Environmental Flow Requirement And Water Scarcity In The Huangqihai River Basin

Water palys an important role in maintaining ecosystem health. However, with the rapid develop-ment of urbanization and increasing population growth, water scarcity occur more and more frequently. Meanwhile, the unreasonable water consumption results in environmental flow scarcity, following the degradation of ecosystem. Previous water scarcity assessment mostly focused on the social water con-sumption assessment, but only a few concentrated on environmental flow requirement. Therefore, to calculate the river environmental flow requirement, and consider this part into basin water scarcity as-sessment is of importance for watershed ecosystem protection and integrated river basin management.In this study, we take the Huangqihai river basin for example, which is located in the arid and semi-arid area, in Inner Mongolia. Firstly, the APEX model was established to simulate hydrological processed in this basin; then, the Tennant method was selected to calculate the river environmental flow requirement (EFR); and finally, an approach was developed to assess water scarcity by considering both water quantity and quality, while at the same time explicitly considering EFR. The main findings are as follows:(1) APEX model performs well to simulate the hydrological and sediment process in the Huangqihai river basin:The Ens values ranged from 0.43 to 0.75, R2 values ranged from 0.52 to 0.81, and the APE values were within 20%, for annual and monthly stream flows and monthly sediment yields during both calibration and validation periods. (2) The interannual runoff presents a great change for the last 30 years, although with a downward trend:About 90% of the river runoff occurs during April to September, while the runoff of the two main rivers is 10 times of the other rivers. To keep the river health stand at a "good" level,26% of the total water resources should be distributed to meet the environmental flow requirement.(3) Huangqihai river basin faces serious water scarcity, including water quantity and water qualitiy: The average annual water resource in this basin is 144 million m3, with the annual blue water footprint accounting for 94%. The annual grey water footprint is 2 billion m3, about 14 times of the total water resources. Synthesing water quantity and water quanltiy, the local water scarcity indicator of 15.5 was far higher than the threshold of 1.0, indicating that the basin was suffering from serious scarcity prob-lems. The current water consumption has resulted in river ecosystem degradation, and especially the EFR cannot be met in May, June and July.Huangqihai river basin is a typically inland watershed with both water scarcity of quantity and quality. The government should consider the environmental flow requirement for their integrated water resources management. There are serveal effective altenratives to mitigate water scaricity and achieve sustainable water consumption, including implementing the stringent water management system, de-veloping water-saving agriculture, reducing emissions, and improving pollution management.