Strategies and Resources for Evaluating and
Adapting to Climate Change Effects
Climate Change is Real—
16 SOURCE fall 2014
By Ben Wright and Ben Stanford
THE CHALLENGE—FOR WATER INDUSTRY PROFESSIONALS charged with managing the nation’s
water supplies, arguments over the cause of the demonstrable changes in the earth’s climate are both
distracting and largely irrelevant. We already know that our water resources are being stretched to
their limits by rising populations causing an increased need for food and power, the management of
environmental effects of discharges and withdrawals, and stricter regulations to control resulting impacts.
Add climate change, whether it’s natural or man-made, and planning for the future with confidence
becomes even more difficult.
A common adage applied to climate change is that “Station-arity
is dead.” The truth is that stationarity (the concept that
climate patterns remain constant for a given region) never
existed in the first place. It has simply been convenient to assume
that historical observations of hydrology are representative of future
hydrology, a strategy which has served water supply managers well
over the years. However, paleoclimate analysis has established that
hydrology has the potential to vary far more widely than has been
recorded in the observed record. This means that, given the scientif-ic
evidence supporting climate change, we need to look beyond his-torical
observations to ensure that we have adequate water supplies.
A more productive alternative is to understand the reliability of our
water systems so that we can plan for continued capacity.
Global circulation models (GCMs) are the best representation
we currently have of how the earth’s climate functions. In addition,
we have access to computational power and statistical tools to cre-ate
and model alternate realizations of weather patterns as never
before. Although climate science was previously limited mainly to
academic and government researchers, climate projections are now
available to the broader community of scientists, engineers and de-cision-
makers who are working to understand potential impacts on
a local and regional scale
How Vulnerable Are We?
While there is still a great deal of uncertainty about potential
impacts of climate change, the general trends for this country are
that wet areas will get wetter, arid areas will get drier, average tem-peratures
will continue to increase and winter snowpack will be
smaller. Extreme events will become worse and will be our most
serious problem in the foreseeable future. These kinds of qualita-tive
assessments are not sufficient, however, to make informed de-cisions.
What is necessary is to quantitatively evaluate local climate
projections in the context of local non-climate-related conditions.
For example, it is impossible to know if a 10 percent reduction in av-erage
annual rainfall is problematic without knowing such variables
as the population of an area and its water demand trends, applicable
regulations, water rights structures and levels of allocation and how
these influence water resource need and availability.
Evaluating System-Specific Impacts
There are multiple approaches to evaluating potential impacts
from climate change, each requiring varying degrees of effort. Most
basic is typical climate change data that include temperature and
precipitation at a monthly or daily scale for multiple potential real-izations
of the future climate. At the screening level, this data can
be compared to known thresholds for vulnerable conditions. Typical
examples of this application include: if average winter temperatures
are above X, the snowpack will be too low; if summer temperatures
are above X and precipitation is below Y, peak demands will be a
problem; if summer temperatures are above X, reservoir release
temperature will be too warm for downstream fisheries. This type
of analysis provides only a partial picture of potential vulnerabili-ties,
but in many cases it can be a first step that can lend support for
a more rigorous analysis.
At the other end of the spectrum is a process, already in use by
some water utilities, in which the full range of potential climate and
non-climate uncertainties are evaluated to gain insight into the con-ditions
(singularly or in combination) under which a water supply
system fails to perform adequately. Robust Decision Making (RDM)
is a framework for conducting decision-making analyses under deep