Gary Halvorson, Oregon State Archives [Attribution], via Wikimedia Commons
Hydrology of Little Lava Lake
Little Lava Lake is the official headwaters of the mighty Deschutes River. Interestingly, there is no above-ground inlet supplying water to the lake. Only in extremely wet years is there enough water from nearby Big Lava Lake to overflow and run through an open channel into Little Lava Lake. So where does the water come from?
Ten thousand years ago, during one of Mt. Bachelor’s eruptions, thick lava flows blocked the ancestral Deschutes River and also formed Sparks Lake seven miles to the north. Sparks Lake has no visible outlet, but the water does flow somewhere. Instead of flowing above ground, water from Sparks Lake flows underground into Little Lava Lake, emerging here and helping to form the Deschutes River.
Interesting side note: during the severe drought of 1977 no outflow occurred from Little Lava Lake into the Deschutes River; springs fed the Deschutes River just downstream from its usual headwaters source.
Logging this Earthcache
Please email or message the cache owner with answers to the following questions:
1. What types of rock layers does the groundwater travel through?
2. What effect does the layer of impermeable rock have on the groundwater?
3. From the interpretive sign, walk over to the lake. There are two large gray rocks embedded in the shoreline. Approximately how many inches apart are these rocks? (an estimate is fine, most people don't bring tape measures to the lake!)
Photos are welcome, but not required.
Once you have emailed your answers, feel free to log your find immediately - you do not need to wait for a response. Please do not post the answers to the questions within your log. Thank you!
References
- Corridor Management and Interpretive Plan 2011, U.S. Forest Service.
- Johnson et al (1985). Atlas of Oregon Lakes. Oregon State University Press.