A multi-compartment hydrologic model to estimate groundwater recharge in an alluvial-karst system

Estimation of groundwater recharge is essential for sustainable groundwater management planning in arid and semiarid areas. Accurate recharge estimation in a distributed scale is a great challenge, especially when multiple recharge sources exist and available data are limited and uncertain. There are various sophisticated direct and indirect methods such as water balance method to estimate this parameter. Conventional spatially and temporally lumped models cannot take into account spatial variation of hydraulic properties of an aquifer, land use, and hydrometeorological conditions in the water balance estimation. In this study, a semi-distributed hydrologic model is developed and applied in a complex alluvial-karst system in Firouzabad catchment (Iran) to estimate groundwater recharge from precipitation, subsurface inflow from adjacent karst aquifer, return flows, and riverbed infiltration. The proposed multi-compartment model considers groundwater balance in alluvial and karstic aquifers and surface soil layer. Furthermore, it contains a multi-cell aquifer model which is used to understand the macro mechanism of the alluvial aquifer. A parameter calibration procedure is implemented wherein groundwater head data are used in parameter estimation. The performance of the proposed model is assessed by evaluating the coefficient of determination (R-2) and the coefficient of efficiency. The results of the groundwater balance model are analyzed to quantify the seasonal longterm (16 years, from 1992 to 2008) groundwater recharge components. The proposed model is straightforward, efficient, and easy to apply, and its results are reasonable and acceptable.