Estimate of the evaporation rates from Pyrenean reservoirs

Abstract

This paper estimates the evaporation rates from open water surfaces using data from meteorological stations, which are closely located to seven Pyrenean reservoirs. The studied reservoirs have marked differences in their location characteristics, patterns of management and storage volume-surface flooded relationship. The combination of the evaporative rates with the daily changes on surface flooded by dams enabled us to obtain a realistic assessment of the annual volume of water lost by evaporative processes. Climate is not always the main factor to explain differences in water losses. Reservoirs morphology and the management patterns of the reservoirs may have a larger influence than the evaporative rates. Currently, water losses by evaporation do not represent a key-problem in water resource management of the region, since they do not ever exceed a 6% of the storage capacity, nor a 2% of river flows. Nevertheless, losses might become a higher problem as temperatures will warm and water resources availability will decline, according to mid-term projections for the region.