This research studies the effect of barrages on upstream river water quality and on its self-assimilative. Also, the impact of barrages on upstream water temperature profile is studied. The amount of entrained air in water at river downstream side as a result of barrage existence is also studied. Constructing barrages in river reaches will alter its hydraulics and thus its water quality and thermal regime. A mathematical model is developed to simulate river hydraulics, water quality parameters and temperature. A case study of a Nile River reach in Egypt was studied, to investigate the impact of the existence of Esna barrage on water quality and temperature at its upstream side. Barrages were found to have negative impacts on upstream self-assimilative capacity of rivers. On the other hand, they have positive impacts on DO concentrations and air entrained at the downstream side. Finally, barrages cause a slight decrease in water temperature.
Keywords: self-assimilative capacity, water quality, barrages, mathematical modelling, dissolved oxygen concentrations, photosynthesis and respiration, water temperature