Why did Hezekiah's people stop up the springs outside Jerusalem?

Answer: So Assyria would find no water

Facing Sennacherib, the people stopped up the springs, asking, "Why should the kings of Assyria come and find plenty of water?"

“he consulted with his leaders and mighty men about stopping up the waters of the springs outside the city, and they helped him carry it out.”— 2 Chronicles 32:3 (BSB)