A watershed is defined as a region of land that is bounded by high topographic points in which water will natrually flow and drain into a basin, lake, or ocean. The above coordinates will bring you to a sign that talks about the San Juan Creek Watershed, of which Oso Creek is part of, much more in detail. A watershed is an important aspect in hydrology, a subset of geology. Before I go too much into detail, I must first dicuss some terminology of watersheds.
The headwaters are the orginal of a river or creek. It is where a river begins and is typically found at the highest point within the watershed. The terminus is where the river or creek ends and is typically found at the lowest point within the watershed. This is usally at an ocean or lake. The surrounding area between these two points (bounded by topographic highs) is considered the watershed for that specific creek or river.
Watersheds can be year-round or seasonal. With growing urbanization (especally in Southern California) most watesheds that were seasonal are now becomming year-round. Watersheds often contain thier own unique ecosystem and geological propertes. For example, here in the San Juan Creek Watershed tall grasses help trap sediment as they flow out to the ocean, providing nutriens for the plants and animals that live within the watershed. Additially, the grade (or slope) of the watershed can dictate how fast the water flows out of it. This can create murky waters if flow is inhibited or clear waters if flow is constant and consistant. If the water is murky, it means that the flow velocity of the water is low. If the water is clear, it means that the flow velocity of water is high. Low flow velocites allows particulates and sediment to settle out, allowing the water to become transparent. While fast flow velocites creates turbulent waters which pick up and suspend sediments in the water.
During times of large storm events, larger sediments such as boulders can be easily moved downstream and deposted near the terminus as flow velocity decreases near the shore. Storm deposits, as they are called, can be seen usually along the upper banks of a creek or river and typically appear to have freashly cut surfacaces. They appear rough as aposed to river rocks that are more round and smooth.
When this area was being developed in the 60s and 70s, Oso Creek was widened and, in some portions, fit with concrete channels so that it could accomdate more runoff. During the widinging process, many types of marine fossils were found. Walking along the creekbed, one may find fossils. This entire area, about 5 million years ago, was under water (part of the Pacific Ocean). Baleen and Toothed Whales, among other sea animals, lived in the waters above Mission Viejo and southern Orange County. Their remains have been preserved in the sandstone deposits of the Monterey Formation, which can be found locally in southern Orange County.
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER ALL THE QUESTIONS BELOW. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER TO SEND YOUR ANSWERS. ANY INCORRECT ANSWERS MAY RESULT IN A CLARIFICATION RESPONSE FROM ME.
1. "San Juan Creek Watershed - Oso Creek" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Take a picture of your finger pointing to where you are on the watershed map. The correct map should be in blue. Be sure to not show any other part of the sign in your photos.
3. Look down below at Oso Creek. Is the water murky or clear? What does this tell you about its flow velocity?
4. Look down below at Oso Creek. Do you see any evidence of storm deposits? How can you tell?
5. What type of fossils can be found along the creekbed? Do you see any evidence of fossils in the rocks that make up the creek bed? Explain.
6. Is Oso Creek seasonal or year-round?
7. Do you think you are standing on a watershed divide? Or do you think you are standing within the watershed itself? Explain using the waterhed map and your observation of the local topography from this vantage point.