Albert Barnes Commentary 2 Chronicles 32:3

"he took counsel with his princes and his mighty men to stop the waters of the fountains which were without the city; and they helped him." — 2 Chronicles 32:3 (ASV)

To stop the waters ... — Compare 2 Chronicles 32:30. Hezekiah’s objective was probably twofold—to hide the springs outside the city in order to distress the Assyrians, and to convey their water underground into the city in order to increase his own supply during the siege.