A little advice to add to this, if you’re gonna be adding more water while cooking to mitigate the excess evaporating water, add hot water, so as to not cool the soup prematurely while its cooking.
Also, make sure to run the vent fan over your stove, otherwise your kitchen will be extra humid.
My roommate suggested using aluminum foil in place of the missing lid. Sounds good enough to me, good luck 👍