Environmental Sciences: Towards a Sustainable Future Chapter 7

Water: Hydrologic Cycle and Human Use

The Water Cycle Exists to Purify Water There are three principal loops in the water

cycle. Human have managed to pollute or

compromise the function of each loop. We are running out of water in terms of

quantity and quality. Water conservation and stewardship are

imperative actions.

Earth’s Water

Water Cycle Processes Evaporation: water molecules move from

liquid to gaseous state; e.g. steam Condensation: water molecules move from

gaseous to liquid or frozen state; e.g. water droplets on cold beverage container

Purification: occurs as a result of evaporation and condensation; impurities are left behind

Condensation

Precipitation Adiabatic cooling: warm air rises,

expands and cools 100% relative humidity + cooling =

clouds Increasing condensation = water

droplets

Global Precipitation Global precipitation distribution

depends on patterns of rising and falling air currents

Two main factors: global convection currents rain shadow effect

Rain Shadow Effect

The Water Cycle

A

B

C

D

E

Water Cycle Filters

Ground WaterLoop

Surface RunoffLoop

EvapotranspirationLoopF

G

A

B

C

D

E

Water Cycle

F

G

H

Human Impacts on the Water Cycle Changing the earth’s surface Pollution Withdrawal for use

Changing Earth’s Surface Through Urbanization Decreased infiltration Increased runoff

Water Pollution

Water Use

Consequences of Overdrawing Water Supplies Surface waters:

shortages ecological effects

Water Use

Vanishing Wetlands

Chemical and Biological Values of Wetlands: Hydrological Cycle Purify waters Control floods Protect shorelines Recharge groundwater

Chemical and Biological Values of Wetlands: Chemical Cycles Nitrogen cycle Sulfur cycle Carbon cycle

Chemical and Biological Values of Wetlands: Increase Biodiversity Terrestrial ecosystems Aquatic ecosystems

Wetland Values - Economic Pelt and skin harvesting (alligator) Waterfowl hunting Sport and commercial fishing Timber harvesting (hardwood and

cypress swamps) Energy source Food source

Wetland Values - Intrinsic Bird watching and wildlife

photography Recreation (hiking, boating) Biological laboratory for students of

all ages

Consequences of Overdrawing Groundwater:

Falling water tables Diminishing surface waters (wetlands) Land subsidence Saltwater intrusion

Aquifer Exploitation

Sinkholes: YIKES!

Saltwater Anyone?

Using Less Water Irrigation

Surge flow Drip irrigation $$$$

Municipal uses Incentives and regulations limiting

water use Gray water

Desalting Seawater Reverse osmosis Distillation

Storm Water Mismanagement

Other Consequences of Storm Water Mismanagement Stream bank erosion Increased pollution

Fertilizers Pesticides Pet fecal matter Road salts and chemicals Oil

Channelization: Solution or Problem? Stream bed was straightened and lined

with rock or concrete Passed the problem of flooding

downstream to your neighbors

Water Stewardship Working Together Louisiana Wetlands Conservation and

Restoration Trust Fund $1.5 billion to restore LA wetlands