Spatial Patterns of Chemical and Microbial Water Contamination Associated with Nkunga Open Dumpsite in Kenya

Open dumpsites can affect nearby surface water when rainfall mobilises contaminants through leachate and runoff. This study characterised selected chemical and microbial indicators in water sources associated with Nkunga Open Dumpsite in Meru County, Kenya. A descriptive environmental case study assessed five surface-water locations comprising one upstream background point, two near-site points and two downstream points, together with four leachate locations. The indicators were pH, temperature, orthophosphate as phosphorus, iron, copper, Escherichia coli and faecal coliforms. Surface-water values were arithmetic means across three sampling visits on 7, 11 and 16 August 2026; zone means summarised the corresponding site means. Comparisons with the upstream point were interpreted without inferential testing because the design included only one independent upstream location. Orthophosphate, iron, copper and both microbial indicators were lowest upstream, highest near the dumpsite and lower downstream. Near-site means were 1.30 mg/L orthophosphate as phosphorus, 2.10 mg/L iron, 0.28 mg/L copper, 2,200 CFU/100 mL E. coli and 4,000 CFU/100 mL faecal coliforms. The near-site microbial means were 122.2 and 88.9 times their respective upstream counts. Mean leachate values were 7.03 mg/L orthophosphate as phosphorus, 8.02 mg/L iron, 0.86 mg/L copper, 227,500 CFU/100 mL E. coli and 377,500 CFU/100 mL faecal coliforms. E. coli was detected at every surface-water point, including the upstream background location. The spatial pattern, concentrated leachate and observed drainage pathways were consistent with a dumpsite-associated contribution to contamination, although other catchment sources could not be excluded. The findings provide a baseline for stormwater diversion, leachate interception and repeated seasonal monitoring. They support precautionary water protection without establishing exclusive source attribution or quantifying exposure among water users.