A nonlinear time variant rainfall‐runoff model for augmenting monthly data

Abstract

Deficiency of data is a serious obstacle to river basin management in developing countries. A lumped, nonlinear, seasonally time variant rainfall‐runoff model is applied to the problem of augmenting limited monthly runoff data for the Todzie River basin, Ghana. When the trade‐off between model realism (and therefore complexity) and its practical usability for a developing nation is considered, a proper balance may have been achieved in the model presented here. Though the model is nonlinear, it is simple and easily calibrated or identified by gradient search procedures. The model produced estimates of seasonal evapotranspiration (assuming four distinct seasons per year) that were extremely close to available historical data. It also gave a good fit to available runoff records for the more important wet seasonal flows.