Water Rights: Does the Owner of a Lakebed Own the River That Feeds It

My question involves real estate located in the State of: NY

I live on the former Lucky Lake in Sullivan County. It drained when the dam broke leaving only the Ten Mile River that fed the lake.

One neighbor across the former lake bought the lake bed and is denying us access to the Ten Mile River even though all our deeds have easements granting access to the former lake.

Does ownership of a lake bed also give ownership of the riverbed that fed the lake? And do existing easements to a lake become invalid when a lake partially drains?

Water Rights: Does the Owner of a Lakebed Own the River That Feeds It