Siltation and Pollution of Rivers in the Western Highlands of Cameroon: a Consequence of Farmland Erosion and Runoff | Envasement et Pollution des Rivières dans les Hauts Plateaux de l'Ouest-Cameroun: une Conséquence du Ruissellement et de l'Erosion des Terres Agricoles

إنجليزي. peer reviewed

إنجليزي. In the Western Highlands agro-ecological zone of Cameroon, rivers are constantly silted and polluted with eroded sediment and waste from cultivated land. This study characterizes and quantifies the amount of material coming from plots cultivated in the Méloh Watershed. In a natural rocky-bottomed well measuring 0.90 m deep, 3 m long, and 2.5 m wide, for a period of three years we performed the collection, differentiation, and measurement of trapped sediment in the cultivated part of river that runs through the watershed. Both cultivated sides of the watershed had fairly regular slopes of 14% on one side and 17% on the other side. The material retrieved consisted of soil, plant residues, chemical packages, and plastic casing used for irrigation. During the years 2012 and 2013, farmers practiced both flatbed cultivation and ridging along the steepest slopes. These two methods of land preparation are inefficient in terms of water conservation, as evidenced by the collection of 10.429 t.ha-1 average total sediment per year during this period. Tied ridging cultivation method was experimented during the 2013 crop year and adopted on 75% of plots in 2014. We subsequently collected 3.586 t.ha-1 total sediment, a decrease of 65.61% compared to the average of previous years. The tied ridging cultivation method significantly reduced siltation of the Méloh River (p<0.05). This study showed that traditional agricultural practices are a principal cause of siltation and pollution of the Méloh River. By extrapolation, we can state that the problem must occur in almost all rivers in the study area with similar topography and agricultural practices