Cache Creek Info Page
The following estimation is just that, an estimation. These are not recommended flows.
Flow Information
The flow on the wilderness runs consists two different flows,
A) the flow on the North Fork, which needs to be at least 250cfs, but no more than 2,000cfs
B) the flow on the Main Stem, which needs to be at least 2,000cfs, but no more than 6,000cfs
North Fork Cache Creek Flow
The flow on the North Fork is influenced by the upstream reservoir, Indian Valley. The current release is on a USGS guage. If the reservoir is still rising, the present release is highly likely to continue, and in rare cases may even rise. The current state of the reservoir is available daily from the DWR Info Site. The "storage" column shows if it is rising or falling, and is updated for weekdays, but sometimes doesn't show up for a day or so. The current flow above the reservoir is on a USGS guage or the DWR alt. These are real-time so they show the effect of a storm. If the flow there rises to 5,000cfs, the release from the dam is likely to rise, though usually to no more than just a fraction of the inflow. Because put-in is 15 miles downstream of the dam, after storms there can be enough side inflow to make it runnable even if the dam release is the minimum of 10cfs. My best guess for this is four to five times the flow on nearby Bear Creek (DWR alt.)
Main Stem Flow
The flow on the Main stem is influenced by both the North Fork and Clear [sic.] Lake. The current flow downstream in Rumsey is on a DWR guage. This puts an upper bound on how much flow there is on the wilderness run. It can be trusted when above 3,000cfs; there will be enough flow. Below that, it could contain a lot of side inflows. To tell if this is the case, look for large fluctations with storm events. If it is a steady +/-10% per day, it is mostly from Clear Lake. If the flow is +/-50 or 100% with storms, it is being strongly influenced by the side inflows.
There is a direct reading of Clear [sic.] Lake's elevation on a DWR site, but no conversion from feet to cfs of lake outflow. Based on my experience, a reading of at least 5.6 feet makes the wilderness run runnable; the flood warning stage of 7.6 feet is still runnable, and even the flood stage of 9.0 feet is not insane, corrosponding to about 7,000cfs at Rumsey. The flooding that happens at these levels is in the Clear [sic.] Lake basin, not in the channel downstream. However, when the Lake is that high, and a storm comes in, the flow at Rumsey can quicly climb to 12,000cfs.