Assessment of groundwater quality for irrigation purpose in Amol Plain, Iran

Groundwater is a valuable source of water for agricultural activities in the arid and semi-arid area. Nearly, 80% of Amol Plain in north of Iran are covered by irrigated land such as rice fields and citrus groves. Groundwater samples were collected from 27 wells during rainy season and 30 wells during dry season of 2009. Sodium percentage (Na %), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC) and water hardness were used as indicators for evaluating the suitability of water for irrigation purpose. Kriging was used as the advanced interpolation technique for predicting spatial distribution of groundwater quality for agriculture activities in the study area. Analysis showed that 76% water sample in dry season and 74% in rainy season were classified as very hard water. Based on RSC, 40% and 49% water samples in dry and rainy seasons respectively are not suitable for to be used for irrigation. Based on interpolation map, west and central sections of Amol Plain, the water quality is suitable for agricultural activities. The values of RSC, water hardness, and SAR and sodium percentage increase gradually from west to east and north-east where groundwater has been influenced by dissolution of carbonate rocks and intrusion of Caspian Sea water. It is concluded that hardness was a major problem for agricultural activities in the eastern section of study area