Application Of HEC-HMS In The Beizhangdian Watershed

Being one of the most important cycle processes in the world, the hydrological cycle process is concerned all the time by different realm experts, especially for hydrologists trying to understand basic laws of the hydrological cycle. However, due to its complexity, the understanding of hydrologic phenomenon is still in its infancy. Most of the hydrological models perform well in humid areas or the corresponding areas, while they perform badly in other areas. With respect to this, the Hydrologic Engineering Center belonging to the US Army Corps of Engineers developed the HEC-HMS model, to make the classic and common computation methods modularly in sub-procedures of the hydrological process, which includes plant interception, depression, infiltration, the overland flow, base flow and concentrated flow of river channels, etc. In addition, the HEC-HMS model provides a modular multilevel interaction platform to simulate the watershed rainfall-runoff process in different complex conditions, which can be widely used in arid, semiarid, humid and sub-humid climate areas.Firstly, the annual variation and intra-annual distribution of hydrological factors which include precipitation, runoff and evaporation were researched in the Beizhangdian watershed. The results indicated that the annual variation of rainfall and runoff of the watershed was remarkable, the intra-annual distribution of rainfall and runoff was extremely uneven, and rainfall-runoff mainly occurred in flood season. The maximum precipitation occurred in July accounted for26.3%of annual precipitation. The maximum monthly runoff occurred in August accounted for21.6%of annual runoff. There is a good unanimity between the variation tendency of runoff and rainfall. The maximum monthly evaporation occurred in May accounted for15.5%of annual evaporation.Secondly, according to the analysis of storm flood data in the Beizhangdian watershed, it revealed that the runoff generation is quite complicated which includes infiltration excess runoff and stored-full runoff at the same time. The peak discharge may be large or small. The flood peak generally appeared in the rain stops. Flood hydrograph expressed in peak with rising and dropping steeply, or peak with rising and dropping slowly. The flood peak pattern had various morphologies with single peak, double peak, multi-peak, explicit peak, hide peak, or a combination of implicit and explicit peak. Thirdly, by processing30-meter resolution DEM provided by International Scientific Data Service Platform, Computer Network Information Center, Chinese Academy of Sciences, river network features were extracted by applying HEC-GeoHMS.12natural subbasins were divided according to the Beizhangdian watershed terrain characteristics. Within each subbasin, basic units of spatially distributed hydrological models are built up through superposing the land use digital maps.Fourthly, based on analyzing the characteristics of storms and floods in the Beizhangdian watershed, the effect that base flow impacted on runoff was neglected in this model, two schemes were determined by making use of the interactive platform provided by HEC-HMS. The first one selected initial abstraction steady infiltration method, Kinematic wave method and Muskingum method, while the other one used SCS curve law, SCS unit hydrograph method and Muskingum method. Both of them were applied to rainfall-runoff simulation in the Beizhangdian watershed.Finally, according to the results computed by the simulation of two schemes, in the cheme1, the passing rate of flood capacity was84.6%, the passing rate of flood-peak was92.3%, the average of certainty coefficient was0.85and the flood peak appearance time difference was54minutes. In the cheme2, the passing rate of flood capacity was84.6%, the passing rate of flood-peak was100%, the average of certainty coefficient was0.81and the flood peak appearance time difference was96minutes. In terms of certainty coefficient, flood capacity and flood-peak, the model perform well in Beizhangdian watershed. However, in terms of the flood peak appearance time, the calculation methods of runoff generation and concentration need to be analyzed and combined, and the accuracy of simulation needs to be improved.