Analysis Of Rainfall Characteristics And Research On Response Mechanism Of River Hydrology And Water Quality In Urban Areas

Under the changing environment,urban water security is facing serious challenges.Urban rivers are the most vulnerable part of the urban water security system and extremely sensitive to climate change and urbanization.Urban flooding and water pollution are the two serious problems,which seriously affect the water environment of the urban river basins and the sustainable development of urban areas.Pingshan River is located in the northeastern part of Shenzhen and adjacent to Huizhou.It is the core basin of Shenzhen and Huizhou.However,the impact of industrialization and urbanization has led to frequent floodings and serious river pollution problems in the basin in recent years.At present,the research on the analysis of rainfall characteristics and the response of river hydrology and water quality in this basin is still insufficient.This study selects Pingshan River as the research basin.First,using mathematical statistics,based on meticulous rainfall data,to summarize the temporal and spatial distribution of rainfall and typical rainfall characteristics in the Pingshan River;uses the K-means clustering algorithm to analyze the rainfall patterns of Pingshan River with fuzzy recognition method;then conducts the SOBEK water volume model to analyze the river's response to rainfall runoff,and selects typical rainfall events to explore the spatial distribution of runoff in the basin under typical rainfall events.Then use the Water Quality Index method(WQI)and multi-factor analysis of variance to assess the overall water quality of the basin and analyze the factors that affect the water quality indicators.Finally,a SOBEK water quality model is established to reveal the migration of pollutants along with the runoff,and the conception of event mean concentration of runoff pollution(EMC)is introduced to reveal the rainfall characteristic parameters that affect the concentration of pollutants.The main contents and conclusions of this research are as follows:1.Analysis of the temporal and spatial distribution of rainfall and rainfall characteristics in Pingshan River:The wet season in Pingshan River is mainly concentrated from April to September.The rainfall in the wet season accounts for about 85% of the annual rainfall,and the proportion of light rain and moderate rain in the overall rainfall level.The frequency is 54.33%and 21.84%,respectively.In terms of rainfall contribution rate,the contribution rate of robust rainfall reaches 55.29%.Affected by topographical factors,the spatial distribution of rainfall in the basin is uneven.The rainfall in the southwest region is relatively large,and the rainfall in the northeast region is small;the typical rain pattern of the basin is the front-peak type,and the proportion is much higher than the middle-peak and back-peak rain type.2.Research on the response of the river runoff to rainfall:Establish the SOBEK water volume model of Pingshan River and evaluate the simulation effect of the model systematically using statistical indicators such as NSE,correlation coefficient,RMSE,and PBIAS.The results show that the SOBEK water volume model can simulate the rainfall and runoff well in Pingshan River,and the assessment criteria are relatively good.The average NSE is higher than 0.75,the average R~2 is higher than 0.75,and the average PBIAS absolute value is less than 15%.The SOBEK water volume model shows reliability in Pingshan River.The spatial distribution of runoff in the basin under typical rainfall events is further analyzed,and it is found that middle area of the basin is the most vulnerable area in terms of runoff influences.3.Research on the water quality response of the river to rainfall:Based on the WQI method,the overall water quality of the basin was evaluated.The results showed that the water quality in the lower reaches of Pingshan River was the worst.The water quality in the wet season is better than that in the dry season;Based on multi-factor analysis of variance we found that the interactive effect of rainfall intensity and station location has the most significant impact on water quality;then the SOBEK water quality model is conducted to reveal the migration of pollutants with streamflow.Finally,the concept of EMC is introduced to reveal the rainfall characteristics that affect water quality.The results show that the rainfall interval,rainfall depth,and rainfall duration have impacts the water quality.This research provides a method for rainfall runoff simulation,water quality assessment and simulation analysis in urban river basins.At the same time,it provides a certain reference for urban rainwater management,rainwater utilization and river water quality management.