On the application of METRIC-GEE to estimate spatial and temporal evaporation rates in a mediterranean lake

Abstract

Lakes and reservoirs are vital resources for food security and economic prosperity. High evaporation rates can result in a greater water loss leading often to water shortage. Data scarcity prevents the estimation of such phenomenon in many lakes throughout the world. Recently, Google-Earth Engine (GEE) has been ho sting the widely acknowledged Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) system that enables the spatial and temporal estimations of the evaporation rates. Evaporation rates retrieved through METRIC-GEE system were compared to other lake variables between 2014 and 2018. A spatio-temporal assessment of the evaporation rates within the studied lake as well as a comparison to another regional lake (i.e. Kinneret) has been conducted. Results show that thermal stratification was already established in Lake Qaraoun in May. This strong persistent stratification (up to 13 °C) continued in June and July, then it started to weaken at the beginning of August. Evaporation correlated slightly better with thermal stratification than with surface temperature, with values of 0.71 and 0.67, respectively. The lowest monthly evaporation rates were found in December (30 mm) and the highest rates in August (above 200 mm). The highest spatial variations were found between May and August. Retrieved monthly evaporation rates were found comparable to those of the nearby studied Lake Kinneret and pan evaporation records from a close station. Such findings highlight on the relation between evaporation and understudied variables and the use of METRIC-GEE system to estimate evaporation rates in data scare regions.