Determining Water Quality of Agricultural Wells for Use in Pressurized Irrigation Systems of Sarab Plain, Iran

Extraordinary withdrawal of groundwater resources has caused severe damages to aquifers, and the country's plains are facing subsidence due to this situation. In this regard, following the encouragement of the government by offering financial supports, many of farmers have volunteered to run pressurized irrigation systems. Therefore, gathering proper quantitative and qualitative data of water resources is necessary for sustainable agriculture. In this study, water quality of 103 agricultural wells in Sarab plain, which owners are applying for the operation of pressurized irrigation system, was investigated. To determine the water quality conditions of these wells, the magnesium absorption ratio (MAR), permeability index (PI), salinity potential (PS), Kelley's Ratio (KR), sodium absorption ratio (SAR) and soluble sodium percentage (SSP) indices were evaluated along with some other chemical parameters in the studied plain. The EC, SAR, MAR, PS and chloride indices indicated a decline in water quality from east to west and from south to north of plain. Approximately, water in 50% of wells were in the C3S1 class and the average KR of all wells were in a suitable condition with the value of 0.46. Except for one case with the value of 15.52, the remaining wells water had non-alkaline water with the SAR values less than 15. Only 17% of wells water had SSP values over 40% and they were not suitable based on this indicator. Most of the samples were located below the standard limit of 50% for MAR. Finally, in this study condition the application of sprinkler and tape irrigation systemsfor 90% of wells is recommended and for 10% of the rest of wells gated the pipes irrigation system may be adapted.