Since living environment has improved, waterfront space using and clear water demand have increased. Ministry of Environment (ME) designated polluted reservoir (worse than 4th grade) as a priority management reservoir to improve water quality (better than 3rd grade) accordingly. Minstry of Agriculture, Food and Rural Affairs (MAFRA) aims reservoir water quality 4th not 3rd grade. And water quality of agricultural reservoirs was not a great interest. For this reason, there are very few water quality monitoring data. However after designating as a priority management reservoir, reservoir manager should start water quality and flow monitoring of reservoirs and inflow streams. This process makes it possible setting complex model to accurate prediction of reservoir water quality and volume. Mulwang reservoir designated as a priority management reservoir in September 2014. In this study, BASINS/WinHSPF and EFDC-WASP were used to predict effect of water quality improvement countermeasures in Mulwang reservoir. To improve water quality of Mulwang reservoir, Siheung-si and Korea Rural Community Corporation (KRCC) established water quality improvement countermeasures. However result of simulation adapting these countermeasures cannot achieve 3rd grade. So 4 additional scenarios were adapted and the result satisfied 3rd grade. This study could help to establish water quality improvement countermeasure by using complex modeling.

Objectives:Since the enactment of the 「Han-River Watershed Act」, comprehensive analysis about direct and indirect contributions and effects of various environmental policies and water quality improvement projects for the preservation of water quality in the Han-River watershed is insufficient. Especially, effect of pollutant source location regulation should be inferred and estimated through model prediction because it does not exist unregulated conditions. As development pressure in non-urban areas near the metropolitan area is increasing, it is necessary to analyze the effects of pollutant source location regulation.Methods:In this study, average pollutant density of Gangwon-do, Gyeonggi-do, and Chungcheongbuk-do, where the regulation areas located, and average pollutant density of water source management areas were compared and analyzed. After that changes in pollutant sources in regulation areas were estimated by assuming load of pollutant sources in unregulated areas that load of pollutant sources in regulation areas. Since many reservoirs are located in Han-river watershed, it is difficult to simulate the water quality of Paldang reservoir using only watershed model, BASINS/WinHSPF and EFDC-WASP were linked. Through this, change in water quality of Paldang Lake was tried to predict when the pollutant location regulation was not implemented, and to analyze the effect of the pollutant location regulation.Results and Discussion:Water quality improvement of Paldang reservoir was evaluated by applying the discharge load when the pollution source location regulation was not implemented to the calibrated model. As a result of the pollution source location regulation, discharge load in the location regulation area was analyzed to reduce by 53.90% and T-P by 48.58%, and the BOD and T-P improvement effect of Paldang Dam was analyzed 6.77% and T-P 6.62%. Since the water quality improvement effect of Paldang Lake is accumulated to the entire upstream, it is evaluated relatively less than pollutant load reducing effect.Conclusion:It was analyzed that pollutiont source location regulation has water quality improvement effect, despite the small area which only located in near Paldang reservoir compared to the total area of the Han-River watershed.