Impact of ecological restoration in mainland China on the terrestrial water budget using GRACE/GRACE-FO and other data.

Large-scale ecological restoration (ER) has been successful in curbing land degradation and improving ecosystem services. Previous studies show that ER changes individual water flux or storage, but its net impact on total water resources remains unknown. Here we quantify ER impact on total terrestrial water storage (TWS) in the Mu Us Sandyland of northern China, a hotspot of ER practices. By integrating GRACE with other satellite observations and government reports, we construct a TWS record that covers both the pre-ER (1982-1998) and the post-ER periods (2003-2016). We observe a significant TWS depletion after ER, a substantial deviation from the pre-ER condition. This contrasts with a TWS increase simulated by an ecosystem model that excludes human interventions, indicating that ER is the primary cause for the observed water depletion. We estimate that ER has consumed TWS at an average rate of 16.6 ± 5.0 mm yr^-1 during the post-ER period, an alarming rate comparable to those caused by groundwater irrigation in California’s Central Valley and North China Plain. We further discuss whether the trend will continue under different ER strategies given a projected warming and wetting climate. Our study explores a new interdisciplinary application of GRACE/GRACE-FO in quantifying land use change impact on freshwater availability. Our findings show that ER can exert excessive pressure on regional water resources. Sustainable ER strategies require optimizing ecosystem water consumption to balance land restoration and water resource conservation.