Resource Planning & Supply
Uncertainty
Ralph P. Marra
Water Administrator
Presented to:
4th Bi-National Workshop
Universidad de Sonora
Hermosillo, Mexico
May 7, 2010
Tucson
Second
Active
Largest
Management
Urban
Area
Community in
Arizona
Central Arizona Canal
City of Tucson
Tucson Active
Management Area
(TAMA)
Water Use by Sector: 1940-2000
Tucson Active Management Area
600
400
Industrial
Industrial
Total
Total
700
600
500
400
300
300
200
200
100
100
0
0
1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000
2000
Year
(Millions of Cubic Meters)
Water Use
(Thousands of Acre Feet)
500
Municipal
Municipal
Water Use
Agricultural
Agricultural
1940
1945
1950
1955
1960
1965
1970
50
25
1975
1980
1985
1990
1995
50
2000
…Leads to Subsidence in the Central City
2000
3”-4”
2”-3”
50
1”-2”
Source:USGS 2000
(1987 - 1998)
Need to Shift from Groundwater Mining
to Renewable Supplies
Colorado River Water
Renewable Groundwater
Reclaimed Wastewater
Future Resource Uncertainties

How will Tucson meet growing future water
demand with highly reliable water supplies?

Will Tucsonans accept indirect potable reuse of
effluent?

Will emerging contaminants reduce the
availability of current and future supplies?

How much will our Customers be willing to
conserve?

What additional water supplies will be available in
the future and when?
Future Resource Uncertainties (con’t)

How much will our Customers be willing to pay for
additional supplies?

How large will future Colorado River water
shortages be? And will they be temporary or
permanent?

How might climate change impact seasonal water
demand?

How will climate-change mitigation plans impact
the cost of energy and therefore water?

Will States engage in high-stakes conflict OR
creative cooperation to mitigate future climatechange impacts?
Adaptive Planning for Future Flexibility
Alternatives
Alternatives
One-Dimensional
Planning
A
B
C
D
Equally
Possible
Futures
Possible Futures
Scenario
Planning
Elements
Common to A-D
Elements
Common to A-B
Elements
Common to A-C
A
B
C
D
Long-Range Planning Area
Our Population is Projected to Increase…
1,400,000
Population Projection
1,200,000
1,000,000
800,000
600,000
400,000
200,000
0
2000
2010
2020
2030
Year
2040
2050
And So Will Our Projected
Total Water Demand
300
300
200
200
150
100
100
50
0
0
2000
2005
2010
2015
Actual Demand
2020
2025
Years
2030
2035
2040
2045
2050
Millions of Cubic Meters
Thousands of Acre Feet
250
Water Resource Utilization Plan
Fully Utilize Existing
Renewable Supplies
Potable
Demand
Acre-Feet
200,000
Increase
300
Conservation
Total
Demand
200
150,000
?
?
?
100,000
2032
100
50,000
0
2000
Millions of Cubic Meters
300,000
250,000
Acquire Additional
Supplies
0
2010
2020
2030
Year
2040
Ground Water
Reclaimed
Additional
Colorado River Water
CAGRD
Incidental Recharge
2050
Water Bank Recovery
Key Common Planning Elements

Reduce Groundwater Use to Sustainable Rate

Utilize All Available Renewable Resources

Increase the Level of Per Capita Conservation

Acquire Additional Water Resources to Reinforce
Vulnerable Supplies and for Growth

Replace Aging Infrastructure

Increase Revenue to Pay for All the Above

Develop Multi-State Strategies to Mitigate Future
Colorado River Supply Shortages
http://www.tucsonaz.gov/water/longrange.htm