Unit 4 12.net
Unit 7 Day 9
Freshwater resources
Freshwater systems
◆ Water may seem abundant, but drinkable water is rare
◆ Freshwater = relatively pure, with few dissolved salts
◆ Most is tied up in glaciers, ice caps, and aquifers
◆ As water is cycled it redistributes heat, erodes mountains, builds river deltas, maintains ecosystems and organisms
◆ It also shapes civilizations and political conflicts
◆ Surface water = on Earth’s surface
◆ 1% of freshwater
◆ Runoff = water that flows over land
◆ Water merges in rivers and ends up in a lake or ocean
◆ Tributary = a smaller river slowing into a larger one
◆ Watershed (drainage basin) = the area of land drained by a river system (river and its tributaries)
Water is renewed and recycled as it moves through the hydrologic cycle
[pic]
Lakes and ponds are ecologically diverse
◆ Lakes and ponds = bodies of open, standing water
◆ Littoral zone = region ringing the edge of a water body
◆ Rooted aquatic plants grow in this shallow part
◆ Benthic zone = extends along the bottom of the water body
◆ Home to many invertebrates
◆ Limnetic zone = open portion of the lake or pond where sunlight allows photosynthesis
◆ Profundal zone = water that sunlight does not reach
◆ Supports fewer animals because there is less oxygen
◆ Oligotrophic lakes and ponds = have low nutrient and high oxygen conditions
◆ Eutrophic lakes and ponds = have high nutrient and low oxygen conditions
◆ Eventually, water bodies fill completely in through the process of succession
◆ The largest lakes are known as inland seas
◆ Great Lakes, The Caspian Sea
◆ Wetlands = the soil is saturated with shallow standing water
◆ Freshwater marshes = shallow water
◆ Plants grow above the surface
◆ Swamps = shallow water in forested areas
◆ Can be made by beavers
◆ Bogs = ponds covered in thick floating mats of vegetation
◆ A stage in aquatic succession
◆ Wetlands are extremely valuable for wildlife
◆ They slow runoff, reduce flooding, recharge aquifers, and filter pollutants
◆ People have drained wetlands, mostly for agriculture
◆ Southern Canada and the U.S. have lost over half of their wetlands
◆ In 2006 the Supreme Court told the Army Corps of Engineers it must create guidelines to determine when wetlands are valuable enough to protect by law
◆ Groundwater = water beneath the surface held in pores in soil or rock
◆ 20% of the Earth’s freshwater supply
◆ Aquifers = porous, sponge-like formations of rock, sand, or gravel that hold water
◆ Zone of aeration = pore spaces are partly filled with water
◆ Zone of saturation = spaces are filled with water
◆ Water table = boundary between the two zones
◆ Recharge zone = any area where water infiltrates Earth’s surface and reaches aquifers
[pic]
◆ Confined (artesian) aquifer = water-bearing, porous rocks are trapped between less permeable substrate (clay) layers
◆ Is under great pressure
◆ Unconfined aquifer = no upper layer to confine it
◆ Readily recharged by surface water
◆ Groundwater’s average age is 1,400 years
◆ It may be tens of thousands of years old
◆ Groundwater becomes surface water through springs or human-drilled wells
◆ The world’s largest known aquifer
◆ Underlies the Great Plains of the U.S.
◆ Water is unevenly distributed in space and time
◆ Different areas possess different amounts of water
◆ People erect dams to store water
◆ Climate change will cause
◆ Altered precipitation patterns
◆ Melting glaciers
◆ Early season runoff
◆ Intensified droughts
◆ Flooding
◆ We have achieved impressive engineering accomplishments to harness fresh water
◆ 60% of the world’s largest 227 rivers have been strongly or moderately affected
◆ Dams, dikes, and diversions
◆ Consumption of water in most of the world is unsustainable
◆ We are depleting many sources of surface water and groundwater
◆ Proportions of these three types of use vary dramatically among nations
◆ Arid countries use water for agriculture
◆ Developed countries use water for industry
◆ Consumptive use = water is removed from an aquifer or surface water body and is not returned
◆ Irrigation = the provision of water to crops
◆ Nonconsumptive use = does not remove, or only temporarily removes, water
◆ Electricity generation at hydroelectric dams
◆ Rapid population growth requires more food and clothes
◆ The Green Revolution uses irrigation
◆ We use 70% more irrigation water than 50 years ago
◆ Irrigation can double crop yields
◆ 18% of land is irrigated but produces 40% of our crops
◆ Irrigation is highly inefficient
◆ Water evaporates in “flood and furrow” irrigation
◆ Over irrigation leads to waterlogging and salinization
◆ Reducing world farm income by $11 billion
◆ Wetlands are being lost as we divert and withdraw water
◆ Channelize rivers, build dams, etc.
◆ As wetlands disappear, we lose ecosystem services
◆ Filtering pollutants, wildlife habitat, flood control, etc.
◆ Many are trying to protect and restore them
◆ Groundwater is easily depleted
◆ Aquifers recharge slowly
◆ Used by one-third of all people
◆ As aquifers are mined, water tables drop
◆ Salt water intrudes in coastal areas
◆ Sinkholes = areas where ground gives way unexpectedly
◆ Aquifers can’t recharge Wetlands dry up
◆ Water for human consumption and other organisms needs to be:
◆ Disease-free
◆ Nontoxic
◆ Half of the world’s major rivers are seriously depleted and polluted
◆ They poison surrounding ecosystems
◆ Threatening the health and livelihood of people
◆ The invisible pollution of groundwater has been called a “covert crisis”
◆ Pollution = the release of matter or energy that causes undesirable impacts on the health and well-being of humans or other organisms
◆ Point sources = discrete locations of water pollution
◆ Factories, sewer pipes
◆ Addressed by the U.S. Clean Water Act
◆ Nonpoint sources = pollution arises from multiple inputs over larger areas (farms, city streets, neighborhoods)
◆ The major source of U.S. water pollution
[pic]
• Nutrient pollution from fertilizers, farms, sewage, lawns, golf courses leads to eutrophication
◆ Fertilizers add phosphorus to water, which boosts algal and aquatic plant growth
◆ Spreading algae cover the surface, decreasing sunlight
◆ Bacteria eat dead algae, reducing dissolved oxygen
◆ Fish and shellfish die
◆ Solutions include treating wastewater
◆ Reducing fertilizer application
◆ Using phosphate-free detergents
◆ When algae blooms occur because of nutrient pollution in water ways the effects can be devastating
◆ The bloom dies off then sinks to the bottom
◆ Decomposing bacteria then rapidly multiple to consume the algae
◆ The bacteria use the oxygen in the water for respiration
◆ The lake becomes hypoxic which destroys the animal live that depend on the oxygen in the water
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- ap psychology unit 4 frq
- unit 4 test review math answers
- weekly writing frame unit 4 week 1
- ap microeconomics unit 4 test
- unit 4 macroeconomics quiz
- phonics spelling grade 5 unit 4 week 1 page 94
- unit 4 world history answers
- grade 1 unit 4 week3
- practice grade 5 unit 4 week 3
- unit 4 review nuclear chemistry
- unit 4 ap biology quizlet
- ap chemistry unit 4 test