Spatial and Temporal Variations of Groundwater Quality Parameters in Qorveh- Dehgolan Plain and Its Relationship with Drought

In most regions of Iran the requisite water for populations and industry are supplied by groundwater resources. Drought is an important factor, which effects groundwater quality. Demand for groundwater resources is increasing in Qurveh - Dehgolan plain due to its position and limited access to surface water resources. In this research, the effects of drought on water quality of wells in Qurveh – Dehgolan studied. Water quality data in 38 wells for 21 years (1992 to 2013) used to define dry and wet period the Standardized Precipitation Index (SPI) for 3, 6, 12 and 24 months’ time scales calculated. Using Mann-Kendall tests, the trend of ground water quality parameters investigated and the relation between climatological drought and groundwater quality parameters calculated using correlation coefficients. Study of correlation coefficients between quality parameters and SPI showed in 22.2% of cases, drought effected on groundwater quality (at 95% level). Correlation coefficients were positive in some wells and were negative in other wells. Also in most quality parameters, with increasing of SPI time scale, the rate of correlation was increased. The results of Mann-Kendall test showed the most parameters of water quality had increasing trend and Cl-, HCO3- and Mg2 had negative trend in 60.53%, 60.53%, and 52.63% of wells respectively. In addition, CO32- had not trend in any wells. Zoning map of water quality showed that most reduction of ground water quality was happened in eastern part of plain, because the ground water level downfall in mentioned part was higher than other parts.