Subsurface Water in River Beds as Source of Rural Water Supply Schemes

This paper describes the assessment of subsurface water in the river bed of Bharathapuzha at a location near Thrithala in Palghat District of Kerala State, India for a rural water supply scheme which is to service a rural population of about 0.5 million. Field data obtained through hydrologic and hydrogeologic data monitoring, geophysical surveys, and aquifer performance tests are analyzed to obtain estimates of the critical period of water demand when the river can be expected to be dry, saturated thickness as well as permeabilities of the aquifers, and gradients of subsurface flow. These results are in turn used to quantify the groundwater contribution from both banks into the river course, subsurface flow along the river course, and subsurface storage within the river bed at the proposed location of the scheme. The feasible subsurface water withdrawal through an infiltration gallery‐based water supply scheme is finally estimated as $50\times {10}^{6}L/\mathrm{day}$ during periods other than the critical period and $25\times {10}^{6}L/\mathrm{day}$ during the critical period.