Groundwater

Freshwater Glaciers Atmosphere Groundwater Lakes Soils Rivers Wetlands 3% of total Earth 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 that can store and release usable amounts of water. Aqua – water Ferre – to carry

Where is Groundwater? Water found in pore spaces, seams cracks, and fractures in geologic material or soils beneath the surface of the earth Sands Silts Gravels Muds Clays Rock Water-bearing Unit 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 grains of sand, gravel, clays, or rock fragments Water held in cracks, fissures and seams in 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 Hawaiian Islands. 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 mi 2 and averages 80 to 160 ft in thickness Carbonate formations include limestone (CaCO 3 ) 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 Permeability Geologic or Soil material Water High Permeability Unconfined Aquifer Saturated Zone Groundwater table Saturated Zone thickness dependent on rainfall Open to the surface, but confined at greater depth by 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 Recharge 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 runoff Lakes Streams Rivers Wetlands Sinkholes

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-renewable Aquifers 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 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 often Associated with Water Mining Withdrawals exceed recharge creating deficits in the aquifer The world water deficit is concentrated in China, the Indian subcontinent, 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 currently Withdrawing more Groundwater than Is replenished.

GROUNDWATER (Mm3/a) COUNTRYShare of demand *Total useNon-renewable Algeria54%2,6001,680 Saudi Arabia85%21,00017,800 Bahrain63%25890 Egypt7%4, UAE70%9001,570 Jordan39% Libya95%4,2803,014 Oman89%1, Qatar53% Tunisia59%1, Yemen62%2, *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 can contaminate 1 million gallons of drinking water 1 ppm

Metals Nutrients Pesticides Petroleum Solvents