Water Surplus Variability Index as an Indicator of Drought

Abstract

Drought assessment requires considering not only precipitation but also the other meteorological parameters such as an evapotranspiration. This paper presents the water surplus variability index (WSVI) as an indicator of drought. The calculation procedure incorporates both precipitation and reference evapotranspiration through the estimation of water surplus at different timescales. The WSVI is compared with the standardized precipitation index (SPI) and the reconnaissance drought index (RDI) based on 1-month, 3-month, 6-month, and 12-month timescales using data from four weather stations located in humid and subhumid climate. To approve the proposed procedure, the graphical and statistical tools such as the scatter plots, the linear trend, the coefficient of determination