The author has identified the following significant results. The snow melt for a small watershed (5130 sq km) in Central Alaska was successfully monitored with ERTS-1 imagery. Aerial photography was used as supporting data for periods without satellite coverage. Comparison both with actual measurements and with a computer model showed good agreement

Carlson, R. F.

Kane, D. L.

Wendler, G.

English

NASA Technical Reports Server

E 7.4- 1 0. 1 5 1.
"Made avilable under NASA 9onMnor, /in the interest of early and ih -.
seinination of Earth Resources Survey
Program information and wiiloat ',aility
for any use made thereof." BREAK-UP CHARACTERISTICS OF THE
CHENA RIVER WATERSHED, CENTRAL ALASKA
(FI- 19151) BREAK=UP CHARACTERISTICS OF N7-I~6 i19N
THE CH7NA RIVER WATERSHED, CENTRAL ALASKA
Interim Scientific Report, Nov 1973
(Alaska Univ , Fairbanks ) 12 p HC Unclas
$3, 0 Se CSCL 08H G3/13 C0 151
Gerd Wendler, R. CarinLand D. Kane
Institute of Water Resources
University of Alaska
Fairbanks, Alaska 99701
December 1, 1973
Interim Scientific Report
NASA Contract NAS5-21833
ERTS Project 110-5
Original photography MaX h1] w
EROS Data Center
10th and Dakota AvenuqSioux Fls, So ~7198
Prepared for
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Goddard Space Flight Center
Greenbelt, Maryland 20771
https://ntrs.nasa.gov/search.jsp?R=19740005906 2020-03-23T12:03:45+00:00Z
TECHNICAL REPORT STANDARD TITLE PAGE
1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle 3.Report Date
1 December 1973
Break-up Characteristics of the Chena River Perming Orgation Code
Watershed, Central Alaska
7. Author(s) 8. Performing Organization Report No.
G. Wendler, R. Carlson, and D. Kane
9.. Performing Organization Name and Address 10. Work Unit No.
Institute of Water ResourcesUniversity of Alaska 11. Contract or Grant No.
University of Alaska NAS5-21833
Fairbanks, Alaska 99701 13. Type of Report and Period Covered
12. Sponsoring Agency Name and Address Interim Scientific
National Aeronautics & Space Administration Report
Goddard Space Flight Center 14. Sponsoring Agncy Code
Greenbelt, Maryland 20771
Tpchnical I Otnr: Mr- kward Crump, Code1-
15. Supplementary Notes
ERTS-1 Project No. 110-5
Robert F. Carlson /UN 596
16. Abstract
2
The snow melt for a small watershed (5130 km ) in Central
Alaska was successfully monitored with ERTS imagery.. Aerial,
photography was used as supporting data for periods without
satellite coverage. Comparison both with actual measurements
and with a computer model showed good agreement.
17. Key Words (S, lected by Author(s)) 18. Distribution Statement
Snow melt
Satellite imagery
19. Security Cloassif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price*
Unclassified Unclassified " . 3,0
tI.)
I :
BREAK-UP CHARACTERISTICS OF THE CHENA RIVER WATERSHED, CENTRAL ALASKA
Gerd Wendler Robert Carlson and Doug Kane
Geophysical Institute Institute of Marine Science
University of Alaska University of Alaska
Fairbanks, Alaska 99701 Fairbanks, Alaska 99701
November 1973
Interim Scientific Report, Contract NAS5-21833
Prepared for
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Goddard Space Flight Center
Greenbelt, Maryland 20771
I1
BREAK-UP CIIARACTERISTICS OF THE CIIENA RIVER WATERSHED, CENTAL ALASI
Gerd endler
Robert Carlson
Doug Kane
University of Alaska
ABSTRACT
The snow melt for a small watershed (5130 km2 ) in Central Alaska
was successfully monitored with ERTS imagery. Aerial photography was
used as Supporting data for periods without satellite coverage. Com-
parison both with actual measurements and with a computer model
showed good agreement.
INTRODUCTION
Of the many water resource problems faced by the State of Alaska,
floods are the most widespread; the damage is large in small pop-
ulation centers, and statewide the floods cause annually a great
amount of damage. The art of the prediction of floods, either on a
day-to-day operational basis or as a part of a long term study, has
advanced to a rather high state of knowledge. There are available
a wide'number of computer oriented, graphical, analytical, and
empirical methods which are used successfully with experience.
However, regardless of the degree of knowledge, the engineer or
forecaster is limited by the completeness of the measured input. In
the case of rainfall, the provision of adequate input data, although
not always easy, is quite straightforward. Snowmelt, on the other
hand, provides an input, to the runoff system which is, in itself, the
output of a rather complex process as the snowmelt depends on a
variety of factors; some of a permanent physiographic nature and
others of a more transient environmental nature, (Wendler, 1967).
Because of the complexity of the process, snowmelt measurement on a
pointwise basis and extrapolation of point measurements to even a
relatively small basin become very difficult. This is especially
true of the Chena River in particular and Alaska in general, where
precipitation gauge densities are extremely small (Searby, 1968).
Because of Alaska's rather severe cold climate the surface
hydrology in most areas of the state is only active-during four to
six months. As a result, the spring snow and ice break-up dominate
the cycle and the resulting snowmelt runoff contributes most of the
stream flow and causes many of the floods.
Major floods have ,occurred in the Fairbanks area in 1930, 1937,
1948, 1960, and 1967.
To overcome the shortcomings of conventional point measurements
(Snow Surveys, 1973), satellite imagery has been applied (Barnes and
Bowley, 196Sa,b, 1969; McClaim and Baker, 1969). However, up till
now the resolution of the satellite imagery was insufficient for
small watersheds. The launch of ERTS 1, having a resolution of 100m
together with supporting aerial photography has made it possible to
monitor the snow melt for much smaller basins such as that of the
Chena River (5130 km2 ).
5.9-1
DESCRIPTION OF THE CHENA RIVER BASIN
The Chena River Basin lies in the interior of Alaska, about 100
miles (160 kn) south of the Arctic Circle. The climate is continen-
tal sub-polar, with cold winters and relatively warm summers; the
precipitation is relatively low with a long-term annual mean of
11.3 inches (287 mam) (Searby, 1968). The elevation of the basin
ranges from very small areas in excess of 5000 ft (1525 m) to 440 ft
(134 m), at the confluence of the Chena with the Tanana River (Figure
1). The area is hilly, mostly lying below 2500 ft (760 m) and less
Figure 1. Topographic map with Chena River Basin Boundary outlined.
than 20% has an elevation above this level (Figure 2). The basin
has a size of. 1980 sq. miles. (5130 kin2 ). Major tributaries of the
Chena are the Little Chena River, West, East, and South ForkS and
Munson Creek. The precipitation increases with altitude, as can
be seen from the snow course data (Snow Survey, 1970).
METEOROLOGICAL CONDITIONS DURING BREAK-UP
The climatological data for Fairbanks, the lowest point in the
basin, are shown in Figure 3 (NOAA, 1973). On 28 March 1973 the
average daily temperature rose above the freezing point for the first
time in the season. lHowever, positive temperatures of any longer
duration were observed only after 6 April 1973. During 16-27 April
a cold spell occurred, with temperatures atround the freezing point.
After this period the temperature remained above freezing, and most
of the melting occurred. The dew point remained below the satura-
tion point for water until 7 May 1973, thus indicating that evap-
5.9-2
CIENA RIVER DRAINAGE BASIN
Feet Meters
5000- 1500
1000
3000
-500
1000
0 20 40 60 80 100
Cumulative Percent
Figure 2. Elevation distribution for the Chena River Basin.
* 
,
Lim
Figure 3. Climatologkcal conditions at Fairbanks (temperature, dew
point, wind Speed, cloud cover and precipitation) during
break-up (20 March to 31 May 1973) on the Chena River.
5.9-3
oration occurred, which is typical for the early part of the break-up
(Wendler, 1967). Thereafter, values around the saturation value for
melting snow were observed, showing that the condensation balanced
the evaporation. The wind speeds were relatively low (around 3 m
sec-1), which is typical for the interior of Alaska (Searby, 1968).
The cloudiness with a mean of 6/10 was average for the spring period.
No appreciable precipitation was observed during the break-up until
the latter part of May 1973.
SNOW MELT MODEL
Because of the difficulties of comparing satellite imagery with
spot mneasureme nts of the snow cover, a snow melt model which had
been developed by Carlson and Norton (1973) was used. This model is
based on calculation of energy fluxes at the surface and within the
snowpack. Cloudiness is used to estimate the radiative fluxes,
temperature and wind speed to estimate the sensible heat flux, and
dew point and wind speed to calculate the latent heat flux. Also
the process of melting at the surface and.refreezing at deeper layers
in the snow pack is considered. This model is tested against actual
measurements for the spring of 1973 (Figure 4). It can be seen that
o oo
ISM "I . .
0
on the Chena Basin, 1973.
the agreement is very good, especially if one considers the varia-
bility of the saow tack for point measurements. Hence, data obtained
from this model inight be compared directly with the snow cover extent
of the basin.
ERTS IMIAGERY AND AERIAL PHOTOGRAPHY
Cloudfree ERTS imasery during break-up was obtained on 12 and 30
April and 2 May 1973. Later in Play, it was cloudy at the time the
Satellite passed. Therefore, two aerial flights (height about 12000
5.9-4
ft (3660 m), stereo photography) were carried out on 11 Nay and 20 May
over part of the basin. Altitude lines were transferred from ropo-
graphic maps onto the photographs with a zoom transfer scope (Sausch
and Lomb), and areas were obtained with a planimeter. Patches of
snow were found down to the lowest lying areas on north slopes on
11 Ma-ly, while no snow was found on a slope with southerly exposure
below 1250 ft (380 m) (Figure 5). The percentage of snow-covered area
moo
*OOO / wro -°
0000 id h
- 40.o
$toe$.-oo
- 0 2 so
Figure 5. The amount of snow cover in percent as function of
altitude for northerly and southerly exposure on two
occasions during break-up.
increased with height. A similar percentage cover was attained at
heights some 750 ft (230 m).higher on the south slopes than on the
north slopes on 11 May and 400 ft higher (120 m) on 20 May. The
decrease in snow cover for the greatest-altitude range on 11 M-ay
1973 is at first sight astonishing. However, when the photographs
are analysed, it can be seen, that it is real. The area photographed
did not exceed.2500 ft (780 ni), and hence this area represented the
top of the hills. As no forest is present on these hill tops and
they are thus more freely exposed to the wind, some of the areas were
snow free even before the melting started. An example is given in
Figure 6. Further, it can be seen from Figure 5, that the snow line
ascended about 2000 ft (610 m) in the 9 days from 11 to 20 May 1973.
This rapid ascent of the snow line was caused by the high temperature
(see Figure 3) during this period.
The Chena Basin was outlined on the ERTS imagery for the three
dates, at which pictures were obtained. It was found, that channel
5 (0.5 - 0.6 pm) was the best sui.ted to distinguish the snow cover
from snow free areas. An example is given in Figure 7, showing the
Chensa Basi* t to times during break-up.. It can be seen, that at
the later data, most of the snow in the lower lying areas (compare
with Figure 1) has melted. A VP-$ analyser was used to obtain quant-
itative results. This instrument displays a grey scale in color,
which makes it easier for the eye to distinguish different levets.
Also, an automatic built in planimeter makes it possible to rapidly
measure areas with different snow coverage. Such a task using a hand
planimeter is a very time consuming task. Using this instrument the
5.9-5
S ... .
- Haystach [A t.
Figure 6. Aerial photography of an area north of Fairbanks. (Note
that the southerly and westerly slopes of Haystack
Mountain (2525 ft or 770 m) are snow free, but at altitudes
below 2000 ft (610 m) snow is observed.
following-values were obtained:
Percent of Snow Cover Determined from ERTS Imagery
Chena River Basin
(1980 sq. mi.)
<50% >50%
snowfree broken or
or snow patches continuous snow
12 April 1973 .18 82 %
30 April 1973 28 72 %
2 May 1973 46 54 %
COMPARISON OF THE STAGE OF BREAK-UP
The areal percentage of the basin, which was snow: free, could be
obtained from both the ERTS imagery and aerial photography. These
values are compared with data from the snow melt model, from which
the melt could be calculated for various altitude intervals, and by
knowing the altitude distribution (Figure 2), the percentage of the
area, which was snow free, could be calculated. One can see (Figure
8), that the agreement is very good. To appreciate such an agreement,
one should notice, that a snow melt model never reflects nature in
every detail, and further, that measurements of the snow cover by
satellite or aircraft are hindered by.vegetation and.the shadowing
effects of mountains.
In addition, the amount of discharge, measured in Fairbanks, is
shown in Figure 8. This curve is not totally comparable with the
other ones,. as there is a lag between the time of melting, and the
time at which this water arrives in Fairbanks. A lag time of about
a week was found, which is probably somewhat longer than might be
expected.
5.9-6
CHENA RIVER DRAINAGE BASIN
.14 APRIL 1973
!A
2 MAY 1973
0 100
Kilometers
Figure 7. Imagery of the Chena River Basin as seen from ERTS.
7a. 14 April 1973 (Note that most of the area is snow covered.)
7b. 2 May 1973 (Note that the lower lying areas are snow free.)
5.9-7
100
- ERTS ) or Aerial Photography+
--- Snow Melt Model
80 - -'- Runoff Measurements
60 .
40 I
20
0
20 I 10 20 30 10 20 30
March April May
Figure 8. Variation in snow free area with time for the Chena Basin
during the break-up of 1973. Values obtained from ERTS
and aerial photography, the snow melt model, and direct
run off measurements.
CONCLUSION
It has been shown that ERTS imagery can successfully be used to
monitor the snow melt in a relatively small watershed. Comparison
with actual measurements as well as with a computer model showed good
agreement. These same techniques can therefore be used to study the
snow melt behavior in watersheds where little or no hydrological or
climatological data are presently being collected. Such information
will make it possible to draw preliminary conclusions about the most
dynamic portion of the hydrologic cycle in the Arctic, namely the
spring break-up.
ACKNOWLEDGEMENT
This work was supported by NASA, Grant NAS5-21833. We are
thankful to J. MCDougall who directed the computer model and to
K. Ahlnas, J. Leap and T. 'McClung, who helped in reducing the data.
5.9-8
REFERENCES
Barnes, J.C., and C.J. Bowley, 1968a. Snow Cover Distribution as
Mapped from Satellite Photography. Water Resources Research,
4:2, p. 257.
Barnes, J.C., and C.J. Bowley, 1968b. Operational Guide for Mapping
Snow Cover from Satellite Photography. ESSA Contract No. E-162-
67(N), Allied Research Associates, Concrod Mass., May, ll6pp.
Barnes, J.C., and C.J. Bowley, 1969. Satellite Surveillance of
Mountain Snow in the Western United States. Final Report,
ESSA Contract No. E-196-68, Allied Research Associates, Concord
Mass., June, 78pp.
Carlson, R., and Norton, W., 1973. Modeling Snowmelt Runoff in an
Arctic Coastal Plain. in press.
McClain, E.P., and D.R. Baker, 1969. Experimental Large-Scale Snow
and Ice Mlapping with Satellite Composite Minimum Brightness.
Charts. ESSA Technical Memorandum NESCTM-12, Dept. of Commerce,
Washington D.C., 16pp.
NOAA, 1973. Fairbanks Climatological Data. U.S. Department of
Commerce, March - May.
Searby, H.W., 1968. Climates of the States, Alaska. ESSA, Climat-
ology of the United States, No. 60-49, U.S. Weather Bureau, 23pp.
Snow Survey, 1970. Summary of Snow Survey Measurements for Alaska.
1951-1970, Federal-State-Private, Cooperative Snow Surveys,
U.S. Department of Agriculture, Soil Conservation Service, and
Alaska Soil Conservation District, p. 1-101.
Snow Survey, 1973. Cooperative Snow Surveys for Alaska. Federal-
State-Private, U.S. Department of Agriculture, Soil Conservation
Service, and Alaska Soil Conservation District, Feb. - May.
Wendler, G., 1967. The Heat Balance at the Snow Surface during the
Melting Period (March-April 1966) near Fairbanks, Alaska.
Gerlands Beitrhge zur Geophysik, 76, Heft. 6, p. 453-460.
5.9-9


Break-up characteristics of the Chena River watershed, central Alaska

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