Land degradation,soil conservation and the sediment load of the Yellow River,China: Review and assessment

Ninety per cent of the sediment load of the Yellow River, the world's muddiest river, comes from the loess plateau region in the middle course of the river. Control of this sediment supply is essential to avoid the danger of flooding in the lower reaches on the South China Plain. Since 1971, sediment loads entering the lower reaches have decreased, by 20 per cent as a result of lower precipitation, and by 27 per cent through soil conservation works and reservoir construction. Reductions in erosion can be obtained by restraining the formation of overland flow through promotion of an effective vegetation cover and elimination of the soil surface cover to encourage infiltration. Reservoir operation is a key to control of sediment movement through tributaries and along the main river. Water demands often conflict with sediment control, and, as a consequence, reservoir operation systems have changed several times in the past decade. The possibility of a further reduction in the sediment load of the Yellow River exists, but much depends on how rapidly control of grazing and deforestation leads to the establishment of plant cover on the loess plateau.