Minimum Water Flow for Environmental Requirements in Xinxiang Section of the Wei River

【Objective】 Surface water in rivers has multiple functions serving direct sectors. The objective of this paper is to analyze the minimum water flow (e-flow) in Xinxiang Section of the Wei River (XSWR) for environmental service. 【Method】 We considered three demands: ecological demand for water, demand for water self-purification, and demand for sediment transport. Ecological water demand was calculated using the Tennant method based on the water flow data measured from 1963 to 1982; self-purification demand was simulated using the one-dimensional water quality model; the demand for sediment transport was calculated as the amount of water required to transport unit sediment in flooding season. Spatiotemporal change in water quality due to pollution was calculated using cluster analysis (CA) and discriminant analysis (DA). The e-flow calculated using the range of variability approach (RVA) was compared with the recommended e-flows, as well as the average annual flow measured from 1963 to 1982. 【Result】 Ecological water demand varied greatly between the seven hydrometric stations along the river. Under standard sewage discharge, the demand for water self-purification in Xiuwu and Hehewei station was 0.74 m3/s and 5.98 m3/s, respectively. The demand for sediment transport at all stations peaked in August, though it varied significantly between the seven hydrometric stations. Surplus-deficit analysis showed the e-flow in Hehewei, Jixian, and Liuzhuang station was markedly short of water. The guarantee rates of 7 hydrometric stations were as follows: Guarantee rates in flooding season were lower than in non-flooding season; Qimen station had the highest guarantee rate and Hehewei station had the least. 【Conclusion】 The e-flow was 5.98 m3/s for Hehewei station, 0.74 to 7.28 m3/s for Xiuwu station, 0.85 to 18.51 m3/s for Jixian station, 1.55 to 65.73 m3/s for Qimen station, 0.47 to 34.61 m3/s for Hehegong station, 0.53 to 36.63 m3/s for Huangtugang station, and 0.17 to 61.54 m3/s for Liuzhuang station.