Quantifying volumetric evaporation in a semi-arid region of Iran using the modified Sequent Peak Algorithm reservoir planning model

Open water evaporation from reservoir surfaces constitutes a major demand on available water resources in arid and semi-arid regions of the world, which if not considered during planning of such reservoirs can result in significant under-sizing of facilities. However, despite this, only few planning analysis techniques accommodate the effect of evaporation, because its consideration complicates the analysis and because evaporation measurements are often unavailable. It will therefore be useful if simple rules for evaporation loss adjustment can be provided for use in such circumstances. In this work, reservoir simulation studies based on a modified form of the sequent peak algorithm were carried out to quantify reservoir surface evaporation losses during reservoir critical drawdown periods. The studies used weather and flow data from three basins in north-western Iran and the results were used to develop a tentative rule for adjusting capacity estimates for evaporation in the region.