I would think that ripping 1000L of water out of an environment in a day is going to have more immediate impacts than you eventually pissing on a cactus is going to fix…

Well... It all depends on what you do with the water. Are you sequestering it in some way or are you releasing it? I mean, if the community drank 1000 liters of water, then their next piss is 100% going to fix it. Even watering crops is just releasing the water.

just as damaging as removing 1000L of water a day from a lake and thinking the ecosystem will be fine because you’re going to sweat next to the dry lakebed.

Again, if you're going to sweat 1000 liters, then go for it, I fully endorse this plan. Use as much water as you want, it's fine unless you're shipping it out.