The Investigation of the relationship between groundwater level variation and drought index(Case study: Sharifabad Watershed in Qom Province)

The climate change phenomenon affects water storage in aquifers through changes in rainfall volume. In this study, the aim is to estimate the average groundwater level using the most appropriate geostatistical method and then investigate the relationship between groundwater index and one of the drought indices on monthly and annual scale in order to specify the importance of rainfall in groundwater recharge.

The watershed of this study was Sharifabad watershed located in Qom province with an aquifer area of ​​ 27035/2 hectares. There are 16 observation wells in this area. In this study, during the period of 1384-1384, the water level of observation wells in the area was investigated using variogram models. The average water level was determined using the best model per year, then the SWI index at the watershed was calculated. The SPI index, one of the drought indicators, was also used to investigate precipitation variation and then, using Pearson coefficient, the correlation of these indices was investigated on monthly and annual scale.

The results showed that among the variogram models that were used to interpolate the monthly water level data, Kriging model is the most appropriate. Also, Pearson correlation coefficient between SWI and SPI indicators is not significant on monthly basis at confidence level of 99% in both observations of Mozafarabad and Alborz. Moreover; this correlation coefficient on the annual scale is not meaningful either.

In this study, the insignificance relationship between SPI and groundwater index in the study area indicates that precipitation has a small proportion in groundwater recharge in the water balance of these areas on monthly and annual scale. Therefore, it can be concluded that the most part of rainfall is out of reach due to excessive evapotranspiration and is not able to recharge the aquifer  in the region.