Author(s): Waluyo Hatmoko; Roberus Wahyudi Triweko; Iwan Kridasantausa Hadihardaja
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Keywords: Drought; Hydrological drought; Irrigation; Drought index; Standardized runoff index
Abstract: Flood and drought are two water related disasters having different characteristics. Unlike flood, drought is a creeping phenomenon over time. A drought index is required to identify the onset and ending of a drought disaster. Hydrological drought index of Standardized Runoff Index (SRI) is having two parameters: drought duration and drought severity. From these two basic parameters, two others parameters can be derived, namely drought intensity and drought stress. Drought intensity is defined as the ratio between drought severity and drought duration, while drought stress is the multiplication of drought severity and drought duration. This paper discusses the parameter of hydrological drought intensity and stress in the Pemali-Comal River Basin, and examines its appropriateness as a drought index from their correlation with the observed data on areal of rice field affected by drought. Two irrigation weirs are selected representing the large basin in the western part, and small basin in the eastern part of Pemali-Comal River Basin in Indonesia. Standardized Runoff Indices are computed from 20 years of monthly river discharges in these three irrigation weirs, and the parameters of annual drought duration, severity, intensity and stress are computed. It is concluded that contrary to the flood phenomenon where rainfall intensity plays a very important role, the drought duration and drought stress are significantly having higher correlation with the observed data on drought affected area than the drought intensity.
Year: 2018