Drought evaluation of a thirty-year period (1988 – 2017) in Lurestan Province using the Percent of Normal precipitation Index (PNI)

One of the most important issues, facing the human society and environment, is water resources management. Regarding the drought, this issue turns to a serious challenge for decision makers, and affect the people more than other natural hazards. In Lurestan, considerable number of springs and rivers have been dried in recent years, which are ascribed to precipitation shortage. This study evaluates meteorological drought in Lurestan by applying Percent of Normal Index (PNI) through 1988–2017 time span. The PNI indicates that only low percent (6.6–30%) of the studied time span experienced drought which has been weak drought type. This signifies that the area has not suffered from severe drought during this period. Therefore, symptoms of severe drought, appeared as dried rivers and springs, could not be products of meteorological drought, solely. They could rooted in overexploitation of the groundwater has dropped the water table far beyond the reach of tree roots and springs outlets. Analysis of the return period of the drought also proves an extremely long time of reoccurrence of severe drought. Weak drought also has a very long return period (100–200 years). Therefore, meteorological drought could not be solely responsible for the droughts in Lurestan, and socio-economic drought and associated water management must be the main reason. Based on the reconstructed data for the years without data, reliability for the acquired results in Khoramabad, Aligudarz, and borujerd stations is 100%, for Azna, Dorud, and Noorabad is 56.7%, Poldokhtar 63.4%, and Kuhdasht and Alashtar is 66.7%.