During the Spring and Autumn Period, Duke Zhao of Lu was ousted for his poor governance and forced to flee to neighboring Qi for refuge.
One day, Duke Jing of Qi asked Duke Zhao of Lu, "You lost your throne at a young age—have you reflected on the reason?"
Duke Zhao of Lu replied, "When I was young, many people cared for me, yet I never drew close to them; many offered me advice, yet I never heeded their words. Gradually, I ended up with no one inside the state to help me with all their might, and no one outside to support me with loyalty and filial piety. But around me, there were plenty who flattered me, curried favor, and spoke falsehoods. This was like the autumn tumbleweed—its roots and stems had already withered, yet its leaves and branches still appeared lush and beautiful. But when the autumn wind arose, every leaf and every branch was torn up by the roots."
Duke Jing of Qi, believing that Duke Zhao of Lu was still young and had now recognized his own mistakes and faults, and might perhaps become a virtuous ruler in the future, asked his prime minister Yanzi, "If Duke Zhao of Lu were to return to the state of Lu, could he once again become a wise and enlightened monarch?"
Yanzi thought for a moment and replied, "No. If a man has already fallen into the water, only then to investigate the cause of his fall, or if a man has already lost his way, only then to ask for directions, it is like waiting until danger is upon you to forge weapons for defense, or waiting until food is stuck in your throat to dig a well for water to wash it down—even if you act with the greatest speed, it will be too late."
Duke Jing of Qi nodded in agreement upon hearing this, remaining silent. Later, the idiom "Digging a Well Only When Thirsty" came to be used to describe making preparations only when the situation is urgent.
Source: *Yanzi's Spring and Autumn Annals*
Meaning of the Idiom: Later, the Chinese idiom "临渴掘井" came to describe how making preparations only when the situation is urgent.