Reduction of Reduction of Streamflow From Streamflow From

Upstream Ice Upstream Ice FormationFormationa.k.a. “Ice Bite”a.k.a. “Ice Bite”

Brian ConnellyNorth Central River Forecast Center

Chanhassen, Minnesota

Ice Bite - Ice Bite - What Is ItWhat Is It??

River water temperature is approaching 32°F.River water temperature is approaching 32°F. An ice cover hasn’t formed on the river yet.An ice cover hasn’t formed on the river yet. An extreme cold snap occurs over the course An extreme cold snap occurs over the course

of a few days.of a few days. Cold temperatures rapidly generate a Cold temperatures rapidly generate a

stationary ice cover on the river, and freeze stationary ice cover on the river, and freeze some water sources.some water sources.

Since the river ice is stationary it is removed Since the river ice is stationary it is removed from the downstream flow, and river levels can from the downstream flow, and river levels can drop rapidly.drop rapidly.

Ice Bite – Ice Bite – Who CaresWho Cares??

Low water event, Low water event, notnot flooding flooding An ice bite can have temporary but An ice bite can have temporary but

significant impacts on navigation, significant impacts on navigation, municipal water supplies, and power municipal water supplies, and power plant operations.plant operations.

River levels typically rebound River levels typically rebound somewhat after a few days.somewhat after a few days.

Ice Bite ExampleIce Bite Example

St. Louis, Missouri St. Louis, Missouri – January, 2003– January, 2003

Lower than normal Lower than normal precipitation precipitation during summer and during summer and fall of 2002fall of 2002

Low water entering Low water entering winter seasonwinter season

Concern over Concern over navigationnavigation

St. Louis Stage

-6

-4

-2

0

2

4

6

11/6/02 11/13/02 11/20/02 11/27/02 12/4/02 12/11/02 12/18/02 12/25/02

Date

Sta

ge (

ft)

L&D 10 EADM7 Stage Critical Concern Navigation Halts

Upper Mississippi Air & Upper Mississippi Air & Water TemperaturesWater Temperatures

30

35

40

45

50

55

60

11/1/0211/8/02

11/15/02

11/22/02

11/29/0212/6/02

12/13/02

12/20/02

12/27/021/3/03

1/10/031/17/03

1/24/031/31/03

Date

Wat

er T

empe

ratu

re (

F)

-120

-100

-80

-60

-40

-20

0

20

40

60

80

Air

Tem

pera

ture

(F

)

Approximate River Ice Approximate River Ice Cover Cover BeforeBefore Event Event

Approximate River Ice Approximate River Ice Cover Cover AfterAfter Event Event

Air Temperature & Air Temperature & St. Louis StageSt. Louis Stage

-6

-4

-2

0

2

4

6

8

10

12

1/1/03 1/8/03 1/15/03 1/22/03 1/29/03

Date

Sta

ge (

ft)

-100.0

-80.0

-60.0

-40.0

-20.0

0.0

20.0

40.0

60.0

Air

Tem

pera

ture

(F

)

Forecasting Ice BiteForecasting Ice Bite Monitor ConditionsMonitor Conditions

Significant portion of river must be ice freeSignificant portion of river must be ice free River water temperature must be at or near River water temperature must be at or near

freezingfreezing Watch air temperature forecasts for Watch air temperature forecasts for

prolonged cold snapsprolonged cold snaps Rule of ThumbRule of Thumb

Flow reduced by 50%Flow reduced by 50% Rebounds to about 75% of original flowRebounds to about 75% of original flow Source: Wise forecaster from the NCRFCSource: Wise forecaster from the NCRFC

Flow Reduction Rule of Flow Reduction Rule of ThumbThumb

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

90,000

1/1/021/3/02

1/5/021/7/02

1/9/02

1/11/021/13/02

1/15/021/17/02

1/19/021/21/02

1/23/021/25/02

1/27/021/29/02

1/31/02

Date

Mea

n D

aily

Dis

char

ge (

cfs)

St Louis L&D 22 L&D 18 L&D 14 L&D 11 Missouri R

ConclusionsConclusions

Process isn’t modeled, but it may be possible Process isn’t modeled, but it may be possible to predict using an approach similar to some to predict using an approach similar to some of the ice jam prediction methods.of the ice jam prediction methods.

Potential RFC Forecaster AidsPotential RFC Forecaster Aids Plot latest water temperature observations Plot latest water temperature observations

spatially.spatially. Plot latest ice cover/thickness observations Plot latest ice cover/thickness observations

spatially.spatially. Plot forecast freezing degree days spatially.Plot forecast freezing degree days spatially.

Refine the rule-of-thumbRefine the rule-of-thumb