Measuring the effective conservation of species or landscapes is difficult in the best terrestrial situations, but aquatic systems present even more challenges.  With the unveiling of The Nature Conservancy’s 2015 goal of protecting 10% of all habitat types on earth, our goal was to evaluate the inclusion of viable aquatic ecosystem diversity within Montana’s portion of the Northern Great Plains Steppe Ecoregional Plan based on a suite of indicator-based measures (fish IBI’s, macroinvertebrate MMI’s, etc).  Using a combination of field-collected data and GIS layers, we analyzed the intersection of portfolio sites, 5^th code HUC watersheds, target occurrences, and indicator measures (viability, threats, and protection) to form an effective conservation map of selected MT watersheds.  TNC Portfolio sites encompass most of the known aquatic diversity found within the NGPS ecoregion; 33 of the 34 native fish species and all 15 delineated prairie aquatic system types are represented.  A large percentage of watersheds evaluated (50 of 68) exhibited good to excellent aquatic community biointegrity.  Unfortunately, very few watersheds (6 of 68) met the criteria of being effectively conserved.  Main reasons for this paucity of “effective aquatic conservation” were threats from introduced fish species, dams and small percentages of watershed acres under protection.