Unraveling hydrologic and hydrochemical processes based on long-term concentration–discharge analysis in the Green Lake 4 catchment, Colorado Front Range, USA

Document Type

Article

Publication Date

1-1-2026

Abstract

Concentration–discharge (C-Q) relationships were analyzed over decadal, annual, and seasonal timescales from water years 1982 to 2020 to understand hydrologic and hydrochemical processes in the Green Lake 4 catchment, Green Lakes Valley, Colorado Front Range. Geogenic solutes, along with the magnitude of stable isotopes, were dominated by a strong (p <.05) C-Q power law (C = aQb, where a and b are constants from the curve fitting, with b usually termed the b-coefficient) and consistent patterns over various timescales. The b-coefficients of geogenic solutes were negative, suggesting that those solutes primarily originated from groundwater with higher concentrations and diluted by shallow source waters with lower concentrations (dilution effect). Nutrients other than nitrate were mainly chemostatic without a significant change in their concentrations with an increase in streamflow, indicating temporally variable concentrations in the source waters. The b-coefficients were usually positive for nitrate in the years with a significant C-Q power law (p <.05), indicating that nitrate was mainly generated from shallow source waters (flushing effect). Except for extremely dry water years, geogenic solute concentrations in streamflow were consistently higher during the snowmelt period than the post snowmelt period. This clockwise hysteresis is counterintuitive and suggests that during times of snowmelt, meltwater infiltration triggered additional subsurface flow paths and discharged higher solute concentrations to the stream channel in such flow paths than groundwater already identified earlier (e.g. talus water). With the earlier onset of snowmelt, the analysis also suggests that hydrochemical flushing and dilution effects will shift earlier in the future.

Publication Title

Arctic Antarctic and Alpine Research

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