The account of Sennacherib’s siege of Jerusalem is found in 2 Chronicles:

“When Hezekiah saw that Sennacherib intended to attack Jerusalem, he planned with his civil and military officers to stop up the water of the springs outside the city; and they helped him. They gathered together a large number of people and stopped up all the springs and the stream which flowed through the land. ‘Why should the kings of Assyria come here and find much water?’ they asked … Hezekiah closed the upper outlet of the waters of Gihon and directed them down to the west side of the city of David.” (2 Chronicles 32:2–4, 30)

The account in 2 Kings of Hezekiah’s reign ends with these words:

“The rest of the deeds of Hezekiah, his exploits and how he made the pool [Siloam] and the conduit and brought water into the city are recorded in the Book of Chronicles of the Kings of Judah.” (2 Kings 20:20)