Compensating Effects Between Climate and Underlying Characteristics on Watershed Water Loss

Identifying climate impacts on watershed water loss (evapotranspiration) generally involves the interactions with land surface change (e.g., vegetation dynamics and anthropogenic disturbances). Here, we seek to understand the compensating effects of climate and underlying characteristics on watershed evapotranspiration. In this regard, an analytical solution was derived by using a simple water-energy partitioning framework for separating the individual contributions of climate and underlying characteristics to changes in watershed actual evapotranspiration between 1930-1970 and 1971-2008 over global 87 basins. We found that for the basins with larger increases in the total evapotranspiration, a positive underlying characteristic-related contribution is dominant, rather than the climate-related contribution. Tradeoffs (i.e., the compensating effects) between the contributions of climate and underlying characteristics to evaporative water loss were also identified in a few basins where there were relatively large changes in the underlying characteristic-related evapotranspiration but only a slight change in the total evapotranspiration. This suggests that the climate contribution in evapotranspiration may offset the effect of underlying characteristic-related changes over these basins, associated with stronger hydrological resilience under the double impacts of both climate and underlying factors. The results also indicate that the underlying characteristics exert greater contributions to the changes in the total evapotranspiration rather than the climate variation, and the underlying characteristic-related evapotranspiration variations are closely related to the changes in reservoirs and land-use types of the basins. The presented findings may provide an insightful understanding of interactions among climate, water, and underlying characteristics over global basins.