Muddy water? Pffft! I lived in Virginia and know red clay -- in and out of water. The soil needs a particular flora and fauna to get that color. Virginia's best known crop is tobacco. Even before tobacco, they had a certain selection of trees. (I found out they don't get red much in their fall foliage, because maples aren't native. Maple trees aren't a southern tree, naturally.) Georgia (another state with red clay) is best known for root crops and peaches. None of those crops were known by Egyptians, and Egyptians were bound to need what they grew, so they weren't wasting precious Nile water on unnecessary crops (like tobacco and peaches. I love both those crops, however, they're just not needed.)