High‐frequency in situ sensors have enabled researchers to measure solute concentrations at a time scale that captures the variability in stream discharge. We analyzed discrete samples and high‐frequency time series of solutes to characterize how nitrate (NO3−) and fluorescent dissolved organic matter (fDOM; a proxy for dissolved organic carbon) respond to changes in discharge at annual and intra‐annual timescales across a stream network in New Hampshire, USA. NO3−and fDOM exhibited highly variable concentration‐discharge (c‐Q) behavior at intra‐annual scales. Transport limitation, source limitation, and chemostatic behavior were observed to occur within and among years in all our study watersheds. Annual assessment of c‐Q misclassified streams 31% of the time, as the annual time step missed seasonal and event‐induced shifts in c‐Q dynamics. In some instances, anomalous events lasting less than 5% of the year determine the annual c‐Q behavior for a site. Catchment land use appeared to drive some of the variability among watersheds in c‐Q relationships and their temporal variability. Forested streams had highly variable NO3−c‐Q behavior and streams draining watersheds with more development had greater variability in fDOM c‐Q behavior. Sample frequency impacts how hydrologic systems are characterized and extrapolating c‐Q behavior from discrete samples alone can bias interpretations of c‐Q dynamics and our understanding of solute transport.
This content will become publicly available on December 7, 2024
Processes that drive variability in catchment solute sourcing, transformation, and transport can be investigated using concentration–discharge (C–Q) relationships. These relationships reflect catchment and in‐stream processes operating across nested temporal scales, incorporating both short and long‐term patterns. Scientists can therefore leverage catchment‐scale C–Q datasets to identify and distinguish among the underlying meteorological, biological, and geological processes that drive solute export patterns from catchments and influence the shape of their respective C–Q relationships. We have synthesized current knowledge regarding the influence of biological, geological, and meteorological processes on C–Q patterns for various solute types across diel to decadal time scales. We identify cross‐scale linkages and tools researchers can use to explore these interactions across time scales. Finally, we identify knowledge gaps in our understanding of C–Q temporal dynamics as reflections of catchment and in‐stream processes. We also lay the foundation for developing an integrated approach to investigate cross‐scale linkages in the temporal dynamics of C–Q relationships, reflecting catchment biogeochemical processes and the effects of environmental change on water quality.
This article is categorized under: Science of Water > Hydrological Processes Science of Water > Water Quality Science of Water > Water and Environmental Change
- NSF-PAR ID:
- 10478410
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- WIREs Water
- Volume:
- 11
- Issue:
- 2
- ISSN:
- 2049-1948
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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