Groundwater Qualitative Zoning of Varamin Plain for Agricultural Applications Using Analytical Hierarchy Process Method in GIS

When dealing with the quality of water resources for different uses, collecting samples from all parts of a study area is not economically possible. In this regard zoning methods are powerful tools in the providing the data based on spatial variation. This research aimed in groundwater quality zoning for agricultural uses in the Varamin plain, southern Tehran, using Interpolation methods with Geographic Information System (GIS) and the weightings in the Analytical Hierarchy Process (AHP). Qualitative data from 74 tube wells in the plain of Varamin from 1388 to 1387 is used. Firstly, raster maps were prepared using Inverse Distance Weighted (IDW) method for the study area. These maps prepared for the Sodium Absorption Ratio (SAR), Permeability Index (PI), the Kelley Ratio (KR), Magnesium Adsorption Ratio (MAR), Residual Sodium Carbonate (RSC), Dissolved Sodium Percentage (SSP), Electrical Conductivity (EC), and Total Hardness (TH) Then the final weights of parameters in water quality potential were determined using AHP and the pair wise matrix. Finally, with overlaying maps and applying final weights of the parameters in GIS, the map of qualitative potential of the groundwater resources in the area for agricultural purposes was prepared. The results showed that in the northwestern, southwestern, and western parts, the status of groundwater for agriculture are poor and in the central, northern, and northeastern parts there are the quality of water is suitable for agriculture purposes.