How accurate is this description of the Nile flood?

"Once a year the deluge comes down from above, flowing from the lakes lying far away, large as inland seas. and transforms the dry land into a garden, making the sandy waste to blossom and bear the "double-breasted bounteousness" of two harvests a year, with this new tide of life from the heart of Africa. Not only does the wilderness flush with colour, for the waters, which had been running of a dull green hue, are suddenly troubled and turned crimson. The red oxide of iron mixes with the liquid and gives it a gory gleam in the sunlight, making it run like a river of blood.
There is an antithesis to the inundation in another phenomenon almost as unique. This is found in the steady continuance of the north-wind that blows back the waters and spreads their wealth over a larger surface of soil. and enables the boatman to sail up the river right against the descending current. Everything Egyptian is typical, and when we see how the people figured the two truths of mythology as the two factors of being, and how they personified breath and water, we shall more or less perceive the initiatory import of this wonderful arrangement of wind and tide, and its combination of descending and ascending motive power.
The Nile water is highly charged with ammonia and organic matter, which are deposited as manure. It is, for instance, three times as rich in fertilising matter, whether in suspension or in solution, as the Thames at Hampton Court.
This bounty was spread out for all by the breath of the beneficent wind. Num, Lord of the Inundation, is painted on the monument as the Green God, and the limit of the inundation was the measure of Egypt's greenness. The waters that brought the silt clothed the soil with that colour just so far as they were blown.
From the beginning Lower Egypt, the Delta, was a land literally rained down by the inundation as a gift of the gods. For the clouds arise from their several seas and sail off heavily-laden toward Equatorial Africa, and there pour forth their weight of water during a rain of months on mountain slopes that drain into the fresh lakes until these are brimmed to bursting, and their northern outlet of birth is the Nile. The White Nile at first, until the Abyssinian highlands pour into it their rushing rivers of collected rain with force enough to float a mass of silt that is part of a future soil, the presence of which in the waters makes the Blue Nile; then the river becomes the turbid Red Nile of the inundation, and as it spreads out fanwise towards the Mediterranean Sea, it drops that rich top-dressing of soil or the very fat of land and unctuous mud-manure, every year renewed and rained down by that phenomenal flood." Gerald Massey, A Book of Beginnings

Basically he's right of course : Egypt is a product of the Nile, and the Nile is a product of rainfall in Ethiopia but mostly in Kenya.

Withouth that Egypt would have been mostly uninhabitable - in historic times at least : it seems there was more mosture around in paleolithic times.

BUT, anyway, it seems to be true that Egyptian priesthood was able to predict/calculate the flooding of the Nile with reasonable accuracy.

2> BUT, anyway, it seems to be true that Egyptian priesthood was able to predict/calculate the flooding of the Nile with reasonable accuracy.

IIRC it takes weeks for the "flood" to reach the sea. Thus, if you were in the south of Egypt, you would see the peak of the flood long before it reached the Delta. Thus you could use a nilometer in Aswan to predict how high the flood would be in Memphis, and send word to take flooding or drought precautions if necessary.