- Lincoln County)
(From Atlas of Oregon Lakes, Johnson et al. 1985) Olalla Reservoir is owned and operated by the Georgia-Pacific Corporation who built it in 1957 to supply water for their paper processing mill in Toledo four miles to the south. The reservoir was created by construction of a small earth-fill dam which impounds the waters of the West Branch of Olalla Creek. The hydrology of the reservoir is unusual in that the principal inflow is through a pipe which diverts water from the nearby Siletz River. Only a small amount of natural inflow is derived from West Olalla Creek and two other small streams. The shape of the reservoir is dendritic or branching, typical of impoundments in stream valleys, whether natural or artificial. The term Olalla is a modification of Olathe, the original spelling of the creek name. It is a Chinook jargon word which means berries in general, or salmonberries, and is a word used for a variety of features around Oregon.
The shoreline of Olalla Reservoir and much of the surrounding landscape is owned by the Georgia Pacific Corporation and managed as commercial timberland. Vegetation is predominantly second-growth Douglas fir.Deeply weathered siltstone and sandstone slopes aremoderately steep around the reservoir, but elevations of the surrounding ridges are not great. Public access to the water is permitted by Georgia-Pacific and small boats without motors may be launched. Rainbow and cutthroat trout are stocked by the state and anglers are often quite successful. A company-owned campground immediately downstream from the dam is maintained for public use.
Olalla Reservoir reaches a maximum depth of about 65 feet directly behind the dam at full pool. The water develops a temperature stratification in the summer and oxygen is partially depleted in the deeper water. Mesotrophic conditions are indicated by the combination of the dissolved oxygen profile, water transparency, chlorophyl and total phosphorus concentrations.