EFFECTS OF GEOLOGICAL VARIABILITY AND SELECTED PHYSICAL PARAMETERS OF WATER QUALITY ON FLUORIDE LEVELS IN RIVER NJORO CATCHMENT, KENYA

Abstract

Fluoride levels higher than the World Health Organization (WHO) recommended levels of 1.5 mg/l have to raise serious health issues. Therefore fluoride contamination is a pertinent matter that calls for concern by all people and government especially in countries where the phenomenon of volcanicity has been experienced. The study sought to analyse the effects of geological variability and selected physical parameters of water quality on fluoride levels in River Njoro catchment. The study was guided by the following objectives: to determine the relationship between fluoride levels and surface geology in River Njoro catchment, to determine the relationship between borehole stratigraphy formation matrices and fluoride levels in borehole water in River Njoro catchment, determine the relationship between pH, temperature and Electrical conductivity and fluoride levels in groundwater in River Njoro catchment and finally model spatial variation and distribution of fluoride levels in ground water in the River Njoro catchment. The study sought to highlight the levels of fluoride and give recommendations on identification and delineation of potential sites for safe groundwater for the local population and advice on the water treatment and de fluoridation strategies. Past researches on River Njoro catchment gave much emphasis on land use/cover changes and strong condemnation on elevated fluoride levels in the Njoro catchment and therefore the gap in this research was based on the integration of geological variations and geological stratigraphy of River Njoro catchment and ultimately produce a predictive trend. This study adopted purposive longitudinal survey and quasi experimental research designs. In this research borehole and river water, soil and rock samples from designated points along the River Njoro and its tributaries were collected for laboratory analysis of fluoride levels. The research adopted descriptive and correlation statistical analysis. The sources of data included: field surveys which were used to collect data about the fluoride levels, the remotely sensed, GIS and Geostatistical interpolation, content analysis of the literature on the geology of the Njoro catchment and the hydro-meteorological and geological characteristics data. From the results of the study it was observed that: the fluoride levels in River Njoro catchment varied with the geology of the catchment and fluoride levels in groundwater depended on the borehole stratigraphy matrix, the selected physical parameters of water quality (pH, Electrical Conductivity and temperature) had a significant statistical relationship with fluoride levels in River Njoro catchment and land use/cover changes and variations in the borehole depths. The results through Geostatistical interpolation also observed that there is varied distribution and variation of fluoride levels in River Njoro catchment. Therefore geological variations, borehole depths and lithological formations were manifested in the fluoride level variations in the water and rock sampling points that were located either upstream, midstream and downstream of the River Njoro catchment. Finally the study recommends isotopic analysis of water samples from the sources of water in River Njoro catchment to assist in tracing their origin, contamination of fluoride and fluoride enrichment pathways and water quality alteration within the catchment.