Glacier Water Properties

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NENANARIVERPROJECT
Glacier Water Properties
Prepared by Kim Morris and Martin Jeffries,
Geophysical Institute, University of Alaska
Fairbanks (UAF)
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The amount of water on Earth does not
change. Its place in the water cycle and its
phase do change. Water is in storage when it is
frozen. This can be either short- (snow and
annual ice) or long- (glaciers) term storage.
http//www.usgcrp.gov/usgcrp/images/ocp2003/ocpfy2
003-fig5-1.htm
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Glaciers are perennial accumulations of ice,
snow, sediment, rock and water. They respond to
changes in temperature, snowfall and geologic
forces.
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Hydrology is the science dealing with the
properties, distribution, and circulation of
water the seasonal patterns of a rivers
flow. These hydrographs of the Nenana River near
Healy, AK show the variability of the water flow
within a single year and between years.
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Sources of Water for Rivers
Precipitation events (rainfall) Relatively short
(hours to days), low volume water pulse.
Snow melt Mid-term (days to weeks), high volume
pulse of water.
Glacier melt Long term (months), mid-volume
pulse of water.
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An Example of a Glacier-fed River Hydrology
Beginning in spring the accumulated snow melts,
feeding alpine streams. By late summer, much of
the seasonal snow cover has disappeared from the
landscape. The glaciers continue to melt and this
water supplies the river during the driest part
of the northwest summer. This is particularly
important for summer during drought years.
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Diurnal Glacial Water Flow
Meltwater from Vadret da Morteratsch, Grisons,
Switzerland. The upper picture was taken on a
July morning. The lower picture was taken in the
afternoon after ablation and subsequent runoff
had both increased considerably. Photo J.
Alean. http//www.swisseduc.ch/glaciers/glossary/g
lacier-milk-en.html
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Erosion is the displacement of solids (soil, mud,
rock and other particles) by wind, water, or ice
in downward or down-slope movement in response to
gravity. Weathering is the breaking down of
rock and particles through processes where no
movement is involved, although the two processes
may be concurrent. The rate of erosion depends
on many factors including the amount and
intensity of precipitation, the texture of the
soil, the gradient of the slope and ground cover
(vegetation, bare ground, land use).
http//extension.missouri.edu/explore/agguides/age
ngin/g01509.htm
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Rocks and sediments are added to glaciers through
various processes. Glaciers erode the terrain
principally through two methods abrasion and
plucking.
Plucking is a two part process. When glaciers
flow over the fractured bedrock surface,
subglacial water penetrates the fractures. When
this water freezes it expands and breaks the
rock. The ice expansion also acts as a lever that
loosens the rock by lifting it. Consequently,
sediments of all sizes become part of the
glacier's load.
Abrasion occurs when the ice and the load of rock
fragments slide over the bedrock and function as
sandpaper that smoothes and polishes the surface
situated below. This pulverized rock is called
rock flour (0.002 and 0.00625 mm).
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Sediment and debris can also accumulate on a
glaciers surface due to avalanches, rock
falls and wind deposition.
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During storms, soil is washed from the stream
banks into the stream. The amount that washes
into a stream depends on the type of land in the
river's watershed and the vegetation surrounding
the river. http//ga.water.usgs.gov/edu/characteri
stics.htmlSediment
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Splash erosion Raindrops splash soil particles
short distances. These particles are then much
more vulnerable to erosion by water flowing over
the surface.
Sheet erosion When rain falls faster than the
soil can absorb it, water begins to collect and
flow over the ground surface. Sheet erosion
begins when this surface water begins to carry
along particles that were detached by raindrops.
Rill and gully erosion A rill is a narrow and
shallow incision into soil resulting from erosion
by overland flow that has been focused into a
thin thread by soil surface roughness. As the
rill increases in size it becomes a gully, a
highly erosive water structure. These usually
occur due to a high water flow.
Stream and channel erosion This is mostly caused
by downward scour due to flow shear stress. Side
wall sluffing can also occur during widening of
the channel caused by large flows.
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For a fluid to begin transporting sediment, the
bed shear stress exerted by the fluid must exceed
the critical shear stress of the bed.
Rivers pick up and carry material as they flow
downstream. A river may transport material in
four different ways
Traction - large boulders and rocks are rolled
along the river bed Saltation - small pebbles and
stones are bounced along the river bed Suspension
- fine light material is carried along in the
water Solution - minerals are dissolved in the
water
Rivers need energy to transport material, and
levels of energy change as the river moves from
source to mouth.
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When energy levels are very high, large rocks and
boulders can be transported. Energy levels are
usually higher near a river's source, when its
course is steep and its valley narrow. Energy
levels rise even higher in times of flood.? When
energy levels are low, only small particles can
be transported (if any). Energy levels are lowest
when the river enters the final stages of its
journey (at the mouth).? When a river loses
energy it deposits some of the material it has
been carrying.
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Water is called the universal solvent. This
means it has the ability to dissolve other
substances. There is hardly a substance known
which has not been identified in solution in the
earth's waters. Electrical conductivity is the
ability of a material to carry electrical
current. In water, it is generally used as a
measure of the mineral or other ionic
concentration. Conductivity is a measure of the
purity of water or the concentration of ionized
chemicals in water. However, conductivity
responds to all ionic content and cannot
distinguish particular conductive materials in
the presence of others. Only ionizable materials
will contribute to conductivity materials such
as sugars or oils are not conductive.
High Purity Water Conductivity vs Temperature
Conductivity vs Concentrations at 25C
Conductivity is affected by temperature since
water becomes less viscous and ions can move more
easily at higher temperatures. Conventionally,
conductivity measurements are referenced to 25C
though occasionally a 20C.
http//www.wileywater.com/Contributor/Sample_2.htm
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Turbidity is a unit of measurement quantifying
the degree to which light traveling through a
water column is scattered by the suspended
particles. The scattering of light increases
with a greater suspended load. The more total
suspended solids in the water, the murkier it
seems and the higher the turbidity.
There are various parameters influencing the
cloudiness of water. Some of these
are Phytoplankton Sediments from erosion
Re-suspended sediments from the bottom
(frequently stir up by bottom dwellers) Waste
discharge Algal growth Urban runoff
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NENANARIVERPROJECT
River Water Quality - Field Sampling, I
Measuring turbidity provides a cheap estimate of
the total suspended solids or sediments (TSS)
concentration (in milligrams dry weight/L).

• Field Procedure
• 1) Label the sampling bottle lids before a water
  sample is taken. Use masking tape and marker pen
  (Sharpie) and include the location (Anderson,
  Healy, DEC, Cantwell) and date (expressed as
  YY/MM/DD, e.g., 07/10/06). A sample number, e.g.,
  1, should also be included, even if only one
  sample is taken.
• 2) Obtain a water sample from a free-flowing part
  of the river. Rinse the bottle in the river water
  before collecting a water sample. Fill the 500 mL
  sampling bottle to nearly full. If sampling is to
  be done by walking part way into the water USE
  EXTREME CAUTION. Students should never enter the
  water unsupervised by an adult.
• 3) Secure the lid tightly to the bottle once the
  sample is obtained.
• 4) Return water samples to the classroom for
  analysis.

Prepared by Kim Morris and Martin Jeffries,
Geophysical Institute, University of Alaska
Fairbanks
April, 2008
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Laboratory Procedure 1) Set-up the
Conductivity/TDS Meter as per the instructions in
the manual. 2) Shake the 500 ml sampling
bottle. 3) Immerse the head of the
Conductivity/TDS Probe into the water up to the
immersion level. During the measurement the
lower LCD display will show the temperature of
the solution. 4) Record the water temperature
value. 5) Record the conductivity values (mS). 6)
Record the TDS (P) Note From time to time it
will be necessary to re-calibrate the
conductivity meter.
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Laboratory Procedure - Part I 1) Shake the 500
mL sampling bottle to make sure that the sediment
is evenly distributed throughout the water
(depending on how long the sample has been in the
bottle sediment may have begun to settle on the
bottom of the bottle). 2) Pour the water into
one of the graduated cylinders until the water
level reaches the 250 mL mark. 3) Fold a paper
filter and place it in the filter funnel. 4)
Place the filter funnel and paper into the second
250 ml graduated cylinder. 5) Pour ALL of the
water in the first 250 mL cylinder into the
second 250 mL cylinder through the funnel and
paper. This may take a few minutes, and it may be
necessary to support the funnel so that the
cylinder does not fall over. 5) Remove the paper
filter (with sediment) from the filter funnel,
and set aside. 6) Dry the filter paper and
sample in a location where it will not be
disturbed. (This can be done in the oven at 200F
- do not unfold the filter.)
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• Laboratory Procedure - Part II
• Once the sediment sample is completely dry
• 1) Set up the digital balance on a level surface.
  Calibrate if
• necessary. Make sure that the scale is set
  to grams.
• Do not use in a draughty place.
• 2) Place a dry, unused paper filter on the
  balance,
• record its mass, then tare the scale.
• 3) Weigh the dried sediment sample filter
• and sample and record its mass.

Calculate TSS TSS(mg/L) A/B where A Dried
weight of the sediment?(in milligrams) B Volume
of water filtered?(in Liters) Note 1 g 1000
mg and 1 liter 1000 milliliters
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