Custom Lat Long Contour Map

[#1]

Hi all, 

Playing around with the Custom Map Creator add in and I ran into some trouble when trying to construct borders for a river system. When constructing a custom map border using a a background map the boundaries function does not let me to trace the river pattern as accurately as I would hope (see attached photo). Alternatively, when constructing a border from a background photo the boundaries are easily traceable and easy enough to create accurate constraints for the rivers (see attached photo). My problem is that I have concentration data for specific samples based on log data. The end goal is to use the samples to create a contour map of concentration constraint by the river systems. This was my goal in this discussion post:  

Question #1: Can I make the constraint the river more accurate in the background map? 

Question#2: If constraining rivers for a background map doesn't work how can I use the background photo and sync this to my data set which has log/lat data for concentration in the river system. 

Alternatively, I am available for a call or a meeting where I can share my screen and thoroughly explain what is required from this graphic. 

Thanks!