A Procedure for Evaluating the Compatibility of Surface Water Resources with Environmental and Human Requirements

This paper presents a novel and easy-to-use procedure for controlling and licensing water abstractions from a river based on establishing a balance between surface water resources and environmental and human requirements. Unlike other approaches relying on complex and detailed basin models, this is based simply on the use of the discharge duration curve to represent the available water resources. In particular, the scheme of analysis presented here is composed of four steps: 1) subdivision of a particular river reach into sub-reaches; 2) estimation of the availability of water along each sub-reach over a particular period of time by means of duration curves; 3) estimation of the environmental requirements (minimum instream flow—MIF) and quantities necessary for civil, agricultural and industrial uses over the same period, and 4) establishing a water balance model for each sub-reach, taking into consideration the effects produced by water resource use in the upstream sub-reaches. In particular, this procedure consents (a) quantification of the duration when abstractions are possible along each sub-reach, (b) quantification of the maximum abstraction needed to satisfy the volume requested (thereby enabling comparison with the amount the users can actually obtain through their structures and/or pumps) and (c) identification of situations in which users need to avail themselves of reservoirs for temporarily storing the water abstracted so that they do not exceed the availability on non-abstraction days. The procedure was successfully applied to a basin located in Emilia-Romagna, the Enza River, along which 9 sub-reaches were identified.