How can I tell what is private land and what is public?

We would like to go to Sinker Creek Lake but some sites say that it is on private land. How will we know what is private and what is public?
Please check out the interactive map center on the IDFG website for a detailed map.  After you open the map center, zoom to the area you are interested in.  On the upper left hand side, select turn layers on/off. Scroll down throught the selections and turn on land management status.  This will display property ownership in different colors. This reservoir's shoreline is about 99% private and 1% public (BLM).  Technically, you could legally access the 1% that is public if you had a good GPS unit and a map and if the reservoir was near full pool. However, I would not recommend that anyone try this as the margin for error is small and the fishing is not likely worth it due to recent drought conditions.    
Answered on: 
Tuesday, February 23, 2016 - 4:15 PM MST