Other impacts of dams may be less obvious but nonetheless destructive . Dams trap not only rivers but the contents of rivers the load of nutrient-rich silt and sediments picked up and deposited by the river as it flows over lands. They told the Swiss campaign group, Berne Declaration, that they estimated the annual sedimentation load of the Tigris at 15 to 30 million cubic metres. This would fill up 10-20 per cent of the reservoir s operating capacity within 50 years. And yet the authors of the EIA expect the reservoir to be useful for 80-100 years.
Dams can also affect the quality of the river water both above and below the dam.
They can concentrate pollutants, deplete or increase oxygen levels, alter the river s temperature. All of these impacts alter the lives human, animal and plant the river feeds. The issue of water quality is a very grave concern in the case of the Ilisu dam, one that even Balfour Beatty acknowledges. It is reasonable to assume that the Ilisu dam s reservoir will vastly reduce the ability of the Tigris to purify itself. This will jeopardise water quality and potentially cause major health problems in the major towns, where the infrastructure has already been stretched beyond endurance by the influx of Kurds forced from their rural homes.