Suitability assessment of water for human consumption using water quality index along the Cubango-Kavango River, in Angola and Namibia

River water quality is a critical issue as it directly affects both human health and biodiversity. In the Cubango-Kavango River (CKR) basin, located in Angola, Namibia, and Botswana, anthropogenic and agricultural activities have increased, which exerts significant pressure on the river. This study assessed the suitability of the CKR basin water for human consumption at 12 different sites along the river. A total of 88 water samples were collected throughout the river in two phases: the dry season (August) and the wet season (March). Water quality (WQ) was analyzed both in the field and at the NamWater laboratory using a HANNA HI 9829 multiparameter instrument and an ion spectrophotometer Eco IC Metrohm, respectively. The Water Quality Index (WQI) was calculated based on the weighted arithmetic method using the following water parameters: Total Nitrogen (TN), Nitrate (NO 3 -), Nitrite (NO 2 -), Ammonia (NH 3 ), Organic Nitrogen (ON), Total Phosphorus (TP), Orthophosphate (PO 4 3 -), Electrical Conductivity (EC), pH, Dissolved Oxygen (DO), Total Dissolved Solids (TDS), and Chlorophyll-a (Chl-a). The result obtained showed that the levels of NH 3 and DO exceed the World Health Organization (WHO) 2022 guidelines, and the levels of NH 3 , NO 2 - and Chl-a exceeded the 2013 Namibian Water Quality Guidelines (NWQG). The WQI values ranged as good water (32.13) at Calai, to (39.12) at Ndonga Linena during the dry season. In the wet season, the WQI value ranged as good water as well (31.86) at Rundu and 42.60 at Nkurenkuru. The WQI values indicate that the overall WQ is suitable for drinking; however, continuous monitoring is needed to further assess the impact of human activities within the CKR. • A total of 13 water parameters were analyzed using a multiparameter HANNA HI (9829 and 96733) and an ion spectrophotometer. • The WQI was calculated through the implementation of the weighted arithmetic method. • The concentration of EC, TDS, and salinity were high in dry season, due to high temperatures and lack of dilution. • The DO and Chl-a concentration increased during wet season due to the transportation of nutrients. • The WQ was classified as good, with values ranging from 31.86 to 42.60 classes during both the dry and wet seasons.