基于改进年内展布计算法的季节性小流域最小生态流量研究OA

In order to improve the applicability of the traditional intra-annual distribution calculation method in small watersheds with significant seasonal variations,this study took the Tangyu River in Baoji City as an example to conduct methodological improvements and validation.The Tangyu River Basin exhibits considerable seasonal differences in runoff,making it difficult for the traditional intra-annual distribution calculation method to effectively adapt to small watersheds with pronounced seasonal runoff patterns.Therefore,improvements to the intra-annual distribution calculation method are necessary to ensure that the calculated minimum ecological flow process better aligns with the actual hydrological processes of the river.Based on the monthly flow data from 1966 to 2022 at the Manwancun Hydrological Station on the Tangyu River,the study fully accounted for the river's eco-hydrological processes and the varying demands of intra-annual wet and dry runoff changes and first refined the intra-annual periods by dividing the entire year into four representative periods:December to February,March and November,April to June,and July to October.On this basis,two key improvements were made to the traditional intra-annual distribution calculation method:First,the minimum monthly average flow was replaced with the monthly average flow at a 95%frequency to reduce the impact of extreme low-flow values on the overall calculation;second,the annual average monthly flow was replaced with the annual average monthly flow within the 5%-95%frequency range to eliminate the interference of extreme hydrological events on the average value calculation.Additionally,the results of the improved calculation method were compared with those of the minimum monthly average flow method,the second-minimum value method,the monthly frequency calculation method(at 95%frequency),and the Tennant method to comprehensively evaluate its rationality and applicability.The results show that whether during general water use periods or peak water use periods,the minimum ecological flow process calculated by the improved intra-annual distribution calculation method is relatively more favorable for the ecology of the Tangyu River.The minimum ecological flow values obtained by the improved method are higher than those of the original method in every month and are generally greater than the results of the minimum monthly average flow method.Based on ecological suitability evaluation using the Tennant method,the minimum ecological flow process calculated by the improved intra-annual distribution calculation method is more beneficial to the river's aquatic ecosystem than other comparative methods.Furthermore,the guarantee degree of the minimum ecological flow at the Manwancun Station is relatively high across all months,ranging between 91.2%and 98.2%.The actual ecological flow assurance status of the Tangyu River is good,consistent with the local river health assessment results,further validating the applicability of the improved annual distribution calculation method in this region.By introducing frequency-constrained monthly average flow and segmentally characterizing the intra-annual process,the improved intra-annual distribution calculation method effectively enhances the scientific rigor and adaptability of minimum ecological flow calculations in small watersheds with significant seasonal variations.This study can provide a technical reference for determining the minimum ecological flow in small watersheds with similar hydrological characteristics in northwestern China and has practical significance for balancing water resource development and utilization with ecological protection.