Bob,
Lake Anna was created to act as a cooling lagoon for a nuclear reactor power plant about 30 years ago. It has 3 cooling lagoons connected by navigable canals that are considered the 'hot' side. After the hot water leaves the power plant it goes through the 3 lagoons and then connects via a non-navigable area into the main part of the lake. At this point the water circulates back up the lake on the 'cold' side until it reaches the intake of the powerplant. Then it begins the cycle all over again.
The cold side is about 2/3-3/4 of the entire lake area. the hot side makes up the other 1/3-1/4.
The hot side is also called the private side because the only way to launch a boat there is to own land on it with a launch ramp or be part of a homeowner's association with a community ramp. No marinas or public facilities are on the hot side. When you need to gas up, you either have to pull the boat and drive to a gas station or carry cans down to the boat.
The cold side has a state park, lots of marinas, and public launch facilities. It also has bigger crowds because anyone can launch a boat there.
To give you an idea of the water temp spread, several weeks ago, the water temp at my dock (on the coolest part of the hot side) was about 70. When we traveled up to the power plant, the temp went up to 84. I've been there when it is greater than 95 during the summer- way too uncomfortable. It is a shock to the system to jump in when it is that hot.
Bill lives in an area that allows for access to either side of the lake.
david......