Environmental Geology Midterm Review (WIP)

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43 Terms

1
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Residence Time Equation

Volume of Reservoir / Input or Output

Assumes steady state, such that I ~ O, and the reservoir is neither filling nor emptying

2
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Exponential Growth Equation

N = New population/amount

N0 = Original population/amount

e = Euler’s number (constant)

k = Rate of change coefficient

  • REMEMBER THIS HAS UNITS OF PER UNIT OF TIME

t = Time

<p>N = New population/amount</p><p>N0 = Original population/amount</p><p>e = Euler’s number (constant)</p><p>k = Rate of change coefficient</p><ul><li><p><strong>REMEMBER THIS HAS UNITS OF PER UNIT OF TIME</strong></p></li></ul><p>t = Time</p>
3
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How to Calculate Doubling Time

Once you know “k” in the exponential growth equation, make “N” double “N0” and solve for “t”

You will always end up with ln(2) / k = t

4
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Conservation Equation and Typical Lake Inputs and Outputs

Change in S = Inputs - Outputs

Inputs for a Lake:

  • Precipitation

  • Flow in

  • Groundwater in

Outputs for a Lake:

  • Evaporation

  • Flow out

  • Groundwater drainage

5
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Main Flooding Fatality Events in US (1959-2022)

1969 — Hurricane Camille

1972 — Hurricane Agnes

2005 — Hurricane Katrina

6
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Evaporation and Precipitation Tendencies on Continents and Ocean

Ocean — Evaporation dominates

Continents — Precipitation dominates

7
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Global Energy Cycle — Albedo

102 watts/m2 is reflected and is known as Earth’s albedo

  • The majority of this is cloud cover (79 w/m2)

  • Thus, the water cycle is important

<p>102 watts/m2 is reflected and is known as <strong>Earth’s albedo</strong></p><ul><li><p>The majority of this is cloud cover (79 w/m2)</p></li><li><p>Thus, the water cycle is important</p></li></ul><p></p>
8
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Global Energy Cycle — Latent Heat Flux

Latent Heat — Heat absorbed when water evaporates

  • 80/161 of w/m2 reaching surface used to evaporate water

  • Drives the water cycle

  • Released upon condensation of water

Latent Energy Flux — From lands/ocean to atmosphere

  • Used to determine global rate of evaporation

  • 522000 km3/yr evaporation rate globally

9
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Global Cycles — 2 Ways the Transport Heat from Equator to Poles

  • Ocean currents carrying warm water (thermohaline circulation)

  • Warm air movement (major source at 10N-10S tropics) and Latent heat movement (water vapor)

    • Subtropics inject much latent heat of this due to high PPET

    • Release of latent heat in 30-50 N&S warms atmosphere

10
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Vitousek et. al. — What percentage of the Earth’s Surface has been degraded or transformed

39-50%

<p><strong>39-50%</strong></p>
11
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Vitousek et. al. — Measurements Examples

Carbon

  • Air bubbles (ice cores) in Antarctic and Greenland

  • Sources traced isotopically (before nuclear testing)

    • Direct measurements in atmosphere and tree rings

Land Transformation

  • Satellite Remote Imagine

    • % of cropland, pastures, urban-industrial, and generally impacted areas

12
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Vitousek et. al. — Important Percentage Change Chart

  • Percentage of land surface transformed

  • Percentage of atmospheric CO2 resulting from humans

  • Percentage of accessible fresh surface water used

  • Percentage of N terrestrial fixation caused by humans

  • Percentage of plant species in Canada introduced from elsewhere

  • Percentage of bird extinction in past 2 millennia

  • Percentage of major fisheries fully exploited, overexploited, or depleted

<ul><li><p>Percentage of land surface transformed</p></li><li><p>Percentage of atmospheric CO2 resulting from humans</p></li><li><p>Percentage of accessible fresh surface water used</p></li><li><p>Percentage of N terrestrial fixation caused by humans</p></li><li><p>Percentage of plant species in Canada introduced from elsewhere</p></li><li><p>Percentage of bird extinction in past 2 millennia</p></li><li><p>Percentage of major fisheries fully exploited, overexploited, or depleted</p></li></ul><p></p>
13
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Vitousek et. al. — Main Arguments

  • Human changes in the environment are not a future problem, but currently impacting at a large scale now

    • Wholistic approach; considers basically every system to be damaged

  • All problems traced to growing human population/”enterprise”

  • Our fate depends on how we handle this situation

14
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Current PPM of CO2 in Atmosphere

425 ppm

15
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Basic 3 Soil Horizons according to the Soil Formation paper by Hans Jenny

Horizon A — Material has presumably been leached from here

Horizon B — Substances from A have been deposited

Horizon C — Parent material

O Horizon, if used, addresses organic layer on the surface

16
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Two main soil former kinds

Passive — This is the source of mass that makes up the soil

  • Parent material

  • Age

  • etc.

Active — This is the energy that acts upon this soil mass

  • Biosphere

  • Atmosphere

  • Partly hydrosphere

17
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The Definition of Soil Used in Class

“Upper portion of the earth’s surface that is naturally formed from chemical and physical weathering of regolith; it is layered and contains living and non-living matter.”

18
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The 5 Main Soil Forming Factors

Climate

Organisms

Relief/Topography

Parent Material

Time

CLORPT

19
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What are the 2 best soil types

Mollisols — The BEST

  • Mainly in the Midwest, rain provides enough for grasses to grow without leaching soil

  • Grass life and death over many years deposits nutrients

Alfisols — The (second) BEST

  • Near Great Lakes area primarily

  • Loess from glaciers (I think formed much of it around the Great Lakes…)

20
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How much of the US land area is Mollisol?

22%

<p><strong>22%</strong></p>
21
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Rate of Soil Formation

Age of Soil / Thickness

22
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Chronosequencing

Finding an area of a similar climate, but different soil ages; a constant needed to determine soil formation

Glacial regression

  • Glaciers strip soil as they move forward, so regression allows formation to begin anew

Island Formation

  • As a plate slides over a hot spot, new bare islands are made, while old islands have older soil to compare with

23
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Wilkinson et. al. — Major Findings

  • Deposition of postsettlement alluvium most important geomorphic change currently

    • Farmland erosion (~600 m/m.y.) 3x river sediment loads

  • Per unit area, rate of postsettlement alluvium deposition > cropland erosion loss

  • Mean rates of Phanerozoic denudation:

    • 16 m/m.y.

  • Agricultural practices are primary source of continental erosion now, concentrated in lowland areas

    • Before, elevation was main driver, as it is the main predictor of natural erosion rates

  • We are depleting the soil reservoir

24
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Wilkinson et. al. — Measurements

Phanerozoic erosion rates

  • Deposited sedimentary rock in m/m.y and gt/y

  • How much would need to be eroded to create this thickness of rock

Modern erosion rates (???)

  • Cropland erosion in m/m.y. and gt/y

  • Assumed global farmland erosion rate of ~600m/m.y. based on past estimates; order of magnitude

  • Spatial variation determined by Universal Soil Loss Equation (at least in US figure)

25
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What is the farmland process that leads to its devastating erosion?

Tilling

26
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In what PPET is most agriculture done?

Semi-arid

0.2 < PPET < 0.5

Remember, ratio of precipitation to evapotranspiration

27
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Context of the Climate of Dust Bowl Midwest

Semi-arid, grasses acclimated to drought, drought that caused the Dust Bowl was not out of the ordinary

  • Tree ring records in the area gives this context of drought history

28
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Causes of the Dust Bowl

  • Grasses ripped up by farming practices; deep prairie grass roots vs. shallow crops

  • La Nina caused drought to arrive; Gulf of Mexico water did not reach area

    • Trade winds stronger than usual

    • Great Plains Low Level Jet” affected

  • Government encouragement; homestead act and “Dry Farming” movement

    • One way disk plows and dust mulch; improper use of land

      • Easily eroded, bare, exposed land

    • “Rain follows the plow” pseudoscience

    • El Nino rose confidence in farming

    • Degraded soil

  • Positive feedbacks

    • Dust storms + lack of plants + lack of moisture and moisture retention + lack of soil fertility

El Nino ended Dust Bowl

29
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Recurrence Interval of a Dust Bowl level drought

33 years

( solved with an RI that doesn’t factor in magnitude

RI = #years / #events )

30
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Booth & Jackson — What percentage of effective impervious area results in onset of readily observable aquatic ecosystem degradation?

10%

31
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Booth & Jackson — What were two metrics of degradation

Channel Width — How much had eroded; increased runoff

Observed fish habitat, measured by degradation as by observed erosion, sedimentation, and biological function

32
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Booth & Jackson — Causes of degraded watersheds

Surface flow regime as opposed to subsurface regime caused by:

  • Vegetation clearing — Less riparian vegetation to inhibit flow and channel widening

  • Impervious surfaces — Surface flow; no percolation

  • Soil compaction — Similar to impervious surfaces

  • Gutters — Focused runoff

Leads to increased sediments and much faster and higher peak discharge in streams.

33
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Booth & Jackson — Difference between Total Impacted Area and Effective Impacted Area

Total Impacted Area

  • Fraction of watershed covered by constructed, impermeable surfaces

  • Ignores compacted surfaces

  • Includes impervious surfaces that don’t contribute to the problem

    • Ex. Impervious gazebo next to soil

Effective Impacted Area

  • Impervious surfaces with a direct, hydraulic connection to downstream drainage

34
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Booth & Jackson — Difference between peak standard and duration standard

Peak Standard:

  • Maintain postdevelopment peak discharges at predevelopment levels

Duration Standard:

  • Maintain postdevelopment duration of all sediment-transporting discharges at predevelopment levels

  • Better standard

35
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Booth & Jackson — Problems with retention/detention ponds

It is much too costly to make an optimized pond according to the right standard — Restrictive and costly

36
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Difference between retention and detention ponds

Wet retention ponds

  • Always have water in them

  • Supposedly helps water quality and allows chemicals and sediments to settle

Detention ponds

  • Dry until a storm comes

37
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Hancock — Specific design goal of James City County retention ponds, and how many achieved it?

24 hour inflow-to-outflow centroid lag time for a 1 hour, 24-hours storm

Only 1/5 achieved it; 4/5 failed

38
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Hancock — Problems with retention ponds

Use of “Kerplunk” method

  • States all water from storm drops at once

  • Leads to ponds that can handle water for 24 hours, but centroid lag time occurs at 12 hours

Underprediction of rainfall intensity and runoff curve numbers in determining peak and total runoff from design storms

  • Storm intensities observed were more intense

  • May have underestimated partially pervious surfaces

Didn’t account for piggybacking of storms

  • Back-to-back storms

OVERALL, RETENTION AND DETENTION PONDS ARE NOT BUILT TO STANDARDS, AND WHILE THEY WORK HYPOTHETICALLY, LOOPHOLES HAVE ALLOWED THEM TO BE BUILT UNDER STANDARD ACROSS THE NATION, AND IT IS TOO COSTLY TO MAKE THEM WORK AS INTENDED.

39
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Mekonnen — How did they measure water scarcity, and what was the main finding

Monthly basis using 30 × 30 arc min cells

Ratio of blue water footprint to blue water availability

  • WS > 2 : Severe

Identified seasonal trends for water scarcity, and that 4 billion, or 2/3 of the current population of the study, experienced severe water scarcity at least 1 month of the year

40
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Mekonnen — Causes of differences in water scarcity

  • Hadley Cells

    • Wet at equator, subtropical/desert at 30 degrees N/S

  • Rain Shadow Effect

    • Block precipitation

  • Large Continental Interiors

  • Cold water

    • Less evaporation

  • Human consumption

  • Agricultural irrigation use

41
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Mekonnen — Why does this data have low variability (4 billion people suffer water scarcity point)

Demand and availability usually magnitudes apart

  • Either very high demand and low availability

  • Very high availability as opposed to relatively low demand

Environmental flow requirement parameters also do not shift much

42
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Mekonnen — Why did past studies fail to capture these spatial and temporal trends

  • Did not account for environmental flow requirement in rivers

    • Assumed people could take more water than they could

  • Did not account for monthly trends, just annual

  • and/or

  • Did not examine at a high enough resolution

    • Just river basins

43
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What metric do they use to determine how much available freshwater there is?

Streamflow to ocean

  • Counts for evapotranspiration

  • 46000 km2/yr

Convert with 1000 m cubed to determine how much each person gets