Long-term suspended sediment and particulate organic carbon yields from the Reynolds Creek Experimental Watershed and Critical Zone Observatory

Authors: GLOSSNER, KAYLA - IDAHO STATE UNIVERSITY; LOHSE, KATHLEEN - IDAHO STATE UNIVERSITY; APPLING, ALISON - U.S. GEOLOGICAL SURVEY (USGS); Cram, Zane; MURRAY, ERIN; GODSEY, SARAH - IDAHO STATE UNIVERSITY; Van Vactor, Steve; MCCORKLE, EMMA - IDAHO STATE UNIVERSITY; Seyfried, Mark; PIERSON JR, FREDERICK

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2021
Publication Date: 1/22/2022
Citation: Glossner, K., Lohse, K., Appling, A.P., Cram, Z.K., Murray, E.M., Godsey, S., Van Vactor, S.S., McCorkle, E., Seyfried, M.S., Pierson Jr., F.B. 2022. Long-term suspended sediment and particulate organic carbon yields from the Reynolds Creek Experimental Watershed and Critical Zone Observatory. Hydrological Processes. 36(2). Article e14484. https://doi.org/10.1002/hyp.14484.
DOI: https://doi.org/10.1002/hyp.14484

Interpretive Summary: Long-term records of suspended sediment and particulate organic carbon yields are necessary for understanding linkages between climate, erosion, and carbon losses from western rangelands. Longterm yields of sediment from Reynolds Creek Experimental Watershed in southwest Idaho were summarized and showed consistently low erosion rates except following fire when yields increased by ten times and remained elevated for several years compared to before fire. The suspended sediment came from within the stream channel and was controlled by the amount of stream flow and not by how much sediment was available in the watershed. Particulate carbon was strongly correlated with the amount of suspended sediment and was primarily controlled by yearly amounts of steam flow driven by yearly variations in precipitation along with landscape disturbances such as wildfire. These results provide vital baseline estimates of erosion and carbon losses that can be used by land managers in environmental assessments of conservation practices and assessments of the impacts of wildfire. Results also establish baseline estimates for the role erosion plays in the overall carbon balance for extensive semi-arid rangelands across the western US.

Technical Abstract: Long-term (>20 yr) suspended sediment (SS) and particulate organic carbon (POC) yield records are relatively rare and yet are necessary for understanding linkages between climate, erosion, and carbon export. We estimated long-term (>23 yrs) SS and POC yields at the Reynolds Creek Experimental Watershed and Critical Zone Observatory (RC CZO) in southwestern Idaho, USA. We also analyzed the effect wildfire may have on these yields. Mean annual SS and POC yields varied from 20-89 g m-2 yr-1and 0.87-11.0 g m-2 yr-1, respectively, across five subcatchments that range from <1-56.54 km^2. SS and POC yields peaked in the year following fire, at 611 and 35.4 g m-2 yr-1 respectively, and they remained elevated in the second year, at 466 and 27.5 g m-2 yr-1, owing to a high water year. Larger subcatchments exhibited more positive concentration-discharge (C-Q) relationships than smaller ones, and most catchments were dominated (80%) by clockwise hysteretic curves with the exception of a granite-dominated catchment that exhibited a mixed (50%) clockwise and counterclockwise response. In contrast to expectations, seasonal exhaustion and shifts in ratio of POC to SS export were not observed in the three years of POC collection. Lack of exhaustion, positive C-Q, and clockwise relations indicate that these systems are transport- rather than supply-limited, and that sediment and POC appear to be sourced from channel/bank erosion and remobilization. The spatiotemporal variability in SS and POC yields driven by hydroclimate variability and fire across this intermediate-scale catchment were similar to those observed at continental scales.