Spatial Variations of quality Groundwater use Geostatistical Method

Nowadays, groundwater contamination is considered as one of the most important environmental issues. Because of its land use diversity, the Piranshahr Watershed (23385 ha) in East Azarbaijan Province was chosen as the study area for this research. Water quality samples were collected from 145 wells across the watershed. After variogram analyses and determination of spatial variations of the water quality parameters, different interpolation methods were applied to map the spatial distribution of the parameters. The methods with lowest RMSE were selected as the best interpolators. The results showed that, for pH, Ca, Mg and TH, radial-basis functions; for Na, inverse distance weighting (IDW); for TDS, exponential kriging; and for No3, ordinary kriging have the lowest RMSE values. The resulting maps indicated that, all parameters except Na and TH, have no limitation for drinking purpose. Spatial distribution of nitrate in groundwater indicated that highest concentrations of nitrate occur in the areas with high permeability and barren and agriculture land uses (east and south of the watershed). Results showed that water quality in the region has a degrading trend that is due to overexploitation of water for agriculture uses.