Drought monitoring in the last two centuries in the arid and semi-arid reigon using dendrochronology, a Case Study of Karkheh basin

Through a measurement of the annual growth of a tree ring and finding out of its chronology, the possibility of study and reconstruction of Palmer Drought Severity Index (PDSI) in the habitat areas is provided. The aim followed in this research is to reconstruct PDSI using dendrochronology, and drought monitoring within Karkheh basin. Throughout the research the chronology index of two tree species, namely Quercus brantii, and Quercus infectoria, in the central Zagross region during the period of 1840-2010 were used to reconstruct Palmer Drought Severity Index in KarkhehBasin. Correlations between Palmer Drought Severity Index and regional chronology index were positive and significant within 1% of confidence level. With regard to this fact, the Palmer Drought Severity Indexes from year 1840 to 2010 were reconstructed. The values of observed vs. reconstructed Palmer Drought Severity Index within the common statistical period are consistent with each other. Within further steps, the hydrological conditions during chronology period were studied and accordingly, hydrological drought was analyzed within the Basin for years, 1840 to 2010. Severity and duration of the droughts as well as decades of the highest number of drought and wet events were determined. In addition, the results were compared with those obtained by other researchers as well.