Dam operation for environmental water releases; the case of Osborne dam, Save catchment, Zimbabwe

There is limited capacity in terms of knowledge and experience on how to calculate the environmental water requirements (EWR) in Zimbabwe. In this paper the EWR were assessed using the desktop model developed by [A Desktop Model used to provide an initial estimate of the ecological instream flow requirements of rivers in South Africa. Institute for Water Research, Rhodes University, Grahamstown, 2001] and a spreadsheet model (Waflex) was developed to incorporate a component of EWR in reservoir simulation. The paper assesses whether EWR as established by Hughes method can be incorporated into a reservoir simulation and water allocation model, and if it is possible to derive EWR directly from naturalised flow series.