Is the Federal government (Bureau of Reclamation etc.) legally required to provide any compensation if it diverts a river [in Western US]?

Question

Does the Federal government have to provide any legal compensation for proprietors downstream of a river whose waters are largely diverted? Any notable examples when such compensation was provided? E.g. 90% of the waters of the Trinity river [in California] were diverted to the Sacramento river (which flows in a different direction).

AFAICT, a delayed form of water justice can have strange results, e.g. Wikipedia says:

In 2015 Humboldt County won a lawsuit against the Westlands Water District for an extra 50,000 acre-feet (62,000,000 m3) of water from the Trinity River for in-stream flows. Previously, the Bureau of Reclamation had included this sum in the water released for fishery management. Although this means more water for the Trinity River, no provision was made for commensurately reducing Central Valley Project water diversions, increasing the risk that Trinity Lake could be drained to "dead pool" in drought years.

So, under Western US water doctrine, everyone has the "right" to more water than actually exists in some rivers after such diversions? Some proprietors being entitled because of physics and some because of law?

Or is that 2015 suit unrelated to the diversion, and the Federal government either doesn't have to pay compensation at all for something like that, or has paid something separate to proprietors downstream of the original Trinity, but that's not mentioned in Wikipedia?

Answer 1

It has happened. "[T]he claimants were entitled to recover damages [from the United States] under the Reclamation Act if they could establish their rights under the state law."

Water and Water Courses: Diversion--Right of a Riparian Owner to Damages under Article XIV

WATERS AND WATER COURSES: "DIVERSION-RIGHT OF A RIPARIAN OWNER TO DAMAGES UNDER ARTICLE XIV, SECTION 3 OF THE CALIFORNIA CONSTITUTION.—
One of the purposes of the Central Valley project is to redistribute the water resources in California. Briefly the plan is to arrest the water in the highland basins by Shasta Dam in the north, and Friant Dam in the south. By a system of smaller dams, canals, and pumping stations, the water is to be distributed so as to make more land available for cultivation. Under the plan former riparian owners are to receive sufficient water, either from the depleted river supply or the redistribution system, to satisfy their irrigation needs.

After the construction of Friant Dam, the claimants, in a recent case before the United States Supreme Court (United States v. Gerlach Live Stock Co., 70 S. Ct. 955), brought a claim against the United States to recover damages resulting from the diversion. These claimants owned land riparian to the San Joaquin river. The seasonal overflow of the river annually submerged their lands, and they contended that by impounding the water the government deprived them of the right to the annual inundation of their land. The Supreme Court held (Douglas dissenting) that the project was one of reclamation, rather than of navigation, and, thus, the claimants were entitled to recover damages under the Reclamation Act if they could establish their rights under the state law. The court concluded that the state law permitted the recovery of damages, and it affirmed an award of the Court of Claims.

[Emboldening added.]

The Reclamation Act of 1902 has not been substantially changed since enacted. In United States v. Gerlach Live Stock Co., 339 U.S. 725 (1950), several sources were used by the court to decide the case (and five others related to diversion). The important provision in the law may be found at 43 U.S. Code § 383 - Vested rights and State laws unaffected.

Nothing in this Act shall be construed as affecting or intended to affect or to in any way interfere with the laws of any State or Territory relating to the control, appropriation, use, or distribution of water used in irrigation, or any vested right acquired thereunder, and the Secretary of the Interior, in carrying out the provisions of this Act, shall proceed in conformity with such laws, and nothing herein shall in any way affect any right of any State or of the Federal Government or of any landowner, appropriator, or user of water in, to, or from any interstate stream or the waters thereof.