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

Abstract

Effective utilization of rainfall in semi-a~'d areas is very much depeliaent on lahd cha;"(lctelistics, land use, and managemellt practices. Important land cl19racteristics include soil, type, soil hy~ draulic properties down the profile, soil valiation along-the catena,_slope and vegetation cover. In most semi-mid areas -of'Tan'zallia~ three soil types dominate tlie c~tena. The top of the catena is normally occupied byLithisols. The middle piirt is usually subjected to erosion mzd is occupied by a complex of soils but usually Cambisolsl Arenosolsl Ferrosols. Soils with vel1ic propel1ies commonly Verlisols 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, detemzine the amount of runoff, erosion and the potential for rainwater harvesting (RWH). These factors also have a velY impOl1QIlt ilif/uence 011 the ability of the soil to receive, store, redis~libute and release rainwater. This paper presents case studies from' sites in Mwanga, Same, Morogoro' and Maswa Distlicts, Tanzania to elaborate the role of these factors in RWH. It is concluded that the landscape is an impOl1Q/zt factor in dete171zining 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.