What Are Slack-Water Pools?

Wherever there is a dam or a lock and dam system on a lake you may have the development of slack-water pools. Along the Mississippi River the Corps of Engineers maintains these, along with dredging during seasons when the river is navigable. Many of these areas are used by sportsmen in the warm seasons.

  1. Origins

    • Slack-water pools were designed by the U.S. Army Corps of Engineers to aid in the navigation of shipping along major rivers. They are nine-foot-deep pools of water that are created by movable dams. They were first considered by the Corps of Engineers in the 1840s but were not effectively put into use until the Davis Island Lock and Dam was finished in 1878 on the Ohio River. The modern versions are not stuck out into the rivers, as their predecessors have gates that actually move up and down to raise or lower the water level to keep it at the navigable nine-foot standard.

    Dam Operation

    • Each dam is operated independently, with approval from the Corps of Engineers. Each time they close a gate the water has to back up somewhere. That means that they have to coordinate with the lock above.

    Safety of Citizens

    • When the project was in full steam along the Mississippi River the Corps of Engineers purchased low-lying land that could be prone to flooding. These areas would turn into recreation areas along the shores of the rivers. It also became a natural flood plain. Although the river was normally flooded these areas, it was now controlled except in the most extreme cases. One such case was the heavy flooding in the St. Louis region in 1993. During this time the levee system and the slack-pools did not hold up to the pressure. The flood lasted from April 1 to September 30, 1993.

    Recreational Areas

    • The controlled flooding of these lands created numerous areas where fish and other wild game can live. Full consideration is given to the impact on the environment before the dams are used. This is in conjunction with the Anti-Drawdown Law of 1934. It also specifies that the draw-down pools need to be maintained as if regular river traffic was present. This was to the benefit of shipping and sportsman.