Water rights

Possibly. The Corps, under federal law, controls navigable waterways of the United States. However, if this lake is not part of the actual waterway the state may also control.

In positioning a dam on a river, if that dam takes your property (or its value) on a very significant basis, you may have recourse to compensation under the takings clause.

In any case, without more specifics I would recommend discussing the matter in full with an attorney who can properly analyze the case and let you know of your options.

In addition to the answer provided previously, you may also want to consider whether the Army Corps of Engineers (ACOE) has properly completed an Environmental Impact Statement/Environmental Assessment under the National Environmental Policy Act (NEPA), which would likely be required in this case. If not, it is likely that the ACOE would need to do so. If the ACOE has completed its NEPA requirements, they may be deficient, in which case that NEPA deficiency could form the basis for a legal challenge. Such documents would be published in the Federal Register.