Little Zab River water suitability assessment applying three water quality index mathematical models (Horton, National Sanitation Foundation (NSF) and Malaysia)

Surface water is considered one of the most common sources of water supply, due to the various environmental challenges. Therefore, it has become necessary to conduct monitoring of surface water quality to ensure it is safe for use. This led to increasing interest in models-based research for water quality determination. This research investigated the evaluation of water quality index (WQI) for the Little Zab River in the Northern region of Iraq for 14 years. Several parameters were selected including (pH, DO, BOD5, PO4-3, NO3- , alkalinity, TDS, Cl- and temperature). The results showed that the (temperature, pH, alkalinity, NO3-, Cl- and TDS parameters were all within the permissible limits, while (DO, BOD5, and PO4-3) were sometime higher in some years. Three mathematical models were selected in WQI evaluation including (Horton, National Sanitation Foundation (NSF) and Malaysia). The resulting WQI values for the three proposed models are 45.45, 77 and (28-30) % respectively. Also, the river suitability for irrigation is assessed through several indices including (Kelley's Index (KI), Sodium Adsorption Ratio (SAR), Magnesium Hazard (MH), Soluble Sodium Percentage (SSP), Permeability Index (PI), and Total Hardness (TH)). The results fall within the permissible limits, except for PI in some years. Future studies should prioritize tasks the development of water quality assessment models, using machine learning and artificial intelligence for predictive modelling and risk evaluation, in a sustainable and environmentally friendly approach.