Wisconsin's Role in Great Lakes Restoration - American Water ...

Evaluating Changes to Wisconsin Evapotranspiration under a Future Climate
**Douglas R. Joachim, UW-Madison Department of Civil and Environmental Engineering,
Madison, WI, djoachim@wisc.edu
Steven P. Loheide II, UW-Madison Department of Civil and Environmental Engineering,
Madison, WI, loheide@wisc.edu
Evapotranspiration (ET) is the second largest component of Wisconsin’s water budget after
precipitation, but relatively little work has been done evaluating how ET will change in the
state under a future climate. Changing precipitation and cloud cover patterns may have a
significant impact on soil water content and the availability of incoming solar radiation.
Additionally, increasing temperatures will cause a lengthening of the annual growing season,
which may increase the importance of transpiration in total ET. Vegetation will also experience
a change in stomatal conductance due to changing climate factors such as temperature,
vapor pressure deficit, and CO2 concentration which will affect the ability of plants to transpire
in the future
To evaluate ET changes in several different regions under a variety of vegetation types, we
have developed hydrologic model using Matlab that calculates ET via the FAO Penman-
Monteith method. The model was parameterized for specific vegetation types using data
obtained from Ameriflux eddy covariance sites in Wisconsin and nearby states. Records of
latent heat flux (observed ET) were compared with estimated ET from available climate data
(predicted ET). Downscaled global climate model (GCM) data was then integrated with the
Matlab model to estimate ET at sites across Wisconsin under a future climate. A user-friendly
graphical user interface (GUI) was then created to allow the public to easily estimate how ET
will change for a specific location and vegetation type over time to aid in water resource and
agricultural planning.
** Graduate student presentation
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