Trade-offs between midstream agricultural production and downstream ecological sustainability in the Heihe River basin in the past half century

• We simulate impacts of land use change on hydrology using improved top–down model.
• We link trade-off between economy and environment to hydrological model and RS image.
• We construct trade-off between agricultural development and ecosystem sustainability.
• We propose integrated water resources management at catchment.

There is a knowledge gap and limited tools to readily identify trade-off relationships between competing economic and environmental goals, and between the upstream and downstream areas, of river basins. In this paper we aim to construct the trade-off relationship between midstream agricultural development and downstream ecosystem sustainability at the basin scale, using the Heihe River basin as an example. An improved top–down method was developed to understand the impacts of land use change on catchment hydrology. Based on this, trade-off relationships between cereal production in the midstream area and the runoff flowing downstream, and between cereal production in the midstream area and ecosystem service values in the downstream area, were constructed. The results showed that from 1960 to 2000 every 1000 t of increased cereal production in the midstream area (Zhangye catchment) was at the expense of 0.52 million m3 of runoff flowing to downstream and $0.052 million of ecosystem service values in the downstream area (Ejina oasis). The analysis also showed that water productivity increased six-fold in the recent study period which greatly offset the trade-off impacts on downstream ecosystem sustainability. Linking conventional trade-off analysis involving competing economic and environmental goals to a simplified hydrological model and remote sensing image analysis to determine land use is a useful tool for integrated river basin management and will enable more transparent, informed, and inclusive water governance.