Research On Water Environmental Impact Of The Development For Heishanxia Reach Of The Yellow River

As the last river section in the upper reaches of the Yellow River that can be built as a high dam and has not yet been developed,the Heishanxia has a very important strategic position in the development of the Yellow River.Over the years,the Heishanxia has been in the development program at the first,second and fourth levels.However,no matter what kind of development plan,it will affect the river environment in different degrees.The Heishanxia and the following mainstream of the Yellow River River are multi-sand rivers,and sediments have an impact on the physical,chemical and biological processes of the water.Therefore,how to combine the environmental effects of sediment water,compare and analyze the water environment impacts of different development schemes on the Heishanxia reservoir,and provide the basis for the water environment impact determination is key problem of the paper.In this paper,based on the environmental effects of sediment,according to the basic principles of pollutant migration and transformation in water environment,water environment system analysis theory,on-site investigation,numerical simulation and other technical methods,studying the water environment characteristics,water environment effects of sediment;researching river Analysis of the comprehensive degradation characteristics of the pollutants in the section;predicting the impact of different development plans of the Heishanxia on the hydrological situation and water quality in the reservoir area and under the dam,the main achievements are as follows:(1)The water environment in the river section is controlled by the runoff regulation of the Long Yangxia?Liu Jiaxia Reservoir and the artificial drainage.The amount of water in the river is mainly controlled by Long Yangxia?Liu Jiaxia Reservoir.After the operation of Long Yangxia?Liu Jiaxia Reservoir,the measured runoff of the river section during the wet period was reduced,and during the dry season was increased.At the same time,a large number of artificial canal systems are distributed in the river section,which makes the measured runoff of the river section gradually decrease along the path.In 2014.the quality of the main stream was good,basically meeting the requirements of Class III water.The water quality of local river sections(such as Shizuishan and Dengkou section)exceeded the standard,which was basically Class IV.The water quality of the tributaries and drainage ditch is generally poor,basically inferior to the V category.(2)The comprehensive degradation coefficient of pollutants in the river section is gradually increasing along the path.The river section is dominated by fine-grained sediment,with high sediment concentration and increasing along the path,resulting the adsorption of pollutants by sediment is enhanced.The paper adopts literature research,statistical analysis and other methods.The COD and ammonia nitrogen degradation are consistent with the first-order kinetic reaction characteristics.The COD degradation coefficients of Lanzhou-Xiaheyan,Xiaheyan-Shizuishan and Shizuishan-Toudaoguai are calculated as 0.088 d-1,0.117 d-1,0.167 d-1.The comprehensive degradation coefficients of ammonia nitrogen were 0.095 d-1,0.11 d-1 and 0.128 d-1.(3)From the perspective of water environment,the primary and secondary development schemes are better.Under the first-level and second-level development schemes,the reservoir meets the requirements of Class ? water quality targets.The water quality of the reservoir is the best in summer,and the water quality is the worst from December to February next year.The water quality under the dam from the Xiaheyan to the Qingtongxia section is good.Except for January,COD and ammonia nitrogen meet the requirements of Class ? water quality targets during the year.The water quality of the river section below the Qingtongxia section is worse,and the water quality of the Shizuishan section is the worst.The dry season and the flat water period do not meet the requirements of the Class ? water quality target.The prediction of water quality of the fourth-level development plan are basically the same as those before the construction.Overall.the water quality of the reservoir after the construction of the Heishanxia of the Yellow River River has improved.The water quality of the dam section is better during the wet season,and the water quality during the dry season is worse,but the water quality category has remained basically unchanged.The primary and secondary development programs have a strong regulatory effect on the water quality of the reservoir area and the dam section.From the perspective of water environment impact,the primary and secondary development schemes are better.