OBJECTIVE ESTIMATION OF DROUGHT SEVERITY AND. ASSOCIATED PARAMETERS

Abstract

Drought is a temporary random and complex phenomenon mainly originating due to lack of precipitation leading to water deficit and causing economic loss. The success to drought alleviation depends on how well droughts are defined and their severity quantified. A quantitative definition identifies the beginning, end, spatial extent and the severity of drought. Among the available indices, no single index is capable of fully describing all the physical characteristics of drought. Therefore, in most cases it is useful and necessary to consider more then one index, examine their sensitivity and accuracy, correlate them and investigate, if they complement each other. In this study, the versatile GIS-based Spatial and Time Series Information Modeling (SPATSIM) and Daily Water Resources Assessment Modeling (DWRAM) software were used for drought analysis on monthly and daily bases, respectively, and its spatial distribution in both dry and wet years. The former utilizes the- popular indices Standardized Precipitation Index (SPI), Effective Drought Index (EDI), Deciles Index and departure from long term Mean and Median; and the latter employs only EDI. The analysis of data from Kalahandi and Nuapada Districts of Orissa revealed that (a) the drought in the area occurred with a frequency of once in every 3 to 4 years; (b) in a year if Pae/PET < 0.6, it is a drought; (c) EDI better represented the drought in the area than any other indices; (d) all SPI, EDI and the annual deviation from mean showed a similar trend. The comparison of all indices and results of analysis led to many useful and practicable inferences in understanding drought attributes in the study area.