Drought Assessment Using Standardized Precipitation Index

Drought assessment and monitoring is very essential in identifying climate and water supply trends and thus to detect the probability of occurrence and the anticipated severity of drought. Drought occurs when precipitation is lower than normal. When this phenomenon extends over longer period of time, precipitation is inadequate to demand of human activities. This paper includes developing a methodology to assess drought severity and monitoring of the study area. Drought originates from a deficiency of precipitation over a given period of time: short time scales (months) characterize meteorological drought, while longer time scales (years) hydrological drought. A useful index for drought monitoring based only on monthly precipitation data is the Standardized Precipitation Index (SPI). It has been proposed to monitor dryness and wetness on multiple time scales. The present situation examines the SPI drought index in application for the Vallabh Vidyanagar Station and it is evaluated accordingly by historical precipitation data (1969-2006) for meteorological station. From the result, the worst drought years of 1974, 1986 and 1987 in the Vallabh Vidyanagar station indicate severe dryness and hence, the irrigation requirement can be evaluated on the rainfall deficits& its severity for the given years. SPI Index is a useful tool to assess the severity of drought for the study area.