Assessment of human-induced evapotranspiration with GRACE satellites in the catchment area of lake Baikal

Evapotranspiration is an integral part of the Earth system studies, but it is challenging to measure it on regional scales. One estimation technique is a terrestrial water budget, i.e., total precipitation minus the sum of evapotranspiration and net runoff equals the change in water storage. Gravity Recovery and Climate Experiment (GRACE) satellite gravity observations are now enabling the closure of this equation by providing information on the terrestrial water storage changes. The main objective of this study was to estimate human induced evapotranspiration (HET) using the water budget and Remote Sensing-Based Vegetation Interface Processes (VIP-RS) model. We compare VIP-RS model ET estimates with Gravity Recovery and Climate Experiment and Moderate Resolution Imaging Spectroradiometer satellite-based estimates in the intensively managed Lake Baikal basin. The GRACE-based ET (0,534–133,570 mm/yr.), considerably higher than VIP-RS ET (0–94,319 mm/yr.), agrees well with existing estimates found in the literature and indicates that human activities contribute to an increase in ET. The evaluated uncertainty of monthly precipitation, runoff, GRACE based terrestrial water storage, ET-GRACE, and VIP-RS is 1,56, 0,04, 1,3, 0,89, and 0,8 km 3 month -1 , respectively. The differences may be utilized as an indicator of water management impacts on ET. We argue that satellite-based ET should yield larger seasonal amplitudes in the lake basin due to the impacts of anthropogenic activities. To date, no such investigation has been available in the existing literature for the Lake Baikal basin. Therefore, the adopted approaches for HET and its result will be regarded as a new and honest contribution to the Lake Baikal basin.