But the land whither ye go to possess it is a land of hills
and valleys
And so could not be watered by the overflow of a river, and by canals cut out of it, and in the manner Egypt was; which was for the most part a plain and flat country, but not so Canaan, in which were many hills and mountains, as those about Jerusalem, Carmel, Tabor, Lebanon, and others; and plains and valleys, as the valley of Jezreel and which made it more delightful and pleasant for prospects; see ( Deuteronomy 8:7 ) and drinketh water of the rain of heaven; by which it was watered, refreshed, and made fruitful; not by means of men, but by the Lord himself, and so with much more ease to men, and without the toil and labour they were obliged to in Egypt, as well as it was both more healthful and pleasant; for the damps that arose from the overflow of the Nile were sometimes prejudicial to health; and during the season of its overflow, which was in the summer, they were obliged to keep in their houses, and could not walk abroad for weeks together; to which inconveniences the land of Canaan was not subject; but then, as its fertility depended on rain from heaven, the Israelites would be under the greater obligation to observe the commands of God, who could give and withhold it at his pleasure, and as they conducted themselves; which seems to be the general drift of this passage.
The Brenton translation of the Septuagint is in the public domain.