Land characteristics, run-off and potential for rainwater haversting in semi- arid areas of Tanzania

Abstract

Effective utilization of rainfall in semi-arid areas is very much dependent on land characteristics, land use, and management practices. Important land characteristics include soil type, soil hydraulic properties down the profile, soil variation along the catena, slope and vegetation cover. In most semi-arid areas of Tanzania, three soil types dominate the catena. The top of the catena is normally occupied by Lithisols. The middle part is usually, subjected to erosion and is occupied by a complex of soils but usually Cambisols/ Arenosols/ Ferrosols. Soils with vertic properties commonly Vertisols are found at the bottom of the catena. The relative proportions of the three sections in a given catena, how they are used and managed, determine the amount of runoff, erosion and the potential for rainwater harvesting (RWH). These factors also have a very important influence on the ability of the soil to receive, store, redistribute and release rainwater. This paper presents case studies from sites in Mwanga, Same, Morogoro and Maswa Districts, Tanzania to elaborate the role of these factors in RWH. It is concluded that the landscape is an important factor in determining yield, control and management of runoff, and hence potential for RWH. The catena is a natural set-up for rainwater harvesting where the top section acts as natural generator of runoff and the bottom section as natural receiver.