Flow and temperature are strongly linked environmental factors driving ecosystem processes in streams. Stream temperature maxima (T [subscript max_w]) and stream flow minima (Q[subscript min]) can create periods of stress for aquatic organisms. In mountainous areas, such as western North America, recent shifts toward an earlier spring peak flow and...
We propose the experimental use of resazurin (Raz) and develop a metabolically active transient storage (MATS) model to include processes that may provide additional information on transient storage from a biogeochemical perspective in stream ecosystems. Raz is a phenoxazine compound that reduces irreversibly to resorufin (Rru) in the presence of...
We used an in situ steady state ¹⁵N-labeled nitrate (¹⁵NO₃⁻) and acetate (AcO⁻) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO⁻ influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl⁻ and Br)...
Headwater streams comprise nearly 90% of the total length of perennial channels in global catchments. They mineralize organic carbon entering from terrestrial systems, evade terrestrial carbon dioxide (CO₂ ), and generate and remove carbon through in-stream primary production and respiration. Despite their importance, headwater streams are often neglected in global...
Surface and subsurface flow dynamics govern residence time or water age until discharge, which is a key metric of storage and water availability for human use and ecosystem function. Although observations in small catchments have shown a fractal distribution of ages, residence times are difficult to directly quantify or measure...
Groundwater–surface-water (GW-SW) interactions in streams are difficult to quantify because of heterogeneity in hydraulic and reactive processes across a range of spatial and temporal scales. The challenge of quantifying these interactions has led to the development of several techniques, from centimeter-scale probes to whole-system tracers, including chemical, thermal, and electrical...
Excess NO₃⁻ in streams is a growing and persistent problem for both inland and coastal ecosystems, and denitrification is the primary removal process for NO₃⁻. Hyporheic zones can have high denitrification potentials, but their role in reach- and network-scale NO₃⁻ removal is unknown because it is difficult to estimate. We...
In a set of streamside mesocosms, stream ecosystem respiration (ER) increased with biofilm biomass and flow heterogeneity (turbulence) generated by impermeable bed forms, even though those bed forms had no hyporheic exchange. Two streamside flumes with gravel beds (single layer of gravel) were operated in parallel. The first flume had...
In field studies of solute transport, transient storage within lateral cavities and other stream features generates
breakthrough curves (BTCs) with pronounced and persistent skewness. Current solute transport
theory requires that the coefficient of skewness (CSK) decrease over time because the system eventually
reaches Fickian conditions. However, published data show that...
Stream functioning includes simultaneous interaction among solute transport, nutrient processing, and metabolism. Metabolism is measured with methods that have limited spatial representativeness and are highly uncertain. These problems restrict development of methods for up-scaling biological processes that mediate nutrient processing. We used the resazurin–resorufin (Raz-Rru) tracer system to estimate metabolism...
We monitored a suite of stream chemistry parameters for April and May, 2013, at Oak Creek, Oregon, USA. The dataset can be downloaded at the following URL: http://dx.doi.org/10.7267/N9JW8BSJ, via the Dataset Query Tool. The dataset is hosted by The Oregon Hydrologic Information Server (OHIS), which is an on-line database repository...
Stream temperature will be subject to changes because of atmospheric warming in the future. We investigated the effects of the diurnal timing of air temperature changes – daytime warming versus nighttime warming – on stream temperature. Using the physically based model, Heat Source, we performed a sensitivity analysis of summer...
We provide an efficient method to estimate processing rates through simple algebraic relationships derived from the transient storage model equations. The method is based on the transport equations, but eliminates the need to calibrate highly uncertain (and intermediate) parameters. We demonstrate that under some common stream transport conditions dispersion does...
We investigated scaling of conservative solute transport using temporal moment
analysis of 98 tracer experiments (384 breakthrough curves) conducted in 44 streams
located on five continents. The experiments span 7 orders of magnitude in discharge
(10⁻ ³ to 10³ m³/s), span 5 orders of magnitude in longitudinal scale (10¹ to...
Accurate estimates of mass-exchange parameters in transient storage zones are needed to better understand and quantify solute transport and dispersion in riverine systems. Currently, the predictive mean residence time relies on an empirical entrainment coefficient with a range in variance due to the absence of hydraulic and geomorphic quantities driving...
In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the...
1. Temperature is a major driver of ecological processes in stream ecosystems, yet the dynamics of
thermal regimes remain poorly described. Most work has focused on relatively simple descriptors
that fail to capture the full range of conditions that characterise thermal regimes of streams across
seasons or throughout the year....
Temperature is a fundamentally important driver of ecosystem processes in streams. Recent warming of terrestrial climates around the globe has motivated concern about consequent increases in stream temperature. More specifically, observed trends of increasing air temperature and declining stream flow are widely believed to result in corresponding increases in stream...
The fate of biologically available nitrogen (N) and carbon (C) in stream ecosystems is controlled by the coupling of physical transport and biogeochemical reaction kinetics. However, determining the relative role of physical and biogeochemical controls at different temporal and spatial scales is difficult. The hyporheic zone (HZ), where groundwater–stream water...
Previous field-scale experimental data and numerical modeling suggest that the dual-domain mass transfer (DDMT) of electrolytic tracers has an observable geoelectrical signature. Here we present controlled laboratory experiments confirming the electrical signature of DDMT and demonstrate the use of time-lapse electrical measurements in conjunction with concentration measurements to estimate the...