites for groundwater recharge. About 4.29 % (8.96km2) and 17.70 % (36.95km2) area in the region show very good and good potentials of artificial groundwater recharge, respectively. On the other hand 61.59% (128.60km2), 11.94% (24.94km2) and 4.48 % (9.35km2) area showed moderate, poor and very poor potentials. Overall accuracy of AGRZ map is 82.05%. 92 check dams, 19 percolation tanks and 7 check walls were found suitable in the region. The effectiveness and prediction ability of the method depends on integrity of the criterion used. AHP based methodology can be useful for precise and reliable analysis and predictions of groundwater in semi-arid regions of India.

AN ASSESSMENT OF SPATIAL VARIATION OF LAND SURFACE CHARACTERISTICS OF MINNA, NIGER STATE NIGERIA FOR SUSTAINABLE URBANIZATION USING GEOSPATIAL TECHNIQUES

AN ASSESSMENT OF SPATIAL VARIATION OF LAND SURFACE CHARACTERISTICS OF MINNA, NIGER STATE NIGERIA FOR SUSTAINABLE URBANIZATION USING GEOSPATIAL TECHNIQUES

Feasibility of Artificial Groundwater Recharge Structures for Urban and Rural Environment of Ranchi in India using Geospatial Technology

Artificial recharge plays a prominent role in the sustainable management of groundwater resources. The study has proposed a methodology to viable artificial recharge structure using geographical information system (GIS) and empirical equation techniques for augmenting groundwater resources in the Ranchi urban and rural area of Ranchi District, Jharkhand. The thematic layers for geomorphology, drainage density, order of streams, runoff and trend has been prepared in the GIS environment using convection and remote sensing data. It has been found that the slope and topographic gradient of Ranchi region is one of the major governing factors, which restricts to hold surface water stagnant. Jumar watershed is found as the most feasible watershed for the construction of check dams/percolation tanks followed by Lower Subarnarekha watershed. Out of 15 deeper exploratory wells, 14 are declining. Harmu watershed is found to be in the worst condition in terms of availability of runoff water. Harmu, Kanke, Bariyatu, Namkum, Doranda, Hinoo and Hatia have found as the most suitable locations for installation of RTRWH within the Ranchi urban area. Based on the available field information, check dams are suggested as the most promising artificial recharge structures for Ranchi rural environment.

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

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

Application of Geoelectrical Resistivity Technique for Groundwater Explorationin Lower Ponnaiyar Sub-Watershed, Tamilnadu, India

GeoelectricalResistivity survey was carried out in Lower Ponnaiyar Sub-watershed, to intercept the sub-surface lithology and groundwater prospective zones. Twenty Vertical Electrical Sounding (VES) of the Schlumberger configuration were performed with an AB/2 separation 100 m. The acquired geoelectric data were interpreted with curve matching and computer iteration using Inverse Slope software. The results showed the presence of six geoelectric layers comprising Alluvium, Sand, Silt, Clay, Clayey sand and Hard Rock. The investigations also revealed the range of resistivityvalues from - 40 to 400 Ωm, while the depth of aquifer ranged between 6 and 100 m. The prospective for theoccurrence of groundwater in the Lower Ponnaiyar watershed was categorized as high, good, moderate and low by interpreting the sub-surface geophysical studies. The groundwater recharge structures like percolation pond, check dam have to be constructed in the moderate and low zones of groundwater potential so as to augment the groundwater resources.