There is a number, but I can't recall it off the top of my head. It's somewhere higher than 30%, but I don't think it's 100%. It's somewhere closer to 45% or 50% getting their drinking water supplied directly from groundwater.
Evidence of meeting #95 for Environment and Sustainable Development in the 44th Parliament, 1st session. (The original version is on Parliament’s site, as are the minutes.) The winning word was pfas.
A recording is available from Parliament.