Water towers
Water and life are closely connected; in tropical ecosystems this linkage is felt more urgently than elsewhere. A sufficient water supply is critical for the survival of the farming communities of inland Kenya which represent over 80% of the national population. Water availability is erratic and irregularly distributed throughout the year. Its spatial distribution is also critical. Ecosystems that are able to receive and store large amounts of rainfall that successively slowly trickles downstream through a multitude of small streams are essential for supporting farming communities.
Africa is a dry continent, water scarcity is due to higher evaporation than rainfall in nearly all its land mass. About 80% of the precipitation that falls over the continent evaporates; this is far more than what happens in other continents. Kenya has great variation in local climate. Permanent snow can be found above 4 600 metres on Mt. Kenya and desert dunes can be seen at Chalbi in the Marsabit district. Rainfall comprised between 200 and 1600 mm/year, while Penman annual evaporation from open water (a standard measure of evaporation) varies between 1 000 mm in Central Highlands to as much as 2 600 mm in the arid North.
About 80 % of Kenya is arid and semi-arid, as little as 17 % of land with high agricultural potential sustains 75 % of the total population. Water resources are decreasing to 500 m3 per person per year; Kenya is critically water stressed and 10 million people lack clean water.
Forests cover less than 2 % of total land area and deforestation is increasing. Only at the summit of the Water Towers (Mount Kenya, the Nyandarwa Range, the Cherangani Hills, the Mau and Mount Elgon) precipitation is greater than evaporation. These five blocks of highland forest, called the Water Towers of Kenya, are able to do just that: receive the rainfall, store it at high altitude within deep forest soils, release it gradually allowing ecosystems donstream to survive the dry seasons. The hydrological role of high altitude forests is well understood by farming communities living in these ecosystems. As an example of this, you could visit Olosho Rongai Forest, where the local Maasai community is protecting a pristine Red cedar forest for preserving their last permanent spring.
