Impact of land use on shallow groundwater quality for domestic use in Mathira East Sub-County in Kenya

Abstract

Shallow groundwater sources of boreholes and springs form major types of water resources used in rural areas of Kenya. Information on their status is inadequate, thus hindering their sustainable management. This study investigated the relationship between land-use types, groundwater sources and water quality. Thirty-six randomly selected groundwater sources were sampled in Mathira East Sub-County from four stratified land-use types of forest, tea, coffee, and urban, with 18 samples collected for either shallow boreholes or springs. The Principal Component Analyses (PCA) grouped groundwater resources into three groups according to groundwater sources and land-use types. Spearman rank correlation, one-way ANOVA and unpaired t-test found that land use types significantly influenced shallow groundwater quality along an increasing gradient of landscape disturbances from the less disturbed forest, then tea, coffee and lastly to the severely disturbed, the urban area. The most affected water parameters were turbidity, conductivity, NO3–N, phosphates and faecal coliforms and their variation was attributed to land-use changes, especially agricultural intensification and urbanisation. The significant variations in other water quality parameters (total hardness, total alkalinity, dissolved oxygen, pH, manganese and fluoride) were attributed to water–rock interactions, climatic factors and land use changes. Calculated Water Quality Index (WQI) with faecal coliforms parameter from groundwater sources were found unsuitable for domestic use, while the ones derived without faecal coliforms parameter were found safe for human use. Overall, shallow groundwater sources were contaminated and unsafe for human use. This study recommends regular monitoring of key water parameters affected by land use changes to support the sustainable management of shallow groundwater resources in Mathira East Sub-County and the larger region of South Sahara Africa.