How did Noah know that the waters were receding?
First, he knew that the waters were going down, because the ark rested upon the mountains. Genesis 8:1-4 says, “And God remembered Noah, and every living thing, and all the cattle that was with him in the ark: and God made a wind to pass over the earth, and the waters asswaged; The fountains also of the deep and the windows of heaven were stopped, and the rain from heaven was restrained; And the waters returned from off the earth continually: and after the end of the hundred and fifty days the waters were abated. And THE ARK RESTED in the seventh month, on the seventeenth day of the month, UPON THE MOUNTAINS OF ARARAT.”
Second, he knew that the waters were completed dried up when the dove came with the olive leaf, showing that plants and trees were again growing. Genesis 8:5-13 says, “And THE WATERS DECREASED continually until the tenth month: in the tenth month, on the first day of the month, were the tops of the mountains seen. And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made: And he sent forth a raven, which went forth to and fro, until the waters were dried up from off the earth. Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground; But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark. And he stayed yet other seven days; and again he sent forth the dove out of the ark; And the dove came in to him in the evening; and, lo, IN HER MOUTH WAS AN OLIVE LEAF PLUCKED OFF: SO NOAH KNEW THAT THE WATERS WERE ABATED FROM OFF THE EARTH. And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more. And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked, and, behold, the face of the ground was dry.”