| The Objectives of this study is to predict the characteristics of the Nakdong river according to the variations of the mass loading such as water quantity and pollutants concentration. The simulation of water quality of the river in dry season of winter was carried out by QUAL2E which in general is widely used for predicting river water quality. Stream section from Kangjung to Mulgum was modelled. At that time, the pollutant loading reduction included the removal of nitrogen and phosphorus by an advanced wastewater treatment system. The results of this study were summarized as follows; 1. The characteristics of water quality in main stream of the river during the dry season of winter ranged from second to third grade as 2.7∼3.6 ㎎/L for upper reaches, from third to forth grade as 3.5∼8.6 ㎎/L for mid reaches, and from fourth and more than one grade as 6.5∼9.6 ㎎/L for lower reaches in water quality criteria as BOD. In particular, the data of water quality shoved that the relationship between BOD and Chlorophyll-a and between BOD and COD have considerably been closed correlation with linear regration equations of ROD=0.027(Chlorophyll-a)+3.634 and COD=1.06(BOD)+1.04, respectively. 2. The percentage of BOD loadings production in the river basin was distributed as 60.6% from population, 16.7% from livestock, 11.2% from land, and 6.9% from industrial facilities, respectively. The percentage of wastewaters discharged from the tributaries also was distributed as 19% from Kangjung basin, 71% from Kumho river, 1% from Hwang river, 6% from Nam river, and 2% from Miryang river, respectively. Thus the results shows that a main pollutant source for the river was Kumho river. 3. For the effect of water quality improvement with the pollutant reduction of the tributaries, it was possible to improve the water quality of the river to be second grade in water quality criteria as BOD by reducing the pollutant loading up to 85% or over in case of an uniform reduction for the tributaries and, up to 90% for Kumho river and 50% for Nam river and Miryang river in case of a graded reduction for the tributaries, respectively. For the effect of dillutiing the contaminated river water due to increase of water quantity by dam construction, the increase of water quantity of 15.85 CMS in Nam river basin reduced 15∼20% of pollutant loading in the lower reaches. On the other hand, in order to improve the river water quality to be second grade in lake water quality as COD, the pollutant loading from the tributaries should be reduced more than 90% for Kumho river and 50% for Nam river and Miryang river with the inflow of 15.85 CMS into the Nam river. |
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