Boulder Creek Watershed MapThe Critical Zone is the permeable near-surface layer of the Earth extending vertically from the top of the vegetation canopy to the base of groundwater. It is where organisms, rock, soil, water, and air all interact and where life is sustained. The Critical Zone provides many important services including those related to water quality and food production. Boulder Creek Critical Zone Observatory (CZO) is one of ten CZOs established by the National Science Foundation to study how geological, physical, chemical and biological processes and their couplings govern critical zone dynamics. The Boulder Creek CZO extends from the western edge of the Great Plains at ~1460 m (4800 feet) to the crest of the Front Range of the Rocky Mountains at ~4120 m (13,500 feet). Strong gradients in climate and ecosystems (plains, foothills, montane, subalpine, and alpine), and differing geology and erosional histories makes the Front Range a natural laboratory to study many aspects of critical zone dynamics.

CWEST Participants: Suzanne Anderson (lead investigator), Bob Anderson, Holly Barnard, Alex Blum, Diane McKnight, Noah Molotch, Sheila Murphy, Hari Rajaram and David Barnard

Boulder Creek CZO Website

Collaborative Research: wildfire impacts on water quality

September 2010, a fire in Fourmile Canyon, Colorado burned 6,400 acres in the Boulder Creek watershed. The USGS and Boulder Creek CZO collaborated to investigate the impacts of the wildfire on water quality. Research about such impacts can be challenging because high-frequency sampling is needed to understand links between landscape and stream chemistry, but many wildfires occur in remote locations that are difficult to instrument and visit frequently. However, because of the proximity of this fire to the USGS and the University of Colorado, USGS researchers Sheila Murphy and Jeff Writer were able to perform an in-depth study of the aftermath of this wildfire. They found that high-intensity convective storms, in particular, caused significant differences in discharges and water quality emanating from burned vs. unburned locations, and the impact persisted for 3 years post-wildfire. Discharges increased by as much as 80-fold at stream sites flowing through burned areas as compared to 0.4-fold at unburned sites. Substantial increases in turbidity, total suspended solids, dissolved organic carbon, and nutrient levels were also observed in waters draining burned areas. The greatest impact on water quality and the aquatic ecosystem was not the wildfire itself, but during storm events that occurred many months and years post-wildfire.

Water Samples from Fourmile Creek

Photo by Sheila Murphy


Murphy, S. F., McCleskey, R. B., & Writer, J. H. (2012, June). Effects of flow regime on stream turbidity and suspended solids after wildfire, Colorado Front Range. In Wildfire and Water Quality — Processes, Impacts, and Challenges, proceedings of a conference held in Banff, Canada, (pp. 51-58).

Writer, J. H., McCleskey, R. B., & Murphy, S. F. (2012). Effects of wildfire on source-water quality and aquatic ecosystems, Colorado Front Range. In Wildfire and Water Quality: Processes, Impacts and Challenges.


CZO Website - WILDFIRE! Fourmile Canyon fire may have long-term effects on water quality

Collaborative research: Boulder County flood of September 2013

Flood Gully

Photo by Noah Fierer

During the week of September 9th, 2013 Boulder County, Colorado and the Boulder Creek watershed experienced an extraordinary rainfall event during which daily, weekly, monthly, and annual rainfall records kept since 1893 were all broken. Nine inches of rain fell in just one day and 17 inches of rain fell in just one week, resulting in severe flooding that mobilized sediment causing substantial erosion, sediment transport and deposition. Boulder Creek CZO, INSTAAR, and USGS researchers are investigating the impacts of the flood on landscapes and streams and assessing whether different drainage areas had different responses to the flood because of factors such as spatial variations in precipitation and alterations to landscapes due to urbanization or wildfire.