If you lose water completely, don't forget you're losing toilets too. In the last Crisis Management plan I wrote, for water loss due to a broken main or failure of our municipal water system, I had contact info from 2 different portapotty companies. We created accounts with them to speed the process if we ever needed to use their services, and I had quotes on file for portable handwash stations, potable water totes, and portapotties to be delivered to our site. Program called for the potable water to be sampled and sent to the local lab as a verification it would be suitable for our equipment washing needs (we too did not use water in our process).
In cases if we received a boil water order, same companies would be scheduled to deliver the water totes only. Again, we can use them for sanitation under the assumption it is delivered as potable for our sanitation use, but we would sample each tote and verify through the lab.
A good crisis program should include shutdown of the operations in the time it takes for these items to be delivered, if it applies to you. Employees washing hands with potentially contaminated water while waiting for a truck of potable to show up is a pretty unacceptable risk, IMO.