The Information Center for the Environment at the University of California, Davis, will be evaluating the methods used to cross-reference the EPA's River Reach File (RF3) to the National Hydrography Dataset (NHD). California's RF3 contains a critical but nonstandard foreign key that is essential to many research applications. In particular, we will be testing how accurately and seamlessly legacy data (formerly tied to RF3 attributes) can be linked to the new NHD. We will present the results of this evaluation including recommendations to enhance the cross-referencing process and a detailed discussion of methods developed to test and verify the data.