study of drought in northern karun watershed

drought is a natural hazard that has significant impact on economic, agricultural, environmental, and social aspects. in the present study details analysis of rainfall data has been carried out for the years 1981-2011. standard precipitation index (spi) has been used to evaluate the precipitation deficit in the karun watershed of iran. the results indicated that 1981-82,82-83,83-84,84-85,88-89,89-90,90-91,93-94,96-97,98-99,99-2000,2000-2001,2002-2003,2007-2008,2008-2009, 2009-2010  and 2010-2011 the spi values is negative. it is very anguish. and also this found threat drought the water resource and agriculture