THERE AND BACK AGAIN: AN ANALYSIS OF WATER AREA AND CLIMATE OF 3 EPHEMERAL LAKES IN THE OREGON CASCADES

Abstract

The Willamette River is the main provider of water to the Willamette Valley. It flows northward through the valley, where 70% of Oregon’s residents reside, eventually connecting to the Columbia River on the border of Oregon and Washington. The headwaters of the Willamette River originate in the Oregon Cascades, specifically in the High Cascades. The large amount of precipitation that falls on the Cascades allows seasonal cycles of water release from the melting of snowpack throughout the dry season. The Oregon Cascade Range, because of its geologic composition, has unique relationships between geology and climate that contribute to the water access to the people and landscape of the Willamette Valley. The Cascades are generally divided into two provinces: the older, eroded, less basaltic, more impervious Western Cascades, which extend from the eastern base of the Willamette Valley to about the Santiam Junction; and the High Cascades, which are much younger geologically (about 4 Ma), more basaltic, and contain vast swaths of porous bedrock. Most of the water flow in the Western Cascades is surface flow, whereas groundwater flow from precipitation penetration into the porous bedrock is the main form of water transportation in the High Cascades. 3 3 seasonal lakes that reside along the border of the Western and High Cascades highlight the interrelationships between the climate and the geology. Fish Lake, Lava Lake, and Lost Lake are similar in the way they fill and drain each year from precipitation and geology. The rates at which they drain and if these rates are dependent on SWE (snow water equivalent), air temperature, and precipitation levels can help to better understand how the geology is impacted by the climate and how this might affect water access downslope in the Willamette Valley.