Relationship Between Hydrologic and Metrological Droughts Using the Streamflow Drought Indices and Standardized Precipitation Indices in the Dez Watershed of Iran

摘要

This research utilizes DrinC software and some codes developed in MATLAB software for calculating the drought indices and determination of trend of climatologic and hydrologic time series data using different nonparametric Mann-Kendall trend tests. The time series data used in this research include the minimum, mean and maximum monthly temperatures, monthly precipitation, and monthly flow discharge (from 1981 to 2012). These data are pertinent to the Dez watershed climatic and hydrometric stations in southwest Iran. Results of this research show that precipitation has no significant trend, but flow discharge has a decreasing trend. The trends of mean, maximum, and minimum temperatures are increasing in summer and autumn but decreasing in spring. In winter, the trend of minimum temperature is increasing, while the trend of mean and maximum temperatures is decreasing. Standardized precipitation index (SPI) and streamflow drought index (SDI) show that the number and intensity of short-term droughts (with 3months time scale) are more than the number and intensity of long-term droughts (with 6, 9, and 12month time scales). Correlation coefficient between SPI and SDI increases as the time scale is increased too.