Sediment Concentration to Water Discharge Ratio Along the

Mississippi (and Missouri) RiverCE 397

Statistics of Water Resources

Yao You

Key Points

•Sediment concentration to water discharge ratio decreases downstream;

•Sediment concentration does not reach the limit of river capacity most of the time.

Sediment Concentration Against Discharge

Anoka, MN

Flow velocity increases

correlation coefficient: 0.6804

The Ratio Compared to Discharge

Anoka, MN

Flow velocity increases

The Ratio Compared to Discharge

St. Louis, MO

Flow velocity increases

Data Source

• Very few sites have both consistent (suspended) sediment concentration and water discharge data;

• Qualified sites have uneven data points (3-20);

• Data comes from different time periods.

Treatment of Data

• Few sites: nothing we can do right now...

• Small number of data points: rank sum+t test

• Time period issue: test for trend.

Results

downstream

Majority Trend: Upstream ≥ Downstream

downstream

≥ ≥

Exception: Upstream < Downstream

downstream

<St.

Louis, MO

Sudden Increase of Sediment Concentration Near St. Louis, MO

St. Louis

Missouri River, major sediment supplier for MS

Mississippi River

Missouri River

Missouri River: Results

St. Louis

•Upstream has much larger concentration to discharge ratio;

Missouri River: Results

St. Louis

•Upstream has much larger concentration to discharge ratio;

•The ratio increases near Sioux, IA and Omaha, NE.

Conclusions

•Sediment concentration to discharge ratio decreases downstream;

•Missouri River contributes a significant amount of sediment into the Mississippi River upstream of St. Louis, MO;

•Rivers are not at their full transport capacity most of the time.

Future Work

•Understand the physics of the observed trends;

•Study more rivers to verify those findings.