Date post: | 01-Apr-2015 |
Category: |
Documents |
Upload: | kennedy-fetherston |
View: | 214 times |
Download: | 0 times |
S
Water ResourcesLT 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..
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..
Management of Freshwater
Poorly managed Charged less than its worth
How would charging less than water’s worth contribute to the mismanagement
of water?
Issues with water
Global
Economic
National and global security issue
Environmental
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
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
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
Reliable Runoff
Usable
1/3 of surface runoff 2/3 lost by seasonal flooding
World-wide averages Domestic: 10% Agriculture: 70% Industrial use: 20%
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
Virtual Water
Water is used indirectly Hamburger, 2400 liters
Virtual water often exported/imported Grains and other foods
Water Shortages
Main factors Dry climates Drought Too many people using a normal supply of water Wasteful use of water
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
Think Box
What do you think we can do to increase freshwater supplies?
Extracting Groundwater
Advantages
Useful for drinking and irrigation
Exists almost everywhere
Renewable if not overpumped or contaminated
Cheaper to extract than most surface water
Disadvantages
Aquifer depletion from overpumping
Sinking of land from overpumping
Pollution of aquifers lasts decades or centuries
Deeper wells are nonrenewable
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
Building Dams and Reservoirs
Advantages
Provide irrigation water
Provide drinking water
Provide recreation and fishing
Can produce cheap electricity (hydroelectricity)
Reduces down-stream flooding of cities and farms
Disadvantages
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
Transferring Water
Transportation of water through aqueducts
California Water Project Transports water from northern California to southern
California
Think Box: What do you think the effects of this might be on both parts of California?
Transferring Water
Advantages
Supply water to areas that lack enough usable water
Allow farmers to grow water-intensive crops in area that lack sufficient water
Disadvantages
Water waste
Degradation to the source
Subsidies for the cost of water transfers encourage overuse
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
Desalination
Advantages
More access to freshwater
Disadvantages
High cost
Energy intensive
Pumping system kills many marine organisms
Produces huge quantities of salty wastewater that must go somewhere