Possible impacts of a greenhouse warming include
changes in precipitation and runoff patterns, sea level
rise, land use and population shifts that may follow from
these effects, and increased demand for irrigation water
in regions with higher temperatures and reduced
precipitation. Introducing climate change into the
planning process involves a sequence of models and
techniques that result in a cascade of uncertainties.
Although climate change is not explicitly cited as an
issue in the Principles and Guidelines (US Water
Resources Council, 1983) used by designated federal
water resources agencies, their planning and evaluation
principles and methods are flexible enough to incorporate
many issues that might arise from the prospect of climate
change. Because it can be expensive and time consuming
to introduce climate change into planning and project
evaluation and the results may be problematical,
discretion and guidance are needed. Climate expectations
are likely to be particularly important for decisions
involving long-lived benefits and costs, irreversibilities,
and one-time, unique investments. When it is determined
that climate change should be introduced into water
planning and project evaluation, the Intergovernmental
Panel on Climate Change’s IPCC Technical Guidelines
for Assessing Climate Change Impacts and Adaptations
(Carter et al., 1994) provide a framework and detailed
approach for assessing the potential impacts and
evaluating adaptation strategies.