WSP00684

• File Number: 8220.101.16
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 1/1/2000
• Author: Webb et al.
• Title: Sediment Delivery by Ungaged Tributaries of the Colorado River in Grand Canyon Arizona
• Water Supply Pro - Doc Type: Report/Study

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Figure 4. Standardized seasonal precipitation for the Grand Canyon region from 1904
through 1998 based on data from 14 weather stations (table 3). A. Summer (July through
September). B. Winter (November through March).

and data from gaging stations on small drainages.
Data are available for sediment yield per year per
unit area for 25 reservoirs (fig. 6). In addition to the
reservoir sedimentation data, we assembled
sediment yield data from 12 gaging stations on
small watersheds in the region (table 4). Data from
eight of these watersheds are previously
unpublished and come from gaging stations
operated by Peabody Coal Company on Black
Mesa (D.R. Hardey, unpublished data, 1999). The
data were combined despite the fact that some
stations have data predominantly from the period
1948-1979 and others from Black Mesa were
collected in the 1980s and 1990s in a period of
higher rainfall (figs. 3-5). In addition, the Hains and

others (1952) data represent total sediment load
whereas suspended load was measured at the
gaging stations.
We combined the reservoir sedimentation data
with the annual sediment yields from gaging
stations in the region, excluding the mainstem
Colorado River (table 4). Fitting a power function
to these data (fig. 6), we obtained

Q, = 193 . A 1.04, R2 = 0.86, (3)

where Q, = sediment yield (Mg/yr), A = drainage
area (km2), and n = 37. We used equation (3),
termed the data regression equation, to estimate
sediment yields from all 768 tributaries, summed by
geomorphic reach (table 6).

STREAMFLOW SEDIMENT YIELD 11