oops my aboves and belows got messed up
Niether the rock nor the guage below filter plant are reliable indicators of passability and minimumbility and functionility. Water is diverted above filter plant run and below the rock "guage". Water is also diverted above the stream guage (mouth of poudre) BUT below Filter Plant run.
But there are some things to depend on. If the guage at mouth of poudre canyon reads above 400, it doesn't matter if water is being diverted Above mouth of poudre guage; there is a minimum of 400 in FP. But sometimes the flow in Filter Plant is 200cfs or greater (i think) than stream guage; so flow of 250cfs, if water is being diverted, could make the run passable.
By the way, in our desperation days, we boated FP in open canoes at about 380cfs or something like that. I would have to be pretty itchy to paddle this run now at 400cfs and then it's still pretty scrapy.
Rather than a minimum, my experience again in open boat, would say 500 cfs is really quite a nice flow--acutally a really nice level to tune your skills and enjoy the run.