(Mt/Ag/EnSc/EnSt 404/504 - Global Change) Water Resources (from IPCC WG-2, Chapter 3) Water...

(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) Water Resources (from IPCC WG-2, Chapter 3)Water Resources (from IPCC WG-2, Chapter 3)

Water ResourcesWater Resources

Primary Source: Primary Source:

IPCC WG-2 Chapter 3 – Freshwater Resources and Their ManagementIPCC WG-2 Chapter 3 – Freshwater Resources and Their Management


Human Activities Affecting Water ResourcesHuman Activities Affecting Water Resources

(modified after Oki, 2005)

clear land

irrigate?

drain?

less ET?

less precip?


Human Activities Affecting Water ResourcesHuman Activities Affecting Water Resources

(modified after Oki, 2005)

veg. change?

soil moisture?

more ET?

more precip ?


Drivers of Water Consumption?Drivers of Water Consumption?

• PopulationPopulation

• Food consumptionFood consumption

• Economic policy (including water pricing)Economic policy (including water pricing)

• Technology (increased efficiency, increased demand)Technology (increased efficiency, increased demand)

• Lifestyle (e.g., recreation)Lifestyle (e.g., recreation)

• Societal value of freshwater ecosystemsSocietal value of freshwater ecosystems


Human VulnerabilityHuman Vulnerability

• 25% of population in coastal regions25% of population in coastal regions

- < 10% of renewable water supply< 10% of renewable water supply

- rapid population growthrapid population growth

• IrrigationIrrigation

- > 70% of water withdrawals > 70% of water withdrawals

- > 90% of non-reusable, consumptive use> 90% of non-reusable, consumptive use

• Water-stressed basins have 1.5 - 2.1 billion peopleWater-stressed basins have 1.5 - 2.1 billion people

• Increased efficiency can yield increased vulnerability!Increased efficiency can yield increased vulnerability!


Current Water StressCurrent Water Stress


Water-Stress EffectsWater-Stress EffectsAmountAmount

TimingTiming- seasonalityseasonality

- droughtdrought

- floodflood

QualityQuality

- salinity- salinity

- nutrientsnutrients

- temperaturetemperature

- toxinstoxins

- pathogenspathogens

- sedimentssediments


A simple surface water budgetA simple surface water budget

Precipitation – Evaporation = Runoff + Precipitation – Evaporation = Runoff + StorageStorage

storage storage includes lots of things:includes lots of things:

soil moisture, aquifers, reservoirs, withdrawals for soil moisture, aquifers, reservoirs, withdrawals for irrigation, glaciers, snowpack, etc.irrigation, glaciers, snowpack, etc.

(From R. Arritt)(From R. Arritt)


Africa: Geographic ChangesAfrica: Geographic Changes2080-20992080-2099

Minus Minus

1980-19991980-1999

(A1B)(A1B)

# models # models with with > 0 > 0

+10

-1

+50%

-50%

21

0


Africa: Water Balance ChangesAfrica: Water Balance Changes

2080-2099 Minus 1980-19992080-2099 Minus 1980-1999 # models with # models with > 0 > 0


South America: Geographic ChangesSouth America: Geographic Changes

# models # models with with > 0 > 0

+10

-1

+50%

-50%

21

0

2080-20992080-2099

Minus Minus

1980-19991980-1999

(A1B)(A1B)


South America: Water Balance ChangesSouth America: Water Balance Changes

+10

-1

+50%

-50%

21

0

2080-2099 Minus 1980-19992080-2099 Minus 1980-1999 # models with # models with > 0 > 0


Multi-Model Runoff ChangeMulti-Model Runoff Change

A1B ScenarioAgree on sign of change?

white: < 66%

stippled: > 90%(derived from Milly et al. 2005)


Runoff Runoff ChangeChange

SRES A2SRES A2

2050s vs.2050s vs.1961-19901961-1990

Seasonality?Seasonality?


Groundwater RechargeGroundwater Recharge Using a global hydrological model - WGHM Using a global hydrological model - WGHM


What is drought?

• One definition:One definition:

• Elements of the definition:Elements of the definition:• deficiency of precipitationdeficiency of precipitation• extended period (how long is "extended"?)extended period (how long is "extended"?)• water shortage for some user ("group or water shortage for some user ("group or

activity") activity")

A deficiency of precipitation over an A deficiency of precipitation over an extended period that causes water extended period that causes water

shortage for some group or activity.shortage for some group or activity.


Drought depends on the user

• Crops rely on stored soil water. Soil water can be rapidly depleted, so that monthly droughts may affect crops.



• Rivers and streams may dry out during seasonal droughts.



• Multi-year droughts Multi-year droughts may deplete ground water that may deplete ground water that supports communities.supports communities.


Drought, more precisely

• Must define Must define the time period the time period over which precipitation is over which precipitation is below normal.below normal.

• Must define what is Must define what is a water shortage a water shortage that affects a that affects a particular activity.particular activity.


Iowa corn yields

1988 drought1993 flood


Recurrence of 100-yr DroughtsRecurrence of 100-yr Droughts

• IS92a IS92a emissionsemissions

• Business-as-Business-as-usual water usual water scenario scenario


Increased Water StressIncreased Water Stress


Runoff Changes - Two AnalysesRunoff Changes - Two Analyses

A1B ScenarioA1B Scenario

Agree on sign of Agree on sign of change?change?

white: < 66%white: < 66%

stippled: > 90%stippled: > 90%

(derived from Milly et al. 2005)(derived from Milly et al. 2005)

(derived from Nohara et al. 2006)(derived from Nohara et al. 2006)

(2081-2100) minus (1981-2000)

Lake MeadLake Mead


Lake Mead Facts• Lake Mead was formed in Black Canyon when the

Hoover Dam was finished in 1935.• Water source for over 22 million people. • Lake Mead supplies water to:

• Las Vegas• 90% of the supply comes from Lake Mead

• Los Angeles• San Diego• Southern California Agriculture

• Extends 110 miles behind the dam• Capacity is 28.5 million acre-feet

• Saylorville = 641,000 acre-feet


Lake Running Dry? The CausesLake Running Dry? The Causes

• Colorado River system is seeing a deficit of Colorado River system is seeing a deficit of

1 million acre-feet of water per year1 million acre-feet of water per year• This amount can supply 8 million people for 1 year.This amount can supply 8 million people for 1 year.

• The water supply is not being replenishedThe water supply is not being replenished• 8 years of continued drought in the region8 years of continued drought in the region• Below average snowfall within the Colorado River Below average snowfall within the Colorado River

watershedwatershed

• Human factorsHuman factors• Human demand has increased as populations in the Human demand has increased as populations in the

southwest have exploded.southwest have exploded.• Increased evaporation off the lakeIncreased evaporation off the lake• Human induced climate changeHuman induced climate change


A ComparisonA Comparison

Lake Mead has dropped over 100 feet in the last 10 years Lake Mead has dropped over 100 feet in the last 10 years to its lowest level since the 1960s.to its lowest level since the 1960s.

September 1998 June 2008September 1998 June 2008


Personal Experience (R. C.-G.)Personal Experience (R. C.-G.)A photo I took of the The same view behindA photo I took of the The same view behind

1998 flood at the dam - the dam in June 2008.1998 flood at the dam - the dam in June 2008.water topped the water topped the 8 years of drought and over-use of water8 years of drought and over-use of water

spillways for 4 days.spillways for 4 days.May 1998 Las Vegas flood and above average snowfallMay 1998 Las Vegas flood and above average snowfall


Update: Update: New Record New Record

LowLow

(Source: Climate.gov)(Source: Climate.gov)


Long-Term TrendsLong-Term Trends

(Source: http://www.arachnoid.com/NaturalResources/)(Source: http://www.arachnoid.com/NaturalResources/)


Water Cycle Changes - ImpactsWater Cycle Changes - ImpactsA1B ScenarioA1B Scenario

(derived from Nohara et al. 2006)(derived from Nohara et al. 2006)

(2081-2100) minus (1981-2000)


Water Cycle Changes – AR5Water Cycle Changes – AR5

Table for Table for next next slideslide


Water Cycle Changes – AR5Water Cycle Changes – AR5Observed ImpactsObserved Impacts


Water Cycle Changes – AR5Water Cycle Changes – AR5Change in Runoff @ +2˚C: GCM Change in Runoff @ +2˚C: GCM GHM simulation GHM simulation

(from Schewe et al. 2013)(from Schewe et al. 2013)


Water Cycle Changes - AR5Water Cycle Changes - AR5

Freq of flood with magnitude of Freq of flood with magnitude of 1971-2000 “100-yr flood”1971-2000 “100-yr flood”

Global exposure to 20 C 100-year flood (or greater) [106 people]

(Hirabayashi et al., 2013)


Water Cycle Water Cycle Changes Changes

AR5AR5

Change in Change in Runoff @ +2˚CRunoff @ +2˚C


Water Cycle Changes – AR5Water Cycle Changes – AR5Human vulnerability to decrease in renewable groundwater res. (by 2050s)Human vulnerability to decrease in renewable groundwater res. (by 2050s)

(from Döll et al. 2009)(from Döll et al. 2009)


Water Cycle Changes – AR5Water Cycle Changes – AR5Table for figure in next slideTable for figure in next slide






ENDEND

Water ResourcesWater Resources

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