ABSTRACT:

Fluvial networks integrate, transform, and transport constituents from terrestrial and aquatic ecosystems. To date, most research on water quality dynamics has focused on process understanding at individual streams and, as a result, there is a lack of studies analyzing how small-scale, physical and biogeochemical drivers scale across fluvial networks. We performed tracer tests in five stream orders of the Jemez River continuum in New Mexico, USA, to quantify reach-scale hyporheic exchange during two different seasonal periods to address: how do hyporheic zone contributions to overall riverine processing change with space and time? And does the spatiotemporal variability of hyporheic exchange scale across fluvial networks? Combining conservative (i.e., bromide) and reactive (i.e., resazurin) tracer analyses with solute transport modeling, we found a dominance of reaction-limited transport conditions in space (for all stream orders) and time (two contrasting flow regimes). Moreover, we found a trend toward more reaction-limited conditions with increasing discharge across all stream orders. While our studied fluvial network did not consistently follow the expectations of decreasing hyporheic exchange contributions with increasing stream order, as it has been previously suggested from modeling studies, we found that processing rate coefficients and Damköhler numbers consistently decreased along the continuum.

The uploaded files in include MATLAB code and tracer concentrations measured during our field experiments. Results are submitted with Gootman et al. (2019) to Water Resources Research.

File Organization:
-The MATLAB code provided is the forward model run for the 4th stream order outputs from 2015 and 2016, which are plotted in Figure 3 of the main text (Code_S1) of the manuscript entitled "Spatiotemporal variability in transport and reactive processes across a 1st – 5th order fluvial network" by Gootman et al. (2019), which was submitted to Water Resources Research. Files may be opened and run using MATLAB.
-The tracer data provided (Data_S1.xlsx) contain experiment information and data concentrations of Br-, Raz, and Rru obtained for 7 tracer studies used in the analysis for "Spatiotemporal variability in transport and reactive processes across a 1st – 5th order fluvial network" by Gootman et al. (2019), which was submitted to Water Resources Research. The first sheet contains each tracer study parameters. Each of the following sheets refers to individual tracer studies.