Water quality indicators of the Nima Creek, and potential for sustainable urban agriculture in Ghana

Urban and peri-urban agriculture, a widely accepted practice of food cultivation in urban centers contributes to positive environment. It has the benefits of job creation, increased access to healthy and affordable food, and important means of improving community health. Use of wastewater or disturbed surface water for urban agriculture is a common practice in the developing world due to lack of adequate infrastructure and widespread poverty. This study assessed the urban water quality parameters of the Nima Creek, a major water resource for peri-urban and urban farming in Southeastern Accra. Water sampled from six locations along the NE–SW stretch of the creek were evaluated for physicochemical parameters including pH, conductivity, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), cations, zinc, iron, oil and grease, Biological Oxygen demand (BOD), Chemical Oxygen demand (COD). Results show high enrichment of nutrients, ammonia (NH3), nitrate (NO3), and phosphate (PO4) as well as elevated levels of BOD, COD, and grease at sites receiving solid and liquid wastes. The physicochemical parameters such as conductivity, TSS, and TDS exhibited periods of elevated values that were congruent with seasonal rainfall patterns within the catchment area. Sodium concentration ranged from 32 to 297 mg/L. Nitrate levels generally ranged from 1.5 to 7.13 mg/L. The cation concentrations showed broad temporal and spatial variation characteristic of disturbed surface freshwater. Principal component analysis of the data discriminated four distinct components accounting for 63.6% of the total variance. The component plots constrained three major classes explaining the physical quality of the water and two other groups defining nutrient and alkalinity levels in the water.