| As one of the two water sources of the hanjiang-to-weihe diversion project,the Sanhekou hydro-junction plays an important role in regulating and controlling the Guanzhong water supply system.This research takes sanhekou reservoir area as the research object,carries on the water quality evaluation and the present situation investigation in the reservoir area,takes the question as the guidance to analyze the present question deeply,in the light of water quality assessment,the Sanhekou Reservoir area was selected to carry out hydrodynamic-water quality simulation study.Finally,in line with above results,the suggestions and countermeasures of River Ecological Rehabilitation were put forward according to the problems of different river sections.The concrete research results are as follows:(1)The measured data and collected data were summarized,and the water quality of Sanhekou basin was evaluated by single factor evaluation method.Single factor evaluation showed that nitrogen content was the main factor leading to the deterioration of water quality in the three tributaries.The experimental results of water quality index show that the water quality of the source and upstream reaches of the Sanhekou tributaries is good,but with the process of water flow,the water pollution is gradually increasing.After passing through the area with poor natural state,the water quality of the main river becomes worse.After the river enters the reservoir area,the water depth is increased,the transparency is reduced,and the overall water quality is maintained water.(2)In the light of water quality evaluation,it is found that the overall state of the water body is good,and the water quality has not changed significantly.Based on the hydrodynamic model,the hydrodynamic-water quality model is constructed,and the applicability of the model is verified by comparing the measured and simulated values.(3)The MIKE21 hydrodynamic model is used to analyze the flow field characteristics of the study area under different hydrological years.The calculation results show that the overall flow velocity of the study area is basically and the flow velocity increases in the narrow part of the river channel.Under the condition of hydraulic calculation of 95%guarantee rate in dry year,the flow velocity shows a significant downward trend.Due to the decrease of water inflow in the upper reaches of the main channel of Ziwu River.(4)Water quality module,through the hydrodynamic-water quality model constructed in this study,the influence of pollutants on river water disturbance under different working conditions is mainly controlled by the concentration difference between the inflow of the river before the confluence and the leakage of pollutants.The maximum concentration of pollutant migration under the characteristic time node is analyzed,and the peak pollution of different spatial sections and the duration of water quality exceeding the standard are compared.Combined with practice,the threat degree of reservoir area under specific working conditions is determined,which provides reference for downstream dam monitoring and early warning.(5)According to the results of water quality simulation and river flow field analysis,suggestions and countermeasures for river ecological restoration are proposed for the ecologically damaged reaches of Sanhekou Basin.In order to build a perfect watershed ecosystem,under the premise of ensuring water quality,river restoration sites are constructed according to the requirements of ecological management.Through the joint stocking of aquatic animals and plants,the living and activity space of organisms can be restored,the species richness can be improved,and the connectivity between water area and surrounding environment can be promoted,which plays a positive role in improving water quality and ecological management of the basin. |
