Water can be made fit to drink again.  I'm reminded of the joke that says:  What do they make today's coffee with on the space station?  Yesterday's coffee.

Can water for agricultural use be reclaimed? Other than it eventually making its way back into the water table?

Water could also be recycled/treated such that it's good for agricultural use but not for consumption, which I imagine would be cheaper than fully reclaiming the water, which could then be used for agriculture rather than fresh water. The extra... lets call them nutrients... that are unsuitable for human consumption may help fertilize the plants as well.