Limitations to spatial scaling of transient storage
Michael N. Gooseff, Civil & Environmental Engineering Department, Pennsylvania State University, 212 Sackett Bldg., University Park, PA 16802, Kenneth E. Bencala, Water Research MS 439, US Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, Brian L. McGlynn, Department of Land Resources & Environmental Sciences, Montana State University, 334 Leon Johnson Hall, PO Box 173120, Bozeman, MT 59717-3120, Martin A. Briggs, Hydrologic Sciences & Engineering Program, Colorado School of Mines, GE Department, 1516 Illinois St., Golden, CO 80401, and Durelle T. Scott, Geosciences Department, University of Nebraska, Lincoln, NE 68502.
The transient storage model (TSM), which characterizes advection, dispersion, the effects of lateral in- and outflow, and exchange between stream channels and storage zones, has been widely used to explore stream solute dynamics. One approach to scaling up our understanding of stream ecohydraulics is to apply models like the TSM over longer and longer stream reaches. The TSM approach was applied to a stream tracer experiment (1972 Uvas Creek (Santa Clara County, California)) to demonstrate that multiple simulations of solute transport within the same reach, over several combinations of stream segment lengths, result in varying estimates of lateral inflow, storage zone size, exchange rate, and storage zone concentration time series – all from equally robust simulations of solute breakthrough curves (R2>0.99). The spatial variability of lateral inflow, storage zone size, and exchange rate resulted in significantly different simulated storage zone concentrations, indicating that the TSM was a limited tool for estimating storage zone concentration dynamics. Thus, simulation of storage zone concentrations within a reach using the TSM is not directly scalable in space.