The current level for this river can be found through the Environment Canada Real-Time Hydrometric Data site, gauge 02EC002 Black River at Washago.
Low flow (ledges mostly or completely dry) is 7.76m (12cms).
High flow (features washed out) is 8.7m (59cms). When the Black River is at high flow or washed out the nearby Head River is usually at a good running level.
A visual check is to look for the three rocks just downstream of the Hwy 169 bridge. If no rocks are showing then it is likely washed out. If one or two, even three, are just showing above the water then most features will be in.