Earlier this month of June 2018, I was fortunate to spend a few days visiting the Cuvelai, Okavango and Zambezi river basins in the north of Namibia to explore opportunities for rainwater and floodwater harvesting. I also met with members of several communities who are essentially pastoralists.
On the question of how the communities coped in the past with water scarcity during the dry season, the answer was that there was (and still is) a practice of preparing hand dug wells along the banks of the river channels, in anticipation of the floods. When the flood came with the river overflowing, these wells were used to trap the flood water. This water would then be stored in the wells after the floods receded and the river eventually ran dry. The water would then be used for the livestock.
This traditional practice is somehow now improved with the current practice of modern earth dams for which the government of Namibia has a standard design, to minimise seepage, evaporation losses and sedimentation.
In addition, the experience shared by Liliana Castillo by the Zenu tribe in north Coast of Colombia is quite similar to what communities do or experience along the Zambezi River do in Namibia, with similar conditions - excess water during the rainy season and deficit during the dry one. They also harvest flood water in natural streams (as opposed to the network of canals in north Colombia) that are perpendicular to the main stem, allowing water to reach areas that are quite far away from the main river. This water is then used during the dry season for livestock and agriculture.
Man made interventions (mostly road infrastructure) are suspected to have interfered with this natural course of flood water. The communities recommended that future designs of such infrastructure takes into consideration this natural movement of water during floods and if possible, further facilitate the process for areas that are naturally prone to receive such excess flood water, which will be used for productive uses, improving food security.