Abstract

In September 2010, the Fourmile Canyon fire burned about 23 percent of the Fourmile Creek
watershed in Boulder County, Colo. Water-quality sampling of Fourmile Creek began within a month
after the wildfire to assess its effects on surface-water chemistry. Water samples were collected from
five sites along Fourmile Creek (above, within, and below the burned area) monthly during base flow,
twice weekly during snowmelt runoff, and at higherfrequencies during storm events. Stream discharge
was also monitored. Water-quality samples were collected less frequently from an additional 6 sites on
Fourmile Creek, from 11 tributaries or other inputs, and from 3 sites along Boulder Creek. The pH,
electrical conductivity, temperature, specific ultraviolet absorbance, total suspended solids, and
concentrations (dissolved and total) of major cations (calcium, magnesium, sodium, and potassium),
anions (chloride, sulfate, alkalinity, fluoride, and bromide), nutrients (nitrate, ammonium, and
phosphorus), trace metals (aluminum, arsenic, boron, barium, beryllium, cadmium, cobalt, chromium,
copper, iron, mercury, lithium, manganese, molybdenum, nickel, lead, rubidium, antimony, selenium,
strontium, vanadium, and zinc), and dissolved organic carbon are here reported for 436 samples
collected during 2010 and 2011.

Citation

McCleskey, R.B., Writer, J.H., and Murphy, S.F., (2012): Water chemistry of surface waters affected by the Fourmile Canyon wildfire, Colorado, 2010–2011. U.S. Geological Survey Open-File Report 2012–1104, 11 p.

This Paper/Book acknowledges NSF CZO grant support.