AP Environmental Science Mr. Grant Lesson 74

1. AP Environmental Science • Mr. Grant • Lesson 74 Freshwater Systems

2. Objectives: • Define the term aquifer. • Explain water’s importance to people and ecosystems, and describe the distribution of fresh water on earth. • Describe major types of freshwater systems.

3. Define the term aquifer. • 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.

4. Explain water’s importance to people and ecosystems, and describe the distribution of fresh water on earth. • Water is a renewable but limited resource, so we must manage it sustainably. • A functioning water cycle is vital to maintaining our civilization and the natural systems that support it. • Of all the water on Earth, only about 1% is readily available for our use. • Water availability varies in space and time, and regions vary greatly in the amounts they possess. • Climate change may bring water shortages in some regions.

5. Gambling with water in the Colorado River basin • 7 states share the Colorado river • Droughts and overuse are threatening supplies • Las Vegas, Nevada, needs more water than it is allotted • Other states will let Las Vegas drill for underground water • Drilling threatens the area’s ecology and people • This issue will end up in Nevada’s Supreme Court

6. The Colorado River • The Colorado River originates in the Rocky Mountains • Draining into the Gulf of California • Its waters chiseled the Grand Canyon • But it has been reduced to a mere trickle • Dams provide flood control, recreation, and hydroelectric power • 30 million people use the water

7. 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

8. Water is renewed and recycled • 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)

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

10. Water Cycle Scramble

11. Groundwater plays a key role • 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

12. A typical aquifer

13. There are two categories of aquifers • 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

14. The Ogallala Aquifer • The world’s largest known aquifer • Underlies the Great Plains of the U.S. Its water has allowed farmers to create the most bountiful grain-producing region in the world

15. Water is unequally distributed across Earth • Water is unevenly distributed in space and time • Different areas possess different amounts of water • People erect dams to store water Many densely populated areas are water-poor and face serious water shortages

16. Climate change may bring shortages • Climate change will cause • Altered precipitation patterns • Melting glaciers • Early season runoff • Intensified droughts • Flooding Lake Mead is already hurting from drought

17. Describe major types of freshwater ecosystems. • 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.

18. Rivers and streams wind through landscapes • Rivers shape the landscape • Braided river = an interconnected series of watercourses that run through steep slopes • Meandering river = rivers in flatter areas • Water rounding a bend erodes soil from the outer bank • Sediment is deposited on the inside of the bend • Rivers become exaggerated oxbows

19. Rivers shape the landscape • Oxbows = areas where river bends become exaggerated • Oxbow lake = erosion cuts off and isolates the oxbow into a U-shaped water body

20. A river may shift course over time • Floodplain = areas nearest to the river’s course that are flooded periodically • Frequent deposition of silt makes floodplain soils fertile • Good areas for agriculture • Riparian= riverside areas that are productive and species-rich • Rivers and streams hosts diverse ecological communities • Algae, insects, fish, amphibians, birds, etc.

21. 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

22. A typical lake

23. Lakes vary in their nutrients and 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

24. Wetlands include marshes, swamps, bogs, and seasonal pools • 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 Species in vernal pools are adapted to seasonal drying

25. Wetlands are valuable • 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