Drought index is an important parameter to detect the onset, ending, and severity of a droughtevent. Until recently there been no internationally accepted hydrological drought index. Insearch of promising hydrological drought index, this paper analyzes the performance ofseveral hydrological drought indices at six irrigation weirs in the Pemali-Comal River Basin,Indonesia. The performance is measured by the correlation between the streamfl ow droughtindex and the irrigation areal affected by drought. It is concluded that in Indonesia, especiallyin the study area of Pemali-Comal river basin, streamfl ow drought index of seasonal thresholdtruncation under Log-Normal distribution assumption is highly correlated with the data onirrigation area affected by drought. The rationale of this fact is due to the, and the nature ofdata that having a Log-Normal statistical distribution. It is proposed to use this hydrologicaldrought index for the area having high seasonal variation in streamfl ow in the tropical region.
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