Lees Ferry - 100 Years of Streamflow Monitoring

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On October 1, 2021, the U.S. Geological Survey Colorado River streamflow gaging site (USGS 09380000) at Lees Ferry will mark its 100-year anniversary of recording continuous streamflow data. As the gage of record for the apportionment of the Colorado River between the Upper and Lower Colorado River basins, the Lees Ferry site is arguably one of the most important streamflow sites in the U.S.


Date Taken:

Length: 00:02:26

Location Taken: AZ, US


On October 1, 2021, the U.S. Geological Survey streamflow gage at Lees Ferry will mark its 100-year anniversary of recording continuous streamflow. 

At the gateway to Grand Canyon, and just below one of the largest reservoirs in the United States, is the Colorado River’s most important streamflow gage. 

For a century, USGS employees have maintained the site for the benefit of water managers, researchers, outdoor enthusiasts, and others who depend on the highest-quality streamflow and water-quality data available. 

The Colorado River Compact of 1922 divided the drainage basin into two parts: the Upper Basin which includes Utah, Wyoming, Colorado, and New Mexico; and the Lower Basin which includes Nevada, California, and Arizona. 

The dividing point between the two basins is about one mile below the Lees Ferry gage, downstream from the confluence of the Paria River. 

15-miles upstream is Glen Canyon Dam, completed by the US Bureau of Reclamation in 1966. It provides water and power to millions of people in the southwest United States. 

Flow on the Colorado River varied substantially before the construction of the dam, sometimes producing enormous floods, or, in dry periods, providing less than adequate supplies of water to downstream communities.  

Along with discharge; water quality, sediment, and biological data are also collected at the site, paving the way for scientists to analyze the long-term trends in these data. 

The Lees Ferry gage provides scientists with some of the most important environmental data collected in the Colorado River Basin. 

It gives managers accurate discharge values so they know how much water is entering Grand Canyon from Glen Canyon dam. 

It even tells fishermen and rafters how much water is in the river when they launch their boats at the Lees Ferry ramp. 

Given the scarcity of water in the American southwest, it's essential that every drop is measured. 

Preserving this vital resource depends on the faithful service of the Lees Ferry gauge, and now it's one hundred years old.