Geographical Information System Techniques for Evaluation of Groundwater Quality

Problem Statement: The present paper tries to assess groundwater suitability for irrigation purpose in Damghan plain (5400 ha). Approach: Twenty four water samples were collected from the active wells. Parameters such as Electrical Conductivity (EC), pH, Total Dissolved Solids (TDS), were recorded in the field and major anions and cations (Ca²⁺, Mg²⁺, K⁺, Na⁺, CO3^2-, HCO^3-, Cl^-, SO4^2- and NO^3-) were analyzed in the laboratory. The data of water wells were imported into the GIS software and the different water quality maps were produced using point data. Then Suitability index of groundwater quality determined by overlaying of water quality maps. Results: Suitability index values revealed that the ground water in Amin Abad, Abdi, Abd Abad, Nasr Abad and parts of Shams Abad villages of study area had "Suitable" quality with the suitability index range between 75-100 and therefore can be used for irrigation usage. Suitability index of the groundwater in Hasnie, Gani Abad and parts of Shams Abad villages were "Moderate" quality with the range between 35-70 and Abas Abad, Abir Abad and Shaman villages had "unsuitable" quality and cannot be used for irrigation purposes. In respect of all evaluating criteria, villages of study areas that had "Suitable" and "Moderate" quality could safely be used for longterm irrigation purposes. Conclusion: The present study demonstrated high efficiency for GIS to analyze complex spatial data and groundwater quality suitability.