Agriculture CanadaPrairie Farm Rehabilitation Administration
Engineering Service
DETERMINATION OF ICE THICKNESS
FOR SMAll WATER BODIES
IN THE CANADIAN PRAIRIE REGION
Hydrology Report '119
Regina, Saskatchewan
March, 1990
Prepared by:
D. E. Kelln, P. Eng.
Hydrology Division
Submitted by:
F.R.J. Martin, P.Eng.
Manager, Hydrology Division
SYNOPSIS
This report consolidates the PFRA data bases of ice thickness measure
ments for dugouts and small reservoirs and presents procedures for determin
ing (estimating or predicting) the ice thickness of small water bodies on
the Canadian Prairies. Although ice formation is primarily a function of
air temperature and snow cover, a pract ica1 procedure to determi ne ice
thickness could not be developed which encompassed both factors. However, a
map showing isopleths of mean annual ice thickness for small water bodies
was developed, along with an average monthly rate of ice formation through
out the winter. A simple graphical relationship was developed to determine,
in a rather crude manner, the ice thickness for any year at any given loca
tion using only the departure from normal of winter air temperature.
Depending upon the user's intent and available information, an estimation or
prediction of ice thickness could involve the use of the map of mean annual
ice thickness, the recorded data and/or the ice thickness-air temperature
relationship.
1. INTRODUCTION .
TABLE OF CONTENTS
...................
PageNumber
1
2. ICE THICKNESS DATA BASES
2.1 Dugout Data ....
2.2 Small Reservoir Data
3. PROBLEMS IN DETERMINING ICE THICKNESS ANDRATIONALE FOR THE APPROACH ADOPTED ....
4. ANALYSIS OF DATA
4.1 Mean Annual Ice Thickness (MAlT)
4.2 Monthly Ice Formation ..
3
3
3
9
11
11
14
4.3 Relationship Between Ice Thickness and Winter AirTemperature . 15
5. PROCEDURES TO DETERMINE ICE THICKNESSAND POTENTIAL APPLICATIONS . 21
5.1
5.2
5.3
Procedure 1: Using MAlT to Estimate Ice Thickness
for an Average Year .
Procedure 2: Using Recorded Ice Thickness Datafor 'Design' Purposes .
Procedure 3: Using Winter Air Temperature (WAT)to Determine Ice Thickness .
21
21
22
6. CONCLUSIONS
REFERENCES .
APPENDIX A - DEPARTURES FROM NORMAL OF WAT
AT VARIOUS LOCATIONS ....
25
27
A-I
Table
Number
lA
IB
2
3
4
5
6
FigureNumber
1
2
3
4
LIST OF TABLES
Location Information for Dugouts
Location and Size Information for Small Reservoirs
Dugout Ice Thickness Data ..
Small Reservoir Ice Thickness Data
Spatial and Temporal Ice Developmentin the Canadian Prairie Region
Winter Air Temperatures at Regina
Airport for the Period 1951-88 .
Departures from Normal of Winter Air Temperatureat Regina and Corresponding Regional
Average Ice Thicknesses for the Period 1976-88 .
LIST OF FIGURES
Locations of Dugouts and Small Reservoirsin the Ice Thickness Study .
Mean Annual Ice Thickness (MAlT)for Small Prairie Water Bodies
Regional Average Ice Thickness as a Functionof Departure from Normal of Winter Air
Temperature at Regina .
Determination of Ice Thickness at a Location
Using Winter Air Temperature (Procedure 3)
PageNumber
5
5
6
7
15
16
17
PageNumber
4
12
18
20
1. INTRODUCTION
In March of 1976, the Hydrology Division of PFRA (Prairie Farm Rehabili
tation Administration) initiated a five-year study to investigate the
spatial and temporal variability of ice thickness on dugouts in the Prairie
region of western Canada[l]*. The study was intended to evaluate the
effect of factors such as air temperature, exposure, snow cover, orientation
and water depth on ice formation. In addition, it was anticipated that the
geographic distribution of the dugouts would reveal the pattern of ice
thickness across the region and any significant differences in ice develop
ment over the wi nter season. Better knowl edge of ice formation woul d be
useful in the des ign and operation of dugouts and small reservoi rs and in
the design of appurtenant structures.
In 1979, near the end of the Dugout Ice Thickness Program, the Hydrology
Division of PFRA began collecting ice thickness data on the small reservoirs
that were included in its Spring Runoff Monitoring Program. These measure
ments continue to be made.
This current report has been prepared to address two objectives:
1. To consolidate the PFRA data bases on ice thickness for small
prairie water bodies; namely, dugouts and small reservoirs,and
2. To analyze available ice thickness data, reports and infor
mation with the intent of developing a practical, easy-to-use
procedure for determining (estimating or predicting) icethickness on small water bodies in the Canadian Prairie
region.
The following sections of this report describe the PFRA data bases of
ice thickness, the development of a map of mean annual ice thickness for the
Canadian Prairies and practical procedures that were developed to estimate
or predict annual and monthly ice thickness.
* Square brackets refer to references.
- 2 -
- 3 -
2. ICE THICKNESS DATA BASES
2.1 DUQout Data
Dugouts are extensively used in the Canadian Prairie region to
store runoff water from the surrounding land. Typically, a dugout stores
from 2000 to 12 000 m3 (2 to 12 dam3) of water and has a surface area of
1900 to 3800 m2 (0.19 to 0.38 ha) and a depth of 3 to 6 m. Smaller dug
outs are commonly used for agricultural and rural domestic water supplies,
whereas larger dugouts are sometimes used for municipal purposes.
For five consecutive winters beginning in 1975, field officers from
each of the then twenty di stri ct offi ces of the PFRA Water Development
Service (now a part of the Soil and Water Conservation Service) measured ice
thickness on dugouts on the 15th of each month from October to April. Each
office was responsible for measuring and reporting ice thickness at two
separate poi nts on each of two dugouts located near the di stri ct offi ce.
The two measurements on each dugout were averaged to obtain one reading per
dugout. Figure 1 and Table lA provide the location of each pair of dugouts.
Besides ice thickness, a number of other parameters were either
measured or observed. These parameters included snow cover on the ice, dug
out orientation, exposure and water depth.
The maximum recorded ice thickness on each
each of the five years of the program[ 1] is given
are identified by the year in which the winter ends.
omitted due to extenuating circumstances, as noted
table.
2.2 Small Reservoir Data
of the 40 dugouts for
in Table 2. The data
Certain data have been
at the bottom of the
In connection with the Hydrology Division's Spring Runoff Monitor
ing Program, staff from the Division have measured ice thickness prior to
spring breakup at 27 small reservoirs in southern Saskatchewan over the past
decade. Figure 1 and Table IB provide the location of each of these reser
voirs. Table IB also provides storage and flooded area at FSL (Full Supply
Level) information for the reservoirs. In addition to measuring ice thick
ness, Hydrology Division staff estimated the average snow cover depth over
the ice surface.
..,.,US'e..,(\)
t-"r0()01r+0'::::ICJ)0..•..0e100er+CJ)
01::::I0-(fJ3Ol;0(t)CJ)(t)..,<:0=;'CJ)
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(t)?J
en»en
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--T----- .----. -----------r--------\
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LEGEND:• Dugout•• Reservoiro Town or cIty
.po
Table 1A
Location Information for Dugouts
Dugout Location
Map
Water Development
Location
D18trict III
1
Brandon SW17-11-19-WPMRZ08-11-18-WPM
2Dauphin SIi11-2(-16-wJ.BW05-25-20-ll1
3Gravelbourg SIi0(-11-05-W3BW31-10-0(-W3
(Hanna BW06-33-13-114SB09-31-13-W(
5Lethbridge NEH-08-26-11(SIf31-09-2(-II4
6
Maple Creek NE22-11-26-l13BW32-10-25-W3
7
Medicine HatNE15-12-06-W(SW17-12-06-W4
8
Meltort SE03-(6-18-W2RZ2(-45-18-W2
9
Melville SW20-21-06-W2BW02-22-06-W2
10
Moose Jaw NW07-17-27-112SW23-17-28-W2
11
Morden SW21-03-05-wJ.SIf31-02-05-Wl
12
Rorth BattletordSW19-(7-17-W3NW18-(6-17-W3
13
Peace RiverNW34-83-21-W5SBH-8(-22-W5H
Red Deer SE32-36-27-W(SW36-36-28-W(
15
Roeetown SIi21-30-H-W3SW36-29-15-W3
16
Sbaunavon SE13-07-21-W3SI!l3(-07-20-W3
17
Swift CurrentRIil6-16-H-W3NW23-15-13-W318
Vegrevi11e SEl7-52-H-W(RZ2(-52-15-W4
19
Weetlock SW09-60-27-W(RZ26-59-27-W(
20Weyburn NE12-08-H-W2SW35-08-15-112
Table 1B
Location and Size Information for Small Reservoirs
StorageFlooded Area
Map
FSLat FSLat FSL
Location
ReservoirLand Location(Ill(daIl3)(ha)
21
Adair SW36-16-10-W2609.0245616.1
22
Brownhill SW31-16-07-W2629.4135513.7
23
Cabri SE28-19-18-W3629.6031216.0
24
Caron SE23-17-28-W222.56*73020.5
25
Ceylon SW13-06-20-W2696.5829011.6
26
Cleland NE33-31-15-l13624.383159.5
27
Craik NE23-24-28-W2554.8962H200.3
28
Davideon NE27-26-29-W2610.21752(0.6
29
Deadmocae Lake SWOl-39-23-112540.11132 0001 400
30
BHroe NW14-32-H-II255(.9(52(17.4
31
Eeterhazy NW33-19-01-112(91.342 983159.3
32
!IuIIIboldt(Burton Lake)SW17-38-22-1125(5.003 52263.7
33
Indian Head Ro. 1NEl1-18-13-W2599.(2482.7
34
Indian Head Ro. 2RIill-18-13-W2605.031365.3
35
Indian Head No. 3ANEl1-18-13-W2607.50723.0
36
Kerrobert NE18-3(-22-l1365( .902(217.2
37
Kipling (Rew) NEI0-13-06-W267(.7959518.1
38
Kipling CRR NE08-13-05-W2678.5328611.7
39
Lucky Lake NW2(-23-09-l13639.06H27.1
(0
Melville SW06-23-06-112559.(6( U6171.1
41
Muenster SIi19-37-21-W2573.6721511.9
(2
Parkbeg SE19-17-02-l1330.18*1023.1
43
Redvere NE2(-07-32-wJ.583.3031529.2
H
S••• ne SIi26-28-20-W2562.0525915.5
45
Welwyn NE02-16-30-wJ.33.30*(7919.2
46
Willowe (Rew) NE35-07-29-W2687.932 U747.3
47
willow. (Old) NEO(-08-29-W2699.7(60917.5
*a•• uaed datu.
(J1
- 6 -
Table 2
DUQout Ice Thickness Data
Annual Ice Thickness (m)**
MapWater Development Number of
LocationDistrictDugout19761977197819791980MeanObservations
1
Brandon I0.9140.8231.0361.3110.6400.90 10II
0.7010.8530.9751.0060.732
2
Dauphin I1.0670.9751.189**0.89 8
II1.0060.9140.6710.7010.610
3
Grave1bourg I0.7920.7620.8530.9450.7620.81 10II
0.6400.7320.9140.9450.762
4
Hanna I0.7320.6930.7771.0670.7920.82 10II
0.7620.5940.8830.9600.975
5
Lethbridge I0.2440.2740.5490.5790.3660.43 10II
0.3350.3050.5790.6710.396
6
Maple Creek I0.3660.3960.5180.6100.5490.53 10II
0.3960.4570.8230.7620.457
7
Medicine Hat I0.3350.3660.4880.7620.5180.50 10II
0.3660.3660.5180.7920.518
8
Me1fort I0.7920.8831.1581.1280.8230.90 10II
0.8830.9140.7620.8530.792
9
Melville I0.6400.9140.9140.9140.9140.78 10II
0.6100.6710.8830.7620.549
10
Moose Jaw I0.6100.851*1.1890.7010.84 8II
0.8230.732*1.1580.671
11
Morden I0.6100.8830.7620.6100.7010.87 9II
1.1280.975*1.1891.006
12
North Batt1eford I0.5790.8230.7920.5490.8230.79 10II
0.6400.8230.8231.0360.975
13
Peace River I0.6100.5790.6400.6100.7920.66 10II
0.7010.5490.6710.6710.762
14
Red Deer I0.7320.3690.6400.8840.8530.67 10II0.6550.4720.4570.7920.823
15
Rosetown I0.7010.945*0.8530.6400.82 8II0.7320.792*1.0360.823
16
Shaunavon I0.5790.6101.0970.9140.6710.76 10II0.6100.6400.7011.1580.640
17
Swift Current I0.838 ***0.762 -4II 0.6710.884***
18
Vegrevi11e I0.5640.4270.4880.823*0.60 8II0.5330.4570.6550.838*
19
West10ck I0.5640.5790.6250.5480.7320.59 10II 0.5180.5940.5330.4870.671
20Weyburn I1.1280.945*1.0360.8840.99 8II 0.9750.914*1.1890.823
Minimum
0.2440.2740.4570.4870.366
Maximum
1.1280.9751.1891.3111.006
Mean
0.6770.6860.7540.8740.720
* Certain data were excluded from this analysis due to unre1iabi1ity caused by local conditions. One of the most common conditions was early snowmelt runoff to the dugout and subsequent freezing on top of the existing ice layer, making it impossible to determine a trueice thickness for the purposes of this study.
** The data contained in this table were originally reported in Imperial units and have been
converted to metric units for this study. Thus, the ice thicknesses are shown to threedecimal places, but the mean for each location is rounded to two decimal places to maintainconSistency with the values in Table 3.
- 7 -
Table 3 contains the annual ice thickness measurements that were
made under the Spring Runoff Monitoring Program. Typically, these measure
ments were taken at the end of February or begi nni ng of March and are
indicative of the maximum thickness of ice that formed during the winter.
Table 3
Small Reservoir Ice Thickness Data
Annual Ice ~hickness (m)
MapNUmber of
LocationReservoir 1979198019811982198319841985198619871988MeanObservations
21
Adair -0.90 -------0.76 - 222
Brownhill -0.85 -------0.73 - 223
Cabri -0.69 -0.820.580.410.870.550.550.820.66 824
Caron 1.160.660.700.910.630.590.950.790.500.720.76 1025
Ceylon -0.70 -0.910.490.640.82-0.520.670.68 7
26
Cleland -0.860.761.040.760.721.000.850.700.840.84 927
Craik 0.980.91-0.760.610.63-0.740.660.790.76 828
Davidson 1.160.860.760.820.730.690.830.850.720.880.83 1029
Deadmocse Lake -----0.990.911.160.760.810.93 530
ElfroB -0.840.730.730.550.640.930.790.730.580.72 9
31
Esterhazy* 0.610.41--0.520.660.660.520.550.630.57* 832
Humbcldt (Burton Lake)-0.890.910.940.850.870.881.040.760.730.87 933
Indian Head No. 1**---0.560.430.430.46-0.440.460.46** 634
Indian Head No. 20.730.740.580.790.520.760.81-0.670.760.71 935
Indian Head No. 3A ---0.930.460.580.88-0.670.730.71 6
36
Kerrobert --------0.660.85 - 237
Kipling (New) -----0.730.910.580.640.670.71 538
Kipling CNR 0.950.86--0.670.610.98-0.640.760.78 739
Lucky Lake 0.950.79-0.910.700.530.87-0.460.870.76 840
Melville 0.950.81-1.02 -0.871.040.880.820.870.91 8
41
Muenster --------0.640.67 - 242
Parkbeg --------0.410.64 - 243
Redvers 1.160.70-0.850.550.670.91-0.700.790.79 844
Semans -0.970.610.940.690.811.010.850.730.810.82 945
Welwyn 1.07-0.700.790.670.810.88-0.760.760.81 8
46
willows (New) ----0.580.520.79-0.490.670.61 547
Willows (Old) -0.69 -0.820.52-0.77 -0.440.640.65 6
Minimum·**
0.730.660.580.730.460.410.770.550.410.58
Maximum
1.160.970.9l1.040.850.991.041.160.820.88
Mean***
1.010.810.720.870.620.690.900.830.640.75
* Aerator was located in the reservoir, producing an undetermined effect on ice thickness. A1so, above-normal snow coverwas observed at this site.
** Abcve-normal snow cover was observed at this site compared to others in the immediate area, yielding anomalous ice thickness values.
*** Ice thickness values for map locations 31 (Esterhazy) and 33 (Indian Head NO.1) were ezcluded from this portion of theanalysis.
- 8 -
- 9 -
3. PROBLEMS IN DETERMINING ICE THICKNESS ANDRATIONALE FOR THE APPROACH ADOPTED
From a review of the available ice thickness and associated data for
dugouts and small reservoirs, as well as previous studies, papers and
reports[2,3,4,5,6], a number of problems became apparent regarding the
development of a practical relationship between the ice thickness on a small
prairie water body and its two main determinants, namely air temperature and
snow cover.
Winter air temperature and snow cover data have different attributes
which affect their usability in a practical manner. Winter air temperature
data are readily available at many locations throughout the Prairies and
generally display variability on a geographic scale, having no sharp discon
tinuities. On the other hand, snow cover information for small water bodies
in the region is not readily available and is very site-dependent, often
displaying sharp discontinuities over relatively short distances. (See data
for map locations 33, 34 and 35 in Table 3.) Furthermore, the effect of the
snow cover depends not only upon its depth, but is heavily dependent upon
when the snow accumulates and how it is redistributed over the ice surface
during the winter.
A number of observations regarding the accumulation and redistribution
of snow cover on reservoir ice surfaces have been made by field staff, and
these observations provi de ins ight to the vagari es of snow cover. One
observation relates to the shape of the reservoir and its orientation to the
wind direction. If the reservoir lies parallel to the direction of the
wind, snow is more readily blown about and removed. A second observation
suggests that the amount of trees and bush surroundi ng the reservoi r, as
we 11 as the steepness of the valley walls, affect the \snow catch' effi
ciency of the reservoir. A third observation regards the nonuniformity of
snow cover on reservoirs. Snow cover on small reservoirs is usually not
uniform, with drifts and bare spots being quite typical.
In light of all these considerations and with some regard for
practicality, the most reasonable approach was to assess the ice thickness
data both alone and in conjunction with winter air temperature data only. A
map showi ng the pattern of mean annual (average maximum over-wi nter) ice
th ickness across the Pra irie regi on was developed along with an average
- 10 -
monthly rate of ice formation. In addition, a simple procedure to determine
ice thickness, in a rather crude manner, at any location for any year was
developed using only the departure from normal of winter air temperature and
the mean annual ice thickness.
The approach is based on the assumption that the ice data bases contain
a representat ive and adequate sample of ice th icknesses on small water
bodies in the Prairie region. The representativeness of the sample has two
aspects, namely the physical and the climatic. The physical aspect concerns
the physical features of the water bodies and their surroundings as men
tioned previously in this and other sections. From this perspective, each
water body included in the study is generally assumed to be typical of its
particular area in the region. The climatic aspect pertains to the weather
cond itions, as characteri zed primari 1y by the wi nter air temperature and
snowfall, during the period of ice measurements. In this respect, the
inherent assumpt ion is that the weather cond itions throughout the Pra irie
region during the period of data collection were typical of the normal
climate. Finally, the adequacy of the sample can be subjectively assessed
by referring to Figure 1. From this figure, it can be seen that the number
of sample locations in southern Saskatchewan are ample to determine the
pattern of ice thicknesses in that area. However, due to the paucity of ice
measuring sites in Alberta and Manitoba, other related information was
required to extrapolate the pattern into these areas.
- 11 -
4. ANALYSIS OF DATA
4.1 Mean Annual Ice Thickness CMAIT)
The mean annual ice thickness (MAlT) map shown in Figure 2 is based
on the arithmetic means of the maximum over-winter ice thicknesses which
were measured for a number of years at 39 of the 1ocat ions shown in
Figure 1. A mean value was calculated and plotted for a small reservoir or
dugout pair only if five or more reliable observations were available.
(Although the data for locations 31 and 33 are 'reliable', they were ex
cluded for other reasons which are discussed later. This exclusion reduced
the total number of available values from 41, as shown in Tables 2 and 3, to
39.) Upon plotting the 39 values at their locations on a map, no obvious
difference between the two types of mean ice thickness values was apparent.
The isopleths of Figure 2 were based primarily on the plotted data, with
appropriate consideration being given to the following information:
a) number of years of record at each site,
b) measured or observed snow cover depth on the ice surface at asite,
c) normal (1951-80) degree-days below freezing between November 1and February 28 at numerous locations,
d) a map of long-term mean JanuaryCanada[7], and
e) a map of forested areas in Canada[8].
air temperatures for
Of the total 39 values which were plotted, 32 are within 0.1 m of
the value that would be obtained by interpolation of the isopleths. The
remaining seven are considered anomalies; six are within 0.2 m of their iso
pleth values, and the other one is within about 0.3 m. The anomalous data
are for six dugout pairs and one reservoir, whose map locations are 3, 4,
16, 18, 19, 20 and 30. (See Figure 1 for locations.) These anomalies and
the isopleth map are discussed in the following paragraphs.
Of the three anomalous dugout pairs in Alberta (map locations 4, 18
and 19), two have lower mean recorded values and one has a higher mean
recorded value than the respective isopleths would indicate by about 0.15 m
in each case. Because of the sparseness of sites and the apparent lack of
- 12 -
-r-------------1----------
\
;\~CHEW~ I
LEGEND:
Based on Dugout and Small Reservoir DataExtrapolation using Climatological and Forest Cover Data
MONTHLY DISTRIBUTION OF ICE FORMATION:November 30%
//f
,If//
,/(\___ ..-_l.om
\
\I
WInnipeg \
__-1a.8m
December
January
FebruaryTotal
35%
25%
10%
100%
NOTES:
1. Mean Annual Ice Thickness (MAIT) at a location was based on the arithmetic mean
of annual (over-winter) maximum ice thicknesses for either a pair of dugouts or a
small reservoir at 39 locations. No appreciable difference in ice thickness was found
between the two types of water bodies.
2. The ice thickness at a location on the map should be interpolated to the nearest 0.05 m.
Figure 2. Mean Annual Ice Thickness (MAlT) for Small Prairie Water Bodies (PFRA 1990)
- 13 -
an obvious pattern of ice thickness, the supplementary information mentioned
previously was heavily relied upon in drawing the isopleths in Alberta.
No particular explanation could be found for the anomalous data on
dugouts in southern Saskatchewan, namely for map locations 3, 16 and 20.
The dugout pair at map location 3 (Gravel bourg) had a mean recorded value
about 0.15 m higher than indicated by the isopleth map. This departure
could not be explained. The mean recorded value for location 16 (Shaunavon)
is about 0.2 m higher than ind icated by the isop1eth map . Although the
field staff's data sheets did not provide the evidence, freezing of early
snowmelt runoff on the ice surface is suspected to have occurred at this
site, similar to the situation at map location 17 (Swift Current) just a
little north. (See note for the Swift Current site at the bottom of Table
2.) No plausible explanation can be given for map location 20 (Weyburn),
whose data yielded a mean value almost 0.3 m higher than indicated by the
isopleth map.
At location 30 (Elfros Reservoir), the mean recorded ice thickness
value is about 0.2 m lower than indicated by the isopleth map. This devia
tion may be partially explained by the somewhat higher-than-average snow
cover which has been observed at the site compared to the other reservoirs.
This site is more sheltered than others, enabling greater snow accumulation,
as well as reducing snow cover redistribution by wind action throughout the
winter.
As mentioned earlier, the mean recorded values for map locations 31
and 33 (Esterhazy and Indian Head No. 1 Reservoirs) were not plotted despite
their 'reliability'. If they had been plotted, they would have been at
least 0.3 m lower than indicated by the isopleth map. These departures can
be easily explained, as noted at the bottom of Table 3. Esterhazy Reservoir
contains an aerator which may disrupt ice formation, and both reservoirs
consistently accumulate much greater amounts of snow relative to other water
bodies in the area. The ice data for these two reservoirs are definitely
not representative of the MAlT in their locations because of these unusual
circumstances. However, they do provide a benchmark for ice thickness under
similar circumstances.
Since over 80% (32 of 39) of the mean recorded ice thickness values
are within 0.1 m of their corresponding isopleth values, the map shows
fairly accurately the pattern of mean annual ice thickness (MAlT) across the
- 14 -
Prairie region. It is recommended that the isopleths not be interpolated to
less than 0.05 m at any location. For example, the MAlT at Swift Current,
Saskatchewan should be read as either 0.60 or 0.65 m depending on the use,
but not as 0.63 m.
4.2 Monthly Ice Formation
In addition to the development of the MAlT map, the rate of ice
formation during the winter was investigated. For the dugout study (1976
80), ice thickness was measured on the 15th of each month from October
through to April. From this information, two ice formation conditions were
distinguishable, each definable by geographic area. Dugouts in Area A
exhibited their maximum ice development by February 15 and those in Area B
by March 15. Area A is roughly a triangle bounded by dugouts whose map
locations are 18, 5 and 10, while Area B encompasses those expanses which
are outside of Area A.
Dugout ice data for Areas A and B were cons idered separately to
determine if the difference in ice formation with respect to time was
significant. Plotting the average rates of ice formation for each area and
interpolating to obtain end-of-month values (since the measurements were
taken in mid-month) resulted in the percentages shown in Table 4. As
ind icated by th is table, the difference in ice development occurri ng over
time between the two areas is not significant. Thus, for simplicity and
ease of use, a single temporal distribution of ice formation for the entire
Pra irie regi on (Areas A and B combi ned) has been determi ned by averagi ng
the values in Table 4 and rounding to the nearest five percent. The result
ing percentages are shown in Figure 2.
Interestingly, this monthly rate of ice formation fits the general
pattern which the Water Survey of Canada has observed for river ice in
Alberta and Saskatchewan[9]. As these river ice measurements indicate,
ice begins to form sometime in November and increases in thickness quite
steadily well into January. Sometime in February, the insulating effect of
the snow and ice layer over the water and the generally warmer air tempera
ture cause a dramatic decrease in the rate of ice development. Ice forma
tion is negligible during March as air temperature continues to rise.
- 15 -
Table 4
Spatial and Temporal Ice Development in the Canadian Prairie Region
Monthly Ice Formation as a Percentage
of Maximum Ice Thickness
Time Period
Area A*Area B**
October 15 to November 30
32%29%
December 1 to December 31
34%34%
January 1 to January 31
27%22%
February 1 to February 28
7%12%
March 1 to March 15
0%3%
TOTAL
100%100%
* Maximum ice thickness attained by February 15.** Maximum ice thickness attained by March 15.
4.3 Relationshio Between Ice Thickness and Winter Air Temoerature
A simple procedure to roughly estimate ice thickness for other than
average years at any location in the Prairie region has been developed based
on the departure from normal of winter air temperature (WAT). The deriva
tion of the procedure is described in this section.
The monthly mean winter air temperatures and the WAT (winter air
temperature) at Regina airport for each winter in the 1951-88 period are
shown in Table 5. Regina was selected because it is near the centre of the
area in which the majority of ice thickness measurements were taken (see
Figure 1). The WAT as shown in Table 5 is the summation of the monthly mean
temperatures for the four winter months (November to February) divided by
four. The year 1isted in Table 5 is the year in which the winter ends.
This arrangement allows for direct comparison by year between the
temperature data in Table 5 and the ice thickness data contained in Tables 2
and 3. As the values in the table show, the WAT over the 38-year period has
ranged from a high of -8.00C (1987) to a low of -17 .00C (1979), with
both extremes occurri ng when reservoi rice measurements were being taken.
The mean WAT over the 38-year period was -12.10C.
- 16 -
Table 5
Winter Air Temperatures at Reqina Airport for the Period 1951-88
Monthly Mean Air Temperature (oC)
WAT*Year**
NovemberDecemberJanuaryFebruary(0C)
1951
- 9.6-14.9-19.6-16.6-15.21952
- 7.7-17 .6-20.2-12.2-14.41953
- 3.0- 9.2-13.7-11.6- 9.41954
0.2- 8.1-22.4- 3.7- 8.51955
0.5- 6.4-13.4-16.3- 8.9
1956
-13.2-17 .6-17 .4-16.6-16.21957
- 3.8-12.9-18.9-14.1-12.41958
- 3.9- 8.5- 9.0-14.2- 8.91959
- 6.3-12.9-19.5-16.2-13.71960
- 7.8- 7.1-17.6-14.2-11.7
1961
- 6.3-10.5-13.0-11.1-10.21962
- 4.6-18.2-16.3-17.6-14.21963
0.6-10.5-19.5-12.4-10.51964
- 3.3-12.9-11.6- 8.7- 9.11965
- 5.6-19.9-19.9-16.2-15.4
1966
- 8.3-10.9-24.5-16.2-15.01967
-10.4-12.5-16.5-15.9-13.81968
- 4.4-12.3-16.6-11.5-11.21969
- 2.2-15.6-24.6-14.6-14.31970
- 2.8- 9.0-18.8-14.1-11.2
1971
- 6.5-17 .0-21.a-12.3-14.21972
- 4.2-16.4-21.9-18.5-15.31973
- 3.9-17.5-10.2-10.5-10.51974
-11.5-15.0-21. 2-13.6-15.31975
- 2.9- 6.7-14.5-15.9-10.0
1976
- 3.8-12.1-14.7- 8.8- 9.91977
- 5.5-12.3-20.0- 5.1-10.71978
- 6.5-17.6-22.2-16.3-15.71979
- 9.2-15.9-22.0-21.a-17.01980
- 5.2- 8.2-17 .0-13.3-10.9
1981
- 1.6-13.6-11.0- 9.2- 8.91982
0.1-14.1-25.4-15.7-13.81983
- 6.8-11.0-11.4- 9.2- 9.61984
- 2.8-21. 6-11.9- 3.7-10.01985
- 6.5-18.1-16.1-15.4-14.0
1986
-13.6-13.8- 8.1-13.9-12.41987
- 8.2- 8.6- 8.9- 6.1- 8.01988
- 0.7- 6.9-15.8-12.7- 9.0
Minimum
-13.6-21.6-25.4-21. a-17.0Maximum
0.6- 6.4- 8.1- 3.7- 8.0Mean
- 5.3-13.0-17 .0-13.0-12.1
* WAT is the winter air temperature and is the summation of the monthlymean temperatures for November to February inclusive, divided by four.
** Year in which the winter ends.
- 17 -
Table 6 contains the departures from normal of WAT at Regina for
each year of ice measurements plus a regional average ice thickness for each
data base as available. The normal WAT (-12.50C for Regina) for the 1951
80 period was used. The regional average ice thickness for the dugout data
base in anyone year is the mean of all the dugout ice thicknesses in
Saskatchewan as shown in Table 2 for that year. Similarly, the regional ice
thickness values for the reservoir data base are the annual means as shown
at the bottom of Table 3, with the measurements for map locations 31 and 33
having been omitted as noted. (The mean values for the reservoirs could be
used directly from Table 3 because all the reservoirs are in southern
Saskatchewan.)
Table 6
Departures from Normal of Winter Air Temperature at Regina andCorresponding Regional AveraQe Ice Thicknesses for the Period 1976-88
Departure fromRegional Average Ice Thickness (m)Normal of WAT*Year
(OC)Dugout Data Base**Reservoir Data Base
1976
+2.6 0.70 -1977
+1.8 0.77 -1978
-3.2 0.85 -1979
-4.5 0.951.011980
+1.6 0.740.811981
+3.6 -0.72
1982-1.3 -0.87
1983+2.9 -0.62
1984+2.5 -0.69
1985-1.5 -0.90
1986+0.1 -0.83
1987+4.5 -0.64
1988+3.5 -0.75
* The normal WAT is for the 1951-80 Canadian Climate Normal period atRegina (-12.50C).
** Calculated using only the ten dugout pairs in Saskatchewan.
The fifteen data points in Table 6 were plotted on arithmetic graph
paper, produc ing a plot of ice th ickness versus departure from normal of
winter air temperature, which is shown in Figure 3. A curve was drawn pass
ing through the points and intercepting the y-axis at +12.50C. (It was
assumed that no ice would form if the WAT were zero.)
+13
+12+11r--.
(.)+10
0 '--'" +9« Z +8H C) +7Wn:::: +6I- « +5
I-+4« 3 +3
LL+2a
.....J
+ 1
« :20
n:::: a -1z -2:2 a -3n:::: LL -4W
-5n:::: :JI- -6n:::: « -70... W
-80 -9-10
- 18 -
- -..•...•...•.
LEGEND:
••.. ••.. ,-
Dugout Data Base••..
....•Reservoir Data Base
" .... ,....,........
'-""•...~'"
•M
~
-" .'\~\
~\\\~\
.\\.
\\.\\
\.
-110.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
REGIONAL AVERAGE ICE THICKNESS (m)
Figure 3. Regional Average Ice Thickness as a Function of Departure from Normal of
Winter Air Temperature at Regina (PFRA 1990)
- 19 -
Although numerous ice measurement stations were util ized in the
preparation of Figure 3, only the temperature data from one station (Regina)
was used. The validity of using temperature data from only one location to
represent all of southern Saskatchewan was tested by analyzing temperature
data from six geographically widespread stations: Coronation, Swift
Current, Prince Albert, Yorkton, Brandon and Regina. (See Figure A-I in
Append ix A for 1ocat ions.) Averagi ng departures from normal of WAT for
various combinations of these stations and replotting the data points using
these new values did not significantly affect the relationship.
A procedure for determining the ice thickness at any location for a
year which is other than average is provided in Figure 4. The curve relates
differences from MAlT to departures from normal of WAT and is based on the
assumpt ion that MAlT occurs when the WAT is normal (i.e. departure from
normal of WAT is zero). The curve in Figure 4 was developed by selecting a
number of points from the curve of Figure 3. For each point selected, the
0.825 m ice thickness base value (where departure from normal of WAT equals
zero) was subtracted from the regional average ice thickness coordinate, and
the resulting difference was plotted against the departure from normal of
WAT coordinate. A curved line was then drawn through these points. The use
of this procedure for determining ice thickness is discussed and illustrated
in the next section.
If adequate information had been available, the Prairie region
could have been divided into a number of subregions, and the method
described in this section could have been employed on a subregional basis.
The outcome of such a approach would have been either the confirmation of
the relationship shown in Figure 4 or the development of a unique relation
ship for each subregion. However, since the requisite amount of ice thick
ness data was not available, the relationship shown in Figure 4 is assumed
to apply to the entire Prairie region.
- 20 -
4
10""
-I
" ""--I
" ""-I
""""
-I
,.
""-I
\ \\\-I
\ \-I
\
-I
\+
I
'\-I
\\,\\\\\
\\
\\\\\ -\ \
NO
ICE
10
MAIT = Mean Annual Ice Thickness
from Figure 2
Figure 4. Determination of Ice Thickness at a Location Using WinterAir Temperature (Procedure 3) (PFRA 1990)
- 21 -
5. PROCEDURES TO DETERMINE ICE THICKNESS AND POTENTIAL APPLICATIONS
The results from this study may be used to determine the ice thickness
on a small water body in the Canadian Prairie region for a variety of hydro
logic, hydraulic and design assessments. The suggested procedures outlined
in the following three subsections may be used to determine the ice thick
ness for an average wi nter, an histori c winter or even a hypothet ica1
winter. Some potential applications of the procedures and their limitations
are illustrated by examples.
It is strongly recommended that the user become acquai nted with the
limitations of the ice thickness data bases (by reading the previous
sections), which provide the foundation for these procedures, before utiliz
ing any procedure(s). In general, the greatest confidence may be placed in
procedure 1, which pertains to an average winter. Of the remaining two pro
cedures, which are used to determine ice thicknesses for other than average
conditions, more confidence should be placed in procedure 2 than in proce
dure 3.
5.1 Procedure 1: Using MAlT to Estimate Ice Thicknessfor an Averaqe Year
Figure 2 can be used to determine the ice thickness that may be
expected on a small water body on the Canad ian Pra iries in an average
winter. After determining the appropriate MAlT (mean annual ice thickness)
to the nearest 0.05 m pertaining to the location of interest on the map, the
MAlT may be multiplied by the monthly percentages of ice formation presented
in Figure 2 to estimate the amount of ice development during each winter
month. This procedure provides a more realistic ice thickness value for use
in reservoir simulations, which assess available water supply for example,
than simply using a nominal value (such as 0.9 m) for all locations in the
Prairie region. As Figure 2 shows, 0.9 m is the appropriate MAlT for
Yorkton, Saskatchewan; however, only one-half that amount (0.45 m) is the
appropriate value for Lethbridge, Alberta.
5.2 Procedure 2: Using Recorded Ice Thickness Datafor 'Desiqn' PurDoses
The MAlT may be adequate for some uses, such as water supply anal
yses, but is not appropri ate for other app1icat ions, such as determi ning
- 22 -
extreme ice thickness values for 'design' purposes. In these cases, a
perusal of Figure 1 (map showing locations of ice measuring stations) and
Tables lA and 18 (location and size information) should be made to locate
one or preferably two water bodi es whi ch are deemed representative of the
site and location being investigated. Then, by referring to Tables 2 and 3,
a review of the historical data should provide the user with a range of ice
thicknesses that may be expected. In addition, a frequency analysis may be
performed using this data, or possibly an analogue year may be selected and
compared with historical winter air temperature (WAT).
For example, assume that a user is interested in determining a
'design' ice thickness value for a small reservoir in the Moose Jaw area of
Saskatchewan. From Figure 2, the MAlT appears to be about 0.75 m. A per
usal of storage and flooded area data contained in Table 18 reveals that
Caron Reservoir (map location 24) is similar to the reservoir under
consideration. A review of the data in Table 3 for Caron Reservoir indi
cates that ice thickness has ranged historically from 0.50 m in 1987 to
1.16 m in 1979. Realizing that the winter of 1979 was the fourth coldest of
the 92 years on record for the area, the user could determine an appropriate
ice thickness value for design purposes based on this recorded ice thickness
and air temperature information. In addition, a frequency analysis of the
recorded ice thickness values could be performed. Then the results from
these two methods could be compared and a 'design' value could be
determined. If monthly values are required, the monthly distribution per
centages in Figure 2 may be applied.
5.3 Procedure 3: Using Winter Air Temperature (WAT)to Determine Ice Thickness
If the recorded ice thickness data is deemed to be inappropriate, a
third procedure may be employed. This procedure, which is described in
Figure 4, simply uses the departure from normal of wi nter air temperature
(WAT) along with the MAlT to determine the ice thickness value. With the
appropriate 'departure from normal of WAT' (Step 2), the corresponding
'difference from MAlT' may be selected from the curve in Figure 4 (Step 3).
Applying this difference to the appropriate MAlT value from Figure 2 (Step
4) will yield a rough estimate of the ice thickness.
- 23 -
This procedure may be used to either estimate historical ice thick
nesses or predict a hypothetical ice thickness. For instance, the histor
ical approach may be used for the period prior to recorded ice thicknesses
to estimate a series of ice thickness values upon which, for example, a
frequency analysis could be performed. Alternatively, a hypothetical
'departure from normal of WAT' may be used to predict a 'design' ice
thickness value.
To aid in the application of this procedure, departures from normal
of WAT have been determined (Steps I and 2 of Figure 4) for various loca
tions throughout the Prairie region for a number of years. These values are
presented in Appendix A along with a location map for reference. The data
conta ined in Append ix A can be used in conjunct ion with Figures 2 and 4
(starting at Step 3) to estimate the historic ice thickness for any year or
a period of years at any location in the Prairie region.
In spite of its ease of use, this procedure should be employed with
caution. Since it is based on a regional relationship between average ice
thickness and departure from normal of winter air temperature (Figure 3),
the procedure may underestimate high extreme values or overestimate low
extreme values at a specific location. Utilizing the example from procedure
2 illustrates this point. The 'departure from normal of WAT' for 1979 at
Regina from Table 6 (or Table A-I in Appendix A) is -4.50C (Step 2).
Entering Figure 4 with this value yields a 'difference from MAlT' of about
+0.15 m (Step 3). Adding 0.15 m to the MAlT for Moose Jaw (Step 4) yields
an ice thickness of 0.90 m, underestimating the measured value (1.16 m for
map location 24 in Table 3) by 0.26 m. Following a similar procedure for
1987 (departure from normal of WAT of +4.50C) leads to an overestimate of
the actual value by 0.06 m. Depending upon the use, these tolerances mayor
may not be acceptable.
- 24 -
- 25 -
6. CONCLUSIONS
The following conclusions have resulted from the study of ice thickness
on small water bodies in the Canadian Prairie region.
1. Mean annual ice thickness (MAlT) increases in a northeasterlydirect ion from 0.4 m in southern Alberta to 1.0 m on the
northern fringes of the region. (See Figure 2.)
2. The average rate of ice format ion over the wi nter does not
vary significantly throughout the region and has the followingtemporal di stri but ion: November 30%, December 35%, January25% and February 10%.
3. Developing a direct relationship between ice thickness and thema in causat ive factors of air temperature and snow cover is
not practical due to the vagaries in the amount of snow cover.However, a simple graphical relationship has been devised to
determine the maximum ice thickness that may be expected or
may have occurred in any winter at any location using only the
departure from normal of winter air temperature and the mean
annual ice thickness. (See Figure 4.)
- 26 -
- 27 -
REFERENCES
[1] Woodvine, R.J., Report on 1979-80 DUQout Ice Thickness, HydrologyMemorandum #34 (includes 1976-80 data), Hydrology Division, PFRA,Regina, October, 1981.
[2] Edwards, D., PFRA DUQout Ice Thickness Study, Co-op Work Term Report
(Engineering), University of Regina, September, 1983.
[3] Fertuck, L.J., Spyker, J.W., Husband, W.H.W., Numerical Estimation ofIce Growth as a Function of Air Temperature. Wind Speed and Snow Cover,
The Engineering Journal, EIC, Vol. 14, No. B-9, December, 1971.
[4] Donchenko, R.V., Peculiarities of Ice Cover Formation on Reservoirs, The
Role of Snow and Ice in Hydrology, Proceedings of Banff Symposium,
September, 1972 (International Association of Hydrological SciencesPublication 107, Vol. 1).
[5] Williams, G.P., Freeze-up and Break-up of Fresh Water Lakes, Proceedingsof a Conference on Ice Pressures Against Structures, Quebec City,November, 1966 (Technical Paper No. 286, Division of Building Research,National Research Council, Ottawa, October, 1968).
[6] Mitchell, S.C., Analysis of Ice Accumulation on Farm DUQouts Around
Saskatoon, Kel sey Institute of Appl ied Arts and Sci ences, Saskatoon,Saskatchewan, May 8, 1978.
[7] Fisheri es and Envi ronment Canada, Hydrol OQica1 Atl as of Canada, Supplyand Services Canada, Ottawa, 1978.
[8] Energy, Mines and Resources Canada, National Atlas of Canada, Map Number25.1, Supply and Services Canada, Ottawa, 1983.
[9] Water Survey of Canada (Calgary District), Ice Thickness of SelectedStreams in Al berta. Saskatchewan and the Northwest Territori es, Inland
Waters Branch, Calgary, September, 1971.
- 28 -
A-I
APPENDIX A
DEPARTURES FROM NORMAL OF WAT AT VARIOUS LOCATIONS
A-2
0---------I//r/,
LEGEND:
A-3
--T-------------r-----------\
;;;:J t: \TCHEW~ I
////////(\
\
\I
• Location for which historical Departures from Normal of WAT (Winter Air Temperature) are provided
LOCATION
Brandon
CalgaryCold Lake
Coronation
DauphinEdmonton
LethbridgePeace River
Prince Albert
Regina
Swift Current
WinnipegYorkton
1951-80 NORMAL
WAT (oC)
-13.9-7.5
-13.4-11.3-13.7
-7.5-5.6
-13.9-15.4-12.5-9.7
-13.3-14.0
Figure A-i. Location Map and Normal WATs for Stations in Table A-l(PFRA 1990)
A-4
Table A-I
Departures from Normal of WAT* at Various Locations
YEAR"" PEACE RIVERCOLD LAKEEDMONTONCORONATIONCALGARYLETHBRIDGE
1912
-1.0 -2.4-.6-.21913
-1.3 -2.5-1.8-.71914
.1-2.6-2.7 .71915
--2.1-2.1-.81916
---.1--1.2-3.41917
---1.0 --.7-2.91918
- .1-.5-.81919
2.4-3.9-4.32.91920
-.8-.0-.6-2.01921
.8-2.5-2.31.71922
-.7--.8--1.6-3.21923
1.0 .8-.4-.21924
.0-4.4-3.73.11925
-2.7 --2.1 --1.6-1.81926
9.4-4.8-6.14.91927
-.7--.9--.3-.51928
-.9--.6--.9-2.11929
1.4-.9-.4-2.61930
-.1-1.4-.7-.51931
7.3-8.2-7.27.21932
-.3-.5.9.3.71933
-4.0 --.2-.5.6.41934
-1.9 -1.8-2.72.71935
-1.9 -.7-2.21.91936
-3.3 --5.3 --4.2-4.21937
1.5--.9--1.4-3.41938
.0--1.1 --.8-.81939
2.1-.4-.7.81940
5.4-3.3-2.72.61941
.9--.7-1.41.01942
5.7-3.9-3.22.81943
-.1--1.8 --1.0-1.21944
7.0-5.6-5.14.71945
2.7-2.01.32.01.01946
-1.2 --1.4-1.1.1.91947
-1.5 --1.3-1.6-.5-1.01948
3.3-2.1.7.81.11949
-2.4 --2.0-2.5-3.0-3.31950
-2.7 --2.5-3.4-2.9-3.11951
-4.3-2.1-2.1-2.6-1.6-.71952
-.7-2.2-1.1-1.5-1.6-1.11953
4.12.53.83.32.63.21954
2.0.53.22.91.82.71955
4.84.25.44.44.23.91956
-5.5-4.9-4.9-5.6-5.8-5.01957
2.01.02.0.4.1-.31958
4.43.63.83.13.43.81959
-1.5-.7.1-1.0-.4-.81960
3.22.53.22.01.61.61961
2.93.43.32.73.73.61962
-2.1-2.4-1.8-1.7-.5-1.21963
2.11.53.03.42.72.71964
2.73.12.53.62.92.81965
-4.2-3.8-3.7-2.4-2.8-3.11966
-3.0-2.7-3.4-2.9-2.6-2.01967
-2.5-1.2-1.7-.9-.5.51968
.41.3 .81.81.3.71969
-5.6-2.4-5.3-3.6-5.5-6.21970
2.32.41.52.02.72.61971
-3.2-3.0-4.0-2.8-1.9-1.51972
-4.6-3.4-3.7-3.2-3.7-3.61973
.0.7-.11.0.5.91974
-3.1-2.7-3.4-1.9-1.7-.81975
2.33.11.72.21.51.01976
1.52.31.52.52.62.71977
6.04.14.22.84.93.61978
-1.4-2.0-2.9-3.8-3.9-4.41979
-3.4-3.6-3.6-4.5-3.7-4.81980
3.61.91.1.81.11.11981
4.13.73.63.34.43.61982
-2.9-2.0-1.8-1.4-1.5-1.91983
1.21.41.71.13.53.11984
3.32.62.5.72.01.31985
-1.6-1.7-1.5-2.5-.4-1.11986
1.5.41.1.61.3-.41987
5.14.14.44.15.14.11988
5.03.34.42.54.23.5
Minimum
-5.6- 4.9-5.3-5.6-5.8-6.2Maximum9.44.28.24.47.27.2
* WAT is the winter air temperature and is the summation of the monthly mean temperatures for November to February inclusive,divided by four. The normal for each location was calculated using A.E.S. records for the 1951-80 period. (See Figure A-I.)
** Year in which the winter ends.
A-5
Table A-I (continued)
Departures from Normal of WAT* at Various Locations
YEAR" SWIFT CURRENTREGINAPRINCE ALBERTYORKTONDAUPHINBRANDONWINNIPEG
1912
-2.0-2.5-.6.1-1.1-1.9-1.31913
2.0.11.2.91.5.0.21914
2.31.83.4.91.91.12.21915
1.71.82.31.62.91.71.21916
-1.7-2.6.0-1.7.7-1.9-.61917
-4.1-2.9-.9-2.0.0-2.9-2.71918
.1-1.5.2-.7-.5-.4-1.01919
3.62.75.42.25.22.63.61920
-.8-2.1.9-2.7.3-2.7-2.41921
3.83.24.53.94.22.52.91922
-1.2-1.5.5-.3.8-.8-.31923
-.7-1.31.9-.71.2-.7.61924
3.83.35.13.64.63.23.91925
-.6-.7-.1-2.8-.3-1.5-1.11926
4.44.96.24.75.24.53.21927
.1-1.9.2-1.6.4-1.5-.21928
-.8-1.3.3-.51.5-1.8.51929
-.4-.11.2-.12.0-.6.91930
1.1.0.8.0.9-.2-.41931
7.87.28.46.77.46.25.11932
1.92.03.02.93.93.33.81933
.6-1.5-.5-.8-.1-.9-1.51934
4.01.92.51.9-.1.8-1.31935
2.1.42.31.32.51.71.51936
-4.5-6.6-3.8-5.4-4.6-6.0-5.41937
-2.8-3.0-.8-2.3-.5-1.3-1.61938
.1-.9.4-.3.4-.8 .11939
.31.91.02.0.3-1.3-1.01940
3.23.04.73.85.74.84.31941
1.2-.61.3.91.61.21.21942
3.43.35.33.93.24.23.01943
-1.2-1.7-1.7-1.2-.5-.5-1.81944
4.64.45.34.35.14.93.11945
1.01.11.82.03.62.82.41946
-.4-1.4-1.6-1.2-2.9-1.6-1.11947
-1.6-2.4-1.5-.9.4-.2-.11948
-.2-1.1-.4-.9.1-.6-1.11949
-3.2-2.9-1.4-1.6-.2-1.2-1.21950
-2.8-2.7-2.7-2.5-2.3-1.2-1.61951
-2.2-2.7-1.6-2.0-1.4-1.1-1.01952
-1.8-1.9-1.6-1.5-.8-.6.31953
3.13.13.23.12.53.23.11954
3.54.02.73.84.13.73.31955
3.43.63.93.32.92.82.81956
-4.1-3.7-3.7-3.1-3.0-3.0-1.71957
-.2.1.8-.5.0-.5.31958
3.53.62.82.62.32.73.11959
-.4-1.2-1.3-.8-.3-.6-1.71960
.9.82.01.31.21.31.71961
3.12.32.42.42.11.71.61962
-1.8-1.7-2.3-2.1-2.6-1.8-1.51963
2.12.0.91.8.61.7.61964
3.33.42.92.62.52.32.11965
-2.7-2.9-3.4-2.5-2.6-2.7-2.31966
-2.1-2.5-3.4-2.7-2.2-2.7-2.41967
-.7-1.3-1.8-2.2-2.5-2.4-2.71968
1.11.31.51.11.3.8.61969
-3.3-1.8-1.7-1.5-1.4-.6.11970
1.81.32.32.01.81.3.91971
-2.1-1.7-2.9-1.6-1.7-.6-1.31972
-3.2-2.8-3.6-2.9-2.0-1.6-2.21973
1.72.0.3.4.31.1-.21974
-1.6-2.8-2.9-2.8-3.3-2.7-2.51975
1.92.53.53.12.82.52.21976
2.82.62.42.72.41.71.91977
2.11.82.11.3.8.0-1.01978
-3.7-3.2-2.3-2.6-2.2-2.1-2.01979
-5.1-4.5-3.5-4.5-4.3-4.9-4.41980
1.31.61.21.21.31.0.91981
4.23.63.44.24.24.02.91982
-1.6-1.3-.2.2.5.6.41983
2.62.92.22.12.53.93.61984
1.02.53.53.03.33.41.91985
-1.6-1.5-1.9-1.7-1.5-1.3-1.01986
-.3.1.6-.2.2-1.0-1.11987
4.84.54.64.54.93.93.81988
3.03.53.13.32.93.22.6
Minimum
-5.1-6.6-3.8-5.4-4.6-6.0-5.4Maximum 7.87.28.46.77.46.25.1
• WAT is the winter air temperature and is the summation of the monthly mean temperatures for November to February inclusive,divided by four. The normal for each location was calculated using A.E.S. records for the 1951-80period. (See Figure A-I.)
•• Year in which the winter ends.