Groundwater is a vital natural resource that sustains wetlands, rivers, streams, and human habitats 1. Groundwater is a key supply for residential water, particularly in rural India, and its use requires adequate design. Overexploitation of groundwater, growing industrialization, urbanization, mining, automobile industries, climate change, and other human pressures all pose ongoing threats to groundwater resources 2. Heavy rainstorm discharge and droughts are the two most crucial extremes of climate change, as measured by both short and long-term effects on underground water supply. Hydrometeorology, geomorphology, geologic structures, and rock types had altered groundwater conditions, indicating atmospheric anomalies in the hydrologic cycle, putting pressure on aquifer recharge-withdrawal equilibrium. Seasonal variations in precipitation and Land Surface Temperature (LST) have naturally impacted aquifers in numerous states, causing water scarcity difficulties in many areas of the country. Excessive use of aquifer water has the potential to lower water levels across a large area 3. Nearly 65% of our country’s total geographic area is covered in hard rock formations with low porosity and permeability 4. India is the world’s largest user of groundwater, with an estimated 230 km² consumed 5, 6. Groundwater levels fluctuate due to a variety of hydrologic phenomena, the majority of which are caused by human influences 7. Resource planning and development at the local level can lead to an increase in groundwater levels 8. The GIS methodology has grown as a highly compelling method for hydrologic modeling, resource mapping, and delineation of spatio-temporal variation in groundwater levels using statistical data 9, 10. Even basic GIS software tools produce effective results in tracking spatio-temporal trends in groundwater levels, which generate substantial evapo-transpiration due to the temperature range of 35⁰ to 37⁰c in Hunsur taluk. The present study aims to outline the subsurface water mapping and its fluctuation for more than 15 years using simple GIS tool.

Site Description: Hunsur taluk covers 895.79 km² and has elevations ranging from 680mts to 774mts above MSL, making it cold and wet during winter and rainy season (Figure 1) 11. It consists of 4 hoblies, 30 grama panchayaths, 192 inhabited villages and 21 uninhabited villages 12. The watershed is predominantly agricultural, with crops, dispersed vegetation, and inadequate soil cover accounting for most of the land 12. The soil types are red sandy soil, red loamy soil, and deep black soil with different thicknesses up to 6 feet 13. Variation in rainfall causes periodic droughts and excessive groundwater use, which defines the research area. The Lakshman Theertha River, a sub-basin of Cauvery River, flows from south-west to north-east across the study area, supplying water for agricultural and irrigation activities.

Data and Analysis: Survey of India (SoI) toposheets (1:50,000) are efficiently used to extract Hunsur’s taluk boundary. Six observations well stations of groundwater level data from 2003 to 2019 were obtained from the District Groundwater Board (DGWB), Mysuru (Table 1) 14, and trend maps were constructed using IDW tool in ArcGIS v10 (Figure 2, Figure 4) 15. Trend maps of groundwater (m bgl) levels from 2003 to 2019 were extracted during the pre-monsoon season and evaluated for short-term (2003-2007, 2007-2011, 2011-2015 & 2015-2019) and long-term fluctuations (2003 - 2019) (Table 3, Table 4). Only the pre-monsoon (Jan to May) data of groundwater levels were studied for the present study, since these depict the actual representation without considerable influence of seasonal recharges owing to precipitation 1.

Demand for water sources is quickly increasing each year, particularly in the domains of agriculture, industries, manufacturing industries, mining, automobile industries, residential, and others, which may have an impact on the adequate supply process. The trends in groundwater levels during the pre-monsoon season (Jan-May) during a 16-year period (2003-2019) were investigated using GIS-generated maps (Figure 2, Figure 4). Overexploitation of groundwater had been observed near Somanahalli (2015) and Coimbatore colony (2019). Figure 3 shows line graphs of groundwater trend analyses over a 16-year period (2003-19). The GIS-based approach to water resources study produces reliable data that are critical in prediction, validation and scientific decision for making policies 17. Pre-monsoon groundwater level data were collected in order to eliminate seasonal recharges caused by rainfall in the present investigations. The long-term fluctuation map from 2003 to 2019 covers an area of 197.95 km² and demonstrates inclination patterns in water depth (Table 4). The deeper zones of groundwater levels in Hunsur were refilled by the flash flood of Cauvery River in August 2018. Individual well yield decreased when groundwater levels fell, bore wells failed, dug wells dried up, and power usage skyrocketed by the usage of electric vehicles. 18

The use of GIS techniques to investigate groundwater trend analysis produce significant and meaningful results in the form of simple maps. The water table varies greatly between 6.26 m (Gadavagere) to 31.66 m (Somanahalli) due to the undulating geography. The findings of this study will undoubtedly meet the water needs of rural village farmers and aid in the implementation of appropriate agricultural production practices for Hunsur taluk. A scientific periodic to periodic management using even a simple tool of GIS software will undoubtedly solve future water sources challenges. Accurate and appropriate analysis of groundwater monitoring over a longer period will undoubtedly address the environmental and socio-economic demands of water supplies.