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
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