Investigation best number of tanks for hydrological tank model for rural catchment in humid region

Abstract

Hydrological Tank model has proven more capable than many other models in modeling the hydrologic responses from a wide range of humid watershed. Many hydrologists are using this model due to its simplicity of concept and computation while achieving forecasting accuracy comparable with more sophisticated models. Throughout the years, various types of Tank model have been developed. The best was found to be storages series type. However, there is no general agreement regarding the best number of series storage tanks for rural catchment in humid region. In this study, three types of series storage tanks were selected to model the daily and hourly runoff for Bedup Basin, a rural catchment in humid region. These three Tank models that consist of three, four and five series storages tanks are named as 3-Tank-D, 4-Tank-D, 5-Tank-D respectively for daily model, and 3-Tank-H, 4-Tank-H, 5-Tank-H respectively for hourly model. The model performance is evaluated with coefficient of correlation (R) and Nash-sutcliffe coefficient (E2). Results revealed that the best number of tank is four, where average R and E2 yield to 0.6833 and 0.6620 respectively for daily runoff simulation, 0.8985 and 0.8214 respectively for hourly runoff simulation. Besides, sensitivity analysis also demonstrated the infiltration coefficient from forth to fifth tank (C9) has minor impact to runoff peak discharge and side outlet coefficient for fifth tank (C10) doesn’t have any significant impact to runoff peak discharge for both daily and hourly runoff simulation. Thus, these two parameters can be ignored. This result further confirmed that the best number of tanks for daily and hourly runoff simulation for rural catchment in humid region is four.