Congress did try to alter the Cahaba into a river friendlier to navigation between 1880 and 1893 and even allocated $45,000 towards that end. Their efforts failed and a final feasibility study on the Cahaba in 1909 would forever pronounce the river as unfit for further improvement, a fortunate blessing for the future integrity of the river.
LAKE PURDY is a small, 990-acre reservoir at the headwaters of the Cahaba River (dams the Little Cahaba River tributary). Built in 1929 the dam creates a 15,300 acre-feet reservoir that is used as a drinking water supply for Birmingham during the dry months. It has a drainage area of only 43 square miles. The primary purpose of the lake is to provide water supply for the City of Birmingham. The dam and reservoir are owned by the Birmingham Water Works Board.
An often overlooked dam is actually located on the mainstem of the Cahaba on the west side of the Highway 280 bridge. (State of Rivers) This low-head dam measures 15 feet high and backs up the waters of the Cahaba just enough to allow the city of Birmingham to withdraw a steady supply of water from this section. The dam was built in 1891.
MILLERS FERRY LOCK AND DAM which forms DANNELLY RESERVOIR, while not located on the Cahaba but on her bigger sister, the Alabama River does have some minimal impoundment affects on the lower Cahaba to just downstream of the Highway 22 bridge in Dallas County. (Project) The natural union of these rivers is now plunged underwater.