Assessment framework of water conservation based on analytical modeling of ecohydrological processes

The water conservation (WC) function is an important indicator for ecosystem health. However, the commonly-used technical term like water retention (WR) and its computation methods could not well reflect the concept of WC because WR focused on the amount of water retained in vegetation canopy and soil, whereas WC includes WR and water supply as well. This study is to propose a new index for assessing the WC function (WCI) by integrating ecological and hydrological factors including WR, water yield, and vegetation production. We further developed a new framework for calculating spatiotemporal dynamics of WCI using ecohydrological modeling of Soil and Water Assessment Tool (SWAT) and remote sensing data. We then used the framework to assess the spatiotemporal dynamics of WC function in the Weihe River Basin (WHRB), the largest tributary of the Yellow River. Compared to the traditional method, our newly-developed approach is more reasonable because it could reflect water retention amount, temporal stability of water yield, and vegetation quality. Further, the case study can tell it is our new index (with forest being the highest, followed by grassland and cropland), instead of WR (with grassland being the highest and forest being the least), that could reflect the definition of WC and meet our cognition. Spatially, the high WCI (0.4 ∼ 0.6) areas are mainly located in the southern and central-eastern parts of the WHRB, characterized by relatively higher forest coverage (e.g., the Qinling Mountains in the southern part of the study area in southern part and representative ‘Grain-For-Green’ in central-eastern part). In brief, this study enhances understanding of the WC function and also provides a method for assessing the dynamics of WC that can be applicable to other regions.