Conserving Freshwater and Coastal Resources in a Changing Climate

Courtesy of the U.S. Environmental Protection Agency
Figure 5. Image of a Stormwater management model
The present version of the bioclimatic envelope
model uses up to 35 climatic parameters, including annual
mean temperature, maximum temperature of the
warmest period, annual precipitation, precipitation of
the coldest quarter, radiation seasonality, and the highest
period of moisture index. Data is first collected from
the habitat and geo-coded using historic and current
distribution data. Secondly, each climatic parameter is
calculated at every geo-coded site. Next, a statistical
summary – the “bioclimatic envelope” – is made of each
climatic parameter’s range, obtained as mean, standard
deviation, minimum, maximum and percentile value.
Finally, the potential distribution of the target species
is mapped. Matches within the “bioclimatic envelope”
show the area where the species can live. The impacts
of climate change are assessed by examining the potential
distribution of the target species and the potential
changes to the climatic parameter (Lindenmayer et al.,
1991).
Several studies have found bioclimatic envelope
models to be a useful tool to survey the reaction of
various species to climate change. However, criticisms
of the model include the lack of examination of interactions
between species or dispersion of species (Pearson
& Dawson, 2003). Some ecosystems are too complex
to predict an accurate distribution of species, but the
bioclimatic envelope is superior in making speciesspecific
projections, and modeling impacts from
climate change.
Hydrological Modeling
Another group of models can be used to assess the
impacts of climate change on the hydrology of aquatic
systems.
• HSPF, Hydrologic Simulation Program – Fortran
is a public domain software package that
was developed to provide continuous flow
simulation coupled with stream water quality
simulation for rural watersheds. The model
uses lumped parameters to characterize sub-basins
within the modeled watershed, which are additive
in the downstream direction (personal communication,
Bjerklie, 2007).
• SWMM (Storm Water Management Model) was
developed by the EPA in the 1970’s as a single storm
event model and has since been upgraded to
include a continuous watershed runoff modeling
system. Initially designed to model the quantity and
pollutant loading of stormwater runoff from
urbanized areas, the model can also be used in
rural basins. Similar to HSPF, the model uses
lumped parameters to characterize sub-basins,
which are additive in the downstream direction.
Groundwater is simulated as a series of reservoirs
with transfer coefficients associated with each
sub-basin (personal communication, Bjerklie,
2007). SWMM has been used to assess the impacts
of climate change on stormwater runoff and the
data is then used to project the effects on the
watershed and ecosystems in the area (Denault et
al., 2006).
• PRMS (Precipitation-Runoff Modeling System),
developed by the USGS, simulates watershed
response to precipitation within defined hydrologic
response units (HRU’s). Each HRU is defined
by physical characteristics including slope, soil
type, vegetation type, aspect, elevation and
precipitation distribution. PRMS can simulate
daily surface water yields at defined outlet
locations, or can model peak flows using smaller
precipitation time steps. Groundwater is simulated
in a similar manner as HSPF and SWMM. Recent
work has successfully linked the PRMS and the
USGS ground-water flow model (MODFLOW) to
create a new coupled model called GSFLOW,
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Conserving Freshwater and Coastal Resources in a Changing Climate