Transcript US scale study prese..

Water Sustainability in the
United States With a Focus on
Power Generation Cooling
Water Requirements
Sujoy Roy, Karen Summers, and
Robert Goldstein
Tetra Tech Inc, Lafayette, Ca and
EPRI, Palo Alto Ca
US Population and Total
Total Freshwater Withdrawal
and Population
Freshwater
Withdrawal
300
Population (right axis)
400
250
300
200
150
200
100
100
50
0
0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
Year
US Population (millions)
Total Freshwater Withdrawal
(billion gallons per day)
Withdrawal (left axis)
Withdrawal
Consumptive Use
342 bgd
100 bgd
Domestic Use
7%
Dom estic U se
7%
Commercial Use
3%
Commercial Use
1%
Industrial Use
8%
Indus trial Us e
3%
Therm oelectric Us e
3%
Irrigation Use
40%
Mining Us e
1%
Livestock U se
3%
Livestock Use
2%
Mining Use
1%
Thermoelectric Use
39%
Irrigation Use
82%
Why is the Linkage Between Water and
Thermoelectric Generation Important?
• Problems occur at a smaller temporal and spatial
scales
• Power generation demands are often localized, with
significant impacts over small areas
• In some periods of the year, and in some drought
years, competition with other uses can lead to
shortages (municipal, environmental, etc.)
• High population growth areas often correspond with
areas for new electricity demand, many of which
growth are among the more water-short areas in the
country
Approach to Perform a National Assessment
of Water Availability and Demand
I) For current conditions, use available data on
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Population (Census Bureau)
Temperature and precipitation (NOAA)
Water use (USGS)
Electricity generation (EIA)
Endangered aquatic species (EPA)
II) Estimate future conditions by in various water use sectors
 Using available forecasts
 Extrapolating from current rates of change
 Assuming no change in conditions
III) Future water demands based on assumption of
 Rates of water use per unit of activity (i.e., domestic water use per
capita) remain at current levels
 Rates of water use exhibit improvements in efficiency over the next
25 years as they have over the last two decades
Population Change
2000
2025
Electricity Generation, Quadrillion (1015) Btu
Energy demand for different census divisions of the US
4
New England
Middle Atlantic
East North Central
West North Central
South Atlantic
East South Central
West South Central
Mountain
Pacific
3
2
1
0
2000
2005
2010
2015
2020
2025
Year
Energy demand projected by the Energy Information Administration,
Department of Energy (1 quadrillion Btu = 2.398x105 gigawatt-hours).
Thermoelectric Generation
New Electricity Generation Needed by 2025
Available Precipitation*, Averaged Over 1934-2002
*Available precipitation is defined as the difference
between monthly precipitation and potential
evapotranspiration.
Total Freshwater Withdrawal in 1995
(as a percent of available precipitation)
Change in water withdrawal requirements from 1995 to 2025, in
inches per year, for the business-as-usual scenario
Storage Infrastructure Requirements
Summer deficit in 2025 and the change in summer deficit from 1995
to 2025, in inches per year, for the business-as-usual scenario
A Proposed Index of Water Sustainability
Each of the Following is Scored 0 or 1
2 = slightly, 3 = moderately, and 4 = highly susceptible
1) Extent of development of available renewable water:
- Greater than 25% of available precipitation currently used
2) Sustainable groundwater use:
- Ratio of groundwater withdrawal to available precipitation is greater than 50%.
3) Environmental regulatory limits on freshwater withdrawals:
- Presence of two or more endangered aquatic species.
4) Susceptibility to drought:
- Difference between water withdrawal during the three driest months of the year (July,
August, September) and available precipitation is greater than 10 inches, where the lowest 3year average rolling precipitation, based on data from 1934-2002 is considered.
5) Growth of Water Use:
- Business as usual requirements to 2025 increase current freshwater withdrawal by more than
20%.
6) New requirements for storage or withdrawal from storage:
- Summer deficit (difference between withdrawal and available precipitation in an average
year) increases more than 1 inch over 1995-2025.
Water Supply Sustainability Index
Thermoelectric Cooling Constraint Index
Highly constrained: Generation growth > 50%, WSSI >= 3
Moderately constrained: Generation growth > 50%, WSSI >= 2
Findings/Next Steps
• Publicly available data provide a basis to evaluate
sustainable water use and highlight regions that need
more study and/or data; not all water supply/storage
limitations are in the Western U.S.
• Consider different assumptions for growth, including
more sophisticated representations of future water
use by different sectors of the economy
• Consideration of climate change
• Some data needs:
– A better representation of regulatory limits on water
withdrawals, or an estimate of environmental flow
requirements, are needed
– Data on intra-annual use could be important in highlighting
scarcity in the driest months of the year
– More uniform assessment of water quality impairment