WordNet records no synonym and no antonym for lake powell. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the second largest reservoir in the United States; located in southern Utah and north central Arizona and formed by the Glen Canyon Dam on the Colorado River
Synonyms, antonyms and the broader and narrower relations for lake powell come from Princeton University’s WordNet. Full sources and licences.