Performance of real evapotranspiration products and water yield estimations in Uruguay

Abstract

Real evapotranspiration (ETR) is a key variable in socio-ecological systems since it is related to the food supply, climate regulation, among others. Also, ETR strongly determines the water yield (WY) at the catchment level (water available for consumption or irrigation). In that sense, quantifying ETR and WY fluctuations linked to various human pressures is essential for comprehensive water planning. In the last decades, remote sensing ETR estimations have become increasingly performed worldwide for hydrological monitoring. In Uruguay, there are several attempts to quantify the ETR through different approaches. However, assessments related to the performance of the estimates of different sources/products, particularly from remote sensing, are still lacking. The main objectives of this article were: a) to evaluate the performance of different spatial explicit approaches to estimate real ETR and b) to estimate and analyse the variability in water yield derived from the different ETR sources/products for three climatically contrasting years. To achieve this, we used four remote sensing ETR products (PMLv2, MOD16A2, Jackson et al. 1977 and Di Bella et al. 2000), with different spatial and temporal resolutions (from 500 to 1000-m and 8 to 16-d), and two water balance models at two scales, national (INIA-GRAS) and micro-watershed level (Silveira et al. 2016). Our results suggest that MODIS and PMLv2 remote sensing products demonstrated better performances. Both products have high spatial (500-m) and temporal (8-d) resolution, captured seasonal differences between land-covers and showed positive and high correlations with the annual precipitation and productivity. The differences found between products have direct implications on the WY estimates, not only in the quantity but also in its spatial pattern. Future studies should explore MODIS and PML ETR estimations for understanding hydrological and ecological processes, global climate change research, agricultural drought detection and mitigation, and water resource management.