Spatiotemporal Variations in Surface Water and its Significance to Desertification in China from 2000 to 2019

Abstract

Spatiotemporal variations in surface water area (SWA), its dynamics and impacts on desertification in the desertification-prone regions (DPRs) of China are poorly understood. We used the ‘stream burning’ and ‘manual corrections’ methods to define 2440 sub-watersheds at the fifth-order level in China’s DPR. Then the spatiotemporal variations in SWA and their affecting factors (such as temperature, precipitation, evaporation, and irrigation activity) were discussed. We found that the annual average maximum SWA in DPR from 2000 to 2019 was 7165 km2, of which the seasonal SWA increased at a rate of 188 km2yr-1 and accounted for 84% of the total SWA, and the permanent SWA increased at a rate of 46 km2yr-1 and accounted for 16% of the total SWA. The average contributions of SWA in non-desertification-prone regions (non-DPRs) of the same watershed, precipitation, evapotranspiration, and temperature to the seasonal SWA of DPR were higher than those contributions to permanent SWA. In addition, there were spatial differences in the contributions for SWA variation at the watershed scale: except for SWA in non-DPRs, for seasonal SWA, precipitation in HulunBuir (27.63% contribution); potential evapotranspiration in Nunkiang (9.66%), Horqin (17.85%), and Tarim (-6.80%); temperature in Ordos (8.60%), Ala Shan & Hexi Corridor (6.44%), and Junggar (-9.82%); and agricultural irrigation in Otindag (-29.54%) and Qinghai (-34.42%) watersheds exerted higher impacts than the other affecting factors. For the permanent SWA, contributions of precipitation in HulunBuir (16.53%); potential evapotranspiration in Nunkiang (-20.74%), Otindag (14.31%), Tarim (-24.43%), and Junggar (-18.52%); and agricultural irrigation in Horqin (29.03%), Ordos (-19.50%), Ala Shan & Hexi Corridor (64.91%), and Qinghai (28.65%) watersheds were higher than the contributions of other affecting factors. From 2000 to 2019, there were significant spatiotemporal differences for the roles of SWA variation on desertification processes in DPR of China.