معرفی روش EDI در پهنه‌بندی خشکسالی در دشت اراک

Design of drought monitoring systems is an important measure in developing drought mitigation plans. Not all drought indices have the capability to monitor drought. Among required data the time scale is a significant element in the capability of drought monitoring systems. The present research is an effort for designing a drought-monitoring system at a daily time scale basis. The daily drought index called Effective Drought Index (EDI) was selected to evaluate drought within the period of 1998-1999 which seems to be the beginning of recent prolong drought spell in the Arak plain. Furthermore, the sensitivity of EDI to the record length (from 22 to 15 years) was assessed. The results revealed that suitability of this index as a daily monitoring system in this particular study area and time period. In addition, the results showed that the record length has no effect on the quality of outputs, implying stations with 15 years record could be potentially used for more reliable monitoring. Using the drought status of the selected stations and the application of GIS, monthly drought maps of the study plain was produced. These maps reveal that the plain started facing moderate drought from October 1998 to March 1999. From April and May 1999 the drought status worsened especially the central parts of the plain experienced even more severe droughts.