Sanitary Survey of Shallow Wells Within Farms in Ainabkoi Sub-County, Usain Gishu County Kenya

Abstract

Sanitary survey refers to an evaluation and on-site inspection of the physical environment of the water source to identify possible sources of environmental contamination (USEPA, 1999). The information generated by a sanitary survey helps identify existing and potential sanitary risks to the water quality. Groundwater contamination can be as a result of poor sanitation and subsequent leaching from site especially in the vicinity of the well (Rahman, 1996 and Olsen et al., 2002). The aim of the project was to identify and assess the Sanitary Risk Factors(SRF) associated with the wells and subsequently determine the Contamination Risk Score (CRS) as predictors of water quality in different farm sizes. Onsite sanitary survey of the wells and the homesteads were carried out within farms of different sizes through, visual inspection, observations and interviews whereby a score was allocated for a positive answer and no score for a negative answer. There were 11 Sanitary Risk Factors (SRF) adapted to assess the susceptibility of the well water to contamination.  The CRS were categorized as Very High Risk (VHR) = 9-11; High Risk (HR) = 6-8; Intermediate Risk (IR) = 3-5; Low Risk (LR) = 0-2. There were highly significant differences in well CRS within the different farm sizes. Wells within the large and medium mixed farm sizes had an Intermediate CRS because most wells are protected and the well vicinity was relatively clean. Wells within the small farm sizes and which were communal shallow water sources, did not have a wall protection and were located down slope. Rain water flowed into these wells damping collected debris and waste into the wells. Although NO₃-Nconcentrations in the wells did not exceed the statutory guiding limits of 10mg/l, well attributes increase the susceptibility of wells to pollution. The CRS is a predictive factor of well contamination and the most important risk factors to the wells are the well protection constructions and the activities within the well vicinity. There is need for local county initiatives to construct protective raised walls at the communal wells and educate communities on aspects of water quality.