Effects of clear-cut on water quality, coarse particulate organic matter and periphyton in chepkoo river, Kenya

Abstract

Rivers are essential ecosystems that assist in maintaining and supporting functions and ecological processes that are important for sustaining the biodiversity and providing services and resources to people. However, in the tropics they are under threat of deterioration as a result of human encroachment and more so, removal of riparian vegetation. This study aimed at assessing the effects clear-cut of Tumoo forest on water quality, coarse particulate organic matter (CPOM) and benthic algae in Chepkoo River, with a view of enhancing environmental and human health. Three sampling sites were purposely selected to capture the effects of clear-cut along this river. It was hypothesized that clear cutting of riparian vegetation had a direct influence on water quality, CPOM quantity and periphyton abundance and diversity. Sampling was done in the months of April to June 2017, and entailed measurements of physico-chemical parameters, water nutrients, collection of CPOM and periphyton at the three sites. Among the physico-chemical parameters measured, temperature differed significantly among the sites, being higher at midstream site (F(2, 24) = 16.423, p < 0.05). Total phosphorous and soluble reactive phosphorus were in high concentration than the other nutrients in the three sites, whereby the midstream recorded the highest mean value of 0.223±0.038 mg/L. However, the mean difference was not statically significant amongst the sampling sites (F(2, 24) = 0.225, p > 0.05). There occurred a significant difference in mean periphyton abundance among the sites (, p < 0.05) with midstream recording the lowest value (Tukey HSD, α = 0.05). The quantity of CPOM (pooled data from the riverbanks) collected among the sites differed significantly (F (2, 24) = 12.427, p < 0.001) with the midstream site having the highest value (Tukey HSD, p < 0.05). The mean difference of CPOM retention within the stream channel was statistically significant (F(2, 24) = 8.053, p < 0.001) with the upstream site recording the highest amount. Vegetation diversity, using Shannon Wiener diversity index indicated that upstream (2.2), > downstream (1.9), > midstream (1.7). Approximately 32% of the plant species were similar among the three sampling sites. This study confirms that reduced canopy cover leads to reduced water quality, periphyton abundance as well as in-stream CPOM along Chepkoo River. County and national government agencies need to do campaigns on the need for afforestation and reforestation of clear-cut sites on the river’s watershed. Such an intervention strategy will lead to better water quality, and improved human and environmental health.