Hydrology of Crater, East and Davis Lakes, Oregon by Kenneth N. Phillips
WATER SUPPLY TO THE LAKE
The water supply of East Lake is derived from precipitation, surface runoff, and ground-water percolation. None of these elements has been measured. Most of the precipitation in the basin topographically tributary to East Lake percolates into the ground where it falls, and it may follow a path toward East Lake or one radially away from it. There is no information on the altitude or slope of local bodies of ground water.
Because Paulina Lake has a surface outlet that might also carry at least some of the outflow ‘by seepage from East Lake, the outflow of Paulina Lake is used as a tool in estimating the total water supply of the caldera. Information on that outflow is scanty. However, the stage of the lake varies within a narrow range, and its measured outflow usually ranges between 10 and 40 cfs. A low dam and fish screen at the outlet are designed and operated to keep trout from leaving the lake rather than to control the outflow or lake level. Because of the reasonably steady outflow, a few observations provide a fair basis for estimating the order of magnitude of the average annual outflow, about 14,500 acre-feet, as shown in table 8.