Aswan Dam is another classic example. Yes, it has allowed increased agricultural production through irrigation but it has decimated the Nile delta fisheries, removed the natural flushing of salts and nutrient recharge, and increased health problems (bilharzia anyone?). Aside from salts building up in the soils, there is also seawater intrusion into the delta impacting water supplies for millions AND there is no longer replenishment of sediments along the delta. So the delta is retreating and/or sinking.