• Chihiro Yoshimura, Maichun Zhou, Anthony S Kiem, Kazuhiko Fukami, Hapuarachchi H A Prasantha, Hiroshi Ishidaira, and Kuniyoshi Takeuchi.
• Department of Civil Engineering, Tokyo Institute of Technology, Tokyo 152-8552, Japan. yoshimura.c.aa@m.titech.ac.jp
• Sci. Total Environ. 2009 Oct 1; 407 (20): 5356-66.

AbstractA distributed hydrological model, YHyM, was integrated with the export coefficient concept and applied to simulate the nutrient load in the Mekong River Basin. In the validation period (1992-1999), Nash-Sutcliffe efficiency was 76.4% for discharge, 65.9% for total nitrogen, and 45.3% for total phosphorus at Khong Chiam. Using the model, scenario analysis was then performed for the 2020s taking into account major anthropogenic factors: climate change, population, land cover, fertilizer use, and industrial waste water. The results show that the load at Kompong Cham in 2020s is 6.3 x 10(4)tN a(-1) (+13.0% compared to 1990s) and 4.3 x 10(3)tP a(-1) (+24.7%). Overall, the noticeable nutrient sources are cropland in the middle region and urban load in the lower region. The installation of waste water treatment plants in urban areas possibly cut 60.6%N and 19.9%P of the estimated increase in the case without any treatment.

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