Effects Of Sand Harvesting On Water Quality In River Thwake Machakos County, Kenya

ABSTRACT

Sand harvesting is a common economic activity globally and has environmental effects on the riparian land as well as the quality of the river water the activity is carried out. The associated environmental and water quality challenges pose environmental and health risks to the community and the aquatic life. This study was conducted between May and September, 2016 and was aimed at assessing the physico-chemical quality of water in River Thwake and the socio-economic impacts of sand harvesting to community. The general objective of the study was to establish the physico-chemical effects of sand harvesting on the water quality of River Thwake. Its specific objectives were; i) establish the methods used for sand harvesting in the area ii) to determine the effects of sand harvesting on water quality of River Thwake iii) to determine the socio-economic impacts of sand harvesting to the community iv) to find out sand harvesting regulation policies implemented in the area. 8 samples were collected and the physico-chemical parameters measure were; temperature, Hydrogen ion Potential, turbidity, color, electrical conductivity, Lead, Copper, Zinc, Iron, Biological Oxygen Demand and Chemical Oxygen Demand. The study employed purposive sampling to identify water sampling points A (1°28'17.6"S and 37°24'30.6"E) and B (1°27'44.6"S and 37°24'36.1"E) where point A was up-stream and a non-sand harvesting site and point B was a sand harvesting point. Convenience sampling was employed to identify 400 questionnaire respondents who were; 10 key respondents who were environmental officers, 68 harvesters, 46 transporters and 276 community members. Independent sample t test and chi-square tests were used in the study to compare means and establish relationships between point A and B. The study showed that in-stream sand harvesting was most common 80% as compared to off-channel sand harvesting (19%). A chi-square test (p = 0.228) was done and depicted that despite the fact that sand harvesting methods resulted to varied environmental problems, sand harvesting methods do not predict with certainty the type of environmental problem likely to be expected. The study found out that there were significant difference in the means of point A and B water samples as regards to; color (p=0.001), turbidity (p=0.001), Iron (p=0.001) Chemical Oxygen Demand (p=0.001) and Zinc (p=0.02) which was associated with sand harvesting activities at point A. However, Copper (p=0.54), conductivity (p=0.17), temperature (p=0.93), Hydrogen ion Potential (p=0.09), Lead (p=0.85), Biological Oxygen Demand (p=0.63) mean scores were not significantly different despite sand harvesting. The study also revealed that sand harvesting had a positive effect on the socio-economic status of the local community by depicting a significant increase in their weekly earnings (p =0.005). Despite the existence of sand regulatory policies, it was established that 20% of the respondents were aware of the National Sand Harvesting Regulation and 40% of the respondents knew about the Machakos County Sand Harvesting Bill. The study recommends environmental education to raise awareness among the local community on the policies regulating sand harvesting and encourage goodwill and support in the implementation of those policies. It also recommends regular record keeping of water quality status in River Thwake by relevant authorities to ensure that water is safe for usage.