Supreme Court Hears Nebraska’s Suit Against Colorado Over South Platte Water

The U.S. Supreme Court has agreed to hear Nebraska’s lawsuit against Colorado, and the stakes are high for water users along the South Platte.

Nebraska claims Colorado is deliberately obstructing the construction of the Perkins Canal. The proposed ditch would take water from the river near Ovid and send it to a reservoir in Nebraska.

The short version: Nebraska says it has the right to build this canal. Colorado says it is stopping the project to protect local property and water rights.

This isn’t just a legal squabble. It is a fight over the 1923 South Platte River Compact. That agreement, ratified by Congress, requires Colorado to guarantee a flow of 120 cubic feet per second at the state line during irrigation season.

Nebraska argues Colorado isn’t delivering. The state blames urban development along the Interstate 25 corridor and new plans to expand water storage. They claim these activities are causing Colorado to violate the compact.

The Perkins Canal project has a long history. Initial work was done more than a century ago. It was abandoned as unfeasible. Nebraska resurrected the idea in late 2021.

Now, the threat is real. Water users in the lower reaches of the river are worried. If Nebraska builds the canal, it could disrupt the water augmentation process. This system underpins crop irrigation between Fort Morgan and the state line.

Colorado Attorney General Phil Weiser and Gov. Jared Polis have acknowledged Nebraska’s right to build. But they are sworn to protect Coloradans. They argue that Nebraska’s efforts to buy land in the Julesburg area are being blocked by local landowners.

Nebraska sees this resistance as subversion. The state sued Colorado in the Supreme Court in July 2025. The lawsuit alleges that Colorado is obstructing the Perkins project. Nebraska also attacked Colorado’s water augmentation system, claiming it doesn’t work.

The core of the dispute lies in how the two states manage the same water. Colorado operates on the prior appropriation doctrine. This "first in time, first in right" system relies on augmentation to ensure that when water is diverted for use, it is returned to the stream.

Nebraska’s lawsuit challenges the integrity of that return flow. If the canal diverts water before it can be augmented and returned, the flow at the state line could drop below the 120 cubic feet per second threshold.

The Supreme Court’s decision will determine who controls the flow. It will decide whether Nebraska can force its way through Colorado land or if Colorado can maintain the status quo.

Locals along the South Platte are watching closely. Their crops depend on the stability of the augmentation system. A shift in how water is accounted for could change everything.

The Court will hear arguments on whether Colorado’s obstruction is legitimate protection or a violation of interstate compact. The answer will define water rights for the next century.