Hydrology of Crater, East and Davis Lakes, Oregon by Kenneth N. Phillips
WATER LOSS FROM THE LAKE
Nearly all the water that reaches Davis Lake is lost by seepage into the lava flow that dams the channel and fills the valley of Odell Creek. The seepage cannot be directly measured, but its annual volume and its rate at different lake levels can be approximated.
The volume of seepage in a year is approximately equal to the volume of inflow adjusted for change in contents of the lake. This is true because the infalling precipitation and the loss by evaporation are nearly equal and are opposite as elements of the water budget. If the average inflow is 150 cfs, as estimated above, the average seepage rate must be about the same.