Ecological water demand of major rivers in Qinghai Lake basin
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Abstract:
Ecological water demand is proposed in the context of the increasing contradiction between human social water use and natural ecosystem water use, which is the basic basis and key to ecological water use control and regional ecological environment restoration, and at the same time, it is also the amount of water needed to ensure the structural integrity of the ecosystem, the normal functioning of the function, and the stability of the ecological process, which can be divided into ecological water demand of the rivers, wetlands, lakes and other ecological water demand. In order to ensure the healthy development of the ecosystem of Qinghai Lake basin and realize the rational allocation of water resources, it aims to provide an important reference basis for the ecological restoration of rivers and water resources management in Qinghai Lake basin. Based on the measured long time series data from 1961 to 2020 at Buhahekou station and Gangcha station of Hydrology and Water Resources Forecast Center of Qinghai Province, the runoff volume was subjected to trend change analysis and runoff mutation test by sliding T-test and Mann-Kendall test, and the data were verified to be suitable for the study of ecological water demand of Qinghai Lake basin through the triple-sex review. The ecological water demand within the channels of the Buha and Shaliu Rivers was calculated using Tennant, the mean flow of the deadliest month in the last 10 years, the mean flow of the month with 90% guarantee rate, and the intra-annual spreading method. The four methods were compared and analysed with the improved Tennant evaluation criteria and satisfaction degree. The calculation results obtained that it is more reasonable to calculate the ecological water demand of Buha River by the method of intra-annual spreading, and it is more reasonable to calculate the ecological water demand of Shaliu River by the method of 90% guaranteed monthly average flow rate. The following conclusions are drawn: The average flow rate method of the deadliest month in the past ten years has consistent monthly changes within the year, which is not in line with the process of abundance and depletion changes within the year, and the calculation results are not in line with the practical requirements. Tennant method in the ecological flow calculation of Buha River and Shaliu River, some months are lower than the range of Tennant minimum evaluation index, and the calculation results do not meet the requirements. In the analysis of comprehensive water demand and ecological water demand satisfaction, the intra-annual spreading method is more representative for calculating the ecological water demand for Buha River, and the monthly average flow rate method with 90% guarantee rate is more representative for calculating the ecological water demand for Shaliu River. The degree of satisfaction of ecological water demand of Buha River in July is low, and the degree of satisfaction of ecological water demand of Shaliu River in February is low. The contradiction between upstream and downstream supply and demand of water resources in that month should be considered to make a more reasonable water resources scheduling. According to the ecological water demand in the channel of Shaliu River calculated by Buha River and 90% guarantee rate monthly average flow method, Buha River has the largest ecological water demand in July, 31.9×108m3, and the smallest ecological water demand in February, 0.86×108m3; Shaliu River has the largest ecological water demand in July, 10.7×108m3, and the smallest ecological water demand in February, 0.14×108m3.
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