A PRACTICAL APPROACH TO RAINFALL-RUNOFF MODELING IN ARID ZONE DRAINAGE BASINS

A package of simulation models has been developed to study the hydrolo gical processes controlling runoff and to predict flow hydrographs in the Indian arid zone. The models describe rainfall-runoff in the uplan d phase and the interaction between runoff and transmission losses in the channel phase, so as to derive the drainage basin outflow hydrogra ph. In the upland phase the rising limb of the hydrograph is predicted through a regression model and the recession through a conceptual ana logue of discharge from a single leaky reservoir. The leaky reservoir is described by a continuity equation and by discharge-stage and stora ge-stage relationships at the outlet. In the channel phase the governi ng equations for movement of a flood wave subjected to the transmissio n losses are simplified through a time averaging process to develop an ordinary differential equation describing transmission losses as a fu nction of distance, inflow, channel width, time parameters of flow and effective hydraulic conductivity. These models are simplified acid de veloped to require a minimum of observed data for calibration. The pac kage of models can be applied to ungauged drainage basins through para meterization.