I am questioning the Zotac part of the name, as they are using custom PCBs for some of their gpus as a result, a water block may not fit on your card. To cool a gpu, you will need a water block, which is designed to fit over the gpu's processor.
While 970 water blocks exist, they will require a custom cooling loop, as they are not sold attached to radiators, the average water block for a 970 seems to be around $80+ and a custom loop, even a small one would be about $100+, or in effect a $180 dollar minimum price to be able to water cool.
If you cannot afford to spend this fairly large sum of money, (I can't yet...) there is little to do besides ramp up the fan speed and hope it stays cool, which it should do for a reasonable overclock.
If you are wanting water cooling strongly enough, then I would recommend going full blown with a 360, 420, or 480 mm radiator, as you will be able to cool your cpu, and multiple gpus in the future if you decide to go SLI. such a price could be $200+ in cost excluding gpu water blocks.
Hope that was of use.