Flows above 500 cfs are optimal but you can run the river lower. The USGS Gauge for the "San Juan Near Bluff" reflects the releases from the dam on the Navajo Reservoir, located in northwestern New Mexico near the Colorado border and the natural flow of the Animas River out of Colorado.
For up to date levels and info on releases from the Navaho Reservoir contact Pat Page of the US BLM:
Phone # (970) 385 6560
|SAN JUAN RIVER NEAR BLUFF, UT|
|usgs-09379500||500 - 8000 cfs||II||00h17m||599 cfs (running)|
|1y169d07h56m||/San Juan-1. Sand Island to Mexican Hat [UT]||Account of 01/07/18||0 cfs||Ambrose Tuscano|
|4y243d07h46m||@San Juan 1. Sand Island to Mexican Hat [UT]||San Juan River Trip||800 cfs||Thomas O'Keefe|