Groundwater Fundamentals

38% surface62%

ground

43% Public Supply39% Agriculture8.5% Industrial/Commercial4.5% Recreation Irrigation4.0% Domestic Self-supply

62% Agriculture20% Power8% Public Supply6% Recreation Irrigation4% Industrial/Commercial

Reliance on GroundwaterU.S.

Florida

Florida

16 million people withdrawing 8 billion gallons/day

Almost 30 M by 2030

Leading to an over-exploitation of ground-water resources

38% surface62%

ground

43% to Public Supply

China

India

Iran

Israel

Jordan

Mexico

Morocco

Pakistan

Saudi Arabia

South Korea

Spain

Syria

Tunisia

United States

Yemen

• Withdrawals exceed recharge creating deficits in the aquifer

Over-exploitation of renewableand non-renewable aquifers

Water Mining

• Lack of contemporary recharge

 

GROUNDWATER . (Mm3/yr)  

COUNTRY Total use % Non-renewable

Saudi Arabia 21,000 84%

Libya 4,280 70%

Yemen 2,200 32%

Jordan 486 31%

Egypt 4,850 18%

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

Lack of Contemporary Recharge

United States

1/3 of irrigation water comes from groundwater

The 3 largest aquifers are in arid/semi-arid regions

Ogallala Aquifer MidwestCentral Valley Aquifer CaliforniaSouthwest Aquifer System Arizona, Utah, Nevada

Central Valley Aquifer (California)

Pumping 15% more water than is replaced

Southwest Aquifer (Utah, Nevada, Arizona)

Pumping 50% more water than is replaced

Water storage capacity has declined by 50%

High Plains Aquifer (Ogallala)¼ gone in areas of Texas, Oklahoma, Kansas

Water table declines up to 100 feet in some areas

Phoenix Arizona Growing 2 acres/hr

Among the highest water users

Canal 335 miles long

44 billion gallons/yr

7% lost to evaporation

Central Arizona Project

Groundwater and Aquifer Fundamentals

Freshwater

GlaciersAtmosphere

GroundwaterLakesSoilsRiversWetlands

3% of totalEarth water

Aquifer

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

Aqua – waterFerre – to carry

Aquifers/Groundwater

0.6% of total earth water.

98% of all readily available freshwater

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

Where and What is Groundwater?

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

SandsSilts

GravelsMudsClaysRock

Water-bearing materials

Aquifers and Aquifer Types

Unconsolidated

Consolidated

Confined

Unconfined

Aquifer Classification

Unconsolidated Aquifers

Basic Aquifer Classification

Unconsolidated Aquifers

Individual particles: granular sand, gravel, clays, silts

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

Unconsolidated Water-Bearing Unit

Generally high-yield aquifers

Unconsolidated: sand, gravel, and rock fragments

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

thick

thin

174,000 mi²

High Plains Aquifer

Coarse, sedimentary rocks

Aquifer material dates back 2 to 6 million years

Erosion of the Rockies provided sediment that filled ancient channels

Consolidated Aquifers

Water held in cracks, fissures, erosioncavities and seams in solid rock formations.

Consolidated Aquifers

Sandstone, limestone, granite

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

Carbonate formations include limestone (CaCO3) and dolomite (MgCO3)

Exhibit mostly secondary porosity due to fracturing and dissolution openings

Sedimentary

sandstonelimestone

cavity

Consolidated Aquifers: Guaraní Aquifer

Sedimented sandstones deposited during the Triassic and Jurassic periods

overlaid with igneous basalt with low-permeability

Slowly Recharged

37,000 km³ of water

fresh drinking water for 200 years

(166 km³/year)

Transboundary Aquifer: Argentina, Brazil, Paraguay and Uruguay

5% of world population

Florida’s Principal Aquifer is Consolidated Limestone

Calcium and Magnesium Carbonate

Extra Credit:

1. Aquifers and Ground water represent ___% of total earth water.

2. Groundwater supplies _____% of U.S. drinking water.

3. Aquifers in which water is held in pore spaces between grains of sand, gravel, clays, or rock fragments are _________ aquifers.

4. Aquifers in which water is held in cracks, fissures, erosion cavities and seams in solid rock formations are ____ aquifers.

5. Florida’s principal aquifer is composed of __________ limestone.

Confined and Unconfined Aquifers

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

Low permeability – slow water movement

Unconfined Aquifers

Sometimes called “surficial” aquifers

Low PermeabilityGeologic or Soil material

Water

HighPermeability

Unconfined Aquifer

Saturated Zone

Groundwater table

Saturated Zone thickness dependent on rainfall

Unconfined or Surficial Aquifer

Impermeable

Confined Aquifers

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

of clay, rock, or shale.

Impermeable, confining layer

Impermeable confining layer

Water Bearing Unit

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 Flow and Artesian Wells

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

Florida’s Principal Aquifer is Consolidated and Confined