2 Chronicles 32:4

So there was gathered much people together, who stopped all the fountains, by covering over the cisterns and removing all evidences of the presence of any pools, and the brook that ran through the midst of the land, the Gihon, the brook of the Valley of Ben-hinnom, whose waters they deflected into the city by a subterranean channel, saying, Why should the king of Assyria come and find much water? By cutting off the supply of water from the besieging army, the Jews would add materially to its distress and to the difficulties of a siege.