Application of water surplus distribution in assessing meteorological drought

Abstract

The main objective of this study is to apply distributions of water surplus in assessing meteorological drought and to determine the best fitting distribution to standardize the Water Surplus Variability Index (WSVI) that is used to characterized drought. Five distributions which are considered are 3- parameter gamma, 3-parameter log-logistic, logistic, 3-parameter lognormal and general extreme values distributions. The estimation of parameters of these distributions is determined using the L-moment. The adequacy of the distributions based on parameter estimates are evaluated using goodness-of-fit tests. When the goodness-of-fit results for these distributions are compared, it is found that, the performance of the logistic distribution is better than the performance of other distributions. For that reason, the logistic distribution is selected for standardizing the water surplus series to obtain the WSVI. Drought is a natural hazard, which is characterized by the lack of precipitation and classified as meteorological, agricultural, hydrological and socioeconomic drought. It is represented using drought indices that facilitate identification of drought intensity, duration and spatial extent. Adequate estimation of drought characteristics can be helpful for planning the efficient use of water resources, hydroelectric and agricultural production. Therefore, a variety of indices for detecting and monitoring droughts has been developed such as SPI (Standardized Precipitation Index), PDSI (Palmer Drought)