 For example, large snowpacks in the mid-1980s caused the lake to expand from approximately within three years, flooding usually dry areas and damaging a branch of the Oregon Eastern Railway.Soon afterward, drought in the early 1990s reduced the lake size to just , exposing large mudflats and dusty playas.Malheur Lake is a remnant of a much larger Pleistocene lake that drained east to the Malheur River, a tributary of the Snake River.