A numerical model of groundwater flow in Karewa-Alluvium aquifers of NW Indian Himalayan Region

Abstract

Process-based groundwater flow models are an important tool for gaining useful insights into the hydrogeological characteristics of a complex aquifer system. A conceptual model of a multilayer alluvial aquifer system at the base of Karewa mountain front is presented indicating the hydrogeological framework and the various flow processes affecting the groundwater flow system. Based on the conceptual model, a MODFLOW NWT-based numerical simulation model of groundwater flow was developed for the region. As interpreted from the hydrogeological framework, the simulation was carried out in the context of two aquifers, the top minor aquifer which is regarded as confined–unconfined and the lower major predominantly confined aquifer. Hydraulic heads measured in 104 wells during predevelopment period were used to calibrate hydraulic conductivity, natural recharge and evapotranspiration for the steady state model. For validation, observations from 38 wells corresponding to a recent steady state of aquifers were used. Performance statistic R2 = 0.83 and 0.79 for calibration and validation, respectively. Steady-state groundwater budgets including natural recharge were thus estimated. Calibrated horizontal hydraulic conductivity of aquifers is of the order of 0.0015–0.0031 m/s. Total natural recharge to the aquifers from precipitation and mountain subsurface flow corresponding to predevelopment and recent conditions was estimated as 96.39 and 64.21 Mm3/month, respectively. Steady-state simulations indicate an average decline of 2–5 m in groundwater heads over a period of about two decades, attributable to decreased recharge. Results of this model can help in sustainable development of groundwater in the region.