How do you keep your dog out of your pond?

About 2 months ago I rescued a young dog that was in a tiny cage in the hot sun, no food or water and had 9 pups. She's small, probably due to what she's been through, and probably part Rottweiler and part golden retriever. I doubt that she is a year old. She is darling, but continually gets into my used-to-be-beautiful pond (11 X 16). What are some of your ideas to keep her out of the pond? I did buy her a children's pool, but the pond is her favorite. I have another rescue dog that is mostly Rhod. Ridgeback, who, incidentally hates water. Both dogs get along with each other. I'd love some help. Thanks.