Abstract

Study on drought has been considerably regarded on recent years, due to drought increase in Iran. On the other hand, survey on wetness makes it possible to prevent from it flood risk to some extent and attempts to manage water supplies. In this study, Standardized Precipitation Index (SPI) was used in annual period of time to survey on drought. Also, in order to zonation frequency of drought, geographic information system (GIS) software and inverse distance weighted of interpolation method, and Boolean Logic used for extracting dry and wet areas and then layers used to obtain frequency of drought and wetness. Results showed that the most droughts and wetness were of medium. The most years in the considered region were in normal status and lots of costal stations had severe droughts between 2008 to 2009. Generally, occurred droughts and wetness in the stations did not follow a definite order.

Key words: Guilan Province, drought, wetness, standardized precipitation index, zoning, geographic information system.