Just like energy and entropy, it becomes harder to harvest efficiently. There's still just as much water, it's just not easily accessible. The difference between the water in your glass and the water in the cubic foot of earth after you spill your glass on it. You can't drink from the latter.

The water cycle does the collection for us (lakes, rivers, aquifers) but we're draining them faster than they can recharge, particularly problematic are the melting glaciers (in the Himalayas) and the aquifers:

https://en.wikipedia.org/wiki/Aral_Sea

https://www.washingtonpost.com/news/energy-environment/wp/20...

http://lcluc.umd.edu/hotspot/glacial-retreat-himalayas

https://www.nasa.gov/feature/goddard/2017/11-percent-of-disa...

https://www.jpl.nasa.gov/news/news.php?feature=4626

Thank you.

Not exactly. Ocean water isn't usable without removing the salt and other solutes. When a lake or river dries up, it may lose its bedrock and therefore, even when it rains again, the river no longer holds water. So you end up with the water spread out over land, which is useless - because we don't have tree-like roots to just suck low density water out of the ground. We rely on large pools to be efficient.

See levels are rising

Yes, but it is only a small contribution. Most of Earth’s liquid water already is in oceans. https://en.wikipedia.org/wiki/Water_distribution_on_Earth#Di...:

  - Oceans              96,5%
  - Antarctic ice sheet  1,56%
  - Lakes                0,013%

https://en.wikipedia.org/wiki/Antarctic_ice_sheet:

“Approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to about 58 m of sea-level rise.”

⇒ completely emptying all lakes in the world into the sea would rise sea levels by half a meter or so.