The Yahara watershed has 5 locks or dams that control the levels of the 4 lakes in the area as well as the Yahara River. The Tenney Park Locks were originally a dam built for a mill in 1847, were purchased by the City of Madison in 1896 and turned into locks in 1904. Lake Waubesa has the Babcock Lock and Dam which controls lake levels in Lake Waubesa and Lake Monona which was completed in 1938 and Lake Kegonsa has the Lafollette Dam which was also completed in 1938. South of Lake Kegonsa, Stoughton has the Stoughton Dam and the Dunkirk Dam is just south of that. Both are in the Yahara River and both were completed in 1843.

The Tenney Locks are needed instead of a dam because the water level of Lake Mendota can cause large changes to the other lakes and needs to be carefully maintained. Every year there is a spring runoff and some years the lake has flooding caused by rainfall. The minimum lake level after March 1st for Lake Mendota is set at 849.6 feet I believe. This is artificially high and allows for recreational boating near the shoreline of Lake Mendota. The Tenney Locks help keep Lake Monona and Waubesa from flooding during and after heavy rains. During a flood, the Tenney Locks are kept closed and the Stoughton and the Lafollette Dams are opened to allow excess water to flow in to the Yahara river from Lake Monona and Lake Waubesa.

If you have ever gone boating through the locks, it's fun! If you are heading to Lake Mendota from Lake Monona, you will arrive at the Tenney Park Locks and the gate will usually be closed. The gate has a traffic light so you know before you get there if it is open or not. Once you get there, you have to wait a short while for the gate to open. Once the gate opens, you go into a middle chamber and the gate closes behind you and any other boats that are in there with you. Slowly the water rises in the middle chamber and then the gate in front of you opens and voilà, Lake Mendota is before you and ready for you to enjoy albeit with "no wake" buoys for a little while before you are in open waters. It is a fun lake to enjoy during the sunset on a boat.