Agreements between the federal government and a state are not subject to congressional consent under the Compact Clause, U.S. Const. Art. I, § 10, cl. 3; nor are all agreements between or among states so subject, but only those which encroach upon or interfere with the authority of the federal government.
States may engage cooperatively in a broad range of planning activities under the Water Resources Planning Act without obtaining congressional consent, so long as they impose no legal obligation or disability on governmental or private parties.
Congress has given advance consent to planning activities of the statutory river basin commissions, but not to those of interagency committees or multiple state entities.