Yes, Balmorhea Lake and San Solomon Springs are two different water bodies in the Balmorhea area, with the latter at Toyahvale as indicated on my map in post #2. I think I'll add that map to my album on the site.
Did you look at my pics? It's a 77,053 sq. ft. swimming pool wtih a natural bottom. Well, not exactly natural, but native rock bottom, springs, 2 species of endangered pupfish, irritating Mexican tetras* that have been trained to associate divers with food, a few catfish and turtles. (*Tetras are tiny members of the piranha family, with the same jaw structure, and I had one nip both of my ears during my open water class there 6 yrs ago.) It's been popular with locals since Clovis man first settled the area and was indeed improved by the WPA with mule teams dredging during The Great Depression, adding concrete walks and walls, large bathrooms with warm showers, meeting rooms, etc. There is an on-site motel ran by the state, non-smoking, but no food or beverages likely sold outside of Balmorhea this time of year other than soft drinks from the vending machines.
You can expect the water to be around 70+ F, clear aside from duck droppings, nice windbreaks. There is a small fill station outside the grounds, altho I would call to confirm that they are going to be open: ph 432-375-2572. The parks number is 432-375-2370. NOAA predicts the weather this weekend to be mostly clear, highs in the 60s, lows in the 30s. Should be very pleasant diving, altho a little boring.
Park site.
http://www.tpwd.state.tx.us/spdest/findadest/parks/balmorhea/