Illinois. Water Survey
Illinois. State Water Survey
Illinois. Dept. of Registration and Education. Division of State Water Survey
Illinois. Dept. of Registration and Education. State Water Survey Division
ISWS
Illinois Institute of Natural Resources. State Water Survey Division
Illinois. Division of State Water Survey
Illinois. State Water Survey Division
Illinois. Illinois State Water Survey
I.S.W.S
S.W.S
SWS
Illinois. Dept. of Energy and Natural Resources. State Water Survey