A PARAMETRIC APPOACH FOR RECHARGE ESTIMATION

Abstract

Recharge is that part of the infiltered water which reaches the watertable after flowing through the unsaturated zone. The behaviour of the unsaturated zone is highly complex. For proper planning and management of ground water resources, it is important to know both the .magnitude and the time distribution of the recharge which is substantially affected by rainfall and applied Irrigation. There are several prevalent methods for recharge estimation such as Rational methods, Soil moisture accounting model4Parametric models, Solution of Richard's equations. Solution of rechard's equation may not be always possible because of large data requirements. Rational methods are applicable for a particular area under a certain hydrologic conditions. The SMA models do not account for the time lags between infiltration and recharge. Parametric models do not account for the loss from the transition zone and the saturated zone. Hence the physical processes involved from infiltration to recharge are not depicted properly by the above methods. In the present study a composite parametric model following closely the physical process leading to recharge has been developed. The model accounts for, among other loss from the unsaturated zone, delaying of recharge and the associated loss from the saturated zone. The model incorporating four free parameters N,K (Nash Parameters), D(Parameter for delay) and L (Parameter accounting for the loss from saturated zone) has been calibrated for Mayurbhang District(Orissa) using the historical watertable, rainfall and other related data of monsoon months of 1985.