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Water-quality response to a high-elevation wildfire in the Colorado Front Range

December 29, 2015

Water quality of the Big Thompson River in the Front Range of Colorado was studied for 2 years following a high‐elevation wildfire that started in October 2012 and burned 15% of the watershed. A combination of fixed‐interval sampling and continuous water‐quality monitors was used to examine the timing and magnitude of water‐quality changes caused by the wildfire. Prefire water quality was well characterized because the site has been monitored at least monthly since the early 2000s. Major ions and nitrate showed the largest changes in concentrations; major ion increases were greatest in the first postfire snowmelt period, but nitrate increases were greatest in the second snowmelt period. The delay in nitrate release until the second snowmelt season likely reflected a combination of factors including fire timing, hydrologic regime, and rates of nitrogen transformations. Despite the small size of the fire, annual yields of dissolved constituents from the watershed increased 20–52% in the first 2 years following the fire. Turbidity data from the continuous sensor indicated high‐intensity summer rain storms had a much greater effect on sediment transport compared to snowmelt. High‐frequency sensor data also revealed that weekly sampling missed the concentration peak during snowmelt and short‐duration spikes during rain events, underscoring the challenge of characterizing postfire water‐quality response with fixed‐interval sampling.

Publication Year 2016
Title Water-quality response to a high-elevation wildfire in the Colorado Front Range
DOI 10.1002/hyp.10755
Authors Alisa Mast, Sheila F. Murphy, David W. Clow, Colin A. Penn, Graham A. Sexstone
Publication Type Article
Publication Subtype Journal Article
Series Title Hydrological Processes
Index ID 70168829
Record Source USGS Publications Warehouse
USGS Organization Colorado Water Science Center