Painted Rock Reservoir
1993 Water Surface Area and Storage Capacity
Estimate Derived from Landsat Data Classification
EMILY S. BRYANT, TIMOTHY PANGBURN, ROBERT L. BOLUS, GREGORY A. PEDRICK,
GREGORY PEACOCK, BRIAN G. TRACY, AND JOSEPH B. EVELYN
INTRODUCTION
estimated--as much as 500,000 acre-ft--might
This project was conducted to estimate the cur-
have been deposited in the reservoir.
rent storage capacity and the elevation vs. storage
With the large influx of sediment from the 1993
capacity relationship of the Painted Rock Reser-
flood event, the elevation vs. capacity relation-
voir, Arizona, using an elevation vs. surface area
ship for the Painted Rock Reservoir needed to be
curve determined from Landsat Thematic Mapper
updated for managers to maintain effective water
(TM) remote sensing data.
control procedures. The cost of a ground survey
The Painted Rock Dam is located on the Gila
was prohibitive, so it was worth investigating the
River at river mile 126, southwest of Phoenix, Ari-
use of remotely sensed data as an alternative
zona (USACE 1962, 1993). Figure 1 gives an over-
information source. Pertinent references for
view of the region, showing the reservoir in the
methodologies on calculating the effect of sedi-
south with Phoenix to the northeast in yellow
mentation on reservoirs are included in U.S.
tones. The dam and reservoir are managed by the
Army Corps of Engineers Engineering and
Los Angeles District of the U.S. Army Corps of
Design manuals EM 1110-2-4000 (USACE 1989)
Engineers. The dam was constructed between
and EM 1110-2-1420 (USACE 1997).
1957 and 1960 for flood control; closure was made
It is known that the reservoir elevation went
in April 1959. The drainage area above the dam is
from full to empty in 1993, and there possibly ex-
50,800 square miles. The reservoir is empty at
ists a snapshot of the state of the reservoir every
water surface elevation of 530 ft above mean sea
16 days when the Landsat satellite passed over.
level (MSL), with spillway crest at 661 ft and the
Also available is a complete record of water ele-
top of the dam at 705 ft. The reservoir's water sur-
vation at the dam, so the exact water elevation at
face elevation for the period 1959 to 1997 is shown
the time of Landsat overpasses can be retrieved.
in Figure 2.
It is also known that water and land are spectrally
As of a 1953 aerial survey, the water surface
very distinct, making it likely that classification of
area of the reservoir at spillway elevation was
Landsat data will yield a reasonably accurate wa-
53,200 acres and the storage capacity at the same
ter surface area estimate. With this information, it
elevation was 2,491,700 acre-ft. It was estimated in
should be possible to generate updated surface
1962 that 200,000 acre-ft of sediment would be
area values for the selected elevations of the times
deposited in the reservoir (no elevation specified)
of the Landsat overpasses.
over the course of 50 years. As of a 1985 survey,
The updated surface area values for selected
15,631 acre-ft had been lost at spillway elevation.
reservoir elevations can be used to update the
In 1993, the flood of record for Painted Rock Res-
existing complete surface area curve from the
ervoir occurred, and a dam upstream was
1985 survey. An updated elevation vs. capacity
breached as well. This led reservoir managers to
curve can then be created by computing the area
project that much more sediment than originally
under the updated surface area curve.
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