Download ch_6 water - St John Brebeuf

Running Water and Groundwater
Oceans – 97 %
Glaciers/ice – 2 %
Freshwater - < 1 %
Water cycle = the continuous
circulation of earth’s water supply
It is powered by the sun
Evaporation = liquid to gas
Condensation = gas to liquid (forms clouds)
Precipitation = water (s,l ) returns to earth
Infiltration = water that soaks into ground
Runoff = water that flows across the ground
Transpiration = water that plants release
into the atmosphere (gas to liquid)
Earth’s water cycle is balanced
Balanced = earth’s annual precipitation =
the amount that evaporates
Local imbalances do exist like droughts and
floods.
Stream Flow
Velocity is the distance that water travels in
a period of time. (some slow some fast)
Highest velocities in the center of channel
Velocity fastest on the outside bank/bend
when a steam bends/curves
The ability of a stream to erode & transport
materials depends largely on its velocity
5 Stream Velocity Factors
1.
Gradient = slope (how steep or flat)
2.
Shape = crooked vs straight
3.
Size = wide vs narrow & deep vs shallow
4.
Roughness = smooth vs rough
5.
Discharge = the volume of water flowing
past a certain point per unit of time (m3/s)
Stream Profile Changes
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Profile - a cross-sectional stream view
Gradient and roughness decrease as you
go downstream
Discharge, velocity, depth, and width
increases as you move downstream
The ability of a stream to erode increases
as the discharge increases.
Stream Terms
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Tributary – anything that empties into
another stream
Base level – the lowest point to which a
stream can erode its channel
Meander – bends/curves in a river/stream
Oxbow lake – a meander that gets cut off
from the main stream and form a small
lake.
Stream Erosion
The ability of stream to carry a load is
dependent upon 2 factors:
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Competence - the largest particles the stream is
transporting
Capacity – the maximum load it can carry
Steams generally erode “V” shaped valleys &
channels in three ways
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Abrasion
Grinding
Dissolving soluble materials
Stream Deposition
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As the stream slows down material/alluvium begins
to settle out
Larger materials settle out first
Delta – a triangular accumulation of sediment
formed where a stream enters a lake/ocean
Levee – accumulation of sediment along the river
banks
Rivers carve
3 Stages of Stream Development
1 Young – fast, straight, narrow, rapids
2 Mature – slower, meanders, wider
3 Old – slowest, meanders/oxbows, widest
Flooding
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Flood plain – flat areas along rivers that
occasionally flood
Flood contribution factors:
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Paving
Excess precipitation
Methods of control
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Dams and levees
Limiting development
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Drainage basin - the land area that
contributes water to a stream
Divide – imaginary line that separates one
drainage basin of one stream from another
Drainage patterns
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Dendritic
Radial
Braided
Trellis/rectangular
Groundwater
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Zone of saturation – area below ground where all
the pore spaces are completely filled with water
Zone of aeration – all the pore spaces are not
completely filled with water
Water table – the line that divides the two
Groundwater – It’s Underground
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Porosity – the percentage of the total volume of
rock (or sediment) that consists of pore spaces
Permeability – how well water moves through
the rock/sediment
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Well rounded and well sorted grains = high porosity
Aquifer – rock layers or sediment that allow
groundwater to flow freely (sandstone)
Aquitard – does not allow groundwater freely to
flow freely (shale)
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Springs – form whenever the water table
intersects the surface of the ground
Hot springs – water is heated from magma just
below the surface
Geysers – intermittent hot spring/fountain that
periodically erupts (Old Faithful)
Wells – a hole bored into the zone of saturation
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A pump is needed
Cone of depression
Artesian wells – groundwater rises on its own
under pressure and no pump is needed
Read pages 175/176 (env probs)
Caverns
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A naturally formed underground chamber
Usually forms in limestone from carbonic acid
dissolving the rock
Travertine – Calcium carbonate deposits
Stalactites, stalagmites, soda straws,
curtains/ribbons, flowstone, etc
Karst topography – limestone areas with many
caves and sinkholes (collapsed caves)