Effects of Sand Harvesting on River-Water Quality: Case Study of Iuuma River, Kivaa Ward, Machakos County.

The research was aimed at analyzing the impacts of sand-harvesting on river water quality. A case study was done in Iuuma River, Kivaa Ward, Machakos County. Two areas, sand-harvesting area and non-sand harvesting area in Iuuma River were selected for the study. Triplicate samples of sand, sediments and water were collected from the two areas and analyzed.  Physico-chemical water analyses were done for the parameters: pH, turbidity, electrical conductivity, hardness (total, calcium and magnesium), alkalinity, total dissolved solids (TDS), fluoride, chlorine and bromine. The metals: K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn and Sr were analyzed using the standard methods. The sand and sediments were analyzed for: pH, soil total nitrogen, phosphorous (Olsen), electrical conductivity(EC), total organic carbon and the metals: K, Ca, Mg, Mn, Cu, Fe, Zn and Na .The sand and sediment analyses revealed that the two areas had different concentrations of nutrients. For the sand-harvesting area, there were high values of magnesium and electrical conductivity in the sand. In this area the sediments had high values of calcium, magnesium, iron, sodium and electrical conductivity. In the non-sand harvesting area, the sediments revealed a high value for the iron concentration. All the other parameters analyzed for the sand and sediment samples had values within the acceptable range (WHO, Kenya Agricultural and Livestock Research Organization, KALRO). The water parameters were compared to the world health organization (WHO) and the Kenya bureau of standards (KEBS) guideline values. The water samples over the two areas samples had significant differences in the total hardness, calcium hardness, electrical conductivity, TDS, fluoride, chlorine and the turbidity where such parameters were higher in the sand harvesting area. The chemical composition of the sand and the sediments from the two regions revealed remarkable differences in the electrical conductivity, magnesium and calcium values which is a replica of the observation made from the water samples. The analyzed parameters revealed that the water from the sand harvesting area is of a different quality (more dissolved ions and high metal concentration) from that in the non-sand harvesting area and that prior water treatment for the water from the sand harvesting area is essential. Sand harvesting areas should be demarcated from the water collection points. The sand harvesting area can be alleviated though the construction of weirs and dams across the rivers. Alternative water sources to complement the river water sources. The residents should be sensitized on the impacts of sand-harvesting on river-water quality.

Key words: Water quality; Physico-chemical; Sand harvesting; Metals; Iuuma River.

Documentation :