Below Ice-Caps and Cloud Forests: Sustainable Water Management Practices Among the Chagga, MT Kilimanjaro Region, Tanzania

Mt Kilimanjaro has a unique ecology that include glaciers on its summit and a rainforest where numerous perennial and sub-perennial rivers and streams emanate. The Chagga people who cultivate the lower slopes of the mountain use this water to irrigate their home gardens (vihamba). This water supply is now under threat due to climate change and human encroachment of the rainforest. The glaciers on the mountain summit further add to variable water flows downslope. Using historical, ethnoarchaeological surveys, climate and other data, we demonstrate that these events reflect centuries-long developments encouraging the adoption by the Chagga of sustainable water management practices. Chagga settlement of Kilimanjaro coincides with the Little Ice Age (1300-1850), characterised in Africa by declining temperatures and cooling, reduced rainfall and severe droughts. Such climate and environmental change must have triggered the construction of irrigation furrows (mfongo) to direct regular water supplies to the vihamba and nduwa (mini dams) to regulate water flow. With over 2000 mfongo, the hillslopes of Mt Kilimanjaro were significantly modified to support a subsistence system that has remained largely unaltered for centuries.