Assessment framework of main functions of water conservation using a multi-variable calibrated WEP-L model

Study regions The water conservation area in the Yellow River Basin (YRB WCA) of China, a key ecological function zone with high annual runoff coefficients. Study focus Most water conservation (WC) function assessments in large basins focus on quantity. This study proposes a new framework for evaluating both the quantity and three main functions. A distributed hydrological model calibrated with multi-variable data was used to improve accuracy. New hydrological insights for the regions WC quantity significantly decreased only in Region II (Southern Wei River tributaries). Across all regions, vegetation ecological water use (WC-f 1 ) generally improved, flood reduction (WC-f 2 ) remained stable, while baseflow enhancement (WC-f 3 ) weakened only in Region II. Precipitation and NDVI were primary driving factors of WC quantity, with positive effects except in central Region I (above the Lanzhou area). Temperature, evapotranspiration, and DEM also influenced the three functions. In addition, changes in forest, cropland, and built-up areas since 2000 had strong localized influences on WC-f 1 and WC-f 2 , though their overall impacts were weak. Vegetation restoration strategies should vary by downstream water demand and functional priorities: reduce vegetation cover in central Region I to enhance WC quantity; increase vegetation cover in southeastern Region I and Region III (the Yiluo River Basin) to enhance WC-f 2 ; reduce grassland area in northern Region I and western Region II to enhance WC-f 3 .