Characterization of anthropogenic activities influencing surface water quality along molo river ecological system, Kenya



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Ethiopian Journal of Environmental Studies & Management


Surface water is progressively subjected to stress as a result of anthropogenic activities. Systematic observation and characterization of anthropogenic activities along Molo River was done in 2014 to evaluate their effects on surface water quality. Portable GPS receiver was used to identify geographic locations of 23 sites purposively selected; based on their relative positions to the point of anthropogenic activities and included a reference located in the upper reaches. An observation schedule was used to collect data during dry and rainy-season. Chemical parameters were determined by spectrophotometry using standard methods and physical parameters measured in-situ using Wisenschafflich-Technische Werkstätten and pen type Dist 3 Model Meter probes. Data were analyzed using descriptive and inferential statistics. The frequency of occurrence and percentages were computed. Analysis of variance (ANOVA) was used to analyze mean concentrations of various physical-chemical parameters and various sampling occasions. Maximum NO2 was (45.42±3.4 mg∙L−1), NO3 (44.1±0.1 mg∙L−1), SRP 50.25±0.4, DO2 was 0.3±0.0 mg∙L−1, conductivity (616±1.4 μS/cm), and TDS 405.8±8.1 mg∙L−1 while NH4-N 79.69±1.2 mg∙L−1, TN 109.36±09 mg∙L−1, pH was 12.525±8.0 and T ºC 21.4±0.2 ºC. Mean TP was 13.21±1.78 mgL-1 and 2.43±1.70 mgL-1 highly significant at p<0.05 i.e. p= 0.0001. Results indicate that there were significant differences in the means of NO2-N, NO3-N, NH4-N, TN, DO, EC, T°C, and TDS (p=0.0038, 0.0001, 0.0001, 0.0001, 0.0001, 0.0001, 0.0021, and 0.0001) respectively. Observed activities comprised urban-construction/dumping of waste adjacent to riparian-buffer-zones recording 18.4%, domestic animals watered at the river 28.09%, people crossing river using vehicle/motorbikes and/or on-foot 39.2%, children playing in the river 12.9%,water abstraction 11.9%, sand harvesting/quarrying 0.16%, septic tanks-leaks, waste discharged into the river 4% and Washing linen 4.4%.. Washing vehicle/cars/motorbike was highest at the site denoted M3, recording 265 observations. Frequency and intensity of human activities closely relate the results on physical-chemical parameters, interference from direct human activity than natural phenomenon explains the finding. The river water is unsuitable for human consumption.