A grid-based framework for assessing ecological water requirements in arid inland river basins: A case study of the Tarim River mainstream, China

Study region The mainstream of the Tarim River, XinJiang, China. Study focus This study established a 1 km × 1 km grid-based framework, integrating groundwater depth, soil texture, vegetation characteristics, and meteorological conditions to investigate the hydrological controls on EWRs. A hydrologically based EWRs assessment method was developed to quantify vegetation water demand under varying hydrological constraints and to elucidate the roles of groundwater accessibility and soil moisture regulation. New hydrological insights The findings reveal a hierarchical hydrological control mechanism governing vegetation water use in arid riparian ecosystems. The distribution of vegetation along the river exhibits a distinct hydrological gradient: groundwater depth determines the accessibility threshold for root water uptake, whereas soil texture regulates water retention and redistribution processes within the root zone. Under the combined constraints of groundwater depth and soil texture, the estimated mean annual ecological water requirements are 20.05 × 10 8 m 3 , 15.44 × 10 8 m 3 , and 11.33 × 10 8 m 3 for wet, normal, and dry years, respectively. The results demonstrate that groundwater accessibility, rather than total water availability, acts as the primary controlling factor for vegetation distribution and ecosystem water use. These insights underscore the critical role of river–aquifer connectivity in sustaining riparian ecosystems and optimizing ecological water management in arid inland river basins.