Design of drought monitoring systems is an important measure in developing drought mitigation plans. Such systems act as a trigger to activate predefined programs for mitigating negative impacts of drought. Not all drought indices have the capability to monitor drought. The required data as well as their time scales are two of the important issues causing the referred limitations. The present research is an effort for designing drought-monitoring system at a daily time scale basis. The daily drought index, so called Effective Drought Index (EDI) has been selected to be evaluated for monitoring, starting year 1998-99 of the recent prolong drought spell in Tehran province. Furthermore, sensitivity of EDI to the record length has been assessed. The results show suitability of the index for daily monitoring system accompanied with meaningful spatial and temporal variation for the selected year as well as the study area. In the succeeding step, using the drought status of the selected stations and GIS, monthly drought maps of the province have been prepared. These maps reveal that the province started facing moderate drought from October 1998 to March 1999. From April 1999 the drought status worsened with especially the central parts of the province experiencing even more severe droughts.
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