Abstract
<jats:p>Surface water quality is a public health concern. This study assesses the anthropogenic impact on surface water quality in the Ahafo Ano Southwest District, Ghana. Water samples were collected from three locations within the Mankran watershed during both wet and dry seasons and analyzed for key parameters. Pollutant concentrations exhibited marked spatial and seasonal variability, with nitrate ranging from 1.09 to 13.77 mg/L, phosphate from 1.58 to 10.55 mg/L, and total suspended solids from 140.0 to 1680.0 mg/L. Heavy metals frequently exceeded acceptable limits, with zinc ranging from below detection (b.d.) to 0.11mg/L, copper from b.d. to 0.84 mg/L, and lead from b.d. to 0.46 mg/L. Seasonal WQI analysis indicated degraded water quality during the wet season in Baniekrom and Kunsu, due to increased runoff carrying agricultural residues, sediments, and mining contaminants. In contrast, Mmobrem showed improved wet-season quality, attributed to rainfall dilution. The Piper diagram further revealed that the water samples predominantly fall within the Ca–Cl hydrochemical facies, reflecting strong geogenic control through basaltic rock weathering, coupled with chloride enrichment likely intensified by agricultural and domestic inputs. Principal component analysis indicated that multiple anthropogenic and natural factors drive water quality variations across the catchment. Ecological risk assessment identified potential risks to aquatic organisms, particularly algae, resulting from elevated levels of nutrients and metals. Overall, the combined WQI and hydrochemical evidence indicate an intensified nutrient influx during the wet season and increased suspended particulate matter during the dry season, primarily driven by agriculture, deforestation, and mining. The findings underscore the urgent need for sustainable water management strategies to mitigate the impacts of human activities on surface water quality in the region.</jats:p>