Passage 8.28.3
ὅσοι δὲ γῆν διεξίασιν εὖ τῶν ὡρῶν ἔχουσαν καὶ θέρους σφίσι τὸ ὕδωρ πινόμενόν τε καὶ λουομένους ἀνθρώπους ἀναψύχει, χειμῶνος δὲ ἀνιαρὸν οὐκ ἔστι, τούτους ἐγώ φημι παρέχεσθαι σφᾶς ὕδωρ ψυχρόν. ψυχρὸν μὲν δὴ ὕδωρ καὶ Κύδνου τοῦ διεξιόντος Ταρσεῖς καὶ Μέλανος τοῦ παρὰ Σίδην τὴν Παμφύλων· Ἄλεντος δὲ τοῦ ἐν Κολοφῶνι καὶ ἐλεγείων ποιηταὶ τὴν ψυχρότητα ᾄδουσι. Γορτύνιος δὲ προήκει καὶ ἐς πλέον ψυχρότητος, μάλιστα δὲ ὥρᾳ θέρους. ἔχει μὲν δὴ τὰς πηγὰς ἐν Θεισόᾳ τῆ Μεθυδριεῦσιν ὁμόρῳ· καθότι δὲ τῷ Ἀλφειῷ τὸ ῥεῦμα ἀνακοινοῖ, καλοῦσι Ῥαιτέας.
Those rivers whose course traverses land enjoying a mild climate, offering in summer water that refreshes people who drink or bathe in it but is not troublesome in winter—I call such rivers providers of cold water. Indeed, cold is also the water of the Cydnus, which flows by Tarsus, and of the Melas near Side in Pamphylia. As for the Ales in Colophon, even elegiac poets have sung of its coldness. But the Gortynius surpasses these rivers in the coldness of its water—especially during the summer season. Its sources lie in Theisoa, neighboring Methydrium, and as it mixes its current into the Alpheius, people call the place Rheiteai.