Transcript Vogel

Where Will the Water Go?
Hydrologic Impacts of Climate Change
Tufts University
David Purkey, SEI
and
Richard M. Vogel
Department of Civil and Environmental Engineering
Tufts University
SEI Climate Change Symposium
Tufts University
November 30, 2007
Background and Motivation I
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• Previous national water resource assessments were
completed 30-40 years ago:
Wollman and Bonem, 1971; Water Resources Council 1968, 1978
National Water Commission, 1973
• Methods introduced here apply to local, regional,
national and global Climate and Water Assessments
• Water Availability Is Impacted by Climate, Land
Use and Water Use and their Interactions and
Changes
Background and Motivation II
Tufts University
Many recent innovations enable us
to perform water resource
assessments at extremely fine
spatial and temporal scales.
Intellectual quest for an analog to
the ‘Mach number’ or ‘Reynolds
number’ for hydroclimatic
systems
Background
and Motivation
III
Balancing Water for
Humans and Nature
by
Malin Falkenmark
and
Johan Rockström
2004
Methodology for a
National/Global Water Census
Tufts University
Many of the following ideas arise from a
collaboration with Peter Weiskel (USGS) and
others resulting in:
Weiskel, P.K., R.M. Vogel, P.A. Steeves, P.J. Zarriello,
L.A. DeSimone and K.G. Ries, III, Water-Use regimes:
Characterizing direct human interaction with hydrologic
systems, Water Resources Research, 43, W04402, 2007
and several other papers in progress.
Traditionally, water availability is defined in
terms of NET water balance of a watershed
Tufts University
P – ET = SWout
P
* water availability = runoff
* reflects both the traditional
water-supply perspective,
and
an aquatic-focused
ecological perspective P = Precipitation;
ET = Evapotranspiration
SWout = Surface-water runoff
Assume that GWin = GWout = 0
Consider total instead of net
water balance…
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P = SWout + ET
* considers both:
“green water” (ET) demands of
terrestrial ecosystems, including
rainfed agriculture, and
“blue water” (SWout) demands
of aquatic ecosystems and
human withdrawals.
See Falkenmark and Rockström, 2004
From watersheds to
hydrologic units …
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SWin + P = SWout + ET
Unit 1
Unit 2
* Considers landscape position,
as well as climate.
* considers both green and blue
water
Recent GIS datasets (or gridded models) are
essential to this approach: (i.e. National
Hydrography Dataset, PRISM Climate Data, etc.)
Hydroclimatic Regimes
4 Extreme End-members Arise From Total Water Balance
P
P
ET
SW +
GW
headwater
no-flow
headwater
source
ET
SW + GW
SW +
GW
terminal
flow-through
terminal sink
(from Weiskel, Vogel and others., in prep.)
Example from
New England
Potential Water Availability
(= P + SWin) for each of 308
HUC-12’s of the Conn. River
watershed (mean annual)
Map by Sara Brandt, using
regional hydrologic equations of
Vogel and Wilson (1996)
Paper on hydroclimatic regimes
to appear as Weiskel, Vogel and
others, in preparation, 2007
Now, lower case denotes the
normalized water balance:
p + (swin + gwin) = et + (swout + gwout) = 1
- Land-atmosphere fluxes (P, ET)
- Landscape fluxes (GW, SW)
hydrosystem
Map of Potential
Water Availability
for the African
Continent
From MS Thesis by
Sara Freeman
Tufts University
2007
Hydroclimatic
regime plot
Shows relative
magnitudes of
vertical and
horizontal fluxes
Deerfield
River, MA,
HUC-12
Connecticut
River basin,
hydroclimatic
regimes
(for 308 HUC-12’s)
Very humid
Humid
Sub-humid
Semi-arid
Arid
Very arid
ET / P
0 – 0.33
0.33 – 0.66
0.66 – 1.0
1.0 – 1.5
1.5 – 3.0
> 3.0
(data compiled by S.. Brandt
using Vogel et al regressions)
Hydrologic Position Index = p
1
very
humid
0.9
humid
headwaters
sub-humid
0.8
0.7
semi-arid
0.6
hydroclimatic
pathway
0.5
arid
0.4
0.3
0.2
very
arid
0.1
0
0
mouth
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Evapotranspiration Index
= et
1
Integrating human water use
into the water balance …
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SWin + P + Hin
= SWout + ET + Hout
(see Weiskel and others, 2007)
Hout = withdrawals
Hin = return flows + imports
A new conceptual model of the
terrestrial water balance:
…a
water balance with three flux classes:
- Land-atmosphere fluxes (P, ET)
- Landscape fluxes (GW, SW)
- Human fluxes (Hin, Hout)
hydrosystem
Water-use Regimes:
4 end-member (EXTREME) regimes
Hin
P - ET
P - ET
Hin Hout
SW +
GW
churned
surcharged
P ET
P - ET
SW +
GW
undeveloped
Hout
SW +
GW
depleted
(from Weiskel, Vogel and others 2007)
Central
Valley
Aquifer
Water-use
regime plot
Shows relative
magnitudes of
withdrawals versus
return flows and of
human vs.
natural fluxes.
(Weiskel, Vogel and others,
2007)
Selected Water-Use Regimes
Watersheds
Normalized Imports
+Return Flows
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From Weiskel, Vog
and others.,
2007
Normalized Withdrawals
Selected water-use regimes
Aquifers
Normalized Return Flows
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From Weiskel,
Vogel and
others., 2007
Normalized Withdrawals
Seasonal (Monthly) Water Use
Regimes
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Normalized Return Flows
Upper Charles River
Aquifer,
Massachusetts
1989-1998
Regimes are sensitive
to seasonal climate and
water use variations
Normalized Withdrawals
Based on transient
simulations of
Eggleston (2003)
A Water Resource Development
Pathway
Tufts University
Normalized Return Flows
Mississippi River
Alluvial Aquifer,
Predevelopment 1918
to 1998
Water use regimes are
subject to trends
Normalized Withdrawals
Based on transient
simulations of Reed
(2003)
Sustainable Water-Use
Regimes
Tufts University
Normalized Return Flows
A rich topic for
future research
For example relative
Net demand RND
H out  H in
RND 
SWout
Normalized Withdrawals
RND>0.2 implies
STRESS
Green Water Management
Potential
Tufts University
Green water
management strategies
are most attractive in
hydrologic units with
high water use intensity
AND high green water
availability
An Indicator
of Green
Water
Management
Potential
From MS thesis
Sarah Freeman
Tufts University
2007
Summary
Tufts University
Traditional focus has been on net water balance of
watersheds
•Focus was on blue-water demands of humans and aquatic
ecosystems
•Traditional water assessments did not fully incorporate
humans into the water balance
•Focus was on watersheds, whereas water availability
also depends upon location WITHIN watershed
Total water balance of hydrologic units offers a
more comprehensive view of hydroclimatology
Summary
Tufts University
Water Resource Assessments Must Focus on
Hydrologic Units (HU’s) and total water
balance because:
•1- Total water balance focuses on blue and greenwater demands of humans (e.g., rainfed
agriculture) and terrestrial ecosystems
•2-Water is managed in hydrologic units
•3- Spatial datasets are gridded which is consistent
with HU’s
•4-Integrated water balance is needed for full
incorporation of humans into water cycle
Climate Elasticity of Streamflow
Tufts University
Sankarasubramanian, Vogel and Limbrunner, Climate Elasticity of Streamflow in
the United States, Water Resources Research, 2001.