Numerical Simulation to Quantify Present Statusand Future Prediction of Water Quality of To-Lich River, Hanoi, Vietnam

Book Chapter

A few decades ago, the surface waterbodies in Hanoi, Vietnam, were an important source of water for various usages. However, because of the rapid global changes, the current status of most of the river system is very critical from the environmental, aesthetic and commercial usage points of view. Henceforth, this research work focused on assessing the current as well as predicting its future (2030) situation of four rivers (To-Lich, Set, Lu and Kim Nguu) using different scenarios while considering key drivers of global changes namely climate change and population growth along with the mitigation measures as mentioned in an existing master plan. Water Evaluation and Planning (WEAP), a predictive numerical simulation tool, was used to model river water quality using two scenarios viz., Business As Usual (BAU) and Scenario With Measures. The simulated output visualized future wastewater generation and indicated where additional appropriate countermeasures are needed in addition to the current master plan. Results from this study show that current water quality for all streams is moderately to extremely polluted as compared with desirable category i.e., class B given by the local government. In addition, due to climate change and population changes, the water quality (expressed as BOD) will be further deteriorating by average 53.1% in 2030 as compared to the current situation. According to Hanoi city master plan for water resources, all domestic wastewater currently flowing into the rivers except for the Kim Nguu River will be transferred to new wastewater treatment plants. In such case, this study suggests that the rivers should be regularly supplemented with treated wastewater from surrounding wastewater treatment plants or water from other sources to keep the river flow and to improve the water quality significantly as shown in the mitigation plan scenario (85.8% reduction compared to the business-as-usual scenario).