First
Dinkey Lake is reached by a moderate to strenuous hike into the
Dinkey Lakes Wilderness. It is just a few miles from the parking
area and at an elevation of about 9300 feet. The parking area is
accessible by unpaved Forest Service access roads. The roads do get
pretty rough, so a high clearance vehicle would be a very good
idea. Winter snows make the EarthCache inaccessible.
First Dinkey Lake was carved out of the mountain by a glacier,
forming a cirque that in turn filled in with water to become a tarn
(see
South Lake – A Cirque ). From the moment it formed, the
basin began filling with sediment. The process of a lake gradually
filling is called eutrophication. The rate at which this happens is
related to the how much sediment is transported into the lake and
the organic content of the lake.
Each spring, melting snow erodes sediment off the surrounding
mountains and transports it to the streams that fill the lakes of
the Dinkey Lakes Wilderness. While in the streams, the water flow
is fast enough to keep the sediment moving. When the water reaches
a lake, the speed of the water slows depositing the sediment in the
lake. This sediment begins to fill the lake from the point where
the stream enters the lake, forming a delta. This process alone
will bring enough sediment to eventually fill the lake from its
side. However, the in-filling process can be greatly increased by
elevated biologic activity in the lake.
Biologic activity includes shore plants, underwater plants,
freshwater plankton, algae, aquatic life, among other things. As
these things die, they settle to the bottom of the lake filling it
in and providing nutrients for more biologic growth. This process
generally fills the lake in from the bottom up as material settles
to the bottom.
Three stages of lake development have been developed by limnologists to
describe the aging of a lake. These stages are called trophic
states, oligotrophic, mesotropic, and eutrophic. These states are
most easily recognized by the amount of biologic activity in the
lake. Oligotrophic lakes are clear with little biologic activity.
Eutrophic lakes look cloudy and have a lot of biologic activity.
Mesotropic lakes are somewhere in between.
Urban and agricultural runoff can contain various nutrients that
can greatly increase biologic activity. The increased biologic
activity then increases the rate of eutrophication of the lake.
This artificial increase is called cultural eutrophication.
All the stages of eutrophication are natural processes and each
has its own benefits. Oligotrophic lakes would be great swimming
lakes and provide beautiful picturesque landscapes. An eutrophic
lake would probably be an excellent fishery and wildlife
habitat.
Logging questions:
- At these coordinates, what features of the stream show that it
has been filled in by sediment?
- What stage of eutrophication is First Dinkey Lake?
- Based on how the lake is filling in, is it filling in from
mostly biologic activity or a delta?
The above information was compiled from the
following sources:
- http://fli.hws.edu/sos/TSI%20teachers%20page.htm