4th VNU – HCM International Conference for Environment and Natural Resources ICENR 2014 “Green growth, climate change and protection of the coastal environment” 17 th + 18 th of June, Ho Chi Minh City, Vietnam 1 Integrated water quality monitoring of the Thi Vai River: an assessment of historical and current situation Karen Prilop 1 , Nguyen Hong Quan 2* , Malte Lorenz 1 , Huyen Le 1 , Le Thi Hien 2 and Günter Meon 1 1 Leichtweiß-Institute for Hydraulic Engineering and Water Resources, Department of Hydrology, Water Management and Water Pollution Control, University of Braunschweig, Beethovenstr. 51a, D-38106 Braunschweig, Germany, email: k.prilop@tu-bs.de, malte.lorenz@tu-bs.de, huyen.le@tu-bs.de, g.meon@tu-bs.de 2 Institute for Environment and Resources (IER) - Vietnam National University of Ho Chi Minh city, 142 To Hien Thanh, District 10, Ho Chi Minh city, Viet Nam, email: hongquanmt@yahoo.com (*corresponding author), hienev01@yahoo.com ABSTRACT In Vietnam the Thi Vai River was considered as one of the spots with the heaviest water pollution, which was induced by industrial wastewater discharges, especially by untreated wastewater of the Vedan company during the years 1994 to 2008. However, thanks to the consideration on water quality management from local to national authorities, especially the controlling and reducing of wastewater discharges to the river, the surface water quality of Thi Vai River, situated in South Vietnam, has been improved in the recent years. The assessment of the water quality status from the past to present of the Thi Vai River is very essential for water quality management. Within the joint research project “Environmental and Water Protection Technologies of Coastal Zones in Vietnam EWATEC-COAST” funded by the German Ministry of Research and Education (BMBF) and the Vietnam National University of Ho- Chi-Minh City a model-based water management system for the Thi Vai River is developed. The availability and further the evaluation of water quality and quantity data is one necessary basis for this objective. Firstly, historical data from different sources, especially from some recent projects carried out by the Institute for Environment and Resources (IER) - Vietnam National University of Ho Chi Minh city, has been collected and evaluated. Apart other signs of pollutions, very low concentrations of dissolved oxygen and very high concentrations of ammonia were detected in the past. An extreme pollution was recorded in the upper reaches, whereas a lower pollution level existed in the lower reaches. Next, within the BMBF research project EWATEC-COAST, subproject 3 “Surface Water”, the scientists from the Leichtweiss-Institute, TU Braunschweig (Germany) have implemented a monitoring system for water quantity and quality at the Thi Vai River and its main tributaries. The monitoring data provide detailed data for the complex Thi Vai River, which is strongly affected by tide. Previous results indicate that the water quality has improved in comparison to the past until 2008. Nevertheless still signs of pollution exist. High nitrite concentrations, elevated ammonia concentrations as well as partly low oxygen concentrations still occur. Key Words: water quality, river monitoring, tide 1. INTRODUCTION Untreated and poorly treated wastewater from ports and industrial zones was discharged to the Thi Vai River in the past. A section of about 9 km (from the tributary Suoi Ca River to the My Xuan industrial zone) were seriously polluted. This section was regarded as ecologically dead: Fish, shrimps and other aquatic species hardly existed and only plankton and algae species adapted to high nutrient contents occurred [1, 2, 3]. After determining the illegal discharge of waste water by the company Vedan as one of the main factors for the impairment of the water quality of the Thi Vai in 2008, the water quality has been improved by investments in waste water treatment systems and better controls.