Analysis of Droughts and its Trend in Kohkiloie and BoyerAhmad

Precipitation is an important element of atmosphere which has great influence on economy and life of people in every region which its insufficienty has much effect on agriculture, animal husbandry and industrial products. It causes a lot of damages and may destroy above sectors. Most parts of country of Iran are in desert, because of periodic distribution of precipitation, which caused, many regions and many provinces of Iran are drought prone. Drought is one of the phenomena that brings about tragedy, one of the ways for adoption to drought is its intensity and monitoring based on indices that determine its intensity and duration in a specific area. In this paper, we have studied and analyzed drought in Kohkiloie and BoyerAhmad province (intensity, duration, trend and area) using SPI, five time scales (3,6,12,24 and 48 months), percent of normal precipitation index and Z standard index were used. The results show that frequency of short range drought (3 months) in the selected stations has been 13 in the period 1983-2002 but that in long range droughts are lesser. The duration also in long range droughts (24 and 48 months) are longer (80 months).Therefore to return to normal status, hydrological droughts (long range) that related surface and sub-surface water need long time but for (short range) agricultural droughts, daily precipitation is compensated until to be normal. Severe droughts also in the years of 1993 and 1999 covered more than 80% surface area of the region.