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001968 Getting to turn-of-the-century communities such as Yuma, Blythe, Needles and Saint Thomas (now beneath Lake Mead) through the Gulf of California was often a more difficult task than navigating through the Delta and up the river. The gulf is a 1,000-mile long ocean channel that narrows from south to north. Because of its length, tides move in and out of the Gulf, and the surges of water get stronger as the gulf narrows from south to north. During extreme tidal events and high river flows, one of the great anomalies of navigation occurred. When extreme incoming tides met extreme outgoing flows from the Colorado River, the collision created what is known as a "tidal bore." The surge of the incoming tide would be met by the flow of the river that was undercutting the tide and creating a standing wave. Tidal bores can best be described as a horizontal tornado of water, rolling apparently upstream but not moving. There are reports of tidal bores having heights of more than 20 feet. Many vessels were lost over the years to the tidal bores in the Gulf of California. 4 However, the dangers in the Gulf and in the Delta didn't stop the navigation. Other uses of the river caused navigation to cease. Those same uses caused the habitat and open water areas of the Delta to shrink to a shadow of their former scope. Today, the remnants of the Delta ecosystem are confined to a wetland area sustained by agricultural drainage from the United States and a narrow 1 DO-mile long corridor along the Colorado River in Mexico. The habitat in the River corridor has been partially restored with the excess runoff of recent years. However, even that 'habitat is now at risk as water uses in the United States continue to grow. Realistically, the Delta cannot be restored to the conditions of the 1930s, before the waters of the Colorado River were harnessed. It is realistic, however, to expect that a sustainable supply of water allocated to the Delta could maintain the quality of habitat restored during the 1980s and 1990s, when the Delta benefited from larger than normal Colorado River flows. Figure 1 is a LANDSAT image of the irrigated and Delta areas in Mexico. MANAGEMENT OF THE COLORADO RIVER IN'THE UNITED STATES AND ITS RELATIONSHIP TO MEXICO' A. The Law of the River Distribution of Colorado River water within the United States is accomplished through a complex system of physical fadlities. This system is operated to comply with legal obligations under statutes, interstate compacts, court decrees, regulations and contracts, known collectively as "the law of the river." In 1922, the Colorado River Compact divided water between the Upper basin states (Colorado, Utah, Wyoming and New Mexico) and lower basin states (California, Arizona and Nevada). The upper basin states agreed to deliver, on the 4 For a more complete description of navigation on the Colorado River, visit the museum at The Yuma Crossing State Historical Park on the banks of the Colorado River at Yuma, Arizona.