Water Resources & Water Pollution

1. Water Resources &Water Pollution Chapter 9

2. Water is abundant,Usable water is rare • 70% of Earth’s surface is covered by water. • > 97% of Earth’s water is found in oceans salt water • < 3% of Earth’s water is fresh water • Type that can be consumed by humans • ¼ of fresh water resides underground • Most of the fresh water above ground exists as ice and glaciers  not available for human consumption • Small fraction in the form of streams, rivers, wetlands, and lakes

3. Groundwater • Exists within permeable layers of rock and sediment or aquifers • Unconfined aquifers: when water can easily flow in and out (porous rock covered by soil) • Confined aquifers: impermeable or confined layer impedes water flow to or from aquifer (impermeable, not allowing fluid to come through, rock or clay) • Water Table: the surface of the groundwater in an area, fully saturates the rock or soil • Groundwater recharge: when water from precipitation percolates through soil and goes into aquifer • A confined aquifer can’t be recharged unless layer has an opening at surface of land • Aquifers are an important source of fresh water for many organisms

4. Groundwater, cont. • Springs • Occur when water from an aquifer NATURALLY percolates up to the ground surface • A natural source of water for freshwater aquatic biomes • Used directly by humans as sources of drinking water • The well • Obtaining water from aquifers by digging a hole in the ground • Discovered centuries ago • Most modern wells contain pumps  move water up to ground surface against force of gravity • Artesian well  drilling a hole into a confined aquifer releases the pressure on the water  water bursts out of aquifer  rises up in well

5. Groundwater • Age of water in the aquifer varies • Confined aquifers are recharged slowly, 10,000+ years ago; usually much older; less likely to be contaminated by anthropogenic chemicals • Use of water from a confined aquifer is unsustainable because withdrawal is not balanced by recharge • Figure 9.5: Shows what happens when water withdrawn > water entering the aquifer

6. Surface Water • The fresh water that exists above the ground • Streams • Lakes • Rivers • Floodplain: the land adjacent to the river • Excess water from overflowing of river banks during snowmelt or rainfall spreads onto the floodplain • Floodwaters deposit nutrient-rich sediment onto floodplain • Ponds • Wetlands • During heavy rainfall freshwater wetlands absorb and store excess water and release it slowly • An important role in water distribution and regulation because reduces chances of a flood

7. Homework 12/4/12 • What is saltwater intrusion (p. 219)? • Support the statement: Atmospheric water is essential to global water distribution (p. 219-220).

8. Atmospheric Water • Atmospheric water is essential to global water distribution. • Excess water from heavy rainfall events that the ground (pavement or impermeable soil) does not absorb fills the streams and rivers  overflows their banks, may flood lowland areas  may lead to crop and property damage and losses of animal and human lives.

9. Human Management of Water • To maintain a fresh supply of water and to prevent flooding humans… • Channel the flow of rivers with levees • Block the flow of rivers with dams to store water • Divert water from rivers and lakes and transport it to distant locations • Desalinate water to remove salt from water

10. Levees • Construct a levee to prevent flooding • A levee is an enlarged bank built up on each side the river • The use of levees brings several several major challenges. • Natural floodwaters no longer add fertility to floodplains by depositing sediment • Floodplain: the land adjacent to the river • Only prevent flooding at one location. Levees encourage development in floodplains. • Levees force floodwater farther downstream  Can cause worse flooding farther downstream. • Levees can collapse due to tremendous pressure of the water  resulting in massive flooding. • Hurricane Katrina in 2005, p. 220

11. Dikes & Dams • Dikes • Built to prevent ocean waters from flooding adjacent land • Have allow countries to develop areas that would otherwise be under water • Dams • A barrier that runs across a river or stream to control the flow of water • Hold water for a variety of purposes • Human consumption • Generation of electricity – Hydroelectric plants • Flood control • Recreation • Building uses large amounts of energy and materials and displaces people • Environmental Problem: Dams interrupt the natural flow of water • Dams are an impediment to migrating fish such as salmon that migrate to breed • Solution: fish ladder where fish swim up to reach their traditional breeding ground

12. Fish Ladder

13. Aqueducts • Do not hold water back • Canals or ditches used to carry water from one location to another • Remove water from a lake or river to where needed • Cons • Construction of requires $ • Disturbs and fragments natural habitats • Example: Requires removing water from river  less water flowing where naturally has flowed  can cause areas of dryness before river water reaches the ocean

14. Desalination • Removing salt from salt water • Salt water comes from the ocean, salty inland lakes • A way water-poor countries can obtain fresh water • Middle East produces 50% of the world’s desalinated water

15. Homework 12/7/12 • Read pages 224-228

16. Oil Pollution • Pollution of Earth’s oceans and shorelines from crude oil and other petroleum products is an ongoing problem. • Petroleum products are highly toxic to marine life (birds, mammals, fish, algae, microorganisms) • Oil is a persistent substance  it can spread across and below water’s surface  Difficult to remove • Where does the oil come from? • Drilling for undersea oil using offshore platforms • 5,000 offshore oil platforms in North America, and 3,000 elsewhere • Oil platforms experience leaks • FAMOUS OIL LEAK occurred in 2010 during a BP operation in the Gulf of Mexico • Pipe broke on ocean floor; leak from April until August released 780 million liters of crude oil • One of the largest environmental disasters in history

17. Where does the oil come from? • Can come from oil tankers as spills • Spill in Alaska in 1989 killed 250,000 sea birds, 2,800 otters 300 seals, 22 whales • Cleanup efforts have been going on for decades