Evaluation of groundwater resources for sustainable groundwater development in a semiarid river basin of India

There is a growing stress on groundwater due to increase in the frequency and intensity of droughts, and the limited availability of surface water. Therefore, proper assessment of available groundwater reserves is highly essential at a microscale (e.g., block level) to take into account spatial variability. In this paper, a methodology for the effective assessment of groundwater resources is demonstrated considering a semiarid river basin of Western India as a study area. The rainfall data of nine raingauge stations and seasonal groundwater-level data of 132 sites over the basin for 20 years (1990-2009) were used. Groundwater availability in the unconfined aquifer was evaluated at a block level in terms of 'static groundwater reserve (SGWR)' and 'dynamic groundwater reserve (DGWR),' and their spatial and temporal variabilities were analyzed. Furthermore, the status of groundwater utilization in individual blocks was explored considering the level of groundwater development (GWDL) and the trends of long-term seasonal groundwater levels. To sustain available groundwater resources on a long-term basis, the runoff potential in the study area was also evaluated. It was found that SGWR varies from 0.09 to 136.97 MCM (million cubic meters), whereas DGWR ranges from -35.85 to 156.26 MCM. During 'normal' years, around 43% of the study area has a SGWR in the range of 20-40 MCM and DGWR in the range of 0-50 MCM. Although the GWDL in the study area varies from about 12 to 124%, the status of groundwater development in the study area is categorized to be 'safe.' The analysis of runoff potential in the study area revealed that it considerably varies with time and space. About 71% of the study area is suitable for rainwater conservation during 'wet' years, whereas this figure reduces to 33% in 'normal' years. It is emphasized that regular monitoring of groundwater at a suitable spatial scale (at least block level) is necessary on long-term basis and the adoption of rainwater harvesting measures are indispensable for sustainable utilization and management of groundwater resources in semiarid regions.