That is actually Alice’s water dish. For some reason she prefers to drink from that instead of any of the many cat dishes around the house. And even though she has her own cup she still prefers to drink from one of ours. When you have a CRF kitty you are just happy she’s drinking.
My theory is that it’s a sort of grass-is-greener situation: the cat thinks your water is better than their water so they drink (what they think is) your water.
My cat ignores the water in her food dish and drinks from a bowl in my bedroom. She also will drink from any water glass I’ve put down on a surface she can get to.
But yes, no matter what, it’s good to see your cat drinking water.