Zev is drinking slightly more from her water bowl, during this wet weather, but still a small fraction of the water I drink, even scaling for the difference in mass/volume. As others have said, cats evolved for a desert environment, and don't sweat like us, so likely need a lot less fluids in their diet anyway.
If you think he may be lactose tolerant, or are willing to experiment, you could try him with some milk, or get some cat milk, which is generally viewed with more interest than plain water. Having said that, since Whiskas last changed their recipe for cat milk, Zev has lost interest in it, so it may or may not work.