| Abstract:
In this study frequency, intensity and durability periods of drought in Ilam province
during 1972-1998 were evalvated by classification of standard data of annual and
seasonal precipitations. The results of the study show that during the statistical
period, the possibility of annual and seasonal droughts different areas of the
province was very high ability to event in term of annual drought severity, moderate
drought and in term of duration, one year period have the most ferquency. Among
the seasons, drought severty of spring has been more than other seasons.
The distribution comparison of seasonal rainfall and the yield rate of dryland
wheat in the recent droughts (1998-2000) show that the unsuitable distribution of
precipitation during the seasons and also decrease of the annual precipitation have
caused the intensive decrease of yeild rate of dryland wheat so that the yeild rate of
wheat in 1998-2000 in comparison to wet years (1997-1998)has decreased 68.9%
and 69.4% and in comparison to period has decreased 49.2% and 50.2%
respectively. Correlation coefficient between distribution of seasonal precipitation
(independent variable) and yield of wheat (dependent variable) shows that the most
correlation in warm areas of the province is in autumn and winter, and in cold area
of province is in spring and autumn.
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