An optimized irrigation water quality index for evaluating surface water sustainability status of an agricultural watershed.

Maintaining good water quality is essential for drinking and agriculture. High water quality is crucial for irrigation to boost agricultural productivity and ensure sustainable water resource management. This study used in-depth physical and chemical analysis of water samples to evaluate the Kakia-Esamburmbur watershed's irrigation water sustainability. The Irrigation Water Quality Index (IWQI), developed using 19 indicators and Principal Component Analysis (PCA), addressed concerns about soil salinity, sodicity, and plant water toxicity. The analysis revealed SO.Cl-Na is the predominant pollutant. Qualitative water parameter analysis showed 70% of samples were adequate for EC, 90% for SAR and RSBC, and 100% for PI and SSP. However, Na (%), RSC, KI, and MH were lower. PCA identified eight key indicators, with IWQI values ranging from 14.48 to 433.76, with 50% of sites rated 'excellent.' The correlation matrix indicated significant hydrogeochemical impacts from geogenic and anthropogenic pressures. These findings inform policies to promote sustainable agricultural productivity. PRACTITIONER POINTS: Primary ions ranked as Na > K > Ca > Mg and HCO  > SO  > Cl- > CO PCA identified Na, EC, TDS, HCO , SAR, RSC, RSBC, and KI as key indicators. Combining the unique quality rating scale (Qi) and weighting formula makes the IWQI innovative and original. 50% of water samples were rated "excellent" for irrigation. Significant geogenic and anthropogenic impacts stress the need for informed policies on sustainable water management.