Investigation of temporal changes in groundwater quality of Neishaboor Plain and its possible causes

Water resources limitation in the Neishaboor Plain, in addition to a significant increase in water demand in urban, agricultural and industrial sectors, has caused researchers to investigate and provide the basic information necessary for development of a sustainable water management program. In this study the temporal changes in groundwater quality and the possible causes of these fluctuations were studied.
The water quality data used in this investigation included a 9 year (2001-2009) periodically measurements of TDS, total hardness, Na, Ca2, Mg2, Cl- and SO4 2- concentrations.
The results, as were shown by the changes in parameters such as TDS, SAR and hardness indicated a significant degradation of groundwater quality over the period included in this study. The TDS concentration in 77% of the investigated wells increased substantially over this period, with mean increase of 19.63 mg/lit.yr. In regard to possible causes of groundwater deterioration, the decline in groundwater level, geological formations and agricultural activities were considered to be the most important factors. The results showed that for every 0.81m mean annual decline in groundwater level, the TDS concentration increased by a value of 19.63 mg/lit. The geological tertiary formations (Miocene) and volcanic rocks could also be included among the factors affecting the spatial quality changes observed in some parts of the Nayshaboor's aquifer.
The result of this study clearly indicated that there is a strong correlation between the groundwater level decline and the increase in salt concentration of the aquifer. However, due to the lack of adequate data and information, definitive statements on the relative contribution of agricultural activities and geological formation on groundwater quality changes could not be made.