US Army Corps of Engineers
St. Paul District

Locks and Dams

Mississippi River towTo achieve a 9-foot channel in the Upper Mississippi River, the construction of a system of navigation locks and dams was authorized in 1930. Dams are built on rivers to hold back water and form deeper navigation "pools." Most pools in the United States are maintained at a constant minimum water depth of 9 feet for safe navigation. Dams allow river vessels to use a series of locks to "step" up or down the river from one water level to another.

The Corps operates the locks and dams on the Mississippi River for navigation, not flood control. The locks and dams create slack-water pools for navigation during periods of low- and moderate-level water. For each pool, there is a primary control point, where a predetermined water elevation must be kept for navigation to continue.

The St. Paul District operates and maintains 13 locks and dams beginning at Upper St. Anthony Falls in downtown Minneapolis and ending at Lock and Dam 10 in Guttenberg, Iowa.

For recreational craft to pass through a lock and dam, there is a specific locking procedure. It's a fun and unique experience. Interpretive materials and brochures are available at all locks.

Flow and elevation thresholds for St. Paul District Locks and Dams

Find current flow and elevation data at

Lock & Dam Outdraft warning (cfs*) Gates pulled (cfs) Lock closed to navigation (cfs) Lock closed to navigation (pool elevation**)
LSAF 20,000 50,000 40,000 731.60
1 0.2' over dam N/A 40,000 729.40
2 31,000 61,000 116,000 692.00
3 21,000*** 36,000 125,000 683.00
4 60,000 89,000 160,000 671.00
5 70,000 116,000 188,000 664.50
5A 32,000 57,000 183,000 659.50
6 44,600 76,000 200,000 651.50
7 44,000 82,000 235,000 646.50
8 40,200 96,000 225,000 636.00
9 55,000 64,000 220,000 630.50
10 47,000 73,000 238,000 620.50

* cubic feet per second

** elevations listed mean sea level 1912

*** has not been re-evaluated since construction was completed to reduce outdraft

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St. Paul District Locks & Dams

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