Paphnutius, Life of Abba Aaron

Now it happened one year that the Nile did not rise enough to water all our fields, and a multitude of the poor came to Abba Aaron weeping and saying, "Our holy father, we and our children are going to die because the waters have not risen!" He said to them,"Believe in God 

and He will deliver you.  As it is written, 'The prayer of the poor man who is downhearted, he pours out entreaty before the Lord.' Again it says, 'The Lord has heard the desires of the poor.'"  He quoted them numerous other passages from scripture and explained them to them,
and he comforted them, and in this way they departed from him praising God.  Now the holy man Aaron was not unconcerned about their distress, and he would go to the river each evening and immerse himself in the water up to his neck and he would pray to God, saying, "My good Christ, compassionate one, have compassion upon your image and likeness."
Indeed, he continued this practice until God had compassion for his tears and made the waters of the Nile flow over the face of the whole country.

Paphnutius, Life of Abba Aaron, 131.