Study On Runoff Simulation Of Qinghe River Basin Based On SWMM And SCS Model

Qinghe River is located at the junction of Baqiao District,Lantian County and Lintong District in Xi'an.It is a primary tributary of the Honghe River,a tributary of the Weihe River,and is also an outlying watershed in downtown of Xi'an.In the process of expanding urbanization in Xi'an,the hydrological environment of some natural small watersheds around the city will be changed by human factors.These small watersheds,as an important part of the regulation of urban water systems,will have an impact on the water resources planning and flood control decisions of the entire city.Therefore,it is necessary to carry out hydrological studies on small watersheds in the outskirts of cities in Xi'an.This paper takes Xi'an Qinghe River Basin as the study area,and carries out hydrological analysis from the point of the runoff process simulation of the river basin and the total amount of interannual runoff.It provides a certain basis for the water resources planning and flood control dispatching of the water conservancy departments,and provides reference of carring out such studies for other outside small watersheds areas in Xi'an.The SWMM model was selected to simulate the runoff process,and the applicability of the model was discussed.Then the runoff process of the basin under extreme rainfall conditions was simulated,providing a basis for the water conservancy departments to respond to extreme rainfall events.In addition,the SCS model was used to simulate the total annual runoff in the basin,and the changes of the total runoff volume in different rainfall years were analyzed,which provided a scientific basis for the water resources department to manage water resources.The conclusions were summarized in this following:1)Based on the study of Xi'an Qinghe River Basin and SWMM model,a lumped hydrological model without considering the response of complex hydrological units within the basin and a semi-distributive hydrological model considering the mutual response of hydrological units within the basin were constructed.The simulation results show that the lumped model has a better simulation effect and is more suitable for the runoff simulation in the Qinghe River Basin.In addition,lumped mode is more convenient than semi-distribution mode modeling and has better applicability.Different research areas have different geographic characteristics,in the case that the basic geographical data of the study area are not particularly rich,it is possible to construct lumped and semi-distributed hydrological models,and select suitable model categories according to the simulation results.2)As a traditional urban rain-flood model,the SWMM model is mostly applied to the rain-flood simulation in urban areas in China,and it is rarely used in the domestic runoff simulation of natural watersheds.This study successfully applied the SWMM model to the Qinghe River Basin and extended its use in natural watersheds.3)The successful application of the SCS model in the Qinghe River Basin indicates that the model can perform runoff simulations in areas with no data or data scarcity.Due to its simple structure and low parameters,it has reduced the difficulty of performing hydrological simulation in a similarly dataless region,and also provides new ways of hydrological studies in these areas.This paper proposes to use runoff coefficient method to verify the simulation results,which can make up for the lack of actual measurement data.It can also serve as a reference for the hydrological verification method in areas without data.4)The runoff simulation of SWMM model under different rainfall return periods showed that the peak value of flow during each return period basically appeared about 1.5 hours after the start of rainfall.Under different rainstorm conditions,the peak runoff of river basin lags behind urban areas.In the event of more than 10 years of torrential rain,the runoff process of the river basin has changed greatly.The runoff change curve can serve the local water conservancy departments and provide a scientific basis for flood control and disaster reduction.5)The precipitation of rainfall in the Qinghe River Basin has been declining for many years.Combined with the criteria for the classification of the dry years of the basin's multi-year rainfall,it can be judged that the years of rainfall in the basin in the next few years should be classified as flat water years with a fluctuation range of 500-630 mm.From the perspective of inter-annual runoff,the total runoff volume in the dry season was at least 3.6 million m3,and the total runoff volume was the largest in the flood season,reaching 12.19 million m3.Combining the factors of watershed precipitation year in the next few years can predict the total amount of interannual runoff in the Qinghe River Basin in the next few years,which can provide a basis for decision-making by relevant local authorities.