LSJ
(sc. τέχνη), ἡ, the art of discovering water, Gp. 2.6.1; also ὑδροφαντικά, τά, ibid.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
ἡ, sc. τέχνη, die Kunst, verborgenes Wasser zu entdecken.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)