Seasonal and vertical distribution of water quality were investigated from May 2001 to June 2002 in Kumoh reservoir located nearby Kumi City, Kyungpook. Kumoh reservoir that lost the role of agricultural irrigation is currently of rapid eutrophication. The vertical distribution of DO was observed clinograde with hypolimnetic anoxic zone. T-P concentrations at the surface ranged from 0.008 to 0.152 mgP/L and T-N concentrations ranged from 1.4 to 3.0mgN/L. The vertical and seasonal variation of T-N was smaller than T-P. DOC concentrations, indicator of organic matter pollution, ranged from 2.8 to 5.4 mgC/L. Apportionment of Total-DOC (T-DOC) indicated that 14% of T-DOC was attributed to Labile-DOC(L-DOC) and the rest was due to Refractory- DOC(R-DOC). The values of TSI(Trophic State Index) ranged between 44 and 52 indicating that Kumoh reservoir is under mesotrophic condition. The results of this study indicate that Kumoh reservoir is likely to be under influence of eutrophication and thus water quality will be aggravated. Therefore, the Kumoh reservoir requires further treatment to improve water quality and a plan of the reusing water resource should be developed.

Gunsan coastal area is one of region increasing pollution problems. To improve water quality, the reduction of these nutrients loads should be indispensible. In this study, the three-dimensional numerical hydrodynamic and ecosystem model were applied to analyze the processes affecting the eutrophication. In field survey, the average concentrations of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus(DIP) at surface waters were found to be 0.43㎎/ℓ and 0.03㎎/ℓ respectively, which were exceeding second grade of water quality criteria. In hydrodynamic modelling, the comparison between the simulated and observed tidal ellipses showed fairly good agreement. The ecosystem model was calibrated with the observed data in study area. The simulated results of DIN were fairly good coincided with the observed values within relative error of 32.39%, correlation coefficient(r) of 0.99. In the case of DIP, the simulated results were fairly good coincided with the observed values within relative error of 24.26%, correlation coefficient(r) of 0.82. The simulations of DIN and DIP concentrations using ecosystem model were performed under the conditions of 20～80% reductions for pollutant loading. At simulation results, concentration of DIN and DIP were reduced to 20～80% and under 10% in case of the 80% reduction of polltuant loading, respectively.

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 1993～2001. The results of study were as follows. The annual total phosphorus loading from the watershed was calculated to be 55～195tP/yr at lake Soyang, 221～466tP/yr at lake Taechong, 123～278tP/yr at lake Andong, 57～109tP/yr at lake Seomjin. 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, 2.34gP/㎡/yr, 1.78gP/㎡/yr, 0.91gP/㎡/yr, 0.89gP/㎡/yr, 0.86gP/㎡/yr, lake Taechong was 6.71gP/㎡/yr, 7.25gP/㎡/yr, 7.24gP/㎡/yr, 6.53gP/㎡/yr, 6.50gP/㎡/yr, 7.06gP/㎡/yr, 7.04gP/㎡/yr, 4.05gP/㎡/yr, 3.44gP/㎡/yr and TP loading on the surface area of lake Andong, lake Soemjin were 5.39gP/㎡/yr, 4.47gP/㎡/yr, 4.56gP/㎡/yr, 4.45gP/㎡/yr, 3.33gP/㎡/yr, 2.38gP/㎡/yr, 2.53gP/㎡/yr, 2.46gP/㎡/yr, 2.54gP/㎡/yr, 4.09gP/㎡/yr, 4.10gP/㎡/yr, 3.98gP/㎡/yr, 3.73gP/㎡/yr, 2.80gP/㎡/yr, 3.46gP/㎡/yr, 3.22gP/㎡/yr, 2.19gP/㎡/yr, 2.13gP/㎡/yr respectively. The tropic states of four lakes can be assessed as eutrophy because phosphorus loading exceeds the critical phosphorus loading by Vollenweider-OECD model.

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.