Transcript Lorna Stickel - Water Resources Department

Climate Change and Municipal
Water Supplies
Presented by Lorna Stickel
Portland Water Bureau and
Regional Water Providers
Consortium Project Manager
How are Municipal Water Supplies
affected by Climate Change?
1.
2.
3.
4.
Water demands are increased by increases
in temperature in the summer months,
beyond the effects of growth.
The hydrology of sources is affected even
more than the demands.
The competition for water resources is
increased, thereby affecting water rights.
Summer instream flows are less affecting
ESA species/HCP requirements and CWA
permit requirements.
Topics for This Presentation
1.
2.
3.
Past Regional Planning and Climate
Change
Potential impacts of climate change
on municipal supplies, some examples
from the Portland metro area.
How municipalities might deal with
climate change including more
research that is needed.
Water Supply Planning in
Portland Region
 Most Water providers have not considered climate
change directly in their Master Plans, however, two
sources have had climate change studies conducted:
 Bull Run - 2000
 Tualatin Basin - 2004
 Regional planning between 1993-2004 did not
consider the direct effects of climate change, but
did recognize the potential for impacts.
 The RWSP Update of December 2004 does contain
two pages on climate change and the two studies.
Regional Water Supply Plan
 Planning for supplies in the Portland area included
aspects of meeting drought needs within the
Regional Water Supply Plan (RWSP) & Update
through:
• Water Demand Forecasting – Uses the actual climate
patterns of the years 1940-2003 within an econometric
model that predicts daily water demands.
• Integrated modeling in Confluence allowed looking at
weather events of the past so that those (eg. 1968 for peak
season and 1981 for peak day) that drove demands higher
were selected for analysis.
Regional Water Supply Plan
 Conservation Programs selected that focus
on summer peak season uses.
 Interties have been constructed and more
are proposed to connect sources better and
to encourage conjunctive and efficient use
of existing supplies.
 Non-potable and reuse are also encouraged
where feasible and cost effective.
Climate Change and Impacts to
Municipal Sources of Supply
 Impacts to Sources of Supply
• Run of River – Changes in the periodicity of streamflows,
more intense winter flows and lower summer flows
• Storage – Reliability of storage projects changes
– Demands are higher in the peak season
– Less inflow affects both filling of some projects annually and
reduces the amount of surface water inflow during the
summer.
• GW – Not sure of the impact on these systems, but if GW is
pumped more to meet increased needs then declines in
water levels could result and/or impacts on surface water
sources could be greater.
• The past 60 years of record shows great variability for
surface water sources, climate change will result in seeing
even more variability.
Bull Run Summer Inflow 1940-2004 Millions of Gallons (June-Oct)
80,000
Highest Yield
1955 - 71.8 BG
70,000
50,000
40,000
30,000
20,000
Lowest Yield
1987 - 10.9 BG
10,000
20
03
20
00
19
97
19
94
19
91
19
88
19
85
19
82
19
79
19
76
19
73
19
70
19
67
19
64
19
61
19
58
19
55
19
52
19
49
19
46
19
43
0
19
40
Millions of Gallons
60,000
Bull Run Study: Impacts to Snowfall
Climate Change and Impacts to
Municipal Water Demands
 Demands
• Temperature and rainfall are major factors that
affect demand patterns during the peak season.
• Even higher demands in peak season at the same
time that supplies might be less.
• Climate change likely to mean more severe
demand patterns than seen in past, or greater
frequency of “worst” weather years.
• Fish & water quality instream needs also will
compete more frequently with out of stream
demands.
2005 Portland Regional Peak Season (Jun-Oct) Average Water Demand in MGD Over the Weather
Years 1940-2000
280
Highest Value
272.8 MGD
1968
270
250
240
Low est Value 238.2
MGD
1954
230
Peak Season
Maxim um Variation
34.6 MGD
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
1966
1964
1962
1960
1958
1956
1954
1952
1950
1948
1946
1944
1942
220
1940
MGD
260
Bull Run Study : Impacts on Demand
•
Water demands shown to be less affected by
climate change than hydrology
•
8% increase in 2040 drawdown demand
•
4% increase in 2040 average annual demand
Climate Change and Impacts to
Municipal Water Systems
• Most planning for water supplies is based on past
history, and often not a very long history.
• The synergy between lower summer streamflows,
less summer rainfall and higher temperatures
creates an effect that is going to stress municipal
systems more than past.
• If suppliers only evaluate the past history then
we may be creating water supply systems that
are not as reliable.
Dealing with Climate Change
 Planning
• Larger supplies as well as rivers that have multiple intakes
should model climate change impacts as has been done for
Portland’s Bull Run and for the Tualatin Basin.
• Assess the effects on multiple sources at the same time if
possible, more study is needed in the Portland area to
include the Clackamas River particularly, but also the
Willamette and the impacts on storage.
• Include climate change effects on both the hydrology and
water demand patterns.
• Assess the role of curtailment, particularly in light of more
extreme events (drought and flooding) and hardening of
demand through conservation.
Dealing with Climate Change
 Infrastructure Development & Use
• Consider more conjunctive use of sources
including surface, groundwater, and ASR.
• Build more system interconnections and backup
supplies for emergencies or more frequent
shortages of primary supplies.
• More close monitoring & modeling of short term
system operations and put in place strategies for
dealing with summer supplies in real time.
• More storage may be necessary to capture the
higher winter flow events.
Dealing with Climate Change
Programmatic Actions
 Assess the potential impacts of changing flood rule curves on
multiple purpose projects.
 Use Conservation Programs to moderate demand effects,
particularly during the peak season. These programs can be
justified to offset climate change effects on both demand
patterns and instream resources.
 Develop curtailment plans in a regional context.
 Encouraging more active use of water markets and water
banking to provide added flexibility to deal with change.
 Public needs to be included in the decisions about system
reliability in times of uncertainty about future supplies.
Better Knowledge Needed
There is a lot that isn’t known about climate change impacts on
municipal supplies:
• Only limited studies have been done, and even then broad
•
•
•
•
•
assumptions have to be made about the local effects.
The impacts on hydrology are the most important unknowns that
need to be researched, particularly for urban water sources.
Summer climate change impacts on rainfall patterns are not as
well predicted as temperature increases.
Reliable long term data needs to be collected and available for
analysis.
Synergistic effects between flows, fish, flooding, hydro, and
water demand patterns present a complex picture that needs
more study.
The role of conservation and curtailment need to be better
integrated into long term climate change impacts.
Parting Thought
We need to be open
minded to the reality
that the future won’t
be like our recent
historic past. We don’t
need to overreact, but
we need to start now
to
incorporate
the
flexibility we will need
to deal with the
impacts of climate
change on our water
resources.