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LT 6E: Discuss the sustainability of freshwater resources

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1 LT 6E: Discuss the sustainability of freshwater resources
LT 6F: Identify possible solutions to the sustainability of freshwater resources and discuss the benefits and consequences of each..

2 Importance of Freshwater
Necessary for life 60% of us is composed of water Could only survive a few days without it Takes huge amounts to supply us with food, energy etc..

3 Management of Freshwater
Poorly managed Charged less than its worth How would charging less than water’s worth contribute to the mismanagement of water?

4 Issues with water Global Economic National and global security issue
Environmental Global: Lack of access to safe drinking water in less developed countries Economic: vital for reducing poverty and producing food and energy National and global security issue: increasing tensions both within and between nations over access to limited water resources they share Environmental: Water loss/water pollutiondeclining water quality, lower fish populations, species extinctions and degradation of aquatic ecosystems

5 Availability of Freshwater
Only about 0.024% of the planet’s water is available to us as liquid freshwater Sources: Groundwater deposits Lakes Rivers Steams

6 Groundwater Precipitation that seeps into the ground and moves downward through spaces in soil, gravel and rock until an impenetrable layer of rock stops it. Spaces deep in the earth hold more water than at the top Zone of saturation: Deep; Completely filled with water Water zone: top of this groundwater zone Aquifer: Deep; Groundwater flows through them; pumps used to bring water to surface; replenished mainly by precipitation

7 Groundwater Surface water: freshwater from precipitation and melted snow that flows across the earth’s land surface and into lakes, wetlands, steams, rivers, estuaries, and into the ocean. Surface runoff: precipitation that does not infiltrate the ground Watershed (drainage basin): land from which surface water drains into a body of water

8 Reliable Runoff Usable
1/3 of surface runoff  2/3 lost by seasonal flooding World-wide averages Domestic: 10% Agriculture: 70% Industrial use: 20%

9 Water Footprint Volume of water we directly and indirectly
Average American uses 260 liters per day Flushing toilets, 27% Washing clothes, 22% Taking showers, 17% Running faucets, 16% Wasted from leaks, 14% World’s poorest use 19 liters per day

10 Virtual Water Water is used indirectly
Hamburger, 2400 liters Virtual water often exported/imported Grains and other foods

11 Water Shortages Main factors Dry climates Drought
Too many people using a normal supply of water Wasteful use of water

12 Water Shortages More than 30 countries face water scarcity
Rapid urbanization, economic growth and drought are expected to put more stress on water resources in developing countries like China and India 30% earth’s land area experiences severe drought Will rise to 45% by 2059 from climate change Potential conflicts/wars over water Refugees from arid lands Increased mortality

13 Think Box What do you think we can do to increase freshwater supplies?
Reducing unnecessary waste Extracting groundwater Building dams and reservoirs to store runoff in rivers Transporting surface water from one area to another Converting salt water to freshwater (desalination)

14 Extracting Groundwater
Advantages Disadvantages Useful for drinking and irrigation Exists almost everywhere Renewable if not overpumped or contaminated Cheaper to extract than most surface water Aquifer depletion from overpumping Sinking of land from overpumping Pollution of aquifers lasts decades or centuries Deeper wells are nonrenewable More than have of the world’s population relies on aquifers for drinking water Overpumping: Limits future food production, Bigger gap between the rich and the poor, Land subsidence (sinking), Groundwater overdrafts near coastal regions (Contamination of groundwater with saltwater)

15 Building Dams and Reservoirs
Dams are large structures built across a river to control the river’s flow. Reservoirs are created behind dams. Main Goals Capture and store runoff Release water as needed to control floods More than 45,000 large dams in world (22,000 of them in China)

16 Building Dams and Reservoirs
Advantages Disadvantages Provide irrigation water Provide drinking water Provide recreation and fishing Can produce cheap electricity (hydroelectricity) Reduces down-stream flooding of cities and farms Displaces people, destroys forests or cropland Water loss to rivers and stream Deprive downstream cropland and estuaries of nutrient-rich silt Risk of failure and devastating downstream flooding Disrupts migration of some fish 1 out of five of the world’s freshwater fish and plant species are either extinct or endangered because dams and water withdrawal have sharply reduced the flow of many rivers Reservoirs behind dams also eventually fill up with sediments such as mud and silt, typically within 50 years, which makes them useless for storing water or producing electricity.

17 Transferring Water Transportation of water through aqueducts California Water Project Transports water from northern California to southern California Northern CA: Degrades rivers in northern CA Southern CA: More need for water Think Box: What do you think the effects of this might be on both parts of California?

18 Transferring Water Advantages Disadvantages
Supply water to areas that lack enough usable water Allow farmers to grow water-intensive crops in area that lack sufficient water Water waste Degradation to the source Subsidies for the cost of water transfers encourage overuse Lettuce grown in southern CA despite the fact that it is water intensive

19 Desalination Removing of dissolved salts from ocean water or from brackish (slightly salty) water in aquifers or lakes. Two widely used methods: Distillation: involves heating saltwater until it evaporates leaving behind salts in solid form and then condenses as freshwater Reverse osmosis: uses high pressure to force saltwater through a membrane filter with pores small enough to remove the salt 14,450 desalination plants in more than 125 countries (250 in the U.S.) Meet less than 0.3% of the world’s demand and 0.4% of the U.S. demand for freshwater.

20 Desalination Advantages Disadvantages More access to freshwater
High cost Energy intensive Pumping system kills many marine organisms Produces huge quantities of salty wastewater that must go somewhere

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