Oregon State University’s Aaron Wolf, in his studies of conflict and cooperation around international waterways, has found something both counter-intuitive and remarkable. Despite myths of “water wars,” cooperation is far more common than conflict when neighbors share a river and an aquifer, according to Wolf, author of the new Island Press book The Spirit of Dialogue.

This goes beyond simply cooperating over water. “Once cooperative water regimes are established…,” Wolf wrote in a 1999 essay, “they turn out to be tremendously resilient over time, even between otherwise hostile … states, and even as conflict is waged over other issues.”

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Lake Mead as seen from the Hoover Dam with the white band clearly showing the high water level, via Wikimedia Commons

Wolf’s point was put strikingly on display last month at a meeting in Santa Fe, New Mexico, as representatives of the Unites States and Mexico gathered for a formal signing ceremony of an agreement over sharing the waters of the Colorado River.

The Colorado River is often described as being shared among seven states, but the number is really nine—seven in the United States and two in Mexico. U.S. farms and cities use most of the river’s water, and what little is left when it arrives at the U.S.-Mexico border near the towns of Algodones and San Luis is diverted for use by Mexican farms and cities. The last hundred miles of river channel between the border and the Sea of Cortez is usually dry.

The agreement includes provisions for the two nations to share shortages if (when?) drought and climate change shrink the river. The deal gives Mexican water users the ability to store their water in Lake Mead, the massive storage reservoir behind Hoover Dam on the Arizona-Nevada border, near the city of Las Vegas. Storage is critical to give Mexico flexibility in managing its water. U.S. water agencies will contribute under the deal to water efficiency improvements to Mexican infrastructure, with some of the saved water available for use in the United States.

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Satellite view of the Colorado River valley near Yuma, Arizona; the Mexico–United States border runs from left to right just below center, via Wikimedia Commons

Crucially, the agreement also sets aside water for habitat restoration in the dry river channel of Mexico.

The agreement was negotiated over a more than two-year period, but it is really rooted in more than a decade of increasingly deep collaboration between a community of water managers on both sides of the border. When the Trump administration took over in January, there was fear that the carefully crafted deal, so beneficial and important to communities on both sides of the border, would be sidelined by the heated rhetoric over free trade and immigration, over NAFTA and walls. But Wolf was right. Even as conflict raged over other issues, the trust and reciprocity built around the Colorado River proved remarkably resilient. The old saw that “water is for fighting over” was proven wrong again.