A method for assessing compatibility of water withdrawals with minimum in-stream flow

Assessing the compatibility of surface water withdrawals with the constraints imposed by the need to ensure minimum in-stream flow is often difficult, both because of the lack of direct flow measurements and of the complexity of the schemes by means of which water is withdrawn. In fact, for this purpose, it is necessary to know both the natural hydrological regime of the catchment at a given river cross section, in particular the minimum daily flowrates, and the actual flowrates regulated by water schemes. As direct flow measurements are seldom available, the problem of calculating the natural flowrates can be solved resorting to a rainfall-runoff model. On the other hand, the reconstruction of regulated flows, which is rather problematic owing to the complexity of the schemes’ operation, requires implementation of an appropriate software program.