Craig Thomas Snake Headwaters Legacy Act of 2008 - Amends the Wild and Scenic Rivers Act to designate specified segments of the Snake River System in Wyoming as components of the national wild and scenic rivers system.
Requires each river segment to be managed by the Secretary of Agriculture or the Secretary of the Interior (the Secretary concerned) as specified.
Requires the Secretary concerned to develop a management plan for each river segment that is in an area under the jurisdiction of the Secretary.
Requires that each management plan shall contain, with respect to the river segment that is the subject of the plan, a section containing an analysis and description of the availability and compatibility of future development with the wild and scenic character of such river segment (with particular emphasis on each river segment that contains one or more parcels of private land).
Sets forth requirements for the quantification of the water rights reserved by each river segment designated by this Act.
Authorizes the Secretary concerned to carry out activities at United States Geological Survey stream gauges that are located on the Snake River and its tributaries, including flow measurements and operation, maintenance, and replacement.
Bars the acquisition of any property or interest in property within the boundaries of any designated river segment by the Secretary concerned without the owner's consent.
Specifies this Act's effect on valid existing rights, including certain water rights.
Authorizes appropriations.