I'm having this issue as well. I was unable to recruit someone as they thought I had no water. Tried rebuilding the water tank and filling it to different amounts above the requested 20 but nothing seemed to add any water to my amount at the top.
Apologies for the late reply - does the issue still occur when you reload your savefile? Also I have just pushed out a new update v0.65.0 - you can try that and see if the issue persists.
