농업용 저수지 소하천의 통계학적 수질변화 특성 = Statistical Study of the Long-term Changes in Water Quality Parameters of the Small Streams in Agricultural Reservoir

다국어 초록 (Multilingual Abstract)

The results of investigation for the long-term changes in water quality of the small streams in agricultural reservoir indicate that nitrogen is determined mainly by the agricultural activities while phosphorus and suspended solids are affected by the soil particles moved by irrigation return flow or/and rainfall discharge. However, nitrogen is related with factors of the flow more than suspended solids concentration but rather tends to decrease with the abundant stream flows caused by rainfalls. As the use of land for rice paddy in the watershed increases, more nitrogen loss was also observed. It was found that about 50% of the total phosphorus and nitrogen exists in dissolved form. There is a possibility to develop tools which can be used to predict dissolved forms of the nutrient by TDS values easily and reliably measured by electrical conductivity. Coefficient of determination(R²) between TDS and phosphorus concentration was higher than the nitrogen concentration. Especially, the more rice paddy area, the higher correlation coefficient. In addition, TDS was inversely correlated with flow(or depth) due to the dilution effect of rainfall water, so that multiple rating curves from flow depth to approximate TDS and then nutrients could be useful. Most of the water quality parameters were found to have a log-normal probability distribution.