Flood Day 202

Flood stage of the Big Blue River at Blue Rapids is 26 ft or an elevation of 1101 ft.  March 12 was the first day that the river was above 26 ft.  The river crested at 61.32 ft on May 31 (Flood Day 81).  By September 20 the river hat dropped to 35.45 ft (a drop f 25.87 ft).  With significant rains, the river was back up to 39.26 ft.on September 28.

Sunday, September 29 is the 202nd day for the river to be above flood stage at Blue Rapids.  As a point of trivia, the river is now at the same level that it was on April 5 (flood day 25, rising) and September 9 (flood day 182, falling).

A little review of the storage capacity of Tuttle Creek Reservoir.  The lake has three water storage sections.  The normal or Multipurpose Pool level of the lake is 1075 ft above mean sea level.  Above the Multipurpose pool is the Flood Control Storage space with an upper elevation of 1136 ft.  Above the Flood Control Storage space is the Surcharge space, which will only hold water if the flood gates are opened.

Today (Sunday Sept. 29) the lake elevation is 1113.92 ft (38.92 ft above the Multipurpose level).  The Flood Control Space is currently holding 897,155 acre·ft of flood water or 47.67% of its capacity.  The lake currently has a an area of 36,143 acres, which is over 3 times the Multipurpose pool area of 10,900 acres.  This also means the lake is still covering 67% of the area it covered when the Flood Control space was at maximum capacity.

The release rates at Tuttle Creek Reservoir, Perry Lake, and Clinton Lake are essentially dependent upon the flow rate of the Missouri River at Waverly, MO.  Flow rates in excess of 90,000 cfs at Waverly create some lowland flooding.  Today the flow rate at Waverly is 171,000 cfs.  For the last week or so the discharge rate at Tuttle Creek has remained at 200 cfs. According to an article in the Manhattan Mercury on Friday, September 27, the release rate at Tuttle cannot be increased unless the flow rate at Waverly is below 140,000 cfs or the lake level rises to 1114.4 ft (it is very close to that now) at which time the flow rate at Waverly must be below 180,000 cfs.

Link to Manhattan Mercury Article from Friday, September 27:
https://themercury.com/news/local/i-wonder-why-has-outflow-from-tuttle-creek-lake-slowed/article_fe942c50-4246-5b8d-b7ba-50335006cabc.html?utm_medium=social&utm_source=email&utm_campaign=user-share

According the to USACE Three Day Reservoir Forecast, the release from Tuttle is to be 2000 cfs starting on Monday, September 30.  This release rate pretty much offsets the daily inflow so the lake level will remain fairly static.  The inflow on Saturday at MT was 2,700 cfs.

FYI:  A discharge rate of 2000 cfs is roughly equal to 4000 acre·ft/day.  There is still approximately 900,000 acre·ft of water in the Flood Control Space.

Link to USACE Three Day Forecast:
http://www.nwd-mr.usace.army.mil/rcc/nwk/lakepool.txt

Link to USACE 8-Day Reservoir Report
http://www.nwd-mr.usace.army.mil/rcc/nwk/7daylak3.pdf

Link to September 29 USACE Lake Levels Report
http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/MRBWM_Reservoir.pdf

You may have to cut and paste the USACE links into your web browser.

The Flood Control Space at Perry Lake is still at 40.6 percent of its capacity and Clinton Lake's is at 34.7 percent of its capacity.

Milford Lake is 32 ft above normal pool level and its Flood Control Storage space is at 47% of capacity with 356,062 acre·ft of flood water.

Prepared by David Crawford