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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