Plaquette : Making the Senegal river navigable - IAGF 6ème session

~~ ~-~ . /' -------~ ~~-- --~ ~----- .i->: ---- - -- - - - - - -_.- The proliferati on of catta il and its environmental impacts The commissioning of the dams of Diarna' and Manantali had highly positive impacts but they also radically changed the flow regime of the Senegal River. Cattail, an indigenous plant whose development had been previously impeded by salinization, progressively invaded the river and replaced the existing vegetation. In the Delta and the Lower Valley, cattail has developed considerably in terms of both magnitude and speed of propagation . The surface area covered by cattails already exceeded 100,000 ha only a few years ago. When it is torn out, the plant grows back again in eight to ten months . Cattail is therefore a serious threat for biodiversity, through the eutrophication of habitats and the degradation of water quality. In time it can also seriously impede socioeconomic activities such as fishing, agriculture, gaining access to drink ing water for rural populations, and navigation, by altering the natural flow regimes of the river. Cattail is a major barrier and will prevent us from reaching the targets set for irrigated farming if we don 't find a solution. It is also a health problem. TAMSIR NDIAYE , MANAGI NG DIRECTOR OF SOGEM More than million people are affected around the world by the bilharzia and it kills people every year. 6 Water borne diseases are indeed another facet of the problem of cattail. A correlation can be c1early established between the endemic nature of malaria and the presence of this invasive plant. Mirdad Kazanji, the Director of the Pasteur Institute of Guyana, also ment ioned the case of bilharzia (also called schistosomiasis), a disease that is now undergoing recrudescence due to cattail. It affects more than 200 million people around the world and kills 300,000 every year in developing countries . Bilharzia is transmitted by an int esti nal worm and contact with infested water. One biological method of combating it makes use of a crayfish which eats the snails that ad as the vectors of the disease. However, to achieve this, the crayfish have to be reintroduced into the river and their migration made possible by systems that enable it to cross the dams. 3 SeeAppendix 3: the contribution of the Diama dam to the development of water use, p.30