Here’s the straight dope on the Wicked Witch of the West :
. . . the Witch began to shrink and fall away. “See what you have done!” she screamed. “In a minute I shall melt away.”
“I am very sorry, indeed,” said Dorothy, who was truly frightened to see the Witch actually melting away like brown sugar before her eyes.
“Didn’t you know water would be the end of me?” asked the Witch, in a wailing, despairing voice.
“Of course not,” answered Dorothy; “how should I?”