Simulation of solute transport in a mountain pool‐and‐riffle stream: A transient storage model

TLDR

Mountain streams differ from uniform open channels, and their unique physical conditions strongly affect solute transport, yet realistic parameter values remain uncertain. The study aims to use a transient storage model coupling dead zones with a one‑dimensional convection‑dispersion equation to simulate solute transport in a mountain pool‑and‑riffle stream and fit experimental data. The authors applied this transient storage model to a controlled chloride injection experiment, calibrating parameters against measured data and comparing them to values reported for other streams. The model successfully captured solute transport behavior that standard convection‑dispersion alone could not explain, and the parameter values qualitatively matched those reported for other streams.

Abstract

The physical characteristics of mountain streams differ from the uniform and conceptually well‐ defined open channels for which the analysis of solute transport has been oriented in the past and is now well understood. These physical conditions significantly influence solute transport behavior, as demonstrated by a transient storage model simulation of solute transport in a very small (0.0125 m 3 s −1 ) mountain pool‐and‐riffle stream. The application is to a carefully controlled and intensively monitored chloride injection experiment. The data from the experiment are not explained by the standard convection‐dispersion mechanisms alone. A transient storage model, which couples dead zones with the one‐dimensional convection‐dispersion equation, simulates the general characteristics of the solute transport behavior and a set of simulation parameters were determined that yield an adequate fit to the data. However, considerable uncertainty remains in determining physically realistic values of these parameters. The values of the simulation parameters used are compared to values used by other authors for other streams. The comparison supports, at least qualitatively, the determined parameter values.