Streamflow reconstruction using tree rings chronology, and modeling and classification of hydrological drought in the Karkheh Basin

By measuring the annual growth of tree ring and make their chronology, the possibility of study and reconstructions of streamflow in the habitats areas is provided. The aim of this research is to reconstruct streamflow using dendrochronology, and modeling and classification of hydrological drought in Karkheh basin. In this research the chronology index of two tree species, Quercus brantii, and Quercus infectoria, in the central Zagros region during the period 1840-2010 were used to reconstruct streamflow in Karkheh basin. Three gage stations in Karkheh basin were selected, and their high flow periods were determined. Correlations between streamflow in high flow period and regional chronology index for gage stations were positive and significant at 1% confidence level, and with regard to this fact, the average streamflow in high flow period of these three gage stations from the year 1840 to 2010 were reconstructed. The values of observed and reconstructed streamflow in common statistical period are properly consistent with each other. In the following, hydrological conditions during chronology period were studied and accordingly, hydrological drought was analyzed in the Karkheh Basin for years 1840 to 2010. Severity and duration of the droughts as well as low flow and high flow decades were determined. In addition, the results were compared with other researchers as well. After reconstructing streamflow a probabilistic neural network model were utilized in order to classify the periods of very low flow, low flow, high flow, and very high flow. The results showed that provided model is able to recognize the mentioned periods with a high accuracy in the region.