An early warning system for agricultural drought and groundwater storage depletion using eRDI index

Improving the drought quality indicators play an important role in water resources management. In this research, the Effective Reconnaissance Drought Index (eRDI) was used to detect agricultural droughts and present an early warning system in the Jiroft Plain. For this, the reliability of this index was evaluated using the NDVI and its relationship with storage changes of the aquifer was analyzed. According to the findings, the eRDI index shows the same effects in modeling of agricultural drought in different stages of plant growth but its severity is higher in the critical period of vegetation’s growth and therefore this period was considered for the spatial analysis of agricultural drought. The results showed that the occurrence of normal, dry and wet periods are associated with the accessibility or inaccessibility of effective precipitation. The results indicated a significant correlation between eRDI and NDVI in sparsely vegetation areas at the level of 5% (r = 0.87) due to the effective precipitation role in calculating the eRDI, although a weak correlation has been found between the NDVI and eRDI (r = 0.31) in the irrigated area that is probably due to the groundwater pumping and exploitation from the Jiroft dam. As a result, the eRDI-3 and eRDI-7 could be useful for early warning of the agricultural drought and groundwater storage depletion respectively.