Plato, Laws 761b

τῶν ὑψηλῶν εἰς τὰς ἐν τοῖς ὄρεσι νάπας ὅσαι κοῖλαι, τὰς ἐκροὰς αὐτῶν εἴργοντας οἰκοδομήμασί τε καὶ ταφρεύμασιν, ὅπως ἂν τὰ παρὰ τοῦ Διὸς ὕδατα καταδεχόμεναι καὶ πίνουσαι, τοῖς ὑποκάτωθεν ἀγροῖς τε καὶ τόποις πᾶσιν νάματα καὶ κρήνας ποιοῦσαι, καὶ τοὺς αὐχμηροτάτους τόπους πολυύδρους τε καὶ εὐύδρους ἀπεργάζωνται· τά τε πηγαῖα ὕδατα, ἐάντε τὶς ποταμὸς ἐάντε καὶ κρήνη ᾖ, κοσμοῦντες φυτεύμασί

hollow valleys in the mountains: they shall dam the outflows of their flooded dales by means of walls and channels, so that by storing up or absorbing the rains from heaven, and by forming pools or springs in all the low-lying fields and districts, they may cause even the driest spots to be abundantly supplied with good water. As to spring-waters, be they streams or fountains, they shall beautify and embellish them by means of plantations and buildings,