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87 Cards in this Set
- Front
- Back
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Aquifer
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• Saturated sediments that store and transmit water at rates sufficient enough to be useful
• A sediment layer that slows or prevents water transmission is called an aquitard o Examples: thick clay, solid rock without fractures • Vadose zone (unsaturated zone) • Phreatic zone (saturated zone) |
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What makes a good aquifer?
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o High porosity (for water storage)
Porosity: total amount of pore space o High permeability (for water transmission) |
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• Geologic characteristics impact porosity and permeability
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o Solid rock not very porous or permeable
Crystals tightly interlocked o Weathering and fracturing increase porosity and permeablility o Clastic (unconsolidated) sediments have high porosity and permeability |
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Extreme Example: Karst
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• Highly weathered limestone (CaCO3)
• Cave-sized openings |
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confined aquifer
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An aquifer that is situated beneath an aquitard or aquiclude is a confined aquifer
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Three main steps in groundwater cycling”
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I. Recharge
a. Unconfined areas of aquifers may experience groundwater recharge i. Water that reaches the water table to replenish an aquifer ii. Aquifers without recharge are non-renewable resources b. Amount of recharge depends upon what? i. Climate (little or no recharge in the desert) ii. Vegetation cover (transpiration removes water) iii. Soils (permeability) II. Flow (within the aquifer) III. Discharge |
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Flowing wells and flowing springs:
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• Potentiometric surface is higher than the ground surface
o Ex. Great Artesian Basin, Australia o Trafalgar Square, London (not artesian anymore) |
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. Groundwater Flow:• How fast does groundwater flow?
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o Depends on hydraulic head gradient
o Depends on permeability |
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. Groundwater Flow:• Described by Darcy’s Law:
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o Discharge = (Hydraulic conductivity) * (hydraulic head gradient) * (cross-sectional area)
Q = K * A(^h/^I) • In book Example: • H = 25m • Let I =250m • Let k=10m/day o Q= .25 m2 * 10 m/d * (25m/250m) o Q= .25 m2 * 10 m/d * .1 o Q= .25 m3/d |
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3. Discharge
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• Where does groundwater go?
• Groundwater is part of the water cycle • Discharges to other parts of the water cycle |
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Common groundwater discharges:
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• Streams, rivers and lakes
• Oceans (submarine groundwater discharge) • Evapotranspiration • PUMPING WELLS |
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If groundwater discharge exceeds recharge:
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• Amount of water in the aquifer decreases
• Water levels in wells decline |
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Water Resource Withdrawal and Consumption
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• Pumping ground water will lower the water table
o Outflow > inflow • How much and how persistent the lowering depends on the situation: o Cone of Depression: V shape where a well enters an aquifer • Water table decline is a warning sign for aquifer depletion |
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Another potential impact of depletion:
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• Subsidence
o Sediments no longer saturated may compact o Sinkholes may develop (depending on the aquifer) (usually Karst Aquifers) |
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Water Resources of the High Plains (Ogallala) Aquifer
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• Largest Aquifer in North America (and one of the largest in the world)
o Why is it so valuable? Abundant coarse sediments High saturated thickness in many places (up to 500 ft) Usually good water quality |
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Continuing with water resources
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• Turned the High Plaines from a Dust Bowl to reliable and productive agricultural center
• More than 90% of withdrawals are for irrigated agriculture • Supports about 1/3 of irrigated land in the US • Drinking water for almost everyone in the High Plains region (>80%) • Nebraska is the biggest groundwater user in the US • More clay-rich in the south and sand-rich in the north o Recharge rates higher in the north than south Water depletion bigger problem in the south Water contamination bigger problem in the north |
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Water Stress map: supply/demand
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• Water scarcity
o 3.5 billion people (48% of the world’s population) will live in water-stressed river basins by 2025 |
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Water and agriculture
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• Globally, 86% of fresh water consumption is by agriculture
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How we use water:• Domestic non-food per day (Gallons)
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o 1 shower: 20
o 2 teeth brushings: 2 o 1 dishwasher load: 20 o 2 toilet flushes: 6 o 1 clothes wash: 10 o Drinking/cooking: 10 Total: 68 gallons |
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How we use water:• Food per day (gallons)
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o Meat (2 meals): 264 gallons
o Grains: 41 gallons o Vegetables/Fruit: 18 gallons o Dairy: 78 gallons Total with meat: 401 gallons Total vegetarian: 137 gallons |
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“This, gentlemen, is what I have been talking about” Hugh Bennet 1935
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• Politician lobbying for bill that helps prevent soil erosion
• Timed his speech just right so he gave it as the dust cloud came in to DC |
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Soils and Human Activites
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• Soils play a key role in agricultural productivity
o Soils are a source of nutrients o Soils hold and transmit water • Agricultural activities modify soils o Physical Characteristics (cohesion, permeability, etc) o Chemical Characteristics (nutrients, inorganic ions, etc) • Agricultural and other land use decisions need to take account of soil characteristics! |
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Soil Formation
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• Soil is produced by weathering
o Chemical, physical, and biological processes that breakdown rocks o Speed of soil formation varies Climate Topography Source Material o These factors also affect the characteristics of the soil formed |
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Weathering
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• Mechanical weathering and chemical weathering
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• Mechanical weathering: physical breakdown of minerals by mechanical action.
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o No chemical change
o Examples: Frost wedging (freezing water expansion) Salt crystallization (no reactions have taken place, physical processes) |
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• Chemical weathering: breakdown of minerals by chemical reactions.
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o Rock undergoes chemical change
o Example: Calcite weathering o Silicate weathering produces clays o Biological activity often aids chemical weatherin |
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Soil Profiles and Horizons
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• Soils are often stratified(will have different characteristics at different layers)
• Generally recognizable horizons in order of depth: O, A, E, B, C, Bedrock |
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o O Horizon:
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Consists of organic matter
Both living and decomposed |
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o A Horizon:
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Mix of rock and organic matter
Most extensively weathered rock (Because water comes through and takes everything soluble) |
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o E Horizon:
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Less organics
“Zone of Leaching” |
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o B Horizon:
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Zone of accumulation (Zone of deposition)
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o C Horizon:
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Very coarsely broken-up bedrock
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“Reading” a soil
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• Color: dark or light
o Dark soils tend to be rich in organic matter o Light soils generally lack organic matter o Red soils high in iron • Structure: tendency to form peds (clumps) o Ped forming soils resist erosion • Texture: size of fragments o Sand, silt, clay |
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Texture “by feel”
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• Sand:
o Feels “gritty” due to the large size and irregular shapes o Can see grains • Silt: o A “floury”, silky feel o Can discern grains • Clay: o Cannot see individual grains o When moist, sticky and takes a lot of pressure to squeeze |
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Soil texture influences:
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• Susceptibility to transport by wind and water
• Water resources: porosity and permeability • Construction and architecture: response to pressure |
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Pedalfer and Pedocal:
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• A broad categorization based on chemical composition
• Reflects the net effects of chemical weathering, and thus the climate |
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Pedalfer: soil of a humid climate
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• More extensive leaching
• Less soluble material remains after leaching • Enriched in iron and aluminum oxides (less soluble compounds) |
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Pedocal: soil of a dry climate
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• Less extensive leaching
• Soluble minerals are present, including calcium carbonate |
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• Laterite soils (oxisol)
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o Extreme version of pedalfer that forms in tropical climates
o Contains few soluble nutrients o In tropic areas, forest biomass, rather than soil, holds most of the nutrients o Lateritic soils are difficult to cultivate o Slash and burn agriculture quickly depletes the nutrients over time o Red color of laterite soils indicate iron richness |
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• Slash and Burn Agriculture
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o Motivated by low nutrients in lateritic soils
o Releases nutrients stored in biomass and enriches soil o Nutrient pulse into the soils is only temporary o Leads to more slash and burn o Deforestation… |
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Soil Erosion
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• Weathering versus erosion
o Weathering is the breakdown of rock or mineral material o Erosion is the physical removal of the material that has been weathered • Erosion occurs by wind or water |
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Erosion by Water:
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• Rain strikes – breaks up and softens soil
• Surface runoff picks up soil and transports it down-hill • Faster moving water -> larger particles and greater load |
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Erosion by Wind:
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• Wind picks up soil and transports it down-wind
• Fine-grained soils more susceptible • Ex. Dust storm in the Dust Bowl of 1930s |
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Human activities can increase erosion rates
Examples: |
• Vegetation removal
• Over-irrigating • Path erosion • Construction • Over-grazing |
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Soil Erosion versus Soil Formation
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• Consider soil mass balance: are we losing soil faster than we are gaining soil?
• At “steady-state”, formation = soil erosion • Important factors in formation rates: o Climate o Source material • Human activities, including farming, accelerate the loss of soil • Soil losses in U.S. amount to billions of tons per year – about 0.04 cm per year o Faster than natural soil formation rate • Answer: Yes we are losing more soil than gaining. |
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Main impacts of Erosion
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At the point of loss:
• Loss of topsoil and associated nutrients Downstream: • Increase sediment load in streams • Surface water contamination by nutrients, pesticides and fertilizers |
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Strategies for Reducing Erosion
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The general approach:
1. Reduce wind/water energy around vulnerable soils 2. Strengthen soils The Critical role of vegetation: • Leaves reduce the wind energy (e.g. shelterbelts) • Leaves reduce raindrop energy • Root systems hold the soil in place |
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OIL
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• US domestic oil production peaked in 1970
• Demand, and hence imports, have continued to rise |
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Oil and natural gas formation and maturation
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• Typically deposited in oceans or shallow seas
• With increasing temperature and pressure, hydrocarbons break down from more complex/heavy to simpler/lighter |
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Hydrocarbon migration
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• Once solid organic matter is converted to liquids and/or gases, the hydrocarbons can migrate out of the rocks in which they were formed.
• Similarities with groundwater movement: o Flow from higher to lower pressures o Porosity and permeability o Flow stopped by low permeability formations • Differences with groundwater movement: o Lighter than water • Hydrocarbons may become concentrated in pockets o Petroleum traps o Necessary for economic oil and gas deposits |
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Coal formation and maturation:
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• Formed from remains of land plants
o (Not from marine organisms; swampy settings) o Cellulose and woody material of plants • Chemical purification with increasing pressure and time: • PEAT: the first combustible product to form o Forms at the surface given suitable conditions • LIGNITE: softest coal; high impurities -> low energy density • ANTHRACITE: hardest and highest energy density |
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Why are hydrocarbons “fossils”?
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• Relics of ancient depositional environments
• Organic matter being deposited today will not be useful as petroleum products in our lifetime o Formation > 10,000 years • Very few hydrocarbon deposits found in rocks < 1 million years old |
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Finding hydrocarbon reservoirs
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• Petroleum Geoscience
o A subdiscipline of geology • How would you decide where to look? o Consider paleoenvironments o Consider geologic formations (porosity, permeability, and geometry) • Petroleum Geology today: o Most of the easily accessible reserves have been exhausted o New technologies used for finding and extracting o Increasingly turning to the ocean (deep ocean drilling) |
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Supply and Demand for Oil:• Demand
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o Historically (almost) always increasing
o Half of all oil consumption has occurred in the last 25 years! |
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Supply and Demand for Oil:• Supply
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o Reserves: Estimate of the economically extractable oil in known deposits in a given area.
Recoverable with existing technology Commercially viable o Proven reserves and unproven reserves Describes the level of uncertainty of the estimate • Geological • Technical/Engineering • Regulatory/Political o Strategic petroleum reserve: emergency store of oil by the US government (Dept of Energy) |
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Coal Reserves and Resources
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• Currently about 25% of US energy supply
• Abundant proven domestic reserves • Limitations: o Not versatile: Not easy to use for transportation fuel Room for technological improvement! o Not clean To mine, burn, or handle |
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Environmental Impacts of Coal Use
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• Produces carbon dioxide when burned
o Affects the atmosphere’s energy balance • Emits sulfur into atmosphere upon burning o Main cause of acid rain • Creates Ash when burned o Often contains toxic metals • Coal mining safety issues o Mine collapse and lung disease |
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future of hydrocarbon use
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• Global demand will continue to rise
o Primarily developing countries • Peak oil likely within 30 years • Decline in US consumption in the near future is desirable o Environmental and public health o Geopolitical reasons • A decline in US consumption eventually is inevitable • In the mean time… |
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Carbon storage and sequestration
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• Collecting CO2 from power plants and storing deep underground
o To keep it out of the atmosphere where it can affect climate • The role of Geology o Similarities with petroleum geology and hydrogeology o Finding suitable sites o Will it leak? • Examples of locations being tested o Used up oil reservoirs o Beneath thick clay formations |
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Nuclear Safety Concerns
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• Major concerns about reactor accidents/sabotage
• Catastrophic releases of radiation have happened o Chernobyl o Core Meltdown • Fission Produces radioactive wastes o Recycling possible, but not 100% o No permanent storage or disposal sites in operation • Yucca Mountain (Nevada): o No longer under consideration for long-term high level nuclear waste storage |
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Hydropower
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• Falling water as a power source
o At least 4,000 year history in Middle East, Egypt and China |
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• Hydroelectric power
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o A stream is dammed and the discharge turns turbines to produce electricity
o The most widely used renewable source of energy worldwide |
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Hydropower:• In the United States:
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o About 2,400 hydroelectric dams
o About 7% of total power generation (2006 data) o Largest: Grand Coulee Dam, Columbia River, WA |
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Hydropower:• Main Advantages
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o Renewable
o Minimal Pollution o Bonus: Flood Control |
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Hydropower:• Main Disadvantages:
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o High investment costs
o Hydrology dependent (precipitation) o Ecological impacts of stream course alteration o Inundation of local area for reservoir construction o In the US, not many suitable sites left… |
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Biofuels 1
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• Fuels derived from biomass
• Non new (burning trees, etc) • Current emphasis on increasing contribution to transport fuel • Nebraska may have a big role to play! o Corn ethanol and cellulosic ethanol • Production of ethanol from grains: o Simple sugars created by plant photosynthesis o Sugars fermented to make ethanol o Ethanol combusted in an engine to make heat and drive a piston o Now frequently a fuel additive |
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Biofuels 2
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• An attractive source of energy
o Renewable o Plentiful • Challenges o Reduce costs of production o Environmental Issues: water use, nutrient use, soil erosion, etc o Food/fuel competition issues o Net carbon benefit? |
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The hypothesis behind the hype is simple:
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• CO2 emissions from burning fossil fuels have altered Earth’s climate.
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How do we learn about ancient climates?
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• Paleoclimate proxy records:
o Tree rings o Ice cores o Sediment records and others |
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Four components of hypothesis development:
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1. Earth’s temperature is controlled by the global energy balance (early 1800s)
2. CO2 decreases air’s ability to transmit energy (1881) 3. CO2 concentration of air has been rising because of fossil fuel burning (1938) 4. Globally averaged air temperature has been rising (for about 100 years) (1950s) |
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1. Earth’s temperature is controlled by the global energy balance (early 1800s)
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a. Global Energy Balance
i. Earth’s energy comes (mostly) from the sun ii. Temperature is determined by the balance of: 1. Heat gained (incoming solar radiation) 2. Heat lost (reflected solar radiation and heat radiated to space) 3. Heat absorbed (storage in the atmosphere and Earth’s surface) iii. Anything that changes this balance can affect temperatures globally |
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2. CO2 decreases air’s ability to transmit energy (1881)
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a. Air is a gas mixture:
i. 78% Nitrogen (N2) ii. 21% Oxygen (O2) iii. 99% overall b. The remaining 1% i. Mostly argon (Ar) and water vapor ii. Trace gases (measured in parts per million) c. CO2 is the most abundant trace gas i. Currently about 350 ppm d. Lab experiments on CO2 affecting energy: i. Measure the energy absorption of a gas mixture ii. Change trace gas concentration and measure again iii. Repeat |
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3. CO2 concentration of air has been rising because of fossil fuel burning (1938)
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a. There are other sources of CO2:
i. Ex. Volcanoes b. Fossil fuel emissions the only source large enough to account for observed CO2 increases over the last 50 years |
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4. Globally averaged air temperature has been rising (for about 100 years) (1950s)
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a. Chart shows increase
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Complications in the Global warming hypothesis:
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• Other things than CO2 can affect global temperatures:
o Other trace gases o Changes in incoming solar energy |
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Testing the hypothesis about CO2 and climate:
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• Challenges:
o Similar to other environmental geology questions o Large spatial and temporal scales o Cannot run a controlled experiment (which controls for solar inputs, other trace gases, etc) • How to do it? o See if hypothesis can explain natural patterns o Use computer models |
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Is there evidence that Earth’s temperature correlates with CO2 concentration?
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o Past 100 years? : Yes. See graph.
o Past half-million years? : yes. strong correlation between temperature and CO2 concentration |
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o Climate Modeling:
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o General Circulation Models (GCMs)
o Must track anything that affects: Earth’s energy balance Carbon inputs/outputs Feedbacks: relate to situations when one variable in the model changes and this alters the model itself. • Ex. Temperature Warms: o -> Air can hold more water o --> Earth becomes cloudier o ---> More sunlight reflected o ----> Cooling Effect o *An example of a negative feedback |
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Motivation for having environmental laws:
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o Maximizing the beneficial use of finite natural resources
o Promoting environmental quality |
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EX. The Republican River Dispute 1
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o The Republican River is an example of an interboundary river basin
o Shared by Colorado, Kansas, and Nebraska o Drains portions of each state o Main stem runs CO -> KS -> NE -> KS o Republican River Compact of 1942 o Basis for equitably dividing the “virgin annual water supply” |
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EX. The Republican River Dispute 2
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o In 1990s, KS claimed NE was using more than its fair share
o Irrigators in NE pumping shallow groundwater in the river basin o Claim that pumping was reducing streamflows o After unsuccessful talks, KS sued NE (and CO) in the US Supreme Court in 1999 o NE argued that the Compact did not cover groundwater pumping |
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EX. The Republican River Dispute 3
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o The Supreme Court ruled against NE
o “… the Compact restricts a compacting state’s consumption of groundwater to the extent that the consumption depletes stream flow in the Republican River Basin…” o Results have included: A ban on new well drilling in most of the basin The need for computer modeling (of gw/sw connections) |
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The role of environmental geology in law and policy:
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o Understanding geologic/hydrologic processes
o Quantifying resources and making predictions |
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Introduction to Water Resource Law
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o Who gets to use water, and how much?
o For historical reasons, surface water and groundwater are usually subject to different legal principles o Problematic where there are SW/GW interaction (like the Republican River) o Different laws govern water quantity and water quality |
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Surface Water (quantity) Law: part 1
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o Two basic approaches applied in the United States
o The Riparian Doctrine o The Doctrine of Prior Appropriation o The Riparian Doctrine o “whoever owns land adjacent to a stream has a right to use that water” o All those owning property bordering on a given body of water have an equal right to use o Like many American legal principles, it is based on English case law dating back hundreds of years |
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Surface Water (quantity) Law: Part 2
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o The Doctrine of Prior Appropriation:
o “whoever is first to use water from a given surface water source has top-priority rights to that water” “first in time, first in right” o Emerged mainly in the American West where climate is dry and water is scarce. o Not tied to land ownership o Rights maintained by continuing to divert water for “beneficial use” |
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o Beneficial Use:
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o Activities interpreted to be “beneficial” varies from place to place
Typically, from highest to lowest priority: • Drinking water irrigation and livestock power generation mining/drilling recreation |
