My son is two and does the same thing. It is an age that they are trying to establish independence and learn their boundries. That means they are going to test those boundries. most little ones like playing with water and things like that. They learn from it, and it is very interesting to them. If it bothers you I would just pick her up and move her to something else, that she can play with. Explain to her in simple words that she can't play in the doggies dish, that it's messy, and it's for the doggie.
You could also set up something with messy things, water sand, etc. for her to play with in a more controlled manner. this way she gets the learning experience, the interesting sensations, without making a mess wher you don't want it. When she gets a little older it will be easier to get her to start listening more, but right now she's doing a lot of growing and learning. She really doesn't know any better and it will take time for her to learn what is ok and what is not. Telling her no a lot will probably just get her used to hearing it a lot. It's probably better to explain to her why you don't want her doing things, and telling her what you would like her to do. Positive reinforcement, not false praise but praise when they do something that is very good or you are proud of works well. If you see something like that tell her how proud you are, and tell her why you are proud of her, especially when she does something she has had trouble with.
Hope this helps.
Good luck with everything.
V.