Applying the Soil and Water Assessment Tool Model for Integrated Lake Basin Management in Northern Vietnam: Case Study of the Thac Ba Reservoir Basin

Abstract

Recent land use changes in the form of deforestation, agricultural development, industrialization, and urbanization have caused water quality and quantity problems in many watersheds in Vietnam necessitating the development of appropriate policy interventions. This research explores the possibility of using a coupled Geographic Information System and hydrological model (Soil and Water Assessment Tool [SWAT]) to assess the impact of land use changes on stream flows in the Thac Ba reservoir basin in the Northern Vietnam in three different land use change scenarios: expansion of forest lands, return to the nature, and expansion of the urban area. The Nash-Sutcliffe Efficiencies of 0.895 and 0.869 were obtained after the calibration and validation processes, respectively. The nutrient and sediment loadings are currently being assessed pending the acquisition of observed data and model calibration. Further studies will be conducted to have a look at the likely effects of climate changes on the water quality and quantity of the Thac Ba reservoir as well as providing an insight of how the SWAT model for the Thac Ba reservoir basin can be applied to the much larger and nationally more important basin, the HoaBinh reservoir basin which provides drinking water to the capital Hanoi. According to the scenarios of land use change conditions, an increasing trend in stream flow may be expected in the next decades caused by increasing rainfall amounts. Therefore, flooding and the reduced reservoir capacity are major problems in the target area, and there must be improvement of watershed management by applying the Integrated Lake Basin Management concept.