Chapter 2 The Flow of Fresh Water
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Transcript of Chapter 2 The Flow of Fresh Water
Chapter 2The Flow of Fresh Water
Section1The Active River
Rivers: Agents of Erosion• Six Million Years ago the Grand Canyon
was as flat as Pitt County farm land.• The Colorado River has worn down
through the river bed a distance of over 1 mile.
• Erosion is the process by which soil and sediment are transported from one location to another.
The Water Cycle
• The water cycle is the continuous movement of Earth’s water from the ocean to the atmosphere to the land and back to the ocean
0.7 is All!!!• Out of all the water on Earth,
only 2.75 percent is fresh water, including 2.05 percent frozen in glaciers, 0.68 percent as groundwater and 0.0001 percent of it as surface water in lakes and rivers.
River Systems• River System – the network of creeks
and streams that join to form rivers• These river systems drain a land area
of its run off water• Tributary – a creek or stream that
drains into a lake or larger stream• In North Carolina, rivers run down from
mountains in the west and drain/run east until emptying into the Atlantic Ocean
Watersheds• Watershed – the drainage basin of a river
system– The area of land that is drained by a river
system– Greenville, Tarboro, and Washington are in
the Tar River/Pamlico River watershed– Raleigh, Kinston and New Bern are in the
Neuse River watershed.– Divide – high ground that divides watersheds;
example: Continental Divide
North American Divides
Stream Erosion• As a stream forms, it erodes soil and
rock to make a channel• A stream’s ability to erode is influence
by three factors: gradient, discharge, and load.
• Gradient is the measure of the change in elevation over a certain distance. A high gradient gives a stream or river more energy to erode rock and soil
Gradients
Low GradientLess/Slower
ErosionLess Energy
High GradientMore/Faster ErosionMore Energy
Stream Erosion (cont.)• Discharge is the amount of water that a
stream or river carries in a given amount of time. As discharge increases, erosive energy and speed also increase.• Large storms/Snow melt cause increase
• Load is the materials carried by a stream. The size of a stream’s load affects its rate of erosion• Fast moving water can move large particles• Rocks in mountain streams• Sand at the ocean
3 Kinds of River Loads• Bed Load – large materials, such as
rocks and boulders, that are bounced along a stream bed
• Suspended Load – small rocks and soil carried suspended in the water column; gives river its muddy look
• Dissolved Load – material carried in solution; dissolved in the water such as calcium, sodium and oxygen
How Rivers Change Over Time• Young Rivers – narrow, straight &
deep channel, steep gradient, more erosion; many rapids and waterfalls, few tributaries
• Mature Rivers – wide channel, lower gradient, less mass erosion, more tributaries = more water discharge
How Rivers Change Over Time• Old Rivers – wide, flat flood plains;
many curves or bends in the channel, deposit silt and sand along banks
• Rejuvenated Rivers - result of tectonic (earth moving) activity – steep gradient again, forms terraces– Terraces - step like formations; like Grand
Canyon
Chapter 2The Flow of Fresh Water
Section 2 Stream and River Deposits
Deposition in Water• Deposition – the process of rivers
dropping their suspended load of rocks and soil.
• Sediment – the rocks, sand, pebbles and silt that is deposited by a river as its waters slow down
Rocks Pebbles Sand Silt
Fast Water Slow Water
Deposition in water (cont.)• Placer Deposits – where a river slows in a
curve it can deposit heavy minerals like
• Delta – fan shaped deposit where a river empties into a large body of water like an ocean or large lake
• Deposits cause new land to be formed• Eventually very fertile soil
GOLD
Satellite Photo - Nile River Delta
Land build-up with fertile soil showing green plants
Deposition on Land• Alluvial Fan - a fan shaped delta-like
deposit formed at the base of a mountain
Deposition on Land (cont.)• Floodplain – the Pitt-Greenville airport
and the land north of the river is on the floodplain for the Tar River.
• That’s why that land flooded so badly during Hurricane Floyd
Flood Control• Dam –
Across a river to stop or divert water flow
Levee – sediment built up along a river channel to keep river in its banks
Chapter 2The Flow of Fresh Water
Section 3 Underground Water
Location of Groundwater• Water located within the rocks below the
Earth’s surface is called groundwater
Zone of Aeration – spaces between soil & rocks is filled with air
Water Table - Dynamic (changing) boundary between zones
Zone of Saturation – spaces between soil and rocks is filled with water
Aquifers• A rock layer that stores and allows the flow
of groundwater. Affected by…• 1. Porosity - the % of open space between
particles• 2. Permeability – the amount of H2O that can
pass through• Impermeable – cannot penetrate
Permeability & Recharge Zones
Castle HayneAquifer
Springs & Wells• Natural Spring –
where the water table meets the surface of the Earth
• Lake - when the water table is higher than the earth’s surface for a large area
Artesian Springs• Artesian formation - permeable
rock sandwiched between 2 layers impermeable rock
• Middle permeable rock = aquifer• top layer = cap rock• Artesian spring – when cap rock
breaks or cracks at Earth’s surface
• Geothermal (earth heat) heated water = hot spring
• “Old Faithful” Geyser
Well• Human drilling in Earth’s surface down to
water table.• If water is drawn out too much or too
quickly = cone of depression
Underground Erosion and Deposition• Underground water, especially acidic water, can
dissolve underground rock resulting in sinkholes or caves
• Limestone rock is easily dissolved because it is relatively soft
• In caves, form stalactites and stalag ites• If meet in the middle = dripstone column
Sinkholes-Underground Cave Breaks Through
Chapter 2The Flow of Fresh Water
Section 4 Using Water Wisely
Water Pollution• Point Source Pollution – you
can point to the source
• Nonpoint Source Pollution – most by runoff – fertilizers,waste runoff, cattle farms, etc.
Health of a Water System• Dissolved Oxygen – fish kills• Temperature – too hot, low D.O.• Nitrates – Weyerhauser (Neuse)• Phosphates – Texas Gulf Mining
(Pamlico)• pH - acidic• Turbidity – sediment, too much
algae• Biological Indictors – algae, fish
kills
Monitoring Water QualityGround Truthing – Taking samples on the ground to check with satellite images
Monitoring Water Quality
Cleaning Polluted Water• Sewage Treatment Plants – clean waste out of water
– Primary Treatment• 1. Large screen to catch solids, paper, bottle caps, etc.
Add chemicals to make it clump together• 2. Placed in large tank for smaller sludge can settle out.
Oils and scum skimmed off of surface.– Secondary Treatment
• 1. Aeration Tank where H2O & bacteria are added• 2. Settling Tank where particles settle out & Chlorine is
added
• Where Water Comes From:»More than ½ of NC depend on water from Aquifers
• Where the water goes:
The average household uses 100 gallons of fresh water per day
• Water in Agriculture:– Most lost through evaporation and runoff– Ground level drip hoses – a lot more efficient
• Water in Industry:– 19% of world’s water used for industry– Most industrial water is now recycled
• Water at Home:– Conservation - Low-flow Shower Heads
• Wash only full loads of clothes• Plant Native plants to avoid having to water
• (Native-naturally found in that area)