Change in Agricultural Irrigation Water Quality in Mankyeong River

만경강 수계 농업용수의 시기별 수질변화

The water quality at Mankyeong River was surveyed 13 sites of main stream for 6 months from April to September in 1995 and 1997. The monthly average value of $NH_4-N$, $SO_4^{2-}$ and $Cl^-$ showed the highest peak in April while that of $NO_3-N$ showed the highest peak in August. The monthly average value of COD showed the highest peak in September at high temperature season. Concentrations of $NH_4-N$ and $SO_4^{2-}$ in Mankyeong River stream exceeded the standard water quality criteria in many sites. The water quality of Mankyeong River stream was not suitable for the irrigation source excepted the sites such as Hari, Gosan stream and Soyang stream. The floodgate of Mokcheon, Yocheon, Jeonju and Samcheon stream were rapidly polluted by the sewage of city, otherwise the Iksan stream was rapidly polluted by the sewage of swine. The sum of ionic concentrations in Mankyeong River stream was the highest at floodgate of Yocheon by influence of the sewage from city and industry. The order of the major anions and cations concentration in Mankyeong River stream were $SO_4^{2-}$ > $Cl^-$ > $NO_3-N$ > $SO_4^{3-}$ and $Na^+$ > $Ca^{2+}$ > $NH_4^+$ > $Mg^{2+}$ > $K^+$, respectively.