| The Nakdong river being used as drinking water sources for Pusan and Kyungsang province has contaminated due to inflow of inadequately treated wastewaters from the tributaries into the river. In order to predict the characteristics of the river according to the variations of the flow and contaminants loading, water quality of the Nakdong river in winter of dry season was simulated by QUAL2E. The intensive surveys for the characteristics of the river section from Dalsung to Hagueun the downstream end of the Nakdong river were conducted during December 1995 to March 1996. Stream section from Dalsung to Mulgum was modelled. Discharge coefficients were estimated for 15 reaches of the Nakdong river. The results of this study were summarized as follows; 1. The characteristics of water quality in the Nakdong river during the period of this study ranged from third grade to over fourth grade in water quality criteria as BOD. In main stream of the river, in particular, the water quality of the Mulgum which is drinking water intake source for Pusan Metropolitan City, was most worse as 7.5∼9.1 ㎎/L of BOD and 9.4∼12.0 ㎎/L of COD, compared to other sites. 2. In the contaminants loadings from the tributaries in river basin, the Kumho river with 11.2∼17.8 ㎎ BOD/L, 13∼21.3 ㎎ COD/L and 14.7∼25.8 ㎎ T-N/L was the main source of the inflow of carbonaceous and nitrogenous organic matter. 3. The lower reaches from Hanam to Mulgum of the river appeared stagnant phenomenon like the lake due to the decrease of the river flow. Deoxygenation rate (Kd) and reaeration rate(Ka) were in the range of 0.13 to 0.45 day^(-1) and 0.017 to 0.5 day^(-1), respectively. 4. In order to improve the water quality of the Nakdong river to be second grade in water quality criteria as BOD, the waste loads of the Kumho river should be reduced more than 95%, including the removal of nitrogen and phosphorus by an advanced wastewater treatment. |
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