ASSESSMENT OF WATER QUALITY FOR IRRIGATION USE IN NKHWIBVI RIVER THAT RECEIVES SEWAGE WASTE IN MWANZA DISTRICT, SOUTHERN MALAWI.

Water is essential for life and plays a crucial role in maintaining human health and well-being. However, the increasing discharge of domestic sewage and other forms of waste into water sources poses a potential threat to water quality and its suitability for different uses, including irrigation. This study therefore aimed to assess the quality of water in the Nkhwibvi River, Mwanza District, which receives sewage and other waste discharges, and to determine its suitability for irrigation. Water samples were collected from three sampling points along the river: upstream, before the sewage discharge point (Point 1); the middle stream, near the market and immediately after the sewage discharge point (Point 2); and downstream, after the market and residential areas (Point 3). The samples were analyzed for selected physicochemical parameters, including temperature, pH, dissolved oxygen, iron, salinity, calcium, magnesium, electrical conductivity, and nitrate-nitrogen, using standard methods recommended by the American Public Health Association (APHA). The data were analyzed using Microsoft Excel 2013 through descriptive statistics, correlation analysis, analysis of variance (ANOVA), graphs, tables, and the Irrigation Water Quality Index (IWQI).

The results showed that most of the analyzed parameters, including temperature (20.77–22.40 °C), pH (7.62–8.10), dissolved oxygen (4.07–4.50 mg/L), iron (0.13–0.35 mg/L), salinity (0.33–0.70 ppt), calcium (40.00–48.87 mg/L), and magnesium (19.00–29.00 mg/L), were within the recommended guidelines for irrigation water quality. However, electrical conductivity (1,864–3,391 μS/cm) and nitrate-nitrogen (40.34–70.30 mg/L) were elevated, indicating potential concerns regarding salinity and nutrient enrichment. The Irrigation Water Quality Index was calculated as 51.27, indicating that the river water was generally suitable for irrigation within the conditions assessed by this study. Therefore, although some parameters exceeded recommended levels, the overall water quality was not severely impaired by the investigated pollutants. Nevertheless, continued discharge of sewage and other wastes could further deteriorate the river's quality and increase risks to agricultural soils and crops. The Mwanza District Council should therefore strengthen measures to minimize waste disposal into the river and increase community awareness of proper waste-management practices to protect the river and ensure its continued suitability for irrigation.

Water samples were collected from three sampling points along the river: upstream, before the sewage discharge point (Point 1); the middle stream, near the market and immediately after the sewage discharge point (Point 2); and downstream, after the market and residential areas (Point 3). The samples were analyzed for selected physicochemical parameters, including temperature, pH, dissolved oxygen, iron, salinity, calcium, magnesium, electrical conductivity, and nitrate-nitrogen, using standard methods recommended by the American Public Health Association (APHA). The results showed that most of the analyzed parameters, including temperature (20.77–22.40 °C), pH (7.62–8.10), dissolved oxygen (4.07–4.50 mg/L), iron (0.13–0.35 mg/L), salinity (0.33–0.70 ppt), calcium (40.00–48.87 mg/L), and magnesium (19.00–29.00 mg/L), were within the recommended guidelines for irrigation water quality. The Mwanza District Council should therefore strengthen measures to minimize waste disposal into the river and increase community awareness of proper waste-management practices to protect the river and ensure its continued suitability for irrigation.

This study took place at Nkhwibvi River, Mwanza district. Mwanza district is located in
the southern region of Malawi. This river is perennial, and it discharges its water into the
Mwanza River. Water samples were collected during June, which is in the wet season.

District: Mwanza

Coordinates: -15.61255, 34.5446