• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1223-1232
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• 2021

In this study, a new analysis method by using a "Discharge Gini Coefficient" is presented to determine the degree of inequality in daily discharge throughout the year. The Discharge Gini Coefficient can be calculated using the area relationship with the cumulative percentage of the daily mode discharge in the ascending order according to the cumulative percentage of the date of occurrence of the daily discharge throughout the year. The Discharge Gini Coefficient is presented as a value between 0 and 1, and the degree of inequality can be divided into 5 levels. The Discharge Gini Coefficient can be used to estimate the discharge stability of the downstream point relative to the upstream point. In addition, it is possible to quantify the influence of each reference discharge on the total inequality. The applicability of the Discharge Gini Coefficient was reviewed using long-term daily discharge data at eight points upstream and downstream of the four major rivers in Korea. The Discharge Gini Coefficient can also be used to analyze the discharge control effect in the downstream by the upstream dam.

• Journal of Korea Water Resources Association
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• v.54 no.6
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• pp.355-363
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• 2021

The conventional Flow Duration Curve has limitations that it does not consider hydrologic persistence of daily discharge, that the daily discharge is greatly affected by the maximums or minimums, and that the date of occurrence and duration of a specific discharge cannot be known. In this study, we propose a Daily Mode Discharge Curve, which consists of aligning the daily discharge each year by the date of occurrence, calculating the daily mode discharge, and averaging them every 5 days. As a result of reviewing the long-term observational daily discharge data at 8 points upstream and downstream of the mainstream of the 4 major rivers in Korea, it was found that the daily discharge at all points shows hydrological persistence, and the distortion of it was alleviated by using Daily Mode Discharge Curve. We also suggest that the Daily Mode Discharge Curve is useful for utilizing reference discharge such as Drought, Low, Normal, Plentiful, and Flood Discharge.