Drought Characterization For A Snow-Dominated Region Of Afghanistan

Droughts are extreme natural phenomena that cause severe damage to economy, environment, and life. Palmer's drought model is widely used in drought characterization. However, its use in a mountainous snow-dominated region is often a concern because Palmer's method does not take into account the contribution of snowmelt. Snowmelt is an important contributor to renewable water resources in many parts of the world, including Afghanistan. In this study, the standard Palmer method is modified to incorporate snow using a snowmelt module based on the temperature-index method. The Palmer model with and without snowmelt is used in this study to characterize drought, quantify drought severity, and determine the spatial extent of historical droughts in Afghanistan. Reanalysis data for precipitation and temperature over a period of 45 years (1957-2002) are used in the analysis. Results are analyzed using three drought indices-Palmer drought severity index (PDSI); Palmer hydrological drought index (PHDI); and Palmer moisture anomaly index (Z-index). Both the standard and modified Palmer models captured the documented major national droughts, including the severe events in 1971 and 2001. The model with snowmelt is found to represent the historical droughts as less severe compared with the standard Palmer method. In addition, the Panj and Kokcha subbasins, which are located at a higher elevation, showed less severe drought compared with low-lying regions such as Shoretepa and Balkaab during the severe event in 2000-2001. Moreover, larger differences between the standard and modified Palmer's drought models are observed at higher elevations. The authors further observed that the occurrence of meteorological drought does not necessarily mean that there exist agricultural and hydrological droughts. The modified method has the capability to be used in monitoring droughts in snow-dominated regions and thus can assist decision makers in providing suitable mitigation measures. (C) 2017 American Society of Civil Engineers.