This in turn raises the level of the water table in the vicinity of the impoundment. An artificial impoundment creates a groundwater mound near the impoundment. Wetlands can be found adjacent to rivers. These areas are important ecologically for maintaining water quality, providing habitat, and protecting plant and animal species diversity. Just as the water table will return to its original configuration if the dam is drawn down and removed, wetlands can be expected to restore themselves in their original places.
Rivers naturally erode, carry, and deposit sediment.
These processes are what shape the river, form meanders, pools, and riffles. The river deposits its sediment load in the impoundment when the flow velocity slows and the particles settle out. Over time, sediment can fill in the impoundment. Eventually, the impoundment may become so shallow that the sediment must be removed by dredging or other means. The river downstream of the dam is starved for sediment because the sediment naturally flowing in the river has been trapped behind the dam.