Morphometric characterization of sub-basins in a hard-rock aquifer system of Maharashtra, India, using geospatial and geostatistical tools

The presence of groundwater in the Deccan Traps of Maharashtra is governed by the heterogeneities in the basaltic flow morphology, weathered thickness, and morphological features. The rapid growth of population has led to a rise in water demand vis-a-vis severe water scarcity, especially in drought-prone regions. An attempt has been made to locate the areas that are favorable for groundwater recharge by analyzing various morphometric indices for nine sub-basins of Mann River basin in south-eastern Maharashtra, derived using satellite data and geographical information system (GIS). Eleven influential morphometric parameters are considered to prioritize these sub-basins performing the weighted sum analysis (WSA) technique, wherein weights are assigned to individual morphometric parameters based on their importance. The analysis reveals that out of nine sub-basins, sub-basin 6 (SB-6) with suitability index value 2.8 is most favorable whereas, SB-1 with index value 7.48 is least suitable due to its high undulation, greater runoff, poor vegetation cover, and steeper slopes. Furthermore, these sub-basins have been categorized into five classes of groundwater recharge on the basis of prioritization index values. These suggest that 42% of the area spread over sub-basins is of very good to good priority type. Subsequently, principal component analysis (PCA) has been performed to identify the most influencing morphometric parameters for groundwater recharge in basaltic aquifers. The PCA results show that the first principal component (PC1) accounting for 37.44 has preferred the relief ratio, basin relief, and ruggedness number showcasing the relief aspect of morphometry dominates the groundwater recharge process. Principal component PC2 accounts for 29.74 of total variation with stream frequency and drainage density parameters that are inversely related to groundwater recharge. The third principal component PC3 holds account for 26.31 that is strongly loaded with form factor, elongation ratio, and circularity ratio revealing the significance of the shape of the watershed in generating the surface runoff and increasing the amplitude of hydrograph. Thus, it is suggested to adopt conservation measures in high priority areas, like rainwater harvesting, aquifer recharge, and resource management for effective land and water management.