Groundwater

Freshwater

GlaciersAtmosphereGroundwaterLakesSoilsRiversWetlands

3% of totalEarth water

Aquifers/Groundwater

0.6% of total earth water.

98% of all readily available freshwater

Supplies ½ of the drinking water in U.S.and 90% of the drinking water in FL.

Aquifers

Water-bearing formation thatcan store and release usableamounts of water.

Aqua – waterFerre – to carry

Where is Groundwater?

Water found in pore spaces, seamscracks, and fractures in geologic material or soils beneath the surface of the earth

SandsSilts

GravelsMudsClaysRock

Water-bearingUnit materials

Aquifers and Aquifer Types

Consolidated

Unconsolidated

Confined

Unconfined

Aquifer Classification

Basic Aquifer Classification

Unconsolidated or Consolidated

Consolidated: sandstone, limestone, granite

Unconsolidated: granular sand, gravel, clays, silts

Water held in pore spaces between grainsof sand, gravel, clays, or rock fragments

Water held in cracks, fissures and seamsin solid rock formations.

Unconsolidated Aquifers

Unconsolidated sands and gravel

Water-Bearing Unit

Unconsolidated: sand and gravel

saturated thickness ranges from a few feet to more than 1000 feet

thick

thin

174,000 mi²

High Plains Aquifer

27 percent of the irrigated land in the United States overlies this aquifer yields about 30 percent of the nation's ground water used for irrigation

20% of U.S. grain production

provides drinking water to 82 percent of the people who live within the aquifer boundary

Semi-arid Region

Consolidated Aquifers

Consolidated Rock: igneous or sedimentary

Water-Bearing Unit

Rocks formed from the cooling and solidification of molten magma originating in the earth's core

Igneous Rocks

Extrusive rock is formed when the solidification process occurs at or near the ground surface. These rocks are generally very permeable because of the "bubbling" of gases escaping during cooling and solidification.

horizontal fracturing

The Columbia River Plateau covering eastern Washington and Oregon, and Idaho, averages about 500 m in thickness and is one of the largest basalt deposits in the world. Basalt aquifers are critically important water sources for the HawaiianIslands.

Consolidated Aquifers

Granite

Consolidated Rock Aquifers

Sandstone and Carbonate

Sandstone is a cemented form of sand and gravel

St. Peter Sandstone in northeastern Illinois covers more than 290,000 mi2 and averages 80 to 160 ft in thickness

Carbonate formations include limestone (CaCO3) and dolomite

Exhibit mostly secondary porosity due to fracturing and dissolution openings

Sedimentary

Consolidated Aquifers: Guaraní Aquifer

Sedimented sandstones deposited during the Triassic and Jurassic periods

overlaid with igneous basalt with low-permeability

Thickness: 50 m to 800 m

Slowly Recharged

37,000 km³ of water

fresh drinking water for 200 years

(166 km³/year)

Argentina, Brazil, Paraguay and Uruguay

5% of world population

Confined and Unconfined Aquifers

Low PermeabilityGeologic or Soil material

Water

HighPermeability

Unconfined Aquifer

Saturated Zone

Groundwater table

Saturated Zone thickness dependent on rainfall

Open to the surface, butconfined at greater depthby low-permeability material

Low permeability – slow water

Unconfined or Surficial Aquifer

Confined Aquifers

A generally inclined, water-bearing formation located between impermeable layers

of clay, rock, or shale.

Confining units (aquicludes)

Water-bearing unit (consolidated or unconsolidated)

Water-bearing unit is confined between two layers of material that are not permeable to water (confining units).

Confined Aquifers

Water-bearing unit

Impermeable material

Recharge

Flow

High Pressure

Confined and Unconfined

impermeable

impermeable

Recharge

Water-bearing unit

Water-bearing unit

Recharge

Unconfined aquifer (surficial aquifer)

Open to the surface, but confined at greater depth by low-permeability material

Recharge is generally by rainfall and surface water bodies

Confined aquifer

Water-bearing unit is confined between two layers of material that are not permeable to water (confining units).

Recharge is in areas where the upper confining unit is thin or absent

Water-bearing units: sands, gravel, silts, clays, porous or fractured rock

Recharge, Usage, and Water Mining

Aquifer Recharge: precipitation

surface water runoffLakes

StreamsRivers

WetlandsSinkholes

Non-Renewable Groundwater Resources

Groundwater resources are never strictly non-renewable.

In cases where present-day aquifer replenishment is very limited but aquifer storage is very large, the groundwater resource can be termed non-renewable

Non-Renewable Groundwater Resources

Time for Replenishment

Climate Changes

Non-renewable aquifers are often described as “fossil” aquifers.

These are aquifers with no appreciable modern recharge.

“Fossil” Aquifers

Most often found in arid climates, fossil and other non-renewableAquifers are an important water resource for many nations.

Nubian Sandstone aquifer underlying Chad, Egypt Libya and Sudan.

Qa-Disi aquifer between Jordan and Saudi Arabia

Great Artesian Basin of Australia

Groundwater is isolated from modern recharge

Contemporary climate does not support sufficient recharge

formed between 100 and 250 million years ago

Formed 145.5 to 65.5 million years ago

Average rainfall < 5 mm/year Closed water system•Age of most water > 20,000 years,

Settings associated with non-renewable groundwater

hyper-arid area with average rainfall of less than 4 in/yr and prolonged dry periods–bulk of aquifer contains fossil groundwater, which infiltrated during humid period s at least 10,000 years or more ago and still has an active residual flow to a perennial discharge area.

temperate humid region with annual rainfall in excess of 1,000 mm/yr normally generating renewable groundwater resources, but highly-confined portion of aquifer system contains essentially non-renewable groundwater as a result of geological structure and geomorphological history – and this is potentially of local strategic importance.

No recharge

Non-renewable aquifers are oftenAssociated with Water Mining

Withdrawals exceed recharge creating deficits in the aquifer

The world water deficit is concentrated in China, the Indiansubcontinent, the Middle East, North Africa, and North America

Extensive exploitation of renewable and non-renewable aquifers

China

India

Iran

Israel

Jordan

Mexico

Morocco

Pakistan

Saudi Arabia

South Korea

Spain

Syria

Tunisia

United States

Yemen

Countries currentlyWithdrawing more Groundwater than Is replenished.

    GROUNDWATER (Mm3/a)

COUNTRY Share of demand * Total use Non-renewable

Algeria 54% 2,600 1,680

Saudi Arabia 85% 21,000 17,800

Bahrain 63% 258 90

Egypt 7% 4,850 900

UAE 70% 900 1,570

Jordan 39% 486 170

Libya 95% 4,280 3,014

Oman 89% 1,644 240

Qatar 53% 185 150

Tunisia 59% 1,670 460

Yemen 62% 2,200 700

*percentage of total use provided by groundwater

Saudi Arabia and Libya, use 77% of the estimated total world extraction of non-renewable groundwater for urban supply and irrigated agriculture.

The Middle East

End Lecture 16

Sea Levels

Temporary reestablishment of carbonate deposition

Vulnerability

One gallon of gasoline cancontaminate 1 million gallonsof drinking water

1 ppm

MetalsNutrientsPesticidesPetroleum Solvents