Analyses of meteorological drought and its impacts on groundwater fluctuations, a case study: Marand Plain (Iran)

Meteorological drought is one specific type of drought that occurs when precipitation is less than the long-term averages in a particular area. One of the hazardous impacts of this phenomenon observed on subsurface waters is the decline of water level in response to droughts. In this study, the climatic and groundwater data were used to analyze their trends in Marand plain, NW Iran, over the past decades to understand the likely relationship between them. To this, groundwater level data were first analyzed and its temporal trends were extracted. Then, the climatic condition of the region studied using the Ombrothermic diagram. Finally, drought analyses were conducted through drought index (SPI). Based on the results of the study, a descending trend was detected in both monthly and annual fluctuations of the groundwater level. It's also found that the region had a partially dry climate with a period of dry months between May and October. The SPI values showed extremely dry periods in 2001 and 2002 and months of July and June during the study period. The joint analysis of groundwater level and SPI values revealed that the impacts of drought were evident on groundwater level changes. Accordingly, the region's groundwater fluctuations found to be mostly under the control of monthly droughts where water level responds to wet and dry months in an expected manner. However, it's also found that the yearly changes in the groundwater level of the study area were not directly correlated to drought periods, suggesting that other factors might be effective in this phenomenon.