The US Forest Service, from whom I received permission to place
this Earthcache, has requested that I use the Camp Sherman Bridge
as the primary location (coordinates) and the Headwaters as the
additional waypoint. As with all projects on the Metolius, the
Springs are considered the most sensitive to any type of external
perturbation, including our recreational activities. Keep this in
mind when visiting the Headwaters.
I think the best description of the Metolius River is from a
paper describing the geology of the River but originally from
Oregon Geographic Names 'It flows from the north base of Black
Butte, full bodied, and icy cold, and after winding northward
through beautiful pine forests, swings around the north end of
Green Ridge through a canyon of great depth and majestic grandeur,
joining the Deschutes just north of the mouth of Crooked River'. A
spring is a location on the Earth's surface where groundwater
emerges in an amount large enough to form a stream (Manga 2001); in
the case of the Metolius a full blown river. The River is very
unique and belongs to a select group belonging to the National Wild
and Scenic River System, the designation protecting it from
development inperpituity. It is at the headwaters of another very
unique river system, the Deschutes River. The factor that sets this
system apart from other rivers is the fact that it has the most
stable flow, lacking large fluctuations in discharge, than any
river in the United States. This is due to it's exceedingly large
contribution from springs. Approximately 80% of the mean annual
flow of the Deschutes, near Biggs and confluence with the Columbia
River, is from groundwater (Gannet et al 2003).
The Metolius Springs originate as a group about 200 yards apart
immediately to the north of Black Butte at an almost constant flow
of 45,000 to 50,000 gallons per minute (Peterson and Groh 1972).
Another 600,000 gallons of water per minute discharges from
tributaries and springs in the 35 miles from the headwaters to the
Deschutes River.
Metolius River, Oregon at the Headwaters
The geology of the Metolius Springs tells an interesting story
as it is described by Peterson and Groh (1972). The geological
events that dominated the direction of flow of the Metolius River
began with the movement of faults in the region. This faulting
caused Green Ridge to rise along the valley of the Metolius forming
what is called a horst. The faulting also created a graben, an
elongated unit that formed the valley. The result was that the
ancestral river that once flowed west to east now flowed northward
The volcanism in the High Cascade and resultant formations of
basalt and andesite that built the Cascade chain of shield shaped
volcanoes also obstructed the western boundary of the Metolius
River graben. Other geologic forces that shaped the valley were
associated with glaciers that formed in the High Cascades and whose
moraines were carried eastward onto the floor of the Metolius River
valley.
Now move ahead a few milenia to a later period of faulting, this
time in the Metolius Spring area and along a fault within the
graben that occurred some 500,000 years ago (Peterson and Groh
1972). The result was the formation of Black Butte, a cinder cone
that rises above the valley floor about 3,000 feet. With Black
Butte blocking the northward flowing Metolius River and effectively
damming the drainage, we essentially have the landscape we see
today; a northern part where the Metolius River flows today and a
southern part that contains Black Butte Swamp and Glaze Meadow and
the eastward flowing Indian Ford Creek.
The Origin of the Water at Metolius
Springs
In the 1972 paper that I have cited so far, speculate that since
Black Butte blocked the northward flow of the Metolius River, it
forced the river to originate as groundwater and discharge at the
springs we see at the headwater. This paper further states that the
wetland/marsh area on the south side of Black Butte now acted as a
'sump or container' for water that flowed to the area, on the
surface or under ground, from the upstream watershed. The authors
noted that this area was 300 feet higher than the springs on the
north side and likely acted as a standpipe that keep a constant
hydraulic head on the water from the springs, thus maintaining
their constant flow.
More recent studies, using techniques/methods that were not
available 40 years ago, have refined the theories put forth in
earlier investigations (Gannet et al, 2003). Without going into a
lot of detail their studies used regional geology, the distribution
and rate of groundwater recharge and discharge, water temperature,
and isotopic tracers. Isotopes are atoms with the same number of
protons, but differing number of neutrons; ie, different forms of
the same element.
Some of the methods they used to come up with their results
follow:
Oxygen Isotopes as a tracer:
The use of oxygen isotopes in hydrogeological studies, and
specifically at the Metolius Springs, is one way they solved one of
the problems. The ratio of oxygen-16 (the isotope of oxygen 16) to
oxygen-18 in water can aid in the determination of the source of
the water at the recharge area. Concentrations of oxygen-18 tend to
be lower when the air is cooler, for instance during snowfall, the
isotope is heavier and condenses more readily and evaporates less
freely than oxygen-16. Winter ice can be 5-20 per mil lower in
oxygen-18 than summer precipitation. The measurement of these
isotopes at Metolius Springs water strongly suggested the majority
of the water fell as snow at colder elevations of the Cascade
Mountains within the 400 square kilometer watershed(around 50 km
away). This goes along well with the fact that this area has the
highest precipitation, high soil permeability and near-surface
rocks in the watershed.
Heat as a tracer:
Another tracer used in groundwater studies is the use of heat or
the temperature of the water (Anderson 2005). It was known very
early (late 1800's) that deep circulation of groundwater could
account for hot springs. This area beneath the ground surface that
is thought to cause an increase in groundwater temperature is
called the geothermal zone. This zone varies in depth, but
generally occurs below a depth of 10 meters and is usually
represented by an increase of 1 degree centigrade per 20 to 40
meters of depth. Using this information and other data the depth of
the recharge area can be estimated. In the case of Metolius Springs
it was determined that the temperature was about 4 degrees
centigrade above estimated recharge temperature. The conclusion the
researchers came to was that the water discharging at Metolius
Springs followed a relatively deep flow path, in the order of a few
hundred meters. This goes along with the fact that the Upper
Metolius River is more to the liking of the trout than the colder
downstream water that receive water from colder sources.
Use of Tritium to estimate age:
Tritium is a radioactive isotope of hydrogen and has a half-life of
12.5 years. Half-life is the time taken for the radioactivity of a
specified isotope to fall to half it's original value. Tritium is
naturally produced in the environment in very small quantities. As
a result of atmospheric testing of nuclear weapons tritium
concentrations increased to levels significantly higher than
background and because it is added to the environment as water it
enters the hydrological cycle and eventually becomes concentrated
in water at levels detectable in groundwater. Further, because
tritium decays to helium-3, and by knowing the decay rate, an even
more accurate estimate of age can be made. Using this method and
others the researchers estimated the water discharged at Metolius
Springs to be between a decade to a few hundred years.
In summary, it is believed that the water that discharges at the
headwaters of the Metolius River are no older than a couple hundred
years, follow a relatively deep flowpath from the recharge area,
and originate primarily in the higher elevations of the Cascade
Mountains. So, these huge springs tell an interesting story not
only for the river they create, but also for the peculiar Deschutes
to which they drain.
-To Log This Earthcache, answer the following questions and
email them to the developer of the site:
Question 1) There is a large sign near the beginning of the
trail that leads to the Headwaters of the Metolius. Two theories
are mentioned on the sign regarding the origin of the water in the
springs. Which one is correct and give a brief description why.
Answer either question 2 or 3 (or both for extra credit):
Question 2) An olympic size swimming pool is 164 feet long, by 82
feet wide and 6.5 feet deep. If the Metolius spring water was
flowing 50,000 gallons/min how long would it take to fill the
pool?
Question 3) Take the temperature of the Metolius River near the
Camp Sherman Bridge, being careful not to damage the streamside
vegetation. Compare the temperature you find here with that at the
springs (48 F). Give 3 potential reasons for the difference you
observed.
This logging requirement is optional: Take a picture of yourself
or the people in your group and your GPS unit with the viewing
platform at the headwaters in the background and include it in your
log. If nothing else this would assure me that you were at the
site.
References
Anderson, M.P. 2005. Heat as a Ground Water Tracer. Ground
Water. Vol 43, No 6. pp951-968. Review Paper
Gannet, M.V., M. Manga, and K.E. Lite. 2003. Groundwater
Hydrology of the Upper Deschutes Basin and its Influence on
Streamflow, in: A Peculiar River, Geology, Geomorphology, and
Hydrology of the Deschutes River, Oregon. Editors: G. Grant and
J.E. O'Connor, American Geophysical Union
Motzer, E.M. 2005. Age Dating Groundwater. Online Report. 2200
Powell St, Suite 225, Emeryville, CA 94608, pp4
Peterson N.V. And E.A. Groh. 1972. Geology and Origin of the
Metolius Springs, Jefferson County, Oregon. The Ore Bin, Vol 34, No
3, Oregon Department of Geology and Mineral Industries, Portland,
Oregon 97201
Basic Visitor Use and Public Safety Information for
Public Lands in Oregon
All visitors need to plan ahead and prepare for outings in Oregon's
public lands by:
- Knowing the regulations and special concerns for the area you
are planning to visit. Such as obeying the laws that prohibit the
collection or destruction of artifacts.
- Carrying a map and GPS unit and/or compass. Maps are available
for purchase at all BLM and US Forest Service Offices
- Staying on existing roads and trails.
- Planning for extreme weather, hazards, and emergencies.
- Carrying a full size spare tire, extra food and water, and warm
clothes.
- Being aware that cell phones DO NOT usually work in the rural
areas away from major highways.
- Leaving your travel plans with a responsible party, including
the date and time of your return.
- Linking to 'Tread Lightly and leave No Trace' websites (www.treadlightly.org or
www.int.org).
- Remember the geocaching motto of 'Cache in Trash Out'.
Congratulations to elkjim on the first to find