00:00:35
Well, Yosemite
National Park
00:00:37
is home to these two
amazing watersheds;
00:00:40
the Tuolumne River
watershed to the north
00:00:42
and the Merced River
watershed in the south fork
00:00:45
of the Merced
to the south.
00:00:47
Those two major
watersheds really do form
00:00:52
the basis for the boundary of
Yosemite National Park.
00:00:56
We're sitting at the top of
the Tuolumne River watershed,
00:00:59
and basically what
that means is,
00:01:01
there is a drainage divide of
peaks of 11,000 to 13,000 feet,
00:01:06
and basically when precipitation
in the form of rain
00:01:09
or snow falls on this side
of the drainage divide,
00:01:12
it all coalesces in the form
of the Tuolumne River.
00:01:17
Indeed, most of the
Tuolumne watershed
00:01:19
kind of is a large
catcher's mitt,
00:01:21
with the river
being fairly close
00:01:24
to the southern edge
of the watershed
00:01:26
and having the majority of the
watershed from the north.
00:01:33
The Upper Tuolumne,
particularly the Lyell Fork,
00:01:36
is fed by two of the
largest glaciers
00:01:38
left on the western side
of the Sierra Nevada
00:01:41
and those are the Lyell
and McClure Glaciers.
00:01:44
The Lyell Glacier is positioned
beneath Mount Lyell,
00:01:47
which is the highest point in
Yosemite National Park;
00:01:50
it's just over 13,000 feet tall.
00:01:52
And to get to
the Lyell Glacier,
00:01:53
it's about a 12-mile hike
00:01:56
up the Lyell Fork of
the Tuolumne River,
00:01:58
through a big broad
U-shaped Canyon,
00:02:01
and then up
some steep slabs,
00:02:03
and then you clamber over
the loose rocky moraine.
00:02:08
Most of the Lyell Glacier is
visible behind me here;
00:02:12
the west lobe is the
larger of the two.
00:02:15
And we're looking at what's left
really of the Lyell Glacier.
00:02:20
Those glaciers have
decreased dramatically
00:02:23
over the last century
in size and volume,
00:02:26
and the concern or
interest there is that
00:02:29
they are the primary water
source for the Lyell Fork.
00:02:33
So once the snow melts
off each summer,
00:02:35
the flow in
the Lyell Fork
00:02:38
is sustained
almost exclusively
00:02:40
by melting of the Lyell
and McClure Glacier.
00:02:50
So it cascades through
rest of Lyell Canyon.
00:02:52
There are places where you
can't even hear the river,
00:02:54
you're walking
right next to it
00:02:56
and the water is just like
glass carving its way
00:02:59
through this beautiful
incredible grassy meadows
00:03:02
and into Tuolumne Meadows, where
it's joined by the Dana Fork,
00:03:07
its sister fork,
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