湘江生态流量阈值研究

Study on Ecological Flow Threshold of Xiangjiang River

湘江是洞庭湖最大的支流和四大家鱼的重要产卵区,对洞庭湖湿地资源补充及生态保护具有重要意义。随着湘江水电的梯级开发,湘江流域的水文情势和生态环境发生了显著改变。生态流量是衡量河流生态系统健康的关键指标,但关于湘江生态流量阈值研究尚未完善。因此,以湘江主要控制站(湘潭站)天然流量过程(1959~1990年逐日流量)为基础,采用RVA法、年内展布法和数理统计方法建立了湘江适宜生态流量过程。研究获得湘江1~12月生态流量阈值,以及高、低流量脉冲年均发生时间、历时、鱼类敏感期适宜流量变化速率波动范围;此外,水文变异后(1991~2019年)湘江流量大部分时间位于适宜生态流量阈值范围内,但7、8月份流量明显超过适宜生态流量上限,造成高脉冲平均发生时间推迟3 d,低脉冲平均发生时间和历时分别提前8 d和推迟10 d,这些改变均会对四大家鱼的生境适宜性产生影响。研究结果可为湘江流域水库调度及湘江水生态系统保护提供参考。

Xiangjiang River is the largest tributary of Dongting Lake and an important spawning area for four major fish,which is of great significance to the replenishment of wetland resources and ecological protection of Dongting Lake.With the development of cascaded hydropower in the Xiangjiang River,the hydrological regimes and ecological environment have been changed significantly.Ecological flow is a key index to measure the health of river ecosystem,but the research on the ecological flow threshold of Xiangjiang River is not perfect.Therefore,based on the natural flow process(the daily flow from 1959 to 1990)at the main control station of Xiangjiang River(Xiangtan Station),the RVA method,intra-annual spreading method and mathematical and statistical methods were used to establish the suitable ecological flow process of Xiangjiang River.The threshold value of ecological flow in Xiangjiang River from January to December,and the fluctuation range of annual occurrence time,duration of high flow pulse and low flow pulse,and suitable flow change rate in fish sensitive period were obtained.In addition,the flow of Xiangjiang River after hydrological variability(1991 to 2019)was located within the threshold of suitable ecological flow most of the time,but the flow in July and August significantly exceeded the upper limit of suitable ecological flow,resulting in a delay of 3 d in the average occurrence of high pulse and a push of 8 d and 10 d in the average occurrence and epoch of low pulse,respectively.All these changes will have an impact on the habitat suitability of four domestic fishes.The results of the study can provide a reference for reservoir scheduling and Xiangjiang River water ecosystem conservation in the Xiangjiang River basin.