Download Hydrosphere

Hydrosphere
Surface Water and the Water
Cycle
Goals for This Unit
Explain the structure and processes within the
hydrosphere
• Explain how water is an energy agent (currents and heat
transfer)
– understand the role of water in weather and atmospheric
change
– use concepts of fluid density to describe global water
movement and ocean currents and their effect in distributing
heat around the globe
• Explain how ground water and surface water interact
– understand the concepts and dynamics of river systems with
emphasis and examples drawn from NC river systems
– list and describe common methods used to conserve both water
quantity and quality
How Do You Use Water?
The Water Cycle
• A never-ending natural circulation of water
through Earth’s systems powered by the Sun
Steps of the Water Cycle
• Precipitation – rain, snow, hail, sleet
• Runoff or ground seep
• Reservoir – living things, snowfields, glaciers,
lakes, oceans
• Evaporation – from land or bodies of water
• Transpiration
• Condensation
Runoff V/S Ground Seep
• Vegetation
– more vegetation = more ground seep
– less vegetation = more runoff
• Rate of Precipitation
– lighter rainfall = more ground seep
– harder rainfall = more runoff
• Soil composition
– high humus, coarse particles = more ground seep
– low humus, fine particles = more runoff
• Slope
– flatter slope = more ground seep
– steep slope = more runoff
Stream Systems
• Some runoff flows into brooks, creeks,
streams and rivers that eventually empty into
lakes and oceans
• Watershed – all the land area whose water
drains into a stream system
• Stream load – all the materials (living and nonliving) that the water in a stream carries
– Carried in three ways – solution, suspension, bed
load
Solution
• When material has dissolved in a stream’s
water
• Dependent upon the material a stream has
passed through
• High amounts of calcium carbonate and
magnesium
• Groundwater provides most of the dissolved
load to streams
• Expressed in parts per million (ppm)
Suspension
• Particles small enough to be held up by the
turbulence of a stream’s moving water
• Dependent upon volume and velocity of the
stream
– Faster moving water = larger particles
Bed Load
• Sediments too large or heavy to be held up by
turbulent water
• Consists of sand, pebbles, cobbles that are
rolled and pushed along the stream bed
• Abrasion – particles rubbing and scraping
against one another as they tumble in the
water
– Erodes not only sediments in water but also sides
and bottom of stream itself
Stream Carrying Capacity
• Amount of material a stream can transport
• Depends upon velocity and amount of water
moving in the stream
– Affected by channel slope, depth and width
• Discharge – measure of the volume of stream
water that flows over a particular area within a
given period of time
– Discharge(m3/s) = width(m) X depth(m) X velocity(m/s)
• As discharge increases carrying capacity increases
– Impacted by heavy rain, flooding, rapid melting of snow
Floods
• Floodplain – broad, flat area extending out from a
stream’s bank that is covered by excess water
during times of flooding
• As flood water recedes it deposits sediments in
the floodplain that develop highly fertile soil
– Upstream flooding – local
– Downstream flooding - widespread
• Monitoring of streams is provided by the National
Weather Service, weather satellites and the US
Geological Survey (USGS)
Water Cycle Project
• Please draw the water cycle
• Criteria
– Must be accurate
– Must be neat
– Must be on plain paper
– Must be colored
 DUE Tuesday 25 September
Hydrosphere
Stream Development
A Stream is Born
• Precipitation provides the water for the
beginnings of stream formation
• Headwater – region where water first
accumulates to supply a stream
• Stream channel – narrow pathway carved into
sediment or rock by stream waters
• Stream capture – when a stream erodes the
area separating two drainage basins, joins
another stream and then draws away its water
Stream Valleys
• V-shaped channels caused by erosion from
streams
– Grand Canyon, Colorado River
• Streams continue to erode until they reach
their base level, the point where they enter
another stream or body of water
– Lowest possible base level is the ocean
• Eventually v-shaped valleys erode into broader
valleys with gentle slopes
Meandering Streams
• Meander – bend or curve in a stream channel
• Velocity differences
– Straight stream: fastest in the center, slower on the
sides and bottom
– Meander: fastest along the outside of a curve,
deposition occurs on inside of curve where water
slows
• Over time meanders become more accentuated
• Mouth – area of a stream that empties into
another body of water
Sediment Deposition
• Occurs as streams slow (lose velocity)
• Alluvial fan – occur when mountain streams
flow into broad, flat valleys
– Usually found in dry, mountainous regions
– Usually composed mostly of sand and gravel
• Delta – occur when streams join larger bodies
of quiet water
– Usually form a triangle shaped deposit
– Usually composed of silt and clay particles
Alluvial Fan
Deltas
Stream Rejuvenation
• Downcutting – wearing away of a streambed
– Stops when a stream reaches its base level
• Rejuvenation – occurs when downcutting
resumes due to land uplift of the stream bed
or lowering of the base level
– Creates v-shaped valleys
– In meanders, creates deep sided canyons
Hydrosphere
Lakes and
Freshwater Wetlands
Lakes
• Form from many sources
– Streams, runoff, local precipitation, springs, etc
– Created two ways
• Man Made
– Ponds – livestock, fish supplies, attract wildlife
– Reservoirs – stores water for human use
• Naturally Formed
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Oxbow
Landslides
Remnants of prehistoric lakes
Glaciers
Dissolved limestone
Glacier Lakes
• Moraine-dammed
– Form when glacial moraines dam some
depressions and restrict outward flow of water
• Cirque
– Form when cirques that are carved out by high
valley glaciers fill with water
• Kettle
– Form when water fills depressions left by blocks of
ice from melting glaciers
Changing Lakes
• Exist for long periods of time as long as the
supply of water is more than what is removed
by evaporation and human use
• Some only exist during times of heavy rains
• Over time (100,000+ years) will eventually fill
with sediment and become part of the
landscape
Eutrophication
• Process by which lakes become rich in nutrients
from the surrounding watershed, which results in
a change in the kinds of organisms in the lake
– Photosynthesis (plants) add oxygen and waste
products to the lake
– Animals in the lake use the oxygen and add their
waste to the lake
– Decay of dead animals and plants also uses dissolved
oxygen supplies
– Amount of dissolved oxygen helps determine the
health of a lake and if it can support life
Rates of Eutrophication
• Increases with addition of nutrients
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Nitrogen and phosphorus from fertilizer
Animal wastes
Phosphate detergents
Release of toxins from industry and untreated sewage
• Additional nutrients causes excessive algae to
grow
• Causes organisms that eat the algae to multiply
• Overpopulation and decay of large numbers of
plant and animals consumes the oxygen supply
• The lake eventually dies
Freshwater Wetlands
• Land area covered with water most of the year
• Include bogs, marshes, swamps
• Have certain soil types that support specific
plant species
Bogs
• Receive water only from precipitation
• Soil is waterlogged
– Rich in sphagnum (peat moss)
• Peat moss breakdown produces acid
– Acidic soil supports unusual plant species
• Pitcher plants
• Sundew
• Venus flytrap
Marshes
• Common along the mouths of streams and in
areas with large deltas
• Constant supply of water
• Shallow roots of marsh grasses allow for
capture of silt and mud that slows water flow
and expands the marsh
• Diverse wildlife and plants
– Birds, fish, reeds, grasses, sedges and rushes
Swamps
• Low-lying areas often near streams
• May develop from marshes as they fill-in
• Support the growth of larger plants such as
trees and bushes
• Because of increased shade, marsh grasses
begin to die
• Present day coal reserves were once swamps
250 million years ago
Importance of Wetlands
• Help improve water quality
– Trap pollutants, sediments, pathogenic bacteria
• Provide vital habitat for migratory water birds
and other wildlife
• Between 1700 to 1985 the US lost 50% of its
wetlands
• Wetlands are often filled-in to make space for
people
– New York City (Queens, Brooklyn)
– New Oreleans
– Washington, DC