Analysis daily quantification of severity and duration in shahrekord station

Most of the drought indices are not enough in detecting the onset, end and accumulating stress of drought, and they do not effectively take into account the aggravating effects of runoff and evapo-transpiration, which build up with time, also most of them have a limited in monitoring ongoing drought because they are based on a monthly time step, and finally this drought Indies fail to differentiate the effects of drought on surfaced and sub-surface water supply. In the new index is proposed to solve these weaknesses. In the new index daily rather than monthly. Time steps are used. In this method used or the three statistical indices in order determined precipitation (EP). The first index is day’s mean off effective precipitation. This index shows climatological characteristics of precipitation for a station or area. The second index is the deviation of effective precipitation from mean off effective precipitation and the third index is the standardized value of deviation of effective precipitation. By using these three indices the onset and ending drought period is recognized. Finally four additional indices that show drought severity are calculated. Which contain: 1- consecutive days of negative, which show duration and severity the deficit of precipitation. 2- Accumulated precipitation deficit, which shows the precipitation departure from the normal during a defined period. 3-Precipitation for the return to normal and 4- effective drought index. In this study used a new index effective precipitation for drought monitoring in the shahrekord station. In order to fast and accurately writing program EP. In this study analysis daily precipitation shahrekord station for 1980-2001 periods and only in this paper result shows 2001 year.