There are careful explanations of where the rapids are, what they are like, and even in some cases how to run them. Paddlers know that no matter how good a guidebook is, however, it cannot tell you everything. Nor can a guidebook be 100 percent accurate. Rivers change course. Highway departments take out bridges.
Humans make mistakes.
When this happens, you have to be experienced enough to realize that the book or map is wrong and smart enough to figure out what the real situation on the water is. Breining's fine book is no exception. I checked routes I am familiar with, and found the following example. The Blue Earth River trip ends at the confluence with the Minnesota. Well, not exactly.