Study On Water Temperature Of Hige Dam Reservoir Between Cascade Hydropower Station In Upper Yhellow River

The water temperature structure in the reservoir usually has stable thermal stratification characteristics,and the underlying water intake causes the non-seasonal discharge of low-temperature water,thus threatening the viability of fish and other aquatic animals in the downstream rivers.Compared with the high dam reservoir operating alone,the water temperature structure of the cascade high dam reservoir and the influence on the river water temperature may show different forms,which is of great significance to explore the water environment protection of hydropower engineering.Taking Laxiwa Reservoir and Lijiaxia Reservoir in the cascade hydropower group of Longyangxia to Liujiaxia River in the upper reaches of the Yellow River,using the combination of prototype observation and mathematical simulation The water temperature structure form of high dam reservoir between cascade groups,compares and analyzes the difference of reservoir water temperature structure under different inflow change scenarios,and reveals the difference characteristics of the high dam reservoir on the downstream river water temperature.The main research results obtained in the paper are as follows:1.The water temperature distribution characteristics of high reservoir and the influence of leading reservoir on hydrology and water temperature of the downstream river are analyzed.Under current conditions,the water temperature of Laxiwa,Lijiaxia,Gongboxia and Liujiaxia reservoirs basically present mixed or weak stratified distribution;in the early stage,stratified and transition water temperature distribution,clarifying the inflow hydrological situation and water temperature fluctuation are the main factors affecting the transformation of reservoir water temperature structure.2.The three-dimensional water temperature mathematical model of Laxiwa Reservoir and Lijiaxia Reservoir is constructed,conducts the parameter rate determination and verification of the model,simulates the reservoir water temperature distribution under different inflow conditions,and reveals the response relationship of the inflow hydrological potential and water temperature changes to the evolution of the water temperature structure of the reservoir.Due to the influence of the cascade leading reservoir on the downstream hydrological situation,the closer the process of the reservoir is to the natural water temperature,the greater the water temperature of the reservoir in 4-August,the monthly water temperature difference is about 4℃,the reservoir water temperature mst show mixed distribution form3.The change law of the discharge water temperature of Laxiwa Reservoir and Lijiaxia Reservoir is explored,and the difference between the influence of high dam reservoir on the downstream water temperature of cascade reservoir groups is analyzed.The results show that when the high dam reservoir is running separately,the water temperature of the downstream reservoir depends on the low temperature water effect of the reservoir stratified discharge;the downstream water temperature determines the change of the downstream river temperature.