Los Vaqueros Reservoir Earthcache EarthCache
Los Vaqueros Reservoir Earthcache
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As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
Getting There: The best route to the earthcache is from Vasco Rd to Los Vaqueros Rd. It is about 3 miles from the intersection to the cache location.
You should face towards the main body of the reservoir from the cords (even though the map says you're in the lake, you aren't. There is a road that skirts the lake for about 3/4 mile which includes this cache).
There is a fee ($6 at the time of writing) IF there is anyone at the toll booth. On the two occasions I've been there, once the lady just let me through since I promised a "quick in and out." and the other time I was the ONLY one within that entrance of the park.
Logging Requirements:
Send the answers to #1-#4 to me through my geocaching profile. DO NOT post the answers to any logging requirements on this site.
1.List the name “GC2AC5Z Los Vaqueros Reservoir Earthcache” in the first line of your email. Also, list the number of people in your group.
NOTE: for #2 -- We all know that a reservoir lake is NOT round, but rather "spidery" with tendrals of water reaching out from a central bowl. However, the calculation is still a good average, since we are on a point of land that gets us to within a reasonable approximation of volume.
2.Determine the approximate volume of the reservoir (the math term is a hemisphere or half-sphere) Process:
A. Enter these cords into your GPS: N 37*50.362 W 121*43.599. Your GPS will tell you the diameter of the reservoir. Take this distance and divide by two. Take this number and divide it by 5280 (this converts your “miles” mark into a “feet” distance) This is your “radius” or “r” in the following formula.
B. Calculate the volume of the lake by first pretending that it is a complete sphere (think ball). Given a radius r, that volume is: 4/3 * pi * r^3. (pi = 3.14 and r^3 means r*r*r)
C. Divide your answer by two, since really, the reservoir is “1/2 of a ball” in volume, thus a hemisphere.
3.Looking across the reservoir you can see scars, or high water marks on the reservoir bank. Estimate how high above the current level this line is, and state the season (Spring, Summer, Fall, Winter) when you made this observation.
4.Identify (from the description and the view in front of you) two geological consequences of building the reservoir and “burying” the land/rock/ground underwater. In other words, how has the reservoir positively or negatively affected the geology of this region.
5. Post a picture of yourself and your GPS with your log that shows you with the marina of reservoir; OR list the COLOR of all the area buildings around the marina.
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
The process (in a nutshell) of creating a reservoir:
A reservoir's purpose is to store water, usually for drinking/irrigation purposes. Typically, a small watershed is found (one where a relatively small low lying area is surrounded by steep hills of significant height to create a “bowl” that can later be filled with water. The low lying area should contain a stream or river that will “fill” the area once the dam is constructed. The engineers also have to research the types of rocks are present in the hills so that they can choose the correct type of dam to construct...they don't want a dam that will burst or shift!
Geologically there are two items of interest concerning reservoirs and their associated dams.
First, there are several relatively mild negative geological affects of a reservoir. First, when a reservoir is filled, most of the unconsolidated rock and soil is saturated with water and eventually displaced. Thus, if years later the reservoir is drained, the exposed hillsides are denuded of the “top soil” and thus seldom recover the flora and fauna present prior to the dam. This displaced soil often is washed downstream through the dam and often eventually ends up in the San Joaquin delta, which creates its own geological problems discussed by other earthcaches. Also, the scarring associated distinctly with the governed though various depths of the reservoir visually scar the sides of the hills. While this second affect is primarily visual and geological, it does dramatically expose layers of rock that would not otherwise be visible. Any time a lake is formed by a dam (rather in the modern era or as part of glacial “ice dam” retreats, these lines remain for millenia after the dam is eliminated.
Geologically, there is some research being done that believes that dams/reservoirs may lead to seismic activity (earthquakes) that might otherwise not happen. This is called reservoir-induced seismicity. There are four examples of seismic activities in areas that are not seismic prone in California reservoir history: Lake Mendocino in Mednocino County; Lake Crowley in Mono County; Lake Oroville in Butte County; Lake Shasta in Shasta County. These seismic events varied from 5.2 to 6.0. In the case of Lake Oroville, there have been several events, and they seem to be directly related to the volume of water being stored in the reservoir. Most of these seismic events have occurred within 1-5 years of the reservoirs being filled. In all cases, the reservoirs were filled rapidly.
Why does this matter? One of the negative geologic events that could happen with reservoirs would be that the earthquake could split/shatter the dam and cause UNIMAGINABLE DAMAGE to the area below the dam. Can you image the volume of water calcuated for the logging requirements being released on Byron and Brentwood? We would make national/international NEWS! Is this a likely event? The article I read didn't really address this question, though they did guess that reservoirs can hasten seismic activity that would otherwise have eventually happened, but it caused it to happen much quicker. They also postulate that areas considered faulted, but INACTIVE have in some cases become active because of the influence of a reservoir. This area is NOT in the California seismic zone, but one does have to wonder what MIGHT happen if that changed.
History/Information: The Los Vaqueros Project was completed in 1998; the reservoir is so new that it does not appear on all but the most recent maps. The Water District is planning more trails, and an interpretive center, marina, and group picnic area opened in 2001.
All the multi-use trails are in the north end of the watershed (accessible from the Walnut and Dam Staging Areas), while all the trails near the County Line Staging Area are open to hikers only. Experienced hikers can even trek into Morgan Territory Regional Preserve (onto Volvon Trail via Black Hills Trail, or onto Manzanita Trail via Miwok Trail) and Round Valley Regional Preserve (onto and via Miwok Trail), creating the possibility of extended hiking adventures. Trails have been ranked for difficulty by the Water District, so be sure to take those designations to heart while planning a hike; since their map has no topography, it's easy to get in over your head on trails that all seem to be old fire or ranch roads, better suited to four-wheel drives than legs.
Resources:
Reservoir Induced Earthquakes and Engineering Policy by Clarence Allen (California Institute of Technology), 1982. (visit link)
Alt & Hyndman, Roadside Geology of Northern andCentral California. Mountain Press Publishing. Missoula: Montana. 2000.
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