1. © 2011 Pearson Education, Inc. AP Environmental Science Mr. Grant Lesson 71 Freshwater Systems

2. © 2011 Pearson Education, Inc. Objectives: Define the term aquifer. Describe the distribution of fresh water on Earth and the major types of freshwater systems.

3. © 2011 Pearson Education, Inc. Aquifer: A wet underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well. Define the term aquifer.

4. © 2011 Pearson Education, Inc. Describe the distribution of fresh water on Earth and the major types of freshwater systems. Of all the water on Earth, only about 1% is readily available for our use. Groundwater is contained within aquifers. A watershed is the area of land drained by a river system. The main types of freshwater ecosystems include rivers and streams, lakes and ponds, and wetlands.

5. © 2014 Pearson Education, Inc. Freshwater Systems  Water may seem abundant, but drinkable water is rare  Fresh water  water that is relatively pure, with few dissolved salts—only 2.5% of total water  Most is tied up in glaciers, ice caps, and aquifers  One part in 10,000 is easily available for our use

6. © 2011 Pearson Education, Inc. Freshwater systems… another look All Earth's water, liquid fresh water, and water in lakes and rivers.

7. © 2014 Pearson Education, Inc. Freshwater Systems  Water is renewed and recycled as it moves through the water cycle  Precipitation sinks into the ground or runs off into rivers to form lakes or enter oceans  Rivers interact with ponds, wetlands, and coasts  Groundwater exchanges with rivers and ponds  Water moves organisms, sediments, and chemicals

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9. Groundwater plays key roles in the hydrologic cycles  Surface water  water located atop Earth’s surface  Groundwater  water beneath the surface held in pores in soil or rock  20% of the Earth’s freshwater supply  Aquifers  porous, spongelike formations of rock, sand, or gravel that hold water  Zone of aeration  pore spaces 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

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11. Groundwater plays key roles in the hydrologic cycles  Confined (artesian) aquifer  water-bearing, porous rocks are trapped between less permeable substrate (clay) layers  Water here is under great pressure  Unconfined aquifer  no upper layer to confine it  Readily recharged by surface water  Groundwater’s average age is 1400 years  It may be tens of thousands of years old  The Ogallala Aquifer is the world’s largest known aquifer  Current water use for irrigation is not sustainable

12. © 2011 Pearson Education, Inc. The Ogallala Aquifer Its water has allowed farmers to create the most bountiful grain- producing region in the world

13. © 2011 Pearson Education, Inc. Researchers mapping underground water reserves in Africa find huge reservoirs, but warn this may not be a magic bullet solution to the continent's increasing need for fresh water. Much of the water in this region is located deep underground, 100 – 250 m below the surface. MacDonald warns this inaccessibility might make it almost impossible to use the reserves for irrigation or to provide drinking water for new urban centres across the continent. Northern Africa Aquifer

14. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Surface water accounts for just 1% of fresh water  Vital for us and Earth’s ecological systems  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

15. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Watershed (drainage basin)  the area of land drained by a river system (river and its tributaries)  Surface water becomes groundwater through infiltration  Groundwater becomes surface water through springs or human-drilled wells  1.9 trillion L (492 billion gal) each day in the United States

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17. Water is renewed and recycled as it moves through the hydrologic cycle

18. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Rivers shape the landscape  Braided river  an interconnected series of watercourses that run through steep slopes

19. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Meandering river  river in flatter areas  Water rounding a bend erodes soil from the outer bank  Sediment is deposited on the inside of the bend  Rivers form oxbows, areas where river bends become exaggerated

20. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems Oxbow lake  water body formed when erosion cuts off and isolates the oxbow into a U- shape

21. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Floodplain  areas nearest to a river’s course that are flooded periodically  Frequent deposition of silt makes floodplain soils fertile  Good areas for agriculture

22. © 2014 Pearson Education, Inc. Surface water converges in river and stream ecosystems  Riparian  describing riverside areas that are productive and species-rich  Damming prevents large floods and river meanders  Rivers and streams host diverse ecological communities  Algae, insects, fish, amphibians, birds, etc.

23. © 2014 Pearson Education, Inc. Lakes and ponds are ecologically diverse systems  Lakes and ponds are 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  the entire bottom of the water body  Home to many invertebrates  Limnetic zone  open portion of the lake or pond where sunlight allows photosynthesis that produces oxygen  Supports phytoplankton and zooplankton  Profundal zone  water that sunlight does not reach  Supports fewer animals because there is less oxygen

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25. Lakes and ponds are ecologically diverse systems  Ponds and lakes may change over time  Oligotrophic lakes and ponds have low-nutrient and high-oxygen conditions

26. © 2014 Pearson Education, Inc. Lakes and ponds are ecologically diverse systems  Eutrophic lakes and ponds have high-nutrient and low-oxygen conditions  Eutrophication may result from human pollution

27. © 2014 Pearson Education, Inc. Lakes and ponds are ecologically diverse systems Eventually, water bodies may fill completely in through the process of succession The largest lakes are known as inland seas Great Lakes, the Caspian Sea, Lake Baikal

28. © 2014 Pearson Education, Inc. Freshwater wetlands include marshes, swamps, bogs, and vernal pools  Wetlands  systems in which the soil is saturated with shallow standing water with vegetation  Freshwater marshes  shallow water with plants that 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  Vernal pools  pools that form in spring then dry up

29. © 2014 Pearson Education, Inc. Wetlands include marshes, swamps, bogs, and seasonal pools Species in vernal pools are adapted to seasonal drying

30. © 2014 Pearson Education, Inc. Freshwater wetlands include marshes, swamps, bogs, and vernal pools  Wetlands are extremely valuable for wildlife  Louisiana’s coastal wetlands host 1.8 million migratory birds each year  They provide valuable ecosystem services  They slow runoff, reduce flooding, recharge aquifers, and filter pollutants  People have drained wetlands, mostly for agriculture  Southern Canada and the United States have lost over half of their wetlands  Wetlands are affected when we withdraw water, build dams and levees, and introduce pollution

31. © 2014 Pearson Education, Inc. Wetlands are valuable Not all wetlands perform all functions nor do they perform all functions equally well. Wetlands are among the most productive habitats in the world.