The comparable unit (in terms of estimating irrigation needs vs rainfall vs reservoir draw, which are the terms we reason with in this part of the US) would be the hectare-meter, which is 10,000 cubic meters.
For context, https://www.rubyhome.com/blog/swimming-pool-stats/ estimates that there are ~500k residential pools in Arizona. Note that those will likely be smaller than a half olympic-size swimming pool.