[6] Formed by McPhee Dam, the reservoir is about 10 miles (16 km) long and diverts flows of the upper Dolores River for irrigation.

[7] This section of the Dolores River is noted for its exposed sedimentary strata, desert wildlife, and during years of heavy snowmelt for its whitewater.

)[6] Due to diversions on the main stem, the San Miguel is typically the same size as the Dolores if not larger, providing most of the flow below the confluence in dry years.

[10][11] Below the confluence with the San Miguel, the Dolores enters Mesa County, flowing north-northwest past Gateway and then turning west into Utah.

The last segment of the river, entirely within Grand County, joins the Colorado near the historic Dewey Bridge, about 30 miles (48 km) above Moab.

[19] The Dolores is dammed at McPhee Reservoir near Cortez, Colorado to irrigate about 61,660 acres (24,950 ha) of arid plateau land.

[20] In some years, almost all the water entering the reservoir is diverted, leaving only a small legally mandated minimum flow to pass downstream, as a result reducing the 150 mile (242 km) stretch between the dam and the confluence of the San Miguel River to a large creek.

[21] The dam's construction allowed local farmers to extend the irrigation season through September, whereas natural river flows would have been insufficient by July or August.

This fact aggrieves recreational boaters, who claim it is difficult for anyone but a local resident closely watching the gauges to plan trips in advance on the river.

Advocates have proposed establishment of a national monument encompassing 400,000 acres of the Dolores River Canyon and the surrounding region in Mesa and Montrose Counties.