An Investigation of Change Trends of Groundwater Quality in Wet and Dry Years: A Case Study of Gorgan Plain

Droughts have had major effects on chemical quality of groundwaters in Gorgan's plain. In order to determine the trend of groundwater’s chemical and quality changes, due to drought and wet years, 17 wells were selected in different parts of Gorgan plain. The statistical mean of two characteristic months (May as wet and November as dry month) in two typical years (1998 as wet year and 2004 as dry year) were selected and averaged. The results showed that the decrease of rain fall in dry years (such as 2004) caused drastic changes in quality of ground water, so that the Anions and Cations increase.Moreover, TDS, PH and EC in non-superficial (deep to semi deep) aquifers increase. The environmental effects of these changes are manifest as a decrease of well’s Debi in coarse-grain aquifers and settlement in fine-grain aquifers.