Downstream effects of dams: The Lower Sakarya River

Dams and some other hydraulic structures cause some changes in the riverbed downstream after their construction. After constructing the Gökpekaya Dam which started to operate on the Middle Sakarya River in 1975, some changes occurred on the Lower Sakarya River such as river regime, sediment transport rates, and morphological changes. The measurements of sediment rate and the water flow are evaluated graphically. Results show that flood peak discharges in the Lower Sakarya River decreases as 30–50% after 1975. Furthermore, sediment transport rates decrease 50–53% after constructing of Gökpekaya Dam. There is also some degradation in the riverbed. Thalweg elevations of the river for selected Crosssections were determined in 1965 and 1998. It was observed that the level of degradation varies 0–10 m during last 35 years. These changes investigated in this study affect water the table, the irrigation and drainage system, the gravel mining, and the navigability of the river.