Prentice Hall

EARTH SCIENCE

Tarbuck



Lutgens

Distribution of Earth’s Water

The Water Cycle

6.3

Water Beneath the Surface

Distribution and Movement of Water Underground

 Much of the water in soil seeps downward until it reaches the zone of saturation.

 The

zone of saturation

is the area where water fills all of the open spaces in sediment and rock. •

Groundwater

is the water within this zone.

• The

water table

is the upper level of the saturation zone of groundwater.

6.3

Water Beneath the Surface

Distribution and Movement of Water Underground

 Movement • Groundwater moves by twisting and turning through interconnected small openings.

• The groundwater moves more slowly when the pore spaces are smaller.

6.3

Water Beneath the Surface

Distribution and Movement of Water Underground

 Movement •

Porosity

- The percentage of pore spaces - Determines how much groundwater can be stored •

Permeability

- Ability to transmit water through connected pore spaces

Aquifers

are permeable rock layers or sediments that transmit groundwater freely

Features Associated with Subsurface Water

6.3

Water Beneath the Surface

Springs

 A

spring

forms whenever the water table intersects the ground surface.

 Hot Springs • Water is 6–9ºC warmer than the mean air temperature of the locality.

• Water is heated by cooling of igneous rock.



Geysers

• Intermittent hot springs • Water turns to steam and erupts.

Geyser Eruption Cycle

6.3

Water Beneath the Surface

Wells

 A

well

is a hole bored into the zone of saturation.

• An

artesian well

is any formation in which groundwater rises on its own under pressure.

• Pumping can cause a drawdown (lowering) of the water table.

• Pumping can form a cone of depression in the water table.

Cone of Depression

6.3

Water Beneath the Surface

Environmental Problems Associated with Groundwater

 Overuse and contamination threatens groundwater supplies in some areas.

• Treating it as a nonrenewable resource • Land subsidence caused by its withdrawal • Contamination

Groundwater Supplies are Finite!!

• The High Plains Aquifer is an example of Severe groundwater depletion.

• Even if pumping were to stop now, it would take thousands of years to replenish the groundwater.

San Joachim Valley, CA The marks of the utility pole illustrate the sinking of 13,400 sq. km over 9 meters because of the withdrawl of groundwater for irrigation:

subsidence

.

www.aegweb.org/.../ subsidence_Poland.jpg

High Plains Aquifer • About 27 percent of the irrigated land in the US overlies this aquifer system.

• It yields about 30 percent of the nation's ground water used for irrigation. • It provides drinking water to 82 percent of the people who live within the aquifer boundary. [2] http://en.wikipedia.org/wiki/Ogallala_Aquifer

Groundwater Contamination

Common Sources of Water Pollution: 1. Sewage from septic tanks.

2. Farm wastes 3. Inadequate or broken sewers 4. Fertilizers, Pesticides, and Highway Salts 5. Chemicals and Industrial Materials leaking from: a. Pipelines b. Storage tanks c. Landfills d. Holding Tanks

Groundwater Contamination

Groundwater Contamination

Harmful bacteria in aquifer may be purified by: 1. Mechanical filtration 2. Chemical oxidation 3. Assimilation by other organisms http://openlearn.open.ac.uk/file.php/2457/T210_1_014i.jpg

Groundwater Contamination

LANDFILLS: Solid Waste Disposal 1. Open Air Dumps: a. used in US up until 1970, now illegal (standard in rest of world) b. release toxins in air and groundwater c. Attract vermin, breed disease 2. Sanitary: a. Dig hole, line w/ clay and plastic liner, cover w/ dirt daily b. Promotes decomposition, reduces vermin & disease c. Still may leak, check groundwater constantly

Open-air rubbish dump Barrow, Alaska, USA on coastline, This dump site in such fragile environment is polluting groundwater and spoils the tundra.

http://www.gettyimages.com/detail/450076-001/Stone

Sanitary Landfill http://seagrant.uaf.

edu/nosb/papers/2004/images/selawikfig2.jpg

Sanitary Landfill http://blog.pennlive.com/lvbreakingnews/2008/01/chrinlandfill.JPG

US WASTES FACTS

*The US produces more wastes per person than any other nation in the world (10 to 100 X more!!!) Over 200 metric tons/year!!

** 60% of our wastes end up in landfills, 20% is incinerated, and 20% is recycled.

***The US is guilty of “eco-terrorism” a. We are the World Leaders of “e” wastes (500 tons/month) b. We export 80% to Africa and China c. Children harvest the metal for sale and wade through the toxic wastes for food. Also contaminates water supply.

d. One desktop = 9 to 12 pounds of lead, mercury, arsenic, and radioactive isotopes and may also contain a few grams of silver, gold, and copper. (source: NCSU/Bruck)

LANDFILL VIDEO

6.3

Water Beneath the Surface

Caverns

 A

cavern

is a naturally formed underground chamber.

 Erosion forms most caverns at or below the water table in the zone of saturation.



Travertine

is a form of limestone that is deposited by hot springs or as a cave deposit.

Dissolving of Groundwater Creates Caverns

6.3

Water Beneath the Surface

Caverns

 Characteristics of features found within caverns • Formed in the zone of aeration • Composed of dripstone • Formed from calcite deposited as dripping water evaporates • Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor ).

6.3

Water Beneath the Surface

Karst Topography

 Formed by dissolving rock at, or near, Earth's surface  Common features •

Sinkholes

—surface depressions - Sinkholes form when bedrock dissolves and caverns collapse.

• Caves and caverns  Area lacks good surface drainage.

Sinkhole Formation

Water Contamination • Point Source Pollution-pollution that comes from a known/specific location • Nonpoint Source Pollution- does NOT have a specific point of origin

Point Source Pollution • The term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged

Continued

Nonpoint Source Pollution • Excess fertilizers, herbicides and insecticides from agricultural lands and residential areas • Oil, grease and toxic chemicals from urban runoff and energy production • Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks • Salt from irrigation practices and acid drainage from abandoned mines • Bacteria and nutrients from livestock, pet wastes and faulty septic systems • Atmospheric deposition and hydromodification