干旱区生态环境知识资源中心

All deltas undergo alternating construction to destruction phases due to fundamental changes in the relative influence of sediment input from rivers and redistribution by marine coastal processes. During the past 7000 years world deltas, including the Nile, have been in an overall construction phase. However, the Nile delta has converted to a destruction phase during the past 150 years, triggered by water regulation which has disrupted the balance among sediment influx, erosive effects of coastal processes, and subsidence. This former depocenter has been altered to the extent that it is no longer a functioning delta but, rather, a subsiding and eroding coastal plain.

Symptoms of the destruction phase of the Nile delta include accelerated coastal erosion and straightening of the shoreline, reduction in wetland size, increased landward incursion of saline groundwater, and buildup of salt and pollutants to toxic levels in wetlands and delta plain. Without seasonal flushing by floods, the former delta plain surface is now incapable of recycling and/or removing agricultural, municipal and industrial wastes generated by Egypt's rapidly expanding population. Moreover, the remaining capacity of the system to regenerate itself will further diminish as water is diverted away from the delta for new irrigation and municipal projects in the Egyptian desert, and water allocations to Egypt are decreased by upstream countries.

Reestablishing some level of natural hydrology is the only credible solution for attaining equilibrium among sediment accretion on the delta plain to offset subsidence, progradation along the coast to offset erosion, and sufficient water influx to flush and remove the high levels of salt and pollutants throughout the system. However, increased Nile water and sediment discharge could begin to restore a functioning delta system only if there is a substantial reduction in human impacts.