Quantifying and Planning for Climate Change
Impacts on Drinking Source Water Quality

Climate change is likely to cause changes to the hydrologic cycle,
which will have impacts on drinking supply water quality.  This can
profoundly affect drinking water managers who are charged with the
task of guaranteeing a safe and reliable supply of water to the
public.  Potential shifts in water quality that influence treatment
and management decisions have not been well-studied.  As such, the
objective of this research is to develop tools to help inform
long-term process and planning decisions based on the anticipated,
albeit uncertain, effects of climate change on water quality.

This research adopts a case-study approach for which a suitable
framework is developed
and demonstrated. The study first explores the variability of key
water quality variables and their relationship to hydrology and/or
climate. In many drinking source waters, a functional relationship can
be developed to relate streamflow with water quality.  Diagnostics of
historic data from case study utility in Colorado shows that lower
flows are associated with higher total dissolved solids (TDS) values,
which can limit the usage of this source water.  Using this
established relationship, a suite of global climate model (GCM)
projections can be used to determine the impact of climate change on
water quality.  For this Colorado location, one GCM scenario projects
a reduction in annual streamflow of twenty percent.  As such, a
stochastic simulation techniques can be used to develop streamflow
ensembles that are consistent with the climate change projection
scenario.  Next, the projected streamflows can be run through the
established functional relationship to develop a probability density
function (PDF) of TDS under the reduced streamflow scenario.  These
assessments can be evaluated with respect to their implications on key
decision variables for specific utilities.