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Announcements

• Exam grades will be posted by tomorrow• Last weekend for L.E.A.D. Mar 12th. You

must submit your summary by Mar 14th

• Extra credit movies due next Tuesday

• Pollution week!• Today: Water conservation and pollution

– Hydrological cycle– Water exploitation– Water pollution

Dust bowl: 1930 – 1936

South Dakota Oklahoma

What caused the dust bowl?

• Settlement during unusually wet period• Farming with excessive tilling and

without crop rotation• Several years of drought• Solution: Ogallala Aquifer (World’s

largest aquifer, tapped extensively after WWII)

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Readings

• Hogan 2014– Learn about sources of water pollutants

• Postel et al. 1996– Get a sense for how a global water budget is

constructed

Water sourcesPools of water Volume (km3) %Atmosphere 13,000 0.0009Fresh water 2,500,000 0.18Groundwater 8,200,000 0.6Ice 27,000,000 1.9Oceans 1,350,000,000 97.6Sum 1,380,000,000 100

Estimates from Postel et al. Science 1996

Hydrologic Cycle

• Evaporation & transpiration (evapotranspiration)

• Condensation & precipitation

• Purification• Transportation

Human impacts on hydrologic cycle

• Overdrawing water supplies from reservoirs and groundwater (land subsidence, saltwater intrusion)

• Deforestation, over cultivation, overgrazing, and paving: increases flooding, decreases groundwater supply

• Water pollution: harms wildlife, makes water unusable

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Human-logic cycle

• Purify water - municipal treatment plants• Use water (consume, pollute)• Purify water again – waste-water

treatment plants• Mississippi River water passes through

people 7x before it enters Gulf of Mexico

Municipalwater use andtreatment.

WWTP:- Primary- Secondary- Tertiary

Wastewater treatment:1: Remove solids (sludge)2: Break down dissolved

organic material (bacteria)3: Remove nutrients and

chlorinate effluent4: Release

Mr. Floatie’s mayoralcampaign, Victoria, BC

(P.O.O.P. party)

Water exploitation

80% of consumptive use in U.S. is for agriculture

Water exploitation• Ogallala aquifer

– Withdrawal = 5-30 x recharge rate– Lowering ~6 ft per y– Estimated life at current rates ~25 y

• What will happen in 25 y?

• Why is the water overused?

• Should Fed gov’t subsidize water use by agriculture (e.g., cotton) or water conservation?

• How can the US stop overuse?

Figure: Water-level change: Predevelopment to 2005 (Source: USGS 2007)

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Water markets

• AustraliaPrice and use of water varies with availability(More water in 2009 than 2007)

Water entitlements versus allocation. Allocations are tradeable.Water markets have improved efficiency of water use and allocation.

Water markets in US

• No Federal markets• States make their own rules• Rule of Capture: You can pump water

below your own land (with exceptions)• Texas is the only state with a water market

“The Texas Water Exchange”(Started in 2014 for groundwater only)www.texaswaterexchange.com

Water exploitation elsewhere

• India: Withdrawal = 2x recharge rate• China: Water table dropping 5 ft per y• Ganges, Yellow and Nile Rivers barely

reach the ocean

Water conservation

First three photos from: http://www.ers.usda.gov

Percolationloss at lowspot in furrow

Sprinklers drip systems

50% U.S. systemsgravity flow

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Water conservation at home

• Tips for conserving– Don’t water a lawn– New toilets– Short showers– New clothes washer– Use a dishwasher– Stop leaks

Water pollution• Solid Waste (plastics, cigarette butts)• Organic contaminants

– BOD: Biochemical Oxygen Demand– PAH: Polycyclic Aromatic Hydrocarbons– Halogenated Hydrocarbons (adding Cl, F, Br)

• Heavy metals (Pb, Cr, Cu, etc.)• Organo-metals: Methyl-Hg (Neurotoxin), TBT (immunity)• Pathogens (bacteria, viruses)• Water property changes (e.g., temperature)• Excess nutrients

46,000/mi2

Deepwater Horizon: April 21, 20105 million barrels of oil leaked into GOM

Image from US Coast Guard

Water pollution sourcesHalf pound of plastics found inside dead

albatross

Photo from National Geographic

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Water pollution sources

• Primary sources– Runoff & discharges– atmospheric deposition

• Point sources • Nonpoint sources

From Garrison (2002) Oceanography

Sources of pollution in Puget Sound (EPA 2007)←

Wat

er

Air

→

← Water Living things →

Behavior of organic contaminants in water

More polar (charged) compounds remain dissolved in water

Smaller volatile compounds move toward the atmosphere

Biologically active molecules accumulate in the food chain

Fate of DDT

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Biomagnification Puget Sound contaminantsN → S N → S

Organic contaminants in harbor seals from Ross et al. (2013)

Puget Sound contaminants

Organic contaminants in harbor seals from Ross et al. (2013)

Water pollution effects

• Nutrients and eutrophication– Nutrients limit productivity

• Key limiting nutrients: nitrogen and phosphorus– Excess nutrients act as pollutants

• Steps:– Increased N or P– Increased phytoplankton productivity– Decreased water clarity– Mixing rates low: - phytoplankton sink to bottom

- respiration consumes oxygen- aerobic organisms emigrate or die

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Pollution and population size

• N input to coastal zone correlated with population size

Plot from Howarth et al. (2000)

Hypoxia in Hood Canal

Photos from www.psat.wa.gov/Programs/hood_canal

July 31, 2004

Hypoxia and stratification in Hood Canal

outflow

inflow

Average circulation time: 1 to 5 monthsStratification is greatest in summer and fall

Dissolved oxygen in July 2004. Data from Warner (unpublished)

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Global distribution of “dead zones”

From Diaz and Rosenberg, Science 2008

Number of dead zones has doubled each decade since the 1960s

Lake Whatcom

• WWU’s Institute of Watershed Studies monitors Lake Whatcom water quality

• http://www.wwu.edu/iws• Lake Whatcom issues:

– Declining dissolved oxygen in bottom water– Increased growth of cyanobacteria– Increased concentrations of trihalomethanes

Reducing water pollution

• Clean Water Act (1972)• Use alternatives to pesticides and control erosion• Pick up after your pet• Dispose of oil and household chemicals properly

– Disposal of Toxics Facility 3505 Airport DriveBellingham 360-380-4640

Reducing water pollution