Yield-Evaporation-Spill Relationship in Semiarid Reservoirs under Different Operating Rules

Abstract

Semiarid regions are critical for water supply due to deficits in the water balance caused by low precipitation and high evaporation rates. This work studied 50 reservoirs in the Brazilian semiarid region, analyzing the impact of different operational rules on the volumetric reliability (VR) of reservoirs in meeting the demand in relation to the Yield-Evaporation-Spill (YES) effect. Adopting rules with higher rationing reduced overall VR, which varied according to the climatic period (i.e., wet or dry), but improved the reservoirs’ ability to meet human and animal water needs. Moreover, we verified the relationship between the morphohydric characteristics of the reservoirs and the YES relationship, including the relationship between these characteristics and the reservoirs’ ability to meet priority demands. In general, in many cases, large losses due to evaporation and spills were observed and may indicate inappropriate use of reserved resources due to climatic characteristics and improper operation of the reservoirs.