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Applications of a New England stream temperature model to evaluate distribution of thermal regimes and sensitivity to change in riparian condition
Citation:
Detenbeck, N., A. Morrison, AND R. Abele. Applications of a New England stream temperature model to evaluate distribution of thermal regimes and sensitivity to change in riparian condition. New England Association of Environmental Biologists (NEAEB) 40th Annual Meeting, Rockport, ME, March 23 - 25, 2016.
Impact/Purpose:
We have applied a statistical stream network (SSN) model to predict stream thermal metrics (summer monthly medians, growing season maximum magnitude and timing, and daily rates of change) across New England nontidal streams and rivers, allowing us to partition natural variability from anthropogenic effects on stream temperature. Application of this model allows us to quantify the importance of natural green infrastructure in maintaining valued coldwater and coolwater fish communities as well as to evaluate the potential effects of loss and restoration of riparian buffers. Digital maps of stream temperature model predictions under current conditions and restoration/degradation scenarios will be made available to the management community via EPA’s Estuary Data Mapper application (www2.epa.gov/edm) to help inform criteria development, assess reference condition and restoration potential, diagnose potential causes of fish community impairment, and set priorities for conservation of natural green infrastructure.
Description:
We have applied a statistical stream network (SSN) model to predict stream thermal metrics (summer monthly medians, growing season maximum magnitude and timing, and daily rates of change) across New England nontidal streams and rivers, excluding northern Maine watersheds that extend into Canada (Detenbeck et al., in review). We excluded stream temperature observations within one kilometer downstream of dams from our model development, so our predictions for those reaches represent potential thermal regimes in the absence of dam effects. We used stream thermal thresholds for mean July temperatures delineating transitions between coldwater, transitional coolwater, and warmwater fish communities derived by Beauchene et al. (2014) to classify expected stream and river thermal regimes across New England. Within the model domain and based on 2006 land-use and air temperatures, the model predicts that 21.8% of stream + river kilometers would support coldwater fish communities (mean July water temperatures < 18.45 degrees C), 56.5% of stream reaches would support coolwater fish communities (mean July temperatures 18.45 – 22.30 degrees C), and 21.6% of stream reaches would support warmwater fish communities (> 22.3 degrees C mean July temperatures). Application of the model allows us to assess potential condition given full riparian zone restoration as well as potential loss of cold or coolwater habitat given loss of riparian shading. Given restoration of all riparian forest buffers, the percentage of coldwater and coolwater habitat could increase to 81.5 percent of all stream + river kilometers. Conversely, loss of forested riparian buffers could lead to declines of cold- and coolwater fish habitat to 4.5 and 52.6 percent of stream + river kilometers, respectively. In addition to changing the potential extent of cold- and coolwater habitat, the loss of riparian habitat and/or increases in mean temperature could change the distribution of potential coldwater refugia (number of coldwater tributaries to warmwater mainstem reaches). Digital maps of stream temperature model predictions under current conditions and restoration/degradation scenarios will be made available to the management community via EPA’s Estuary Data Mapper application (www2.epa.gov/edm) to help inform criteria development, assess reference condition and restoration potential, diagnose potential causes of fish community impairment, and set priorities for conservation of natural green infrastructure.