Mississippi River Lock And Dam 21 dam
Mississippi River Lock And Dam 21
Mississippi River Lock and Dam 21, also known as Pool 21, is a federal-owned structure located in Hannibal, Missouri. Completed in 1938, this concrete dam plays a crucial role in navigation along the Mississippi River, with a hydraulic height of 11 feet and a structural height of 48 feet. The dam's purpose is primarily for navigation, and it features a single lock that is 600 feet long and 110 feet wide, allowing boats to pass through the river.
With a hazard potential deemed significant, the US Army Corps of Engineers (USACE) actively manages flood risks associated with the dam. Regular inspections, maintenance, and collaboration with local emergency managers are key components of the risk management measures in place. The dam has limited water storage capacity, and water releases may be necessary to manage water levels and ensure the dam's structural integrity. USACE works diligently to address all types of flood risk and maintain the safety and functionality of the Mississippi River Lock and Dam 21, serving as a critical infrastructure for water resource management and climate resilience in the region.
Dam data reference
Condition Assessment
- Satisfactory
- No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
- Fair
- No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action.
- Poor
- A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency.
- Unsatisfactory
- A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
- Not Rated
- The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Hazard Potential Classification
- High
- Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
- Significant
- Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environmental damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
- Low
- Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
- Undetermined
- Dams for which a downstream hazard potential has not been designated or is not provided.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Mississippi River Lock And Dam 21 -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| North River At Palmyra | 6 cfs | → |
| South Fabius River Near Taylor | 36 cfs | → |
| Bear Creek At Hannibal | 1 cfs | → |
| Bear Creek Near Marcelline | 17 cfs | → |
| Wyaconda River Above Canton | 19 cfs | → |
| Salt River Near New London | 1,340 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mississippi River Lock And Dam 21.
Boat launches
- Marion County
- Broadway Hannibal
- 130th Street Lewis County
- Ralls County
- State Park Road Adams County
- Spalding Boat Ramp
Track Mississippi River Lock And Dam 21 in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Mississippi River Lock And Dam 21
Where does the data for Mississippi River Lock And Dam 21 come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the Significant hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Mississippi River Lock And Dam 21.