Solute transport in rivers with multiple storage zones: The STIR model

Abstract

[1] Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges between the surface stream and distinct retention zones. This paper presents a residence time model for stream transport of solutes, Solute Transport in Rivers (STIR), that accounts for the effect of the stream-subsurface interactions on river mixing. A stochastic approach is used to derive a relation between the in-stream solute concentration and the residence time distributions (RTDs) in different retention domains. Particular forms of the RTD are suggested for the temporary storage within surface dead zones and for bed form-induced hyporheic exchange. This approach is advantageous for at least two reasons. The first advantage is that exchange parameters can generally be expressed as functions of physical quantities that can be reasonably estimated or directly measured. This gives the model predictive capabilities, and the results can be generalized to conditions different from those directly observed in field experiments. The second reason is that individual exchange processes are represented separately by appropriate residence time distributions, making the model flexible and modular, capable of incorporating the effects of a variety of exchange processes and chemical reactions in a detailed way. The capability of the model is illustrated with an example and with an application to a field case. Analogies and differences with other established models are also discussed.

Dilution and volatilization of groundwater contaminant discharges in streams

“…Marion et al, 2008;Silva et al 2009). Boundary conditions that deal with heterogeneous and transient aquifer boundaries, river bank effects and storage in low river bends have been proposed and implemented in the literature (e.g., Lees et al 2000;Silva et al 2009;Moench 1995;Gooseff et al 2011;Pedretti et al 2014).…”

Calibrating pollutant dispersion in 1-D hydraulic models of river networks

“…The environmental management of river systems requires accurate and efficient tools to predict pollutant concentration, propagation and dispersion, especially near water intakes when rivers are used as a source of drinking water [4]. A commonly used tool is numerical modelling, which is developed to simulate the hydraulic conditions and the transport and fate of solute or particulate pollutants along river systems [17,15,36,30].…”

Stochastic modeling of nutrient losses in streams: Interactions of climatic, hydrologic, and biogeochemical controls

“…Figure 1 illustrates a schematic representation of this two-compartment conceptual model. This conceptualization is based on the Transient Storage Model (TSM), first proposed by Bencala and Walters [1983] and extensively used in stream denitrification studies [Wagner and Gorelick, 1986;Hart, 1995;Green et al, 1994;Runkel and Chapra, 1993;Harvey et al, 1996;Marion et al, 2003Marion et al, , 2008. While we recognize the limitations of this conceptualization to describe tracer injection studies Wagner and Harvey, 1996], our objective here is to apply it for providing a functional form for v f that can be used for comparison across systems.…”

“…If we assume hyporheic exchange within the streambed to be the dominant transfer mechanism with the transient storage zones, the mass transfer coefficient can be expressed as a function of the average flow rate into the sediments per unit bed area q B (L T −1 ) and the flow depth as a = q B /h [Marion et al, 2008;Worman et al, 2002;Packman and Bencala, 2000]. The mass transfer velocity q B has been shown to be weakly variable within a narrow range (say, between 5 to 15 [cm d −1 ], [see, e.g., Birgand et al, 2007].…”

“…Since the focus of the work is to explore the variability in denitrification rates, biotic uptake term is neglected in our formulation. Moreover, we also neglect the dispersion term, and assume that the dominant transport mechanism is advection (an assumption which is satisfied in many practical applications in rivers [see, e.g., Rinaldo et al, 1991;Rutherford, 1994;Marion et al, 2008]). Under the above simplifications, the mathematical formulation of the TSM is given as follows:…”