14 Groundwater Fundamentals

14 Groundwater Fundamentals - Groundwater Fundamentals...

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Unformatted text preview: Groundwater Fundamentals Reliance on Groundwater U.S. 62% ground 38% surface Florida 43% Public Supply 39% Agriculture 8.5% Industrial/Commercial 4.5% Recreation Irrigation 4.0% Domestic Self-supply 62% Agriculture 20% Power 8% Public Supply 6% Recreation Irrigation 4% Industrial/Commercial Florida 16 million people withdrawing 8 billion gallons/day 62% ground 38% surface 43% to Public Supply Almost 30 M by 2030 Leading to an overexploitation of groundwater resources Water Mining Over-exploitation of renewable and non-renewable aquifers • Withdrawals exceed recharge creating deficits in the aquifer • Lack of contemporary recharge China India Iran Israel Jordan Mexico Morocco Pakistan Saudi Arabia South Korea Spain Syria Tunisia United States Yemen The Middle East Lack of Contemporary Recharge GROUNDWATER . (Mm3/yr) COUNTRY Saudi Arabia Libya Yemen Jordan Egypt Total use 21,000 4,280 2,200 486 4,850 % Non-renewable 84% 70% 32% 31% 18% Saudi Arabia and Libya, use 77% of the estimated total world extraction of non-renewable groundwater for urban supply and irrigated agriculture. United States 1/3 of irrigation water comes from groundwater The 3 largest aquifers are in arid/semi-arid regions Ogallala Aquifer Midwest Central Valley Aquifer California Southwest Aquifer System Arizona, Utah, Nevada High Plains Aquifer (Ogallala) ¼ gone in areas of Texas, Oklahoma, Kansas Water table declines up to 100 feet in some areas Central Valley Aquifer (California) Pumping 15% more water than is replaced Water storage capacity has declined by 50% Southwest Aquifer (Utah, Nevada, Arizona) Pumping 50% more water than is replaced Phoenix Arizona Growing 2 acres/hr Among the highest water users Central Arizona Project Canal 335 miles long 44 billion gallons/yr 7% lost to evaporation Groundwater and Aquifer Fundamentals Freshwater 3% of total Earth water Glaciers Atmosphere Groundwater Lakes Soils Rivers Wetlands Aquifer Aqua – water Ferre – to carry Water-bearing formation that can store and release usable amounts of 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 more than 90% of the drinking water in FL. Where and What is Groundwater? Water found in pore spaces, seams cracks, and fractures in geologic material or soils beneath the surface of the earth Water-bearing materials Sands Silts Gravels Muds Clays Rock Aquifers and Aquifer Types Aquifer Classification Unconsolidated Consolidated Confined Unconfined Unconsolidated Aquifers Basic Aquifer Classification Unconsolidated Aquifers Individual particles: granular sand, gravel, clays, silts Water held in pore spaces between grains of sand, gravel, clays, or rock fragments Unconsolidated Water-Bearing Unit Generally high-yield aquifers Unconsolidated: sand, gravel, and rock fragments Coarse, sedimentary rocks saturated thickness ranges from a few feet to more than 1000 feet thick 174,000 mi² High Plains Aquifer thin Aquifer material dates back 2 to 6 million years Erosion of the Rockies provided sediment that filled ancient channels Consolidated Aquifers Consolidated Aquifers Sandstone, limestone, granite Water held in cracks, fissures, erosion cavities and seams in solid rock formations. Water-Bearing Unit Consolidated Rock: igneous or sedimentary Consolidated Aquifers Igneous Rocks Rocks formed from the cooling and solidification of molten magma originating in the earth's core 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. Granite Consolidated Rock Aquifers Sedimentary Sandstone and Carbonate Sandstone is a cemented form of sand and gravel Carbonate formations include limestone (CaCO ) and dolomite (MgCO ) Exhibit mostly secondary porosity due to fracturing and dissolution openings 3 3 cavity sandstone limestone Consolidated Aquifers: Guaraní Aquifer Sedimented sandstones deposited during the Triassic and Jurassic periods 37,000 km³ of water 5% of world population fresh drinking water for 200 years overlaid with igneous basalt with low-permeability Slowly Recharged (166 km³/year) Transboundary Aquifer: Argentina, Brazil, Paraguay and Uruguay 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 Unconfined Aquifers Open to the surface, but confined at greater depth by low-permeability material Low permeability – slow water movement Sometimes called “surficial” aquifers Unconfined Aquifer Water Groundwater table High Permeability Saturated Zone Low Permeability Geologic or Soil material 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 Water Bearing Unit Impermeable confining layer Water-bearing unit is confined between two layers of material that are not permeable to water (confining units). Confining units (aquicludes) Water-bearing unit (consolidated or unconsolidated) Confined Flow and Artesian Wells Recharge Flow Water-bearing unit Impermeable material High Pressure Confined and Unconfined Recharge Recharge impe Water-bearing unit rmea bl e Wa ter- impermeable bea ring unit 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 ...
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This note was uploaded on 02/10/2011 for the course SWS 2007 taught by Professor bonczek during the Fall '09 term at University of Florida.

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