Sensitivity analysis of the effective reconnaissance drought index

Many drought indicators with different difficulties have been applied in numerous climatic zones. The reconnaissance drought index, which is based on precipitation and potential evapotranspiration, is considered a powerful weather drought index in arid and semi-arid zones. The effective reconnaissance drought index, which is a modification of the reconnaissance drought index, is suggested to enhance ability of the reconnaissance drought index to evaluate agricultural drought. The estimation of this index is based on two climatic variables which are the potential evapotranspiration (PET) and effective precipitation. The FAO Penman–Monteith method is considered the reference equation to evaluate the potential evapotranspiration; however, it is difficult to apply in regions with shortage weather data due to the requirement for a large number of climatic variables. Consequently, this research is applied Hargreaves, Blaney–Criddle, and Thornthwaite methods to assess the impact of the effective precipitation and potential evapotranspiration estimation methods, elevation, and climatic conditions on the effective reconnaissance drought index as well as investigating the correlation between the reconnaissance drought index and the effective reconnaissance drought index. Data from 13 weather stations, over the time interval between 1979 and 2014, cover different elevations, and weather environments within the Greater Zab River Basin, North Iraq, has been selected. The obtained results indicated that there is no important effect on drought severity assessment (at 100% of weather stations) were detected by using the considered potential evapotranspiration methods at different elevations for different climate conditions. However, there is a clear effect for different the effective precipitation and potential evapotranspiration techniques at diverse altitudes and climatic conditions on the aridity evaluation that is assessed by effective reconnaissance drought index (at about 50% of the considered stations). Consequently, concern has to be paid to the effective precipitation and potential evapotranspiration evaluation methods, particularly at high elevations; this is because applying a range of approaches may cause errors in the water resources availability predictions.