If I delete your found log due to lack of following instructions, you can re-log your find when you are able to comply.
As this is an earthcache, there is no container to be found; instead, you will take two sets of measurements while paddling in Lake St. Clair, make observations, and then send answers to the questions below to the cache owner. For this earthcache, you will paddle to two locations to take measurements with special equipment. You will also drive to a nearby location to make observations. Please read the general information text for help in answering the questions.
The two paddling locations for measurement are separated by a peninsula in the lake. There are two launch spots across the street from one another. You may either paddle from one launch spot to the other, or do two launches from the two parking areas for two separate paddles. It is recommended that you do this earthcache in conjunction with GC5HKWG - Octopus Lake as required measurements for that one will be taken at the same two locations.
Equipment needed for this cache:
- a Secchi disk with weight attached
- a ruler.
You may make your own, borrow one from someone, or borrow my Secchi disk and ruler. You may pick up my gear at N 47° 00.366 W 122° 42.185 in the large container next to an old post. My homemade disk will work well enough for the observations needed for this cache, the line is long enough, and it has a weight attached.
Note: to make you own, there are many websites with instructions.
Steps to complete this earthcache may be done in any order. There are three steps:
1. Paddle to the general area of the stated coordinates. Take a Secchi disk reading and a GPS reading. See instructions for using a Secchi disk below.
2. Paddle to the general area of the Waypoint 1 coordinates. Take a Secchi disk reading and a GPS reading.
3. Drive to the Waypoint 2 coordinates and observe the water clarity of Eaton Creek to determine if this may or may not be related to the turbidity of Lake St. Clair.
How to take a Secchi disk reading:
- slowly lower the Secchi disk into the water on the shady side of the boat until it is no longer visible. Record this depth - remember to mark the depth from the water line.
- slowly raise the disk until it just becomes visible once again. Record this depth - remember to mark the depth from the water line.
- average the depths from steps 1 and 2 to get the Secchi depth. - repeat for precision.
Note: the stated coordinates and the waypoint are where I was when I gathered information for the earthcache. They are meant as guidelines to get you to the general areas; your GPS readings may be slightly different.
Questions to answer:
- there may be a delay in my response if I am out of town without internet access. Please log your find as soon as you send answers - don't wait for permission.
Send answers directly to me. Please do not put the answers in your log. If possible, use the message center; my responses will be sent that way. You will need to read the text as well as taking measurements for the answers. Answers must be sent in a timely manner to avoid deletion of your found log.
1. State the source of the Secchi disk you used. Give the Secchi disk reading and the GPS reading at each of the two sites to which you paddled. It is not critical to be at the exact coordinates given to take the readings. Those are simply guidelines to get you to the general locations.
2. Are you surprised at the turbidity readings from your Secchi disk samples? Why or why not?
3. Using what you read and what you observed in the lake and at Eaton Creek, give at least three geological causes for the turbidity of Lake St. Clair.
4. Do you think the flow in Eaton Creek contributes to the results you found?
5. What suggestions would you make to those living on the lake about maintaining or improving water quality in these waters?
6. Each cacher should post a photo of themselves (or their watercraft) while using the Secchi disk at one of the two sites. If your face shows, great, but that's not necessary. Posts without the required photo will be deleted.
General information:
If you did or are doing the Octopus Lake earthcache, you will know that Lake St. Clair is a kettle and is the result of chunks of ice left behind by the receding Puget Lobe of the Vashon glaciation. What began as a result of water in its solid state is now filled with water in its liquid state. Although you cannot typically observe it, some is constantly leaving the lake as water in its gaseous state.
Lake St. Clair has 10.4 miles of shoreline and is at an altitude of ~73 feet. The surface level of the water rises and falls by as much as 6 feet throughout the year.
Due to the irregular shape of the lake with somewhat isolated basins, steep slopes, and great depths, water quality and turbidity varies throughout the many basins. Eaton Creek is the only stream input, discharging into the largest, southwest basin. In addition to Eaton Creek, it has been reported that there may be deep artesian springs discharging into the lake.
Lake St. Clair and therefore the Eaton Creek drainage is a closed sub-basin, meaning there is no surface water outlet for the lake. "Groundwater seeps out of the lake to the north to McAllister Springs, a City of Olympia water supply. The lake is a natural dark brown ”tea-color” which restricts light penetration, limiting aquatic plant and algae growth. Many of the land owners along this lake have maintained the shoreline in its natural condition, providing valuable wildlife and fish habitat. However, increased shoreline development could threaten to alter that condition."
This earthcache concentrates on the causes of the amount of turbidity you observe when using a Secchi disk. Using the Secchi disk, you will measure turbidity, which is the measure of clarity or transparency of a liquid, or the amount of particulate matter suspended in water. Particulate matter in water due to sedimentation and siltation decreases water clarity and also provide attachment places for bacteria. Particulate matter can include clay, silt, and minute particles of organic and inorganic matter. Some sources of particulates are streams, erosion, and urban runoff.
A sample of water taken from the south basin of the lake at depth of about 8 feet was allowed to settle. There was brown sediment on the bottom of the container. If algae was present, it was eaten by the few tiny, unidentified, arthropod creatures who died soon after the container was removed from light sources to inhibit future algal growth. Thus there had been inorganic matter suspended in the water along with a some organic matter.
You will take turbidity readings in both the southwest and the east basins, using the coordinates given for each. These two basins are strongly thermally stratified, meaning that the lake has a warm surface layer of 3-6 feet due to solar radiation, and a cooler bottom layer. The surface water temperature in the east basin reaches 75 degrees Fahrenheit in August. The temperature below 6 feet in both basins is 40-45 degrees Fahrenheit. Generally below 6-10 feet, the water is anoxic, lacking dissolved oxygen.
If you want to know more this and related topics with information given above the level of 6th grade, check out the sources listed.
As you take your turbidity readings (see instructions above) think about how the local geology contributes to your results so that you can answer the questions.
Sources:
http://www.co.thurston.wa.us/health/ehrp/pdf/AR03-05/AR03-05_NisquallyWS.pdf
http://serc.carleton.edu/microbelife/research_methods/environ_sampling/turbidity.html
http://www.co.thurston.wa.us/waterresources/basin/mcallister/chapter2.pdf
http://www.untamedscience.com/biology/biomes/lakes-ponds-biome/