다수질기준 부하지속곡선을 활용한 수질평가 프레임워크 개발

A load duration curve (LDC) illustrates the relationship between streamflow and both observed and target pollutant loads. LDCs are widely used to diagnose water quality conditions, evaluate the effectiveness of water quality management strategies, and assess the achievement of water quality goals. In the current Total Maximum Daily Load management plan, water quality assessments are based on LDCs and exceedance rates of target water quality standards across flow regimes. However, these assessments only consider whether the standards are exceeded, without reflecting the extent of exceedance, which may lead to misinterpretations. To address this limitation, this study proposes an enhanced water quality assessment framework that incorporates multi-standard LDCs, the proportional distribution of water quality grades, and the rate of change in the proportion of “Good quality” water. We applied the framework to the Cheongmicheon in the Hangang basin to evaluate its practical applicability. The results demonstrate that multi-standard LDCs enable intuitive assessment of the distribution of observed loads across water quality grades and the degree of pollution. Additionally, analyzing the proportional distribution of water quality grades makes it possible to identify persistent occurrences of lower water quality grades, detect temporal trends in stream water quality, and characterize water quality conditions while accounting for differences across monitoring stations. Furthermore, when evaluating stream water quality across different flow regime divisions, the differences in the proportion of “Good quality” water were minimal. This study confirms that multi-standard LDCs can provide richer information than conventional LDCs and serve as a useful tool for stream water quality assessment and policy decision-making.