A 1GW plant needs ~50ML/d. And the water is difficult to release to the environment so you are literally evaporating water. So thats ~18GL/yr. Now Mt Piper is one of the sites mentioned. Know this one well so its water is going to come from Thompsons Creek Reservoir, Lake Wallace and Lake Lyell. Full storage - ~20GL and 2 of the three are local recreational sites. So where do you supplement that from - Lake Oberon. That has around 26GL at full storage. So basically, if it doesn't rain, you've emptied everything in just over 2 years and trashed the water supply for 10,000 people.
Farmers Creek Dam is also up that way but its for Lithgow and only holds 0.3GL. And the state govt is putting thousands of homes there atm. They also can get water from Lake Oberon but that just makes things harder.
Now Mt Piper Coal was up there back in the day so the argument you could make is it used a shitload of water as well. The difference being the way the water was used, the evaporative losses would be much less and you could treat and release back to the environment for others to use. So you could ride out the stretches between rain better. Plus with coal, the asset tolerance was much higher so that higher use of water was nice to rather than need to, they could and did cut back during droughts without loss of production (but it did cause assets to fail quicker). I do not see how you can suddenly not need water at a nuclear plant. Rods need to be cooled one way or the other.
Thats why you build them near the coast and use sea water. But thats not working in NSW - everyone lives there. And piping and pumping across the GDR would cost a bomb.
Cannot talk to the others but its not working at Mt Piper if its a 1GW plant.
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