Not sure if serious... but just in case, very simply put...

DC pulls water out of local water supply. DC uses evaporative cooling (not all use closed systems, and even those that do see some loss over time) Water lost to cooling is now in the atmosphere.

If the DC (and other local users) withdraw water faster than local conditions allow it to be replenished, you end up without any local water.

of course not, but as far as i understand there are a few factors that are relevant for local water supplies:

- evaporation from cooling. the water will come down as rain again, but not necessarily in the same region

- when disposing the water into the sewers, the water might get "lost" into the oceans, where it's not available as drinking water

- when disposing water used for cooling into the rivers it was taken from, there might be environmental issues with water temperature. i know that this is an issue with rivers in europe where the industry is allowed to measure and report their adherence to the laws regarding the maximum allowed water temperatures themselves and, to no ones surprise, the rivers are too warm.

so water is not destroyed, but it can be made unusable or unavailable for the locally intended purpose.