Estimates are that only 13 teeny lakes totaling nine acres existed around Boulder before white settlement. The lakes were old oxbows of remnant channels, or the rare low spot between hills, such as Jewel Mountain Lake.
Today, 1127 acres of lakes dot Boulder's landscape. 99% of them are man-made. (One is pictured on the lower right.) Most of them are filled with ditch water.
Jewell Mountain Lake (shown, upper right) is one of the few natural lakes which predate white settlement. This lake on Rocky Flats Open Space, holds water part of the year because of run-off from surrounding hills.