Articles | Volume 20, issue 11
Research article
07 Nov 2016
Research article |  | 07 Nov 2016

Downstream ecosystem responses to middle reach regulation of river discharge in the Heihe River Basin, China

Yan Zhao, Yongping Wei, Shoubo Li, and Bingfang Wu

Abstract. Understanding the oasis ecosystem responses to upstream regulation is a challenge for catchment management in the context of ecological restoration. This empirical study aimed to understand how oasis ecosystems, including water, natural vegetation and cultivated land, responded to the implementation of the Ecological Water Diversion Project (EWDP) in the Heihe River in China. The annual Landsat images from 1987 to 2015 were firstly used to characterize the spatial extent, frequency index and fractional coverage (for vegetation only) of these three oasis ecosystems and their relationships with hydrological (river discharge) and climatic variables (regional temperature and precipitation) were explored with linear regression models. The results show that river regulation of the middle reaches identified by the discharge allocation to the downstream basin experiences three stages, namely decreasing inflow (1987–1999), increasing inflow (2000–2007) and relative stable inflow (2008–2015). Both the current and previous years' combined inflow determines the surface area of the terminal lake (R2  =  0.841). Temperature has the most significant role in determining broad vegetation distribution, whereas hydrological variables had a significant effect only in near-river-channel regions. Agricultural development since the execution of the EWDP might have curtailed further vegetation recovery. These findings are important for the catchment managers' decisions about future water allocation plans.

Short summary
The paper finds that combined inflow from both current and previous years' discharge determines water availability in downstream regions. Temperature determines broad vegetation distribution while hydrological variables show significant effects only in near-river-channel regions. Agricultural development curtailed further vegetation recovery in the studied area. Enhancing current water allocation schemes and regulating regional agricultural activities are required for future restoration.