The work on the eutropication of Youngsan river was conducted from Jul. 1997 to Jun. 1998. The value of water temperature in the study area varied from 4℃ to 32℃ with an annual mean of 17.5℃. DO varied from 4.0㎎/ℓ to 13.5㎎/ℓ with an annual mean 10.2 ㎎/ℓ. BOD varied from 0.8㎎/ℓ to 6.4㎎/ℓ with an annual mean 3.1㎎/ℓ. COD varied from 4.6㎎/ℓ to 9.0㎎/ℓ with an annual mean 6.38㎎/ℓ. Nitrate varied from 1.58㎎/ℓ to 6.77㎎/ℓ with an annual mean of 3.475㎎/ℓ. Total-nitrogen varied from 2.14㎎/ℓ to 8.38㎎/ℓ with an annual mean of 5.083㎎/ℓ. Total-phosphate varied from 0.035㎎/ℓ to 0.588㎎/ℓ with an annual mean of 0.128㎎/ℓ. Chl.a varied from 1.8㎍/ℓ to 75.0㎍/ℓ with an annual mean of 19.55㎍/ℓ. The euthrophic state index of Carlson^16) were showed 61.8(TP) and 71(SD) value

To investigate the water quality characteristics and eutrophication of the Keum River, survey were conducted on samples collected from 6 stations in Aug. and Oct. in 1995 and Jan. and May in 1996. The results were summarized as follows ; Concentration of pollutants were in the range of 1.74∼6.35(mean 3.81)㎎/ℓ for BOD and 1.98∼8.21(5.14)㎎/ℓ for COD and 1.46∼51.94(18.52) g/ℓ for TSS. Water quality were evaluate to be 2∼3 grade of station 1 and other stations were 3∼4 grade of water quality criteria. The concentration of nutrients were in the range of 55.2∼735.3(309.3)㎍-at/ℓ for Dissolved inorganic nitrogen(DIN) and 0.06∼6.03(2.80)㎍-at/ℓ for dissolved inorganic phosphate(DIP). Nutrient concentrations in Keum River were usually high and the DIN/DIP ratio ranged from 72 to 2648. The concentration of chlorophyll-a was in the range of 1.1∼143.7(44.3)㎎/㎥. Chlorophyll-a concentration were high 10㎎/㎥ except station 1, which is the value of eutrophication criteria by EPA. Correlations between nutrients and chlorophlly-a were not significant. According to eutrophication evaluation, Keum river was equivalent to the eutrophic state.

The purpose of this study is to evaluate and to predict of eutrophication in lakes by using Vollenweider-OECD model and total phosphorus concentration and inflow rate which were measurded in 1993-1996. The results of study was as follows. The annual total phosphorus loading from the watershed was calculated to be 181∼195tP/yr at lake Soyang, 591∼680tP/yr at lake Chungju, 420∼466tP/yr at lake Taechong, 229∼278tP/yr at lake Andong, 103∼106tP/yr at lake Hapchon, 57∼59tP/yr at lake Imha, 194∼244tP/yr at lake Namgang, 83∼86tP/yr at lake Chuam, 99∼109tP/yr at lake Somjin. These are discharged, for the most parts, from population and fishfarm facility. TP loading on the surface area at lake Soyang was 3.01gP/㎡/yr, 2.82gP/㎡/yr, 2.84gP/㎡/yr. 3.03gP/㎡/yr, at lake Chungju 7.9lgP/㎡/yr, 6.87gP/㎡/yr, 7.38gP/㎡/yr, 7.18gP/㎡/yr, at lake Taechong 6.7lgP/㎡/yr, 7.25gP/㎡/yr, 7.24gP/㎡/yr, 6.53gP/㎡/yr and TP loading on the surface area of Nakdong river basin, that is, lake Andong, Imha, Hapchon and Namgang were 5.39gP/㎡/yr, 4.47gP/㎡/yr, 4.56gP/㎡/yr, 4.45gP/㎡/yr and 2.20gP/㎡/yr, 2.23gP/㎡/yr, 2.24gP/㎡/yr, 2.17gP/㎡/yr and 4.50gP/㎡/ yr, 4.50gP/㎡/yr, 4.54gP/㎡/yr, 4.43gP/㎡/yr and 8.25gP/㎡/yr, 8.48gP/㎡/yr, 8.48gP/㎡/yr, 10. 39gP/㎡/yr respectively. Also those of lake Chuam was 2.51gP/㎡/yr, 2.61gP/㎡/yr, 2.52gP/㎡/yr, 2.54gP/㎡/yr and TP loading on the surface area at lake Somjin was analysed 4.09gP/㎡ /yr, 4.10gP/㎡/yr, 3.98gP/㎡/yr, 3.73gP/㎡/yr. The tropic states of nine lakes can be assessed as eutrophy because phosphorus loading exceeds the critical phosphorus loading by Vollenweider-OECD model.

Masan bay is one of the polluted enclosed bays, which has red tides problem and the formation of oxygen deficient water in the bottom layer. Most important factors that cause eutrophication and red tide is nutrient materials containing nitrogen and phosphorus which stem from terrestrial sources and nutrients released from sediment. Therefore, to improve of water quality, reduction of these nutrient loads should be indispensible. At this study, the three-dimensional numerical hydrodynamic and eutrophication model, which were developed by Institute for Resources and Environment of Japan, were applied to analyze the processes affecting the phytoplankton production and also to evaluate the effect of water quality improvement plans on phytoplankton production. in field survey, the range of concentrations of chlorophyll -a at surface area was found to be 29.17 - 212.5㎎/㎥, which were exceeding eutrophication criteria. The constant currents defined by integrating the simulated tidal currents over 1 tidal cycle showed the counterclockwise eddies in the southern part of Budo. The general directions of constant currents were found to be southward at surface and northward at bottom over all the bay. The eutrophicatior model was calibrated with the data surveyed in the field of the study area in June, 1993 The calculated results are in fairly good agreement with the observed values within relative error of 30%. The pollutantI load from the sources such as the input from terrestrial sources and release from the sediment was reduced by the rate of 50, 70, 90, 98% to evaluate the effect of phytoplankeon production. Phytoplankton production was reduced to 50% in case of the 90% reduction of the input loads from terrestrial sources and 8% in case of the 90% reduction of the load from sediment.