ارزيابي شاخص خشكسالي پالمر در حوزه هاي ايران مركزي

چكيده انگليسي :

228 Evaluation of Palmer drought severity index in central Iran Sara Azadi Email Adrdress s azadi@na iut ac ir September 2013 Department of Natural Resources Isfahan University of Technology Isfahan 84156 83 111 IranDegree M Sc Language Farsi Supervisors Saeid Soltani Kopaei ssoltani@cc iut ac ir Monireh Faramarzi m faramarzi@cc iut ac ir Advisor Alireza Soltani Tudeshki arsoltani@cc iut ac ir AbstractDrought as one of the most complex natural disasters is a creeping phenomenon With the longperiod in its occurrence it gradually appears to cause damages in different sectors such asagriculture social etc Several indices are used to identify drought in accordance with theirrelevant assumptions One of these indices is Palmer Drought Severity Index PDSI which useshydrologycal and meteorological variables to solve a simple water balance equation in the soil Itconsiders the drought or wet conditions as dynamic phenomenon The main goal of this study wasto assess the PDSI based on its original assumptions its regionalized status and using the outputsof already calibrated and validated hydrological SWAT model in central regions of Iran The PDSIin five methods was calculated These are 1 original Palmer Index without calibration in whichthe climate coefficients and the severity equation derived for Kansas and central Iowa 2 originalPalmer Index in which the coefficients of severity equations were adjusted 3 the Palmer Indexwith the calibration of equations in central areas of Iran 4 the Palmer Index using the soilmoisture and potential evapotranspiration from SWAT model and 5 the Palmer Index using thesoil moisture potential evapotranspiration and runoff from SWAT model These methods wereconducted for 17 major basins covering entire country with a monthly time step for the period1990 2002 Further the drought severity equations were extracted for dry and wet conditions Thenthese methods were applied to account for the PDSI in 160 sub basins in central Iran The resultsshowed that dual coefficients of severity equations for drought and wet years were 0 912 0 13 and0 93 0 047 in method 2 0 892 0 002 and 0 946 0 002 in method 3 0 909 0 011 and 0 945 0 008in method 4 and 0 894 0 009 and 0 922 0 007 in method 5 respectively Though the coefficientswere 0 897 0 333 for both drought and wet conditions in method 1 The overall results of thisstudy indicated that methods 2 and 4 had good agreement with method 3 Although the method 4might address more reliable results as it is based on a robust accounting of physical processes Therefore it can be expected that in the case of inconsistence with method 3 10 the method 4provides more acceptable results The results of our study agreed well for the years 1992 and 2001for which the SPI PNPI indices recognized them as the most wet and dry years during the studyperiod respectively Apart from the agreement that the Palmer Index showed with SPI and PNPI due to the dynamical nature of PDSI it can also detect the start and end of drought period Theapproach used in this study is applicable for regional calibration of Palmer Index and using theoutputs of other hydrological models In addition this research study lays the basis for theassessment of the impacts of climate change on droughts in the future Keywords Palmer Index Drought Calibration SWAT model Central Iran

آزادي، سارا

ارزيابي شاخص خشكسالي پالمر در حوزه هاي ايران مركزي

واسنجي , مدل SWAT