A study of the drainage problems in some part of The Mwea Irrigation Scheme, Kenya

Abstract

The red soils occupy some parts of Mwea Irrigation Scheme. In particular, the Tebere Section of the Scheme has these. soils occurring at higher elevations than the black cotton soils which occur in the depressions. The

black soils are irrigated under rice cultivation. The red soils in Tebere are irrigated to a limited extent. The irrigated plots are grown with vegetable and fruit trees. The red soils (kaolinitic clay loams) have extremely high infiltration rates. The result of their irrigation is that water percolates into deeper layers, consequently finding its way by seepage to lower lying black soils. The main canals which supply irrigation water to Tebere Section also run over the red soils. For all their lengths the canals (left and right branches) are not lined and therefore water losses from them is a possible source on the drainage problems , However, the total surface area of the canal is far less than that of the basin and furrow irrigated plot on which water use efficiency has been studied. Although the present study reveals that canal losses and deep percolation losses contribute substantially to the poor drainage of the black soils, rainfall has also been identified as an important component.