Groundwater Fundamentals. 38% surface 62% ground 43% Public Supply 39% Agriculture 8.5%...
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Transcript of Groundwater Fundamentals. 38% surface 62% ground 43% Public Supply 39% Agriculture 8.5%...
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
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
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: 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
Water held in cracks, fissures, erosioncavities and seams in solid rock formations.
Consolidated Aquifers
Sandstone, limestone, granite
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
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.
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
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