Insights into the hydrogeological framework of the NW Himalayan Karewas (India)

Abstract

Karewas which represent the Quarternary sediments deposited in fluvio-lacustrine/fluvio-glacial environment and peripherally surround the valley of the Jhelum river basin in India are highly devoid of surface water resources. The present study is an investigation of the subsurface regime of watersheds of Jhelum basin, encompassing alluvial and Karewa (fluvio-lacustrine) sediments using various software-based techniques with an aim to understand its groundwater scenario. Geological and hydrogeological framework models were developed to infer vertical and horizontal extent of aquifers. The models predict multiple fine sand aquifers in the alluvial sediments, 0.3 to 48 m thick, encountered at 3 to 10 m below the ground level (m bgl); major potential aquifer of 10 to 50 m thickness in Upper Karewa sediments at a depth of 25 to 35 m bgl and about 20 m thick aquifer in Lower Karewa sediments. Water table location obtained by geospatial (stochastic and deterministic) interpolation of static water levels reveals shallow water table at 0.3 to 10 m bgl within almost the entire alluvium region, deepening to 30 m bgl within the Karewa formations. The confining heads vary from a few meters below the ground surface to a few meters above it within alluvium, and much higher within the Karewas attributable to the location of recharge zones within the tall mountains bordering the study area. The study provides a framework for numerical groundwater modelling of the region. The methodology outlined in this study can be applied to diverse geological environments across local or regional scales to understand the hydrogeological conditions therein.