Navionics has a nice web map that has some incomplete coverage of Lake Sakakawea. Garmin's BlueChart looks to have something for about $160, but appears to be only compatible with GPS units. Don't need the entire lake just a few areas of it. Would like the data to be ArcGIS compatible. I have attempted to do raster to vector in ArcGIS taking screen shots of Navionics web map but haven't had much success. Any ideas / help would be most appreciated.
This solution would take a lot of work, but you could use historical USGS maps to get quite detailed "bathymetry" for Lake Sakakawea. Garrison Dam was only built in the 1950s, so topographic maps from surveys before the 1950s will have the depth below water level (before any fluvial erosion or deposition). I checked on the USGS Topo website and found some 15 minute maps from 1922.
I would suggest contacting the Army Corps of Engineers office which manages the reservoir. They are sure to have the bathymetry in GIS-friendly format. I would hope, at the very least they have a print version that you can geo-reference and digitize the depth contours off of. (I searched through many of the ACOE management reports for a bathy map, or reference of, no luck...)
I would also suggest contacting "Friends of Lake Sakakawea". I work with Lake Association groups and most have this type of information (or at least will point you in the right direction of where to find it).
One more option would be to contact the North Dakota Department of Game and Fish. They manage the fishery and need to have knowledge of the bathymetry to effectively accomplish this task. Game and Fish has bathymetric maps for most other lakes...but not this one [http://gfapps.nd.gov/reports/fisheries/WebpageFishingWatersABC.pdf].
I hope this helps. I am in the process of compiling lakes over a multi-state region and am having mixed results. My biggest data successes are coming from State/Regional Agencies.
Is this any good, USGS site. A simple Google search took me here http://geo-nsdi.er.usgs.gov/catalog/place.php ?