Changes in actual evapotranspiration and its dominant drivers across the Three-River Source Region of China during 1982–2014

Abstract

Evapotranspiration is an essential element of the hydrological process. This study derived the long-term series of evapotranspiration from 1982 to 2014 over the three basins, namely source regions of the Yangtze River (SRYR), the Huang River (SRHR) and the Lancang River (SRLR) in the Three-River Source Region of China by integrating multiple sources of evapotranspiration estimates based on the Bayesian model averaging approach, which made full use of the strengths of land surface models and satellite-based products to constrain uncertainties. Then, we analyzed the influences of climate change on evapotranspiration based on the partial least squares regression model. Results indicate that (1) the agreement between various evapotranspiration products and water balance-derived evapotranspiration estimates varies from region to region in the Three-River Source Region of China; (2) annual evapotranspiration increases in the SRYR (3.3±0.8 mm/yr) and the SRHR (0.8±0.4 mm/yr), whereas no significant trends are observed in the SRLR during 1982–2014; (3) annual evapotranspiration is found most sensitive to precipitation and temperature in the SRYR and the SRHR, while it is dominated by relative humidity and temperature in the SRLR during 1982–2014. Our results have important implications for understanding evapotranspiration variability and future water security in the context of global climate change.

Evaluating the accuracy of gridded water resources reanalysis and evapotranspiration products for assessing water security in poorly gauged basins

“…Based on this claim, it might be argued that GRACE data may not be applicable in this study considering that most of the basins are below this threshold except the Oubangui (499 000 km 2 ). However, several studies (Liu, 2018;Biancamaria et al, 2019;Oussou et al, 2022;Xie et al, 2022) have demonstrated that GRACE can provide acceptable TWSC estimates for basins that are smaller than this threshold. To further minimize errors and uncertainty in the GRACE-derived TWSC in our smaller-size basins, we re-gridded the GRACE mascon solutions from JPL and NASA to a spatial resolution of 0.25 • which is the same spatial resolution for the mascon solutions from CSR.…”

Reply on RC1

“…GRACE data has recently been re-processed to reduce measurement errors and represents a new generation of gravity solutions that do not require empirical post-processing to remove correlated errors, as such, the present data is better than the previous GRACE version that was based on spherical harmonic gravity solution (Wiese et al, 2016). GRACE data was used in this study to estimate ETWB following the approach used in several other studies e.g., (Andam-Akorful et al, 2015;Liu, 2018;Xie et al, 2022).…”

“…Based on this claim, it might be argued that GRACE data may not be applicable in this study considering that most of the basins are below this threshold except the Oubangui (499,000 km 2 ). However, several studies (Liu, 2018;Biancamaria et al, 2019;Oussou et al, 2022;Xie et al, 2022), have demonstrated that GRACE can provide acceptable TWSC estimates for basins that are smaller than this threshold. Encouraging results from these and other studies do therefore suggest that GRACE data can be used in this study; albeit with the expectation of considerable uncertainties in TWSC estimates.…”

How useful are gridded water resources reanalysis and evapotranspiration products for assessing water security in ungauged basins?

“…Based on this claim, it might be argued that GRACE data may not be applicable in this study considering that most of the basins are below this threshold except the Oubangui (499 000 km 2 ). However, several studies (Liu, 2018;Biancamaria et al, 2019;Oussou et al, 2022;Xie et al, 2022) have demonstrated that GRACE can provide acceptable TWSC estimates for basins that are smaller than this threshold. To further minimize errors and uncertainty in the GRACE-derived TWSC in our smaller-size basins, we re-gridded the GRACE mascon solutions from JPL and NASA to a spatial resolution of 0.25 • which is the same spatial resolution for the mascon solutions from CSR.…”