Water demand
planning and
climate change
HOW ARE CHANGES IN CUSTOMER WATER DEMANDS AND CLIMATE
IMPACTING HOW WE THINK ABOUT FUTURE WATER SUPPLY?
Peter Mayer, P.E.
Principal
Climate Change
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Drought
Water shortages
Super storms
Floods
New water supply = time + $$$
Drought @2050 vs. Notorious Recent Historical Droughts
PDSI = Palmer Drought
Severity Index
PDSI was developed by
Wayne Palmer in the 1960s
and uses temperature and
rainfall information in a
formula to determine
dryness.
2040-2060
Source: Dr. Martin
Hoerling, NOAA
Earth System Research
Laboratory
US Drought Monitor
Risks of Climate Change for Water
Providers


Decreased water supply

Reduced snowpack

Earlier runoff
Increased water demand

Hotter and drier

Higher evapotranspiration rates

Increased outdoor demand for irrigation

Increased indoor demand for cooling

Intense and more frequent drought

Variability and uncertainty
Potential Water Provider Responses
to Climate Change
 Increase
water supply, treatment
capacity, and storage
 Manage
 Both
 Nothing
water demand
Greeley Colorado
100 Years of Water Use
City of Greeley Water Production (MGD)
12,000.000
10,000.000
8,000.000
6,000.000
4,000.000
2,000.000
2013
2008
2003
1998
1993
1988
1983
1978
1973
1968
1963
1958
1953
1948
1943
1938
1933
1928
1923
1918
1913
1908
0.000
Climate Conundrum: Uncertainty

Risks of developing new supply, capacity, and
storage
 Demand
doesn’t materialize
 Infrastructure
over-built
 Public
pays for water and infrastructure that wasn’t
needed

Risks of managing water demand
 It
doesn’t work and demand increases.
 It
works and revenue declines
Water Demand Forecasting Takes
on New Importance
Understanding
likely future
demand trends is essential to
preparing effectively for
climate change.
A brief history of demand
forecasting in Seattle, WA
Per Capita Demand and Drought
180
160
140
Gallons per capita per day
1992 - 2002 avg = 149.9 gpcd
120
2003 - 2014 avg = 131.0 gpcd
100
80
Drought
2002-2004
13% reduction in average
system gpcd from 1992 - 2014.
60
40
20
0
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
12,000
3.50
10,000
3.00
8,000
2.50
6,000
2.00
4,000
1.50
Drought
2002-2004
2,000
1.00
-
0.50
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
Net ET (ft)
Seasonal Demand (AF)
Net ET (ft)
Seasonal Demand (AF)
Seasonal Demand and Net ET
Net ET vs. Seasonal Demand
12,000
Seasonal
Impact
Seasonal Demand (AF)
10,000
8,000
6,000
y = 294.54x - 341.63
R² = 0.5154
4,000
2,000
15.0
20.0
25.0
30.0
Net ET - Inches
35.0
40.0
Demand Forecasts that Incorporate
Climate Change Impacts

Example: In Colorado Front Range climatologists
predict 4 - 7˚ F average temperature increase,
but uncertain changes in precipitation

Temperature increase used in ET models for
predict future landscape water requirements

Demand forecasts that include an explicit
outdoor irrigation component incorporate these
potential increases
Scenario planning for multiple futures
(from Colorado’s Water Plan Draft 2014)
Multiple Future Demand Scenarios

Three population scenarios – low, medium and high growth

Two conservation scenarios – passive and active

Two climate scenarios – today’s climate and warmer climate

12 demand forecasts

Variability of demand must also be incorporated
Demand Forecasts Incorporating
Climate Change
35,000
30,000
Annual Demand (AF)
25,000
20,000
15,000
Lower limit of forecast water demand variability.
10,000
5,000
-
Supply and Demand Modeling

Potential impacts of future drought on water supplies

Potential impacts of future climate change on water
supplies

Integration of supply and demand scenarios

12 demand scenarios

2 future drought scenarios

24 combined supply and demand scenarios
Demand Forecast Under Climate Change
The Path Forward

Monitor water supply and demand rigorously

If new supply projects are likely, move forward on planning and
permitting

Identify “sign posts” of additional supply and/or demand management

Implement a “No Regrets” Strategy

Reduce water demand of existing customers

Reduce system water loss

Ensure new customers join the system at high efficiency level

Anticipate demand reductions

Set rates to recover costs even if demand goes down
Thank You!
Peter Mayer, P.E.
Principal
peter.mayer@waterdm.com
720-318-4232
www.waterdm.com