Source : Webster's Revised Unabridged Dictionary (1913)

Water vole \Wa"ter vole`\ (Zo["o]l.)
   See under {Vole}.

Source : WordNet®

water vole
     n 1: common large Eurasian vole [syn: {water rat}, {Arvicola
          amphibius}]
     2: of western North America [syn: {Richardson vole}, {Microtus
        richardsoni}]