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A combination of many features makes Crater Lake an outstanding scenic attraction as well as a most interesting and unique lake. John Wesley Hillman, the discoverer of Crater Lake, recorded in a description of the discovery that he and his companions were impressed with a number of features, among them, that the lake apparently had no inlet and no outlet. That characteristic feature of Crater Lake continues to impress thousands of visitors viewing the lake today from numerous observation points on the rim of the crater in which it is cupped. The realization that there is neither a visible inlet nor outlet, combined with the fact that the water of the lake is fresh, and that its location in the top of a mountain, the structure of which is such as to eliminate the possibility of the lake being fed by appreciable amounts of water from springs, stimulates many questions. Many of the questions concerning the source of water, loss of water, its purity, and changes in lake levels, seasonal as well as changes over a period of years, can be answered. The answers to many of the questions about the unique features of Crater Lake are based on observations which have been made for a number of years.

For this article on Snowfall, Precipitation and Lake Levels of Crater Lake, Ranger W. T. Frost has prepared compiled data for an interesting graph and several charts. Those will be of great value in helping visitors in the park and readers of Nature Notes to gain an appreciation of some of the unique features of Crater Lake.

The observation of snowfall and precipitation at Crater Lake, or, expressed in another manner, observations of inflow of Crater Lake, since the lake receives its water entirely from snow and rain falling within the crater rim, as well as observations of changes in lake levels are not only interesting but of practical value in estimating the supply of spring water in the park, and the inflow of water into streams and lakes beyond the boundaries of the park.

It is interesting to note, from data compiled by the U. S. Reclamation Service, that during the period 1905-1915, when the level of Crater Lake varied less than two feet, the inflow of Upper Klamath Lake – in the valley south of Crater Lake – remained fairly constant. During the period 1915-1934 there has been a constant but gradual lowering of the level of Crater Lake, and a fairly constant decrease in the inflow of Upper Klamath Lake. Since 1934 the level of Crater Lake has varied within 0.89 of a foot and the inflow of Upper Klamath Lake has increased slightly. It is evident that accurate observation of snowfall, precipitation, and lake levels at Crater Lake increase our knowledge of the lake, and certainly such observations are of value to organizations outside the park that are concerned with supply and distribution of water, an appreciable amount of which is no doubt the seepage from Crater Lake.

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(Wed Edition Note: This table contains revisions that were identified in Nature Notes Vol. X, No. 3)

Lake level is falling at an average rate of .51 foot per year.
(Estimated from figures over a 26 year period).