A practical approach to rainfall-runoff modelling in arid zone drainage basins

A package of simulation models has been developed to study the hydrological processes controlling runoff and to predict flow hydrographs in the Indian arid zone. The models describe rainfall-runoff in the upland phase and the interaction between runoff and transmission losses in the channel phase, so as to derive the drainage basin outflow hydrograph. In the upland phase the rising limb of the hydrograph is predicted through a regression model and the recession through a conceptual analogue of discharge from a single leaky reservoir. The leaky reservoir is described by a continuity equation and by discharge-stage and storage-stage relationships at the outlet. In the channel phase the governing equations for movement of a flood wave subjected to the transmission losses are simplified through a time averaging process to develop an ordinary differential equation describing transmission losses as a function of distance, inflow, channel width, time parameters of flow and effective hydraulic conductivity. These models are simplified acid developed to require a minimum of observed data for calibration. The package of models can be applied to ungauged drainage basins through parameterization.