Print PageClimate in the northeastern and north central USA is changing and will continue to change. Seasonal increases in air temperature and precipitation have effects on streamflow regimes. Headwater streams have small contributing areas that are highly responsive to changes in energy, water, and chemical inputs. For example, changes in snowmelt not only affect the timing and magnitude of streamflow, but also biogeochemical processes and the associated flux of elements exported in streamwater. Since low-order stream networks are source waters for larger rivers, they are often considered as harbingers of climate change effects on downstream water yield and quality. We evaluated climate-induced changes in streamflow and water quality at small watersheds and compared them to data from nested watersheds of increasing size to determine if the climate signals that are evident in headwaters are manifested downstream.
Results/Conclusions
Decreases in snowpack depth, water equivalent, and duration are accompanied by higher streamflow during winter and an earlier, more muted peakflow during spring snowmelt. With these changes in hydrology and changing phenology, the timing and magnitude of nutrient export have also shifted. Models run with downscaled climate change projections show continuation of these trends into the future. In downstream river basins, population densities have increased dramatically since 1940. The human imprint has had a major impact on the volume and quality of water that dwarfs the more subtle shifts that are directly attributable to climate change. However, projected increases in extreme events, particularly flooding, may be especially important in urbanized areas with infrastructure that was designed under the premise of stationarity. A more thorough understanding of contemporary and a conceptualization of projected climate change impacts on water supply and quality will enable us to better prepare for and adapt to future change.
phone 202-833-8773