Geochemical Characterization and Suitability of Surface and Sub-surface Waters for Irrigation in Lake Chala Catchment Area, Kenya

摘要

Lake Chala is a transboundary fresh water lake characterized by lack of effluent surface drainage and is located in southwestern Kenya on the Kenya-Tanzania border. This is a semiarid region frequently facing severe water scarcity especially during drought seasons. The major economic activities undertaken within the lake's catchment area include small-scale rain fed agriculture, which accounts for about 75-80% of household income. Over reliance on rain-fed agriculture has often had negative impacts on the people in this area due to water scarcity occasioned by unreliable rains. As such, there is need to tap the lake water for irrigation purposes. In order to determine the geochemical characteristics and suitability of the lake's catchment waters for irrigation purposes, water samples were collected on the Kenya and Tanzania sides of Lake Chala from eleven (11) sites in March 2011 and subjected to analysis for chemical characteristics. Based on hydro-chemical facies, ten water samples show that calcium-Magnesium-bicarbonate waters predominates in the catchment area, while one water sample from a shallow well is a calcium-magnesium-chloride type. The suitability of the water for irrigation purposes was evaluated based on sodium percent, residual sodium carbonate, sodium adsorption ratio and salinity hazard and found to be suitable for irrigation purposes. Crop type and soils may also have a profound influence on water suitability for irrigation. It is, therefore, herein recommended that further study be undertaken to evaluate the suitability of soils for specific crop types.