> How much water is wasted on golf courses...

Zero. You can't waste water, it goes in a cycle.

I mean unless you transport it off-planet.

You can waste the energy you spent cleaning it and pumping it around. But between nuclear and solar we ought to have an overabundance of that.

In a market economy, if it becomes "economically infeasible" to purify used water, the price goes up slightly, and suddenly it makes a lot more sense to treat dirty water, or even seawater.

You see the same type of argument against oil or mineral use; the idea that we'll run out. But people who argue we'll run out almost always look at confirmed reserves that are economical to extract right now. When prices rise, this sends a signal to prospectors and miners to go look for more, and it also makes far more reserves economical.

For example, Alberta's oil sands were never counted as oil reserves in bygone decades, because mining it made no sense at the time. But the economy grew per capita and overall, prices rose, and suddenly Canada is an oil-rich nation.

A similar dynamic applies to water and everything else.

Of course there are finite amounts of oil and uranium and so on, but the amounts just on this one planet are absolutely mind-boggling. The Earth has a radius of 6400km, and our deepest mines are 3-4km. We may expect richer mineral deposits (not oil) as we go further down.

Keep following this price logic and at a certain point it'll make sense to mine the far side of the moon, the asteroid belt, and so on ad infinitum.

> Zero. You can't waste water, it goes in a cycle.

You can waste water because not all water sources are equally renewable. Some underground aquifers recharge slower than we extract from them.

You are not technically wrong, but you are economically wrong.

The water cycle _could_ require spending grid energy to filter/pump water into an economically usable state. Instead if water was better managed, we would not need to build additional grid capacity for water management.

Your argument basically boils down to "If energy was unlimited, we could be wasteful!", which, again, is technically true, but ignores the economic reality.

Water used for nuclear reactor cooling can only be returned to the environment if its temperature is within 0.5 deg F of the local source temperature. I live near a facility that is on the river with several man made cooling lakes. During the winter, there is constant fog and ice by the roads. So much so, that the road to the facility itself has covered bridge crossing one of the lakes.

During drought, the capacity of the plant is reduced due to lack of cooling capacity.

And remember, the reactor is used to generate high pressure steam which produces electricity, hot water and low grade steam. Even with high efficiency gas turbines and heat integration, there is a significant amount of steam that needs to be condensed before it can be feed back into the reactor.

Fresh water in a reservoir above a water treatment plant is not the same as salt water in the ocean even if it's the same molecule in the same cycle.

True. However, substitution of one good for another, or bringing online another source, won’t be instantaneous and thus otherwise needless human suffering will occur. The raw numbers don’t capture that.