Lake Columbia is a cooling pond for a power plant in South Central Wisconsin. Many paddlers utilize Lake Columbia for paddling practice throughout the winter, as it frequently offers water temperatures to around 80 degrees (depending on which side of the lake you're on). These conditions also attract relatively large numbers of people fishing for the record size range fish that enjoy the constant warmth (it's been popular enough to attract ESPN ).
Paddling more than a 100 yards away from the parking lot though will usually provide solitude. There's often a nice layer of fog which helps give a 'rugged' feel to the place. Paddle up the east side of the lake for warmer water and views of the coal pile and rail cars. Paddle up the west for cooler water and a better view of the boilers and plant structure. There's also nice boat ramp on the east side for a lunch/bathroom break.
The Hoofer Outing Club from Madison makes regular trips to Lake Columbia for canoeing and kayaking during the winter. You can view pictures at their site here or learn more about their trips to Lake Columbia here.
Facilities are minimal/non-existent, but you're not going to go for the scenery and relaxation! There used to be a porta potty, but it was removed this past winter (2006).
From Madison, take Highway 51 north, past Poynette (there is a gas station here). Turn left (east) on County Highway V. Turn right (north) into the marked parking lot. Access to the water is down a small hill from the parking lot.
Wisconsin Public Service runs the plant, but couldn't exactly be called upon for a guided trip or campsite information.
Here's a link to Google maps location of Lake Columbia