Many believe that Egypt, over the course of its long history, has developed the most stable farming-based civilization in history. I don't know if this was meant to apply to the entire country, but I'm pretty sure it clearly applies to the agricultural activities associated with the Nile River. And keep in mind that agriculture is also (arguably) the single most crucial development in human history. So it's pretty clear that Egypt knows a thing or two about sustainable ag irrigation. So what is it that they do to garner these accolades?
Their methods have been
perfected over thousands of years and are still to this day dictated
entirely by the flooding cycle of the Nile River. Their approach is a natural form of
irrigation incorporating the three distinct water seasons of every year. The process begins each July through October when the wet season arrives and the Nile floods. On average the river level rises 27 feet, flooding miles of farmland along the river banks under about 5 feet of water. With accurate elevations, they would use a series of manmade ditches to channel these flood waters to basins likely to flood during the normal flood year. All the basins were left sitting saturated for about a month, soaking up all the water they could, before being systematically drained down-gradient over the next month or so.
Then began the planting season (October) when wheat, barley, figs, melons, pomegranates,
flax and other minor crops would begin to grow. Of course the flooding not only brought water, but also mineral rich sediments that replenished the soil nutrients used by the previous crop.
Finally the harvest season would arrive in March after about a 5-month growing season. Hopefully the bounty of the harvest would be brought in quickly and provide all their needs for the year - as in early July the cycle would begin again.
The success of this system lay in its use of a single crop system (which tended to not deplete the soils), and replenished water and nutrients. It also depended on the predictable 27 foot flood stage - which was usual, but never guaranteed. If the flood stage was a bit higher or lower, there would be consequences. Lower stages resulted in un-irrigated lands and loss of production, while higher stages affected villages, people and animals integral to the normal ag production processes. Today the flood stages are more consistent now that the High Aswan Dam has been built and the annual floods are better controlled than before.
With such a set-up, is it any wonder that Egypt's irrigation has remained as stable as it has throughout history? Of course, stable also means little opportunity to grow or increase production, which can be a problem as time marches on - at least to the western mind-set. I wonder how Kansas would manage the waters if the Nile ran through our state? Dream on!!