Before damming, the high granite formations produced a valley with an average depth of 1,800 ft (550 m) and a maximum depth of over 3,000 ft (910 m); the length of the valley was 3 mi (4.8 km) with a width ranging from an eighth to a half of a mile (0.2 to 0.8 km).
The valley floor consisted of roughly 1,200 acres (490 ha) of meadows fringed by pine forest, through which meandered the Tuolumne River and numerous tributary streams.
Kolana Rock, at 5,772 ft (1,759 m), is a massive rock spire on the south side of the Hetch Hetchy Valley.
Hetch Hetchy Dome, at 6,197 ft (1,889 m), lies directly north of it.
The locations of these two formations roughly correspond with those of Cathedral Rocks and El Capitan seen from Tunnel View in Yosemite Valley.
A broad, low rocky outcrop situated between Kolana Rock and Hetch Hetchy Dome divided the former meadow in two distinct sections.

The valley is fed by the Tuolumne River, Falls Creek, Tiltill Creek, Rancheria Creek and numerous smaller streams which collectively drain a watershed of 459 sq mi (1,190 km²).
In its natural state, the valley floor was marshy and often flooded in the spring when snow melt in the high Sierra cascaded down the Tuolumne River and backed up behind the narrow gorge which is now spanned by O'Shaughnessy Dam.
The entire valley is now flooded under an average 300 ft (91 m) of water behind the dam, although it occasionally reemerges in droughts, as it did in 1955, 1977 and 1991.

Upstream from the valley lies the Grand Canyon of the Tuolumne, while the smaller Poopenaut Valley is directly downstream from O'Shaughnessy Dam.
The Hetch Hetchy Road drops into the valley at the dam, but all points east of there are roadless, and accessible only to hikers and equestrians.
The O'Shaughnessy Dam is near Yosemite's western boundary, but the long, narrow, fingerlike reservoir stretches eastward for about 8 miles (13 km).

Wapama Falls, at 1,080 ft (330 m), and Tueeulala Falls, at  840 ft (260 m) – both among the tallest waterfalls in North America – are both located in Hetch Hetchy Valley.
Rancheria Falls is located farther southeast, on Rancheria Creek.
Formerly, a "small but noisy" waterfall and natural pool existed on the Tuolumne River marked the upper entrance to Hetch Hetchy Valley, informally known as Tuolumne Fall (not to be confused with a similarly named waterfall several miles upriver near Tuolumne Meadows).
The waterfall on the Tuolumne is now submerged under Hetch Hetchy Reservoir.
Before damming, the high granite formations produced a valley with an average depth of 1,800 ft (550 m) and a maximum depth of over 3,000 ft (910 m); the length of the valley was 3 mi (4.8 km) with a width ranging from an eighth to a half of a mile (0.2 to 0.8 km). The valley floor consisted of roughly 1,200 acres (490 ha) of meadows fringed by pine forest, through which meandered the Tuolumne River and numerous tributary streams. Kolana Rock, at 5,772 ft (1,759 m), is a massive rock spire on the south side of the Hetch Hetchy Valley. Hetch Hetchy Dome, at 6,197 ft (1,889 m), lies directly north of it. The locations of these two formations roughly correspond with those of Cathedral Rocks and El Capitan seen from Tunnel View in Yosemite Valley. A broad, low rocky outcrop situated between Kolana Rock and Hetch Hetchy Dome divided the former meadow in two distinct sections.
The valley is fed by the Tuolumne River, Falls Creek, Tiltill Creek, Rancheria Creek and numerous smaller streams which collectively drain a watershed of 459 sq mi (1,190 km²). In its natural state, the valley floor was marshy and often flooded in the spring when snow melt in the high Sierra cascaded down the Tuolumne River and backed up behind the narrow gorge which is now spanned by O'Shaughnessy Dam. The entire valley is now flooded under an average 300 ft (91 m) of water behind the dam, although it occasionally reemerges in droughts, as it did in 1955, 1977 and 1991.
Upstream from the valley lies the Grand Canyon of the Tuolumne, while the smaller Poopenaut Valley is directly downstream from O'Shaughnessy Dam. The Hetch Hetchy Road drops into the valley at the dam, but all points east of there are roadless, and accessible only to hikers and equestrians. The O'Shaughnessy Dam is near Yosemite's western boundary, but the long, narrow, fingerlike reservoir stretches eastward for about 8 miles (13 km).
Wapama Falls, at 1,080 ft (330 m), and Tueeulala Falls, at  840 ft (260 m) – both among the tallest waterfalls in North America – are both located in Hetch Hetchy Valley. Rancheria Falls is located farther southeast, on Rancheria Creek. Formerly, a "small but noisy" waterfall and natural pool existed on the Tuolumne River marked the upper entrance to Hetch Hetchy Valley, informally known as Tuolumne Fall (not to be confused with a similarly named waterfall several miles upriver near Tuolumne Meadows). The waterfall on the Tuolumne is now submerged under Hetch Hetchy Reservoir.
Hetch Hetchy