[Alberta's Child]

You won’t get an argument from me on that, but major waterways would seem to be an obvious area of federal jurisdiction.

Do you think the state of Pennsylvania should have the authority to construct dams and basically dry up the Ohio River just because its two largest tributaries — the Allegheny and Monongahela Rivers — flow through that state?

[Jim W N]

Controversies between two or more States are to be decided by the Supreme Court (US Const., Art. III, Sec. 2).

[T.B. Yoits]

Do you think the state of Pennsylvania should have the authority to construct dams and basically dry up the Ohio River just because its two largest tributaries — the Allegheny and Monongahela Rivers — flow through that state?

Dry it up, maybe not, but send fecal waste down it? Sure.

Chicago reversed the flow of the Chicago River into the Missouri and Mississippi Rivers, sending their sewage into those communities down river. Missouri sued Illinois, but the US Supreme Court ruled in favor of Illinois, stating that there was "no evidence that the water quality in the Mississippi River had been affected."

https://theculturetrip.com/north-america/usa/chicago/articles/how-the-chicago-river-was-reversed