Evaluation of drought indices correlation for drought frequency analysis of the Mosul dam watershed

In this paper, drought was evaluated for the Mosul Dam Watershed, Iraq, which is considered one of the most important dams in Iraq. The evaluation of drought was studied using two types of meteorological drought indices, namely Reconnaissance Drought Index (RDI) and Standardized Precipitation Index (SPI), and Hydrological drought index which is Streamflow Drought Index (SDI). Monthly precipitation and air temperature for the period 1979-2013 downloaded from Climate Forecast System Reanalysis (CFSR) were used as weather input data for the RDI and SPI. Streamflow obtained from the gauge station in the study area were used as input data for the SDI. The indices computed by the DrinC software for a 12-month time scale. The results were analysed and the Drought Frequency Patterns (DFPs) were computed for each index. The results showed that potential evapotranspiration plays a major role in causing drought, in addition to precipitation. The RDI gave more dry periods than the other two indices, as it depends on precipitation and potential evapotranspiration. Likewise, all indices are identical in that the period is divided into two parts: the first part, which extends from the beginning of the period 1979 to the end of the nineties 1990s, is considered wet and the second part, which extends to the end of the period 2013, is drier. The Hydrological Drought Index SDI gives a drought of greater severity (Moderate drought for the years 2002, 2003 and 2004) compared to the other two indices.

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