Water Quality Modeling for Bokha Stream by WASP5 Model

WASP5 모형을 적용한 복하천의 수질 예측

WASP5 was applied to evaluate water quality of Bokha stream with 17km of its main stem located in Ichon-city, Kyunggi province in Korea. Boundaries of the stream for the WASP5 were the Jumi bridge, 10 major tributaries and one wastewater treatment system. The stream was divided into 37 segments with about 350m length. The flowrate of the 10 day's average of the stream was obtained from the hydrograph data and the discharge-stage rating curve. Simulated quality constituents included nitrogen, phosphorus, BOD and DO. Monthly records of water quality and loads in 1996 were used for the calibration of parameters of WASP5. Simulation showed high correlations between calculated and observed concentration with monthly runoff ratio in Bokha stream. At downstream boundary, Jumi bridge [Seg.36], similar correlations were appeared. However, simulated concentrations by using annual runoff ratio were somewhat differentiated from those of the observed.

하천 수질예측 모형으로서 WASP5 모형을 선정하고, 복하천에 적용한 결과 다음과 같은 결과를 얻었다. 1. 년평균 유달율을 적용한 결과, 실측치와 계산치 사이에 큰 차이가 나타내므로 시간을 고려한 동적모의발생을 위해서는 계절에 따른 유달율의 변화를 반영하여야 할 것이다. 2. 월별 유달율을 고려한 부하량을 입력하여 계산한 결과, 실측치와 계산치가 거의 일치하므로 유역으로부터의 부하량을 이용한 하천수질 예측모형으로서 WASP5 모형의 활용이 기대된다. 3. GIS를 이용한 부하량 산정, 유역의 최적관리(BMP's)를 통한 발생량 저감, 처리장의 신${\cdot}$증설 등 경계조건이 변동된 경우, 본 WASP5모형에 시기별 유달율을 고려한 자료가 입력된다면 하천수질농도의 예측이나 수질개선효과의 파악이 용이할 것으로 판단된다.