[4] Deposits of kame from the Cordilleran ice sheet blocked outflow from the Missoula floods, eventually forming Newman Lake as well as other nearby water bodies.

[11][12] After receiving a grant from the Washington State Department of Ecology, a hypolimnetic aeration system was installed in 1992 to improve oxygen dissolution in the water;[12][13] this was the first time a submerged pump had been implemented for this purpose on such a large scale.

[14] In 1997, a microfloc alum injection system was installed in the lake, which disperses aluminum hydroxide for the purposes of binding to phosphorus particles in the water.

[13] In 2009, a Total maximum daily load (TMDL) report by the Washington State Department of Ecology described the target total annual gross phosphorus loading as 903 kilograms (1,991 lb) per year, and proposed 11 strategies for reducing phosphorus entering the lake.

These strategies primarily focus on updating the standards and practices of state and local government, as well as property owners and residents throughout the watershed, and emphasize measures to halt erosion, stem runoff from roads and prevent phosphorus leaching from sources along the shoreline.