"The preacher man says it's the end of time And the Mississippi River she's a goin' dry..." Hank Williams Jr.
From the Wisconsin Valley Improvement Company:
"Natural-Lake Reservoirs
The system was initiated in 1907 and 1908 with the acquisition of 16 existing logging dams. These dams are all located at the outlets of natural lakes on streams that are tributary to the Wisconsin River, except for Lac Vieux Desert which is located at the outlet of a natural lake that is the origin of the Wisconsin River. The dams raised the levels of the associated natural lakes by several feet and were used in the late 1800s for transporting logs to downstream industrial facilities. This was done by storing water in the lakes and then opening the dam to cause a large artificial rise in river flow, generally at the same time natural flooding was already occurring, that would then float logs stored in the lakes to downstream markets. When WVIC acquired these dams the operation pattern was changed so that the storage and release of water from the lakes could be used to achieve more uniform downstream river flow. This operation is exactly opposite of that used for logging purposes. These reservoirs are known as natural-lake reservoirs."
Interesting bit of history. It seems that the dams like the ones on North and South Twin Lakes were originally used to create or enhance flooding to move logs downstream. From what I can gather, it is correct that Pioneer Lake does not have a water control structure (dam) to regulate water level. Rather it drains naturally, unfortunately rather slowly, through Pioneer Creek and on to the Wisconsin River.