Vegetation Dynamics and Hydrological Responses to Environmental Flow Releases in the Hotan River

Understanding how desert riparian vegetation responds to managed flow releases is essential for ecological restoration in arid inland river basins. This study examines vegetation dynamics and hydrological responses in the desert reach of the Hotan River, a seasonal river crossing the Taklimakan Desert. To avoid temporal inconsistency, two data windows were explicitly separated: Landsat-derived vegetation information was used to describe long-term vegetation changes from 1985 to 2020, while environmental flow release, river-section water consumption, and groundwater-depth analyses were limited to the period with available hydrological observations, 2006–2020. NDVI and vegetation-cover classes were derived from cloud-screened and atmospherically corrected Landsat imagery, and the response of vegetation indicators to cumulative environmental flow release and groundwater depth was evaluated using transparent regression models with diagnostic statistics. Results indicate that vegetation cover improved overall during the study period, although the response was spatially heterogeneous. Vegetation conditions were generally better near the upper and terminal parts of the desert reach, whereas a relatively vulnerable zone occurred approximately 15–115 km downstream of the river confluence. During 2006–2020, NDVI and grassland area generally increased with cumulative environmental flow release, whereas annual grassland-area change showed large interannual fluctuations and was not significantly explained by cumulative release alone. The revised analysis clarifies that the study contributes a reach-scale synthesis linking long-term vegetation mapping with monitored environmental flow releases and groundwater response in the Hotan River desert reach, rather than a full 40-year ecohydrological attribution. These findings provide a basis for improving environmental flow scheduling and monitoring design in arid desert rivers.