Lakes in the Grand and Glen Canyons

(Source: Hamblin, W.K. and L. Hamblin. 1994. Late Cenozoic Lava Dams in the Western Grand Canyon. Geological Society of America)

Below is a tabulation of dams in the Grand and Glen Canyons during the last 2 million years. The dams were created by Volcanic flows into the Grand Canyon approximately 180 miles downstream of Lee's Ferry. It should be noted that Prospect Lake was much larger than Lake Powell and water would have been backed up water to Moab, Utah. Lava Butte Dam backed up water almost as far as Lake Powell does at full pool (just downstream of Hite, Utah).

When proponents of draining Lake Powell discuss the abrupt change to the ecosystem by building Glen Canyon Dam in a few years, it should be noted that the "major flows" listed in the table were backing up a lake within 24 hours.

Dam

Elevation

Height
Above
River

Type of
Dam

Lake
Length

Water
Fill
Time

Sediment
Fill Time

Prospect

4,000 ft

2,330 ft

3 major flows
600-800 ft
thick

324 miles

23 years

3,018 years

Lava Butte

3,500 ft

1,865 ft

Numerous
thin flows

300 miles

?

?

Toroweap

3,091 ft

1,413 ft

5 major flows
100-200 ft
thick

177 miles

2.62 years

345 years

Whitmore

2,500 ft

900 ft

More than
40 thin flows
10-20 ft thick

108 miles

240 days

88 years

Ponderosa

2,800 ft

1,130 ft

1 major flow
1,000 ft thick

126 miles

1.5 years

163 years

Buried Canyon

2,480 ft

850 ft

8 major flows
100-200 ft thick

108 miles

231 days

87 years

Esplanade

2,600 ft

960 ft

6-8 flows
100-200 ft thick

109 miles

287 days

92 years

"D" Dam

2,295 ft

635 ft

40 thin flows
10-20 ft thick

77 miles

87 days

31 years

Lava Falls

2,260 ft

600 ft

Single flow

77 miles

86 days

30 years

Black Ledge

2,033 ft

370 ft

Single flow

53 miles

17 days

7 years

Layered
Diabase

1,938 ft

298 ft

20 thin flows

42 miles

8 days

3 years

Massive
Diabase

1,826 ft

226 ft

Single flow

40 miles

5 days

1.4 years

Gray Ledge

1,813

203

Single flow

37 miles

2 days

10.3 months

Here is a map showing Lake Powell (light blue) superimposed over Prospect Lake (dark blue).

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