<![CDATA[ABSTRACT Determining and Analyzing the Quality of Ranolangsot Dam Water as a Source of Irrigation Water for Rice Fields based on Government Regulation No. 22 of 2021, as well as to Determine the suitability of dam water quality based on the Sodium Adsorption Ratio (SAR) value. The study was conducted in July 2025 using descriptive methods and laboratory analysis with purposive sampling techniques at three sampling points. The parameters tested included temperature, pH, Total Suspended Solids (TSS), Nitrate, Phosphate, Sodium, Calcium, and Magnesium. The SAR value was calculated using the Ayers & Westcott (1985) formula to determine water quality classification. The analysis results showed that the physical and chemical parameters of temperature 30°C, pH 6.5, TSS 6–10 mg/l, nitrate 0.8–2 mg/l, phosphate 0.02–0.3 mg/l still met the class III–IV quality standards. However, the SAR values at three consecutive points were 34.31, 13.25, and 30.83 mEq/l, indicating water quality ranging from (poor) to (good). The high sodium dominance at several points indicates the potential for soil structure degradation and reduced land fertility if used for irrigation. In conclusion, although most of the Ranolangsot Dam water parameters meet quality standards, the high SAR values at two points indicate that the water is not yet fully suitable for rice field irrigation without further management. Keywords: water quality, Ranolangsot Dam, irrigation, Sodium Adsorption Ratio (SAR), water quality standards]]>
