Using reactive tracer tests to model solute transport across a montane river continuum
Abstract
Rivers and streams integrate biogeochemical constituents within and across drainage basin boundaries, thereby playing a major role in biogeochemical transformations, water quality, and ecology. However, most hydrologic research studies takes place in headwater streams since they tend to be accessible and relatively inexpensive to study. Focusing research efforts on headwater streams contributes to challenges in linking small-scale physical and biogeochemical drivers with large-scale context and consequences across the river continuum. As such, cumulative watershed impacts coupling small-scale riverine drivers with their larger-scale fluvial framework and outcomes are important. We performed reactive tracer tests in 1st-, 2nd-, 3rd-, and 4th- order stream sections of the Jemez River continuum to quantify reach-scale hyporheic exchange. Reactive tracer tests are useful in evaluating streambed hyporheic exchange at multiple spatial scales because they provide high resolution, in situ measurements of riverine processing. We co-injected a conservative tracer, bromide, with a reactive tracer, resazurin (Raz), and combined the measurement of breakthrough curves for Br-, Raz, and its daughter product, resorufin (Rru), at two downstream locations to estimate cumulative effects of hyporheic exchange along the Jemez River continuum. Breakthrough curves were modeled using a 1-D transient storage model that accounts for a single, fully mixed hyporheic zone that undergoes linear exchange with the surface water along each study section. Preliminary results indicated similar downstream tracer arrival times at each sampling station while reach-scale mass recoveries were impacted by dilution. Quantified sediment-water interface hyporheic exchange rates decreased by an order of magnitude with each increase in reach stream-order. This indicated a greater reactivity potential in smaller order reaches of the Jemez River continuum. Larger order reach results suggested that even with relativity smaller bulk reaction rates than their upstream counterparts, these reaches still demonstrated measurable reactivity potential. Our findings provide a better understanding of how reach-scale hyporheic exchange varies across different stream orders that combine to form large-scale fluvial networks.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.H11N..02G
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0496 Water quality;
- BIOGEOSCIENCES;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY;
- 1839 Hydrologic scaling;
- HYDROLOGY