Reale et al., 2015

Paper/Book

The effects of catastrophic wildfire on water quality along a river continuum

Reale J.K., Van Horn D.J., Condon K.E., and Dahm C.N. (2015)
Freshwater Science 34(4): 1426-1442  

Abstract

Maps showing the Rio Grande and the burn perimeter (red) of the Las Conchas (LC) forest fire in north-central New Mexico (A), streamflow gages (S. Felipe = San Felipe), water-quality sondes, streams of interest, perimeter of the LC and Thompson Ridge fires, key landmarks, and the major Hydrologic Unit Codes (HUCs) for this section of the Rio Grande (B), and the burn severity map for the LC fire in relation to monitoring locations (C).

Maps showing the Rio Grande and the burn perimeter (red) of the Las Conchas (LC) forest fire in north-central New Mexico (A), streamflow gages (S. Felipe = San Felipe), water-quality sondes, streams of interest, perimeter of the LC and Thompson Ridge fires, key landmarks, and the major Hydrologic Unit Codes (HUCs) for this section of the Rio Grande (B), and the burn severity map for the LC fire in relation to monitoring locations (C).

To further our understanding of the linkages among wildfire, streamflow pathways, and water chemistry, we used a network of water-quality sensors and streamflow gages to assess initial and long-term effects of wildfire along a river continuum. We assessed water quality of a 2nd- and a 4th-order stream in a single watershed for 5 monsoon seasons before, during, and after a catastrophic wildfire. Fire had significant and sustained long-term effects on both streams. In the 2nd-order stream, variability in dissolved O2 (DO) increased after the fire. Daily total precipitation was unchanged, but episodic storm events resulted in significant increases in stream discharge that led to elevated turbidity and specific conductance (SC). In the 4th-order stream, fire led to minimal measurable effects on turbidity, elevated SC, and greater variability of the DO signal. We also assessed water-quality data from 4 sites along the river continuum for a 4-mo period before, during, and after the wildfire. Large overland and debris-flow events in the 1st- and 2nd-order streams resulted in elevated particles (e.g., soil, sediment, rock, ash, plant biomass) and solutes in transport that elevated turbidity and SC and damped the DO signal. We documented less severe postfire effects in the 3rd-order stream probably because of groundwater contributions and a higher stream gradient with a pool–riffle geomorphology. We observed nominal changes in turbidity, strong SC spikes, and strong DO decreases in the 4th-order stream. Streamflow pathways, geomorphology, physiochemical properties, and biogeochemical processes play a central role in the postfire water-quality response along the river continuum. Our findings highlight the importance of collecting water-quality measurements at temporal and spatial scales that effectively capture hydrological dynamics.

Citation

Reale J.K., Van Horn D.J., Condon K.E., and Dahm C.N. (2015): The effects of catastrophic wildfire on water quality along a river continuum. Freshwater Science 34(4): 1426-1442. DOI: 10.1086/684001

This Paper/Book acknowledges NSF CZO grant support.