A Reach‐Averaged Model of Diurnal Discharge Wave Propagation Down the Colorado River Through the Grand Canyon

Abstract

As part of the Glen Canyon Environmental Studies, we have developed a discharge model that routes daily discharge waves released from Glen Canyon Dam to Diamond Creek, 386 km downstream. Owing to the length of the diurnal discharge wave and the sparseness of the available topographic data, the latter were averaged over the entire length of the system. Terms too small to be significant in the momentum equation were identified by scaling arguments based on data from past dam releases and on channel hydraulic geometry. Channel friction results primarily from form drag on large topographic elements and from variations in cross‐sectional area and flow depth, rather than bed roughness, producing a stage‐dependent friction that is not well represented by a constant value of standard channel roughness parameters, such as Manning's n. Channel friction as a function of stage was determined from field data available at high discharge (792 m3/s) and intermediate discharge (425 m3/s) and by using simple kinematic wave theory together with wave speed measurements to determine channel friction at low discharge (about 142 m3/s). Model predictions of wave speed and shape agree well with data from five streamflow gaging stations and 42 stage gaging stations located along this segment of the Colorado River.

Characterization of the spatial variability of channel morphology

“…Interpreting the variation of channel geometry (Wolman, 1955;Knighton, 1975;Leopold and Wolman, 1957;Speight, 1965;Ferguson, 1975Ferguson, , 1976, evaluating aquatic habitats (Mathur et al, 1985;Bren, 1993;Johnson, 1994;Currier, 1995;Myers and Swanson, 1997), and studying the dispersion of tracers (Hays et al, 1966;Sabol and Nordin, 1978;Nordin and Troutman, 1980;Bencala et al, 1993;D'Angelo et al, 1993;Runkel and Bencala, 1995) 1252 J. A. MOODY AND B. M. TROUTMAN require knowledge of the marginal probability distribution of widths and depths, while flood (Fread, 1985;Rashid and Chaudhry, 1995;Wiele and Smith, 1996) and sediment routing models (Pickup and Higgins, 1979;Miller, 1994;Dietrich and Whiting, 1989) need both the marginal probability distributions and the proper length scales over which relatively small-scale variability can be suitably averaged to provide useful physical parameters for modelling.…”

Effects of three high-flow experiments on the Colorado River ecosystem downstream from Glen Canyon Dam, Arizona

“…Such a depiction of the shoreline requires detailed knowledge of both the water-surface elevation for the flow of interest and the topography of the surface that will be inundated. While models for predicting discharge (Wiele and Smith, 1996;Wiele and Griffin, 1997) and water-surface elevation (Randle and Pemberton, 1987) have been in use for many years, these models lack the level of resolution and coupling with topographic information that would allow their application to the prediction of shorelines.…”

“…In a year with relatively high sand storage, a "larger" HFE may be warranted compared to a year with less sand storage. Wright and Grams (2010) demonstrated how the sand-storage model can be used together with a numerical model of flow releases (Wiele and Smith, 1996) to estimate sand-storage conditions for a range of dam operations. A similar approach would be useful for supporting HFE decisionmaking in near real time, as described in the following section.…”

Ecosystem Modeling for Evaluation of Adaptive Management Policies in the Grand Canyon

“…Further complicating the impact of diurnal flow variation is that diurnal stage (depth) waves at Glen Canyon Dam move down through the system much faster than do water parcels, taking about two days to move from GCD to Lake Mead (Graf 1995, Wiele andSmith 1996). Communities near the dam are subject to deeper water during the day (which tends to reduce production due to reduced light penetration), and then nocturnal drying.…”