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Background Information
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Wikipedia defines a stream as a body of water with a current,
confined within a bed and stream banks. Depending on its locale or
certain characteristics, a stream may be referred to as a branch,
brook, beck, burn, creek, crick, gill, kill, lick, rill, river,
syke, bayou, rivulet, streamage, wash, run or runnel. Obviously, it
could also be called a stream, which is the term that will be used
here. Streams are very important for a variety of reasons. They are
conduits for surface water as an integral part of the overall water
cycle. They provide critical corridors for fish and wildlife
migration, as well as homes for many varieties of fish and
amphibians. Many streams provide a habitat for a wide range of
plants and animals, and often have great biodiversity in their
vicinity. The study of streams is referred to as surface
hydrology.
Northwest Pennsylvania has an abundance of streams. These streams
range from medium sized rivers (such as the Allegheny) down to very
small streams. To distinguish between the various types of streams
there have been a variety of classification systems developed over
the years. These classifications are based on various
characteristics of the stream, and are used to help understand the
similarities and the differences between them. One of the more
popular classification systems was developed in 1952 by Strahler
(Strahler Stream Order Classification Method). This method
classifies streams according to the number of tributaries upstream.
A headwater stream (one with no tributaries) is a first order
stream. Once a tributary enters a first order stream it becomes a
second order stream, and so on. (Interesting side note: the largest
order stream in the U.S. is the Mississippi River, which is a tenth
order; the largest order stream in the world is the Amazon River,
which is order twelve). Figure 1 shows a schematic of this
classification system.
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Figure 1 - Strahler Stream Order Classification
Method
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Another classification system is based on the flow
characteristics of the stream. There are three types: perennial,
intermittent and ephemeral. Perennial streams generally flow
more than 90% of the time. The stream bed for a perennial stream is
below the water table for most, if not all of the year. The primary
source of water is groundwater, but it also carries stormwater.
Intermittent streams flow only during wet periods (usually
30 – 90% of the time), and they flow in well-defined
channels. The stream bed for Intermittent streams is below the
water table for wet parts of the year, but above the water table
during much of the year. It is possible for the groundwater to drop
below the main bed of the stream leaving isolated sections of the
bed to remain below the groundwater level. This results in small
pools during much of the year without any flowing water. The flow
in the stream is often greatly enhanced by stormwater.
Ephemeral streams only flow during storms, and may or may
not have well-defined channels. The stream bed for an ephemeral
stream is always above the water table, so the primary source of
water is storm runoff.
Perennial streams are the most common type of stream that you might
notice. Figure 2 shows a typical, slow moving perennial stream. Of
course, not all perennial stream look like this. They appear in all
sizes, and many are much faster moving, perhaps even with
rapids.
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Figure 2 - Perennial Stream
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Occasionally you might notice an intermittent stream bed. They
are often small, and have distinct banks. Many times they are
characterized by rocks along the bed. Figure 3 shows an example of
this type of stream. At the time this picture was taken there was
no water in the stream.
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Figure 3 - Intermittent Stream
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Ephemeral streams are the least likely ones for you to notice
as you walk through the woods. They may be completely dry and
overgrown at certain times of the year. Sometimes you will notice
an area that looks like there had been water there, but does not
have a well defined channel. Often after a storm these areas will
be a little wetter than the surroundings, and often you can see
animal footprints in the mud. Figure 4 shows an example of this
kind of stream. There was no water in the area at the time the
picture was taken, so it can be difficult to make out the path of
the stream.
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Figure 4 - Ephemeral Stream
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Identifying an Intermittent Stream on a Topographic
Map
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The three types of streams are identified differently on a
topographic map. A perennial stream is indicated by a solid blue
line, or sometimes with a shaded blue area. An intermittent stream
is shown as a dashed or dotted blue line. Ephemeral streams are not
shown. One way to determine if a stream is intermittent or
ephemeral is to see if it is shown on the map. Figure 5 shows a
portion of a topographic map with both an intermittent and a
perennial stream.
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Figure 5 - Topographic Map
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Importance of Intermittent and Ephemeral
Streams
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First and second order streams play an very important role in
any watershed. A recent study in nearby Ohio found that a typical
order 1 stream has a drainage area of less than one square mile.
However, order 1 streams account for over 50% of the total miles of
streams in the state. Add in order 2 streams and the percentage
goes up to almost 77%. These order 1 and 2 streams are often
ephemeral or intermittent streams. In 2006 the U.S. Environmental
Protection Agency determined that between 57 and 69% of surface
drinking water in Erie county came from intermittent, ephemeral, or
headwater streams. A large percentage of headwater streams are
intermittent or ephemeral, so most of these percentages are from
those two types of streams.
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Specific Information About This Cache
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The coordinates for this cache take you to an important
intermittent stream in PA State Gamelands #191. It is the only
stream draining the western portion of these gamelands. It is
difficult to tell from the map if this is an order 1 or order 2
stream. It is likely an order 2 stream which is fed by a variety of
ephemeral streams. This particular stream is obviously intermittent
rather than ephemeral due to the fact that it is shown on the
topographic map of the area. Another indication that it is
intermittent can be found near the given coordinates. If you walk
upstream a short distance (maybe 50 or 60 feet) you will likely
find a pool that still contains some water during dry periods. This
would indicate that portions of this stream bed are below the water
table. This is a characteristic of an intermittent stream, but not
an ephemeral stream.
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Claiming This Cache
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In order to claim this cache you will have to answer several
questions. Most of the answers can be found at the site, but you
may have to research one of them. You may log the cache as soon as
you visit the site. You must email your answers within a week of
logging the cache, or the log will be deleted. I hope you enjoy
your walk in the gamelands.
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Questions
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- What was the weather like when you visited the site? (If
possible, determine what the weather has been predominately like
during the last week and the last month. This has a large impact on
the amount of water flowing in the intermittent stream.
- What characteristics of the site would indicate that this is a
stream bed?
- How would you characterize the flow in the stream during your
visit?
- What is the general direction of the channel (N-S or E-W)?
- What is the general direction of flow? (If there is no flow it
should be pretty easy to determine which way it would be flowing by
the stream gradient)
- (Research) There is a drainage divide running through Erie
County. Water that originates north of the divide flows into Lake
Erie, and ultimately into the Atlantic Ocean. Water that originates
south of the divide flows eventually into the Allegheny River, and
ultimately into the Gulf of Mexico. Using a topographic map try to
determine if the water that flows in this stream ends up in the
Atlantic Ocean or in the Gulf of Mexico. (Hint: Look at a
topographic map to determine where this stream joins a much larger
stream. Then research where that larger stream ends up).
- OPTIONAL - Photos are always nice.
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NOTE: SINCE THIS EARTHCACHE IS IN
THE PA GAMELANDS, BE SURE TO WEAR ORANGE DURING HUNTING
SEASON!!
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Depending on your choice of parking areas you may end up
encountering some posted signs. There is no need to wander onto
private property to reach this cache. Please do not go there.
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References:
Water Resources Research Institute of The University of North
Carolina, “How do you indentify an intermittent
stream?”, Annual Program, 2000-2001
Strahler, A.N., “Dynamic Basis of Geomorphology”,
Geological Society American Bulletin, 63, 923-938, 1952
Ward, A, D’Ambrosio, J.L., Mecklenburg, D, “Stream
Classification”, The Ohio State University Extension Fact
Sheet – Agriculture and Natural Resouces, AEX-445-01,
2008
Wikipedia, “Stream”,
http://en.wikipedia.org/wiki/Stream
http://www.epa.gov/owow/wetlands/science/surface_drinking_water/pdfs/surface_drinking_water_pa.pdf
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