Simulation hydrologic effects of wildfire on a small sub-alpine watershed in New Mexico, U.S.

Transactions of the American Society of Agricultural and Biological Engineers
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Abstract

Streamflow records available before and after wildfire in a small, mixed conifer, sub-alpine monsoonal dominated watershed in New Mexico provided a unique opportunity to calibrate a watershed model (PRMS) for pre- and postfire conditions. The calibrated model was then used to simulate the hydrologic effects of fire. Simulated postfire surface runoff averaged 14.7 times greater than prefire for the 29-year simulation period. The relationship between precipitation and streamflow changed dramatically after wildfire, largely from a decreased influence of antecedent soil moisture (ASM) and increased influence of canopy factors (less interception) and soil factors (greater hydrophobicity, less infiltration) in controlling surface runoff. For higher ASM, simulated pre- and postfire streamflow was similarly variable. However, for moderate and lower ASM, soil water storage was too low to contribute baseflow for either prefire or postfire conditions, and thus postfire streamflow maintained a linear, surface runoff-dominated response to precipitation, whereas prefire streamflow showed little response. Postfire streamflow efficiency increased with ASM from a mean of 0.02 at the lowest ASM to 0.30 at the highest ASM, whereas prefire conditions showed no sensitivity to ASM at low to moderate ASM. Postfire streamflow increased (2.1 times greater median flow than prefire), particularly from increased surface runoff (14.7 times greater), which occurred across all ASM conditions. As a result, streamflow shifted from baseflow-dominated to surface runoff-dominated after wildfire. This result indicates that substantial increases in runoff efficiency (20% or more of precipitation volume) can occur across a range of ASM postfire, which may have severe consequences for flooding. This result also indicates that monitoring of soil moisture would enhance raingauge networks for early flood warning.

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Publication type Article
Publication Subtype Journal Article
Title Simulation hydrologic effects of wildfire on a small sub-alpine watershed in New Mexico, U.S.
Series title Transactions of the American Society of Agricultural and Biological Engineers
DOI 10.13031/trans.13938
Volume 64
Issue 1
Year Published 2021
Language English
Publisher American Society of Agricultural and Biological Engineers
Contributing office(s) New Mexico Water Science Center
Description 14 p.
First page 137
Last page 150
Country United States
State New Mexico
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