The Upper Ewaso Ng’iro North river basin, which drains the north-western slopes of Mount Kenya in central Kenya, epitomises the African highland-lowland system. Extending over a vast region (15,200 km
), it encompasses an extreme eco-climatological gradient that ranges from the glaciated peaks and indigenous forests of Mount Kenya to the semi-arid and arid land of the lowland plains (Fig. 1). The mountain forms a great natural asset in terms of water resources with plentiful rainfall (1500 mm/yr) supplying perennial rivers that radiate lifelines to the dry lowlands below. Thus, Mount Kenya is one of the major “water towers” (Liniger et al. 1998b; Liniger and Weingartner 2000) in Eastern Africa. Increasing pressures on the mountain from population increase and agricultural development have the potential to endanger this asset and cause conflict between upstream and downstream water users (Hurni et al., this volume). Rapid population growth has attained levels as high as 7–8% per annum (Kiteme et al. 1998). Migrants initially moved to the lower mountain slopes, attracted by good soils, high rainfall and proximity to rivers and transport, but latterly, forced by the pressure for land, they have settled on the dry plains, extending the migration zone into marginal areas for production (Kiteme et al. 1998; Liniger et al. 1998a).