| The ecological flow process under natural hydrological conditions in rivers is essential for maintaining the growth and reproduction of organisms inside and outside the river.At present,most reservoirs do not take into account the ecological flow processes required by organisms,resulting in threats to the survival of indigenous organisms in the river.Therefore,It has important practical significance to the sudy based on the threshold of hydrological indicators required for spawning and breeding of domestic fish in the natural hydrological situation of the river in the lower reaches of the Hongshui river to formulate an ecological scheduling scheme in the spawning period of four major Chinese carp species(FMCCS)for relieve the downward trend of natural fishery resources of domestic fish.The result of the annual and monthly runoff trend of the Qianjiang hydrological station analyzed by using the linear tendency estimation and M-K trend test combines with the studied result of the annual and monthly rainfall trend in the same watershed,which is found that the hydropower station construction has a significant impact on the change of monthly runoff trend,and the change of annual runoff trend is affected by rainfall.The variation range method was used to analyze the 32 parameters of the runoff of the Qianjiang hydrological station before and after the construction of Longtan reservoir.The results show that the hydrological situation change degree of Qianjiang station is 86.25%,in which the monthly average flow from January to March and from July to August,the minimum flow of different durations,the maximum flow of different durations,the base flow index,the number of occurrences of high and low flow and its average delay,the average flow reduction rate and the number of annual flow reversals has changed hightly.There is the ecological flow components of ecological significance analyzed and compared the changes before and after the construction of reservoir,especially in the spawning period of the FMCCS,in order to further study the impact on aquatic organisms after the construction of reservoir.The results show that high flow pulses is the main ecological flow components in the spawning period of the FMCCS.Compared with before the construction of reservoir,the peak flow,duration,frequency,rise and fall rates of high flow pulses after the construction of reservoir are significantly different.Meanwhile,the small flood and the large flood have disappeared.The effective flow increase process in the spawning of the FMCCS is defined based on the high flow pulses,from which the eight hydrological indicators that timing,the first rising flow,the first rate of the rising flow,the average daily rate of the rising flow,peak flow,duration,frequency during each water year,the time interal between the peak flow and the next peak flow and number of fluctuations are extracted.The t-test was used to analyze the significant differences in the hydrological indicators during the spawning period before and after the construction of reservoir.The results show that the first rate of the rising flow,the average daily rate of the rising flow,peak flow and number of fluctuations are significantly different.The effective flow increase process in the spawning of the FMCCS the construction of reservoir is regarded as the suitable condition for the FMCCS to lay eggs.The statistical principle is used to calculate the characteristics and the thresholds of the first effective flow increase process and the effective flow increase process of the fish in different ten-day and different precipitation patterns before the construction of reservoir.The thresholds are used as the scheduling restrictions of the spawning period.An ecological scheduling model constructed is used to formulate the ecological scheduling schemes of three typical years of the wet,the normal and the dry,which is solved by the DP algorithm.The scheduling results show that the ecological scheduling scheme can better balance power generation and ecological demand and improve the shortage of natural runoff. |
