بررسی روند تغییرات کیفی و کمی منابع آب زیرزمینی دشت یزد- اردکان در دهه 88-1379

Abstract Background: Nowadays, with population growth and the increase of water demand in different sectors of agriculture, industry, drinking, and health, groundwater resources have faced a lot of pressure. This issue along with severe and prolonged droughts has created the conditions for country particularly for arid and hyper arid areas which has encountered the serious challenges in the field of water quantity and quality. In this study, qualitative changes in the trend of drought and water resources in Yazd - Ardakan plain, ie, one of the most important population centers in central Iran, has been considered. Method: In order to study groundwater quality variations we drew on the qualitative data from Yazd Regional Water Authority related to Yazd Ardakan plain 2000s. using hydro- geochemical(Aquachem) and statistic (Minitab) soft wares as well as spatial and descriptive data and GIS in providing and matching spatial data layers for all underground water quality parameters of the plain. Also for measuring the intensity and duration of climatic drought, we used standardized precipitation index (SPI) and for investigating the trend of falling groundwater levels, we applied the long-term hydrograph of piezometric wells located in Yazd - Ardakan plain. Results: The results of groundwater level variations indicate that in the last four decades, the downward trend of the average annual decline of water table has been around 0.5 meters per year. Also, results of water quality changes in recent decades shows that by increasing frequency of droughts and extreme declining groundwater table, groundwater quality, particularly 1385 to 1389, has had a downward trend. Results showed that during last 50 years, in the study area and the repetition of climatic drought in recent decade compared to the past four decades, has been 4 times in the study area. Conclusion: Considering the results, it can be concluded that the only basic principal method of preventing dangerous consequences of falling water table levels and reducing the quantity and quality of underground water resources is proper and lawful consumption of water to avoid uncontrolled withdrawal of groundwater.     .