Investigation of Impacts of Meteorological and Hydrological Droughts on Groundwater Resources (Case study: Yazd-Ardakan Plain)

Water as a renewable resource, always has been a key element of development. Nowadays, population growth and water demand rise for different sectors including agriculture, industry, drinking and health, groundwater resources have faced severe pressure. This issue along with severe and prolonged droughts particularly in arid and hyper arid areas, has created serious challenges in the field of water quantity and quality. The Yazd-Ardakan plain as the study area in this research is one of the tense populated areas in the Yazd province at central Iran. The existence of large cities in this plain and significant water storages in its aquifers have doubled its importance as a case study. In this study, the intensity and duration of meteorological drought and hydrological drought were evaluated using the Standardized Precipitation Index (SPI) and the Groundwater Resources Index (GRI), respectively. These indices were estimated at monthly and annual time scales. Then, the relationship between these indices was investigated. The results showed that, over the last 50 years, meteorological drought conditions has been approximately 1.3 times more than climatic wet years in the study area. The repetition of meteorological drought in the last decade compared to its past four decades has increased 4 times. The results also revealed that variation in ground water level has been in a downward trend in the last four decades, so that the average annual decline in water table has been around 0.5 meters per year. The relationship between monthly SPI and GRI indices indicated that by increasing the time scale, the regression coefficient will increase. The results also showed that, at the annual scale, there is a 1- to 2-year delay between the occurrence of meteorological and hydrological droughts.