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Sediment Concentration to Water Discharge Ratio Along the Mississippi (and Missouri) River. CE 397 Statistics of Water Resources Yao You. Key Points. Sediment concentration to water discharge ratio decreases downstream;
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Sediment Concentration to Water Discharge Ratio Along the Mississippi (and Missouri) River • CE 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 correlation coefficient: 0.6804 Flow velocity increases
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 < St. Louis, MO downstream
Sudden Increase of Sediment Concentration Near St. Louis, MO Mississippi River Missouri River, major sediment supplier for MS St. Louis
Missouri River: Results • Upstream has much larger concentration to discharge ratio; St. Louis
Missouri River: Results • Upstream has much larger concentration to discharge ratio; • The ratio increases near Sioux, IA and Omaha, NE. St. Louis
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.