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 |
Type
of |
Lake |
Water |
Sediment |
Prospect |
4,000 ft |
2,330 ft |
3 major flows |
324 miles |
23 years |
3,018 years |
Lava Butte |
3,500 ft |
1,865 ft |
Numerous |
300 miles |
? |
? |
Toroweap |
3,091 ft |
1,413 ft |
5 major flows |
177 miles |
2.62 years |
345 years |
Whitmore |
2,500 ft |
900 ft |
More than |
108 miles |
240 days |
88 years |
Ponderosa |
2,800 ft |
1,130 ft |
1 major flow |
126 miles |
1.5 years |
163 years |
Buried Canyon |
2,480 ft |
850 ft |
8 major flows |
108 miles |
231 days |
87 years |
Esplanade |
2,600 ft |
960 ft |
6-8 flows |
109 miles |
287 days |
92 years |
"D" Dam |
2,295 ft |
635 ft |
40 thin flows |
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 |
1,938 ft |
298 ft |
20 thin flows |
42 miles |
8 days |
3 years |
Massive |
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).