Application of conceptual water balance model with limited hydrological data – A case study

Response of a catchment can be modeled by various models ranging from empirical to continuous simulation. The conceptual catchment water balance model developed by Ponce & Shetty (1995) is applied to three different river basins having various climatic settings and sizes (medium to very large) to study the changes in runoff coefficient. This application provides information on hydrological processes/water balance components in the basin with the limited hydrological data. Rainfall-runoff records of these basins were used to develop relations for (1) surface runoff (2) runoff coefficient (3) base flow coefficient (4) runoff gain and (5) base flow gain, all as a function of annual precipitation. The calibrated model parameters (λ_S, W_P, λ_u, V_p) and P_rt/P_a, P_ut/P_a ratios of these three basins represent actual climatic settings of the respective basin. The computed average annual Base Flow Index (BFI) of Parana (South America), Baitrani (India) and Sarada (India) river basins during the base periods is found to be 0.641, 0.377 and 0.299, respectively. Further, runoff coefficients verses annual precipitation relations were developed for different subset time periods in each basin. A comparison of these relations shows distinct variations in runoff coefficients in the catchment. Finally, the model has been used to simulate surface runoff and base flow in Sarada river basin, in which there is no significant change in runoff coefficient over a period of time.