Simulation of Surface Flow Conditions Influenced by Additional Flow from Stream Networks: a Case Study of the Chi River Basin Part 4

Abstract

The purpose of this study is to apply the SWAT hydrological model to analyze surface water flow conditions in the Chi River that flows through the Chi River Basin Part 4, which is a sub-basin of the Chi River Basin in the Northeast. In the implementation, the additional flow from the river network that flows into the Chi River is taken into account, namely the Phong River in the upstream area and the Lam Pao River in the downstream area, respectively. The results indicate that the SWAT model has a reasonable performance in estimating runoff when considering the statistical indices R2, NS, and PBIAS, respectively, after comparison with data from four monitoring stations. For the simulation of the amount of runoff that flows into the Chi River, it was found that there was a dynamic change during the study period between 1992 - 2021 (30 years). The simulated results of annual average runoff at the exit point of the sub-basin receiving runoff from Phong River, Chi River and Lam Pao River were 1,630, 288 and 853 cubic meters per second, respectively. The overall results are close to the runoff at the outlet point of the study area. In analyzing the volume of runoff received from the stream network during the rainy season, it was found that the volume of runoff added to the main river was about 68 - 70 percent, while during the dry season it decreased between 29 - 31 percent. Consequently, the methodology and results obtained from this study are expected to be used to communicate and understand stakeholders as well as provide important information for decision-making in water management planning in the Chi River Basin Part 4 and other basin areas with similar physical characteristics.