Oymapınar Dam

Oymapınar Dam is a hydroelectric dam located in southern Türkiye, approximately 80 km east of the city of Antalya, on the Manavgat River. Construction began in 1977 and was completed in 1984, with the primary purpose of generating electricity. This dam is among the first arch dams built in Türkiye.

The dam is a double-curvature concrete arch structure with a height of 185 metres from its foundation and 155 metres from the riverbed. Its crest length is 360 metres. The volume of the dam body is 575,000 cubic metres (m³). At normal water level, the reservoir capacity is 300 hectocubic metres (hm³) and the surface area is 4.70 square kilometres (km²). The average flow of the Manavgat River at the dam site is measured at 140 cubic metres per second (m³/s). The Oymapınar Dam and Hydroelectric Power Plant (HES) has an installed capacity of 540 MW and produces an average annual electricity output of 1,620 GWh.

Construction and Geological Features

The Manavgat-Oymapınar dam site, built on karstic limestone, has been the subject of extensive and detailed investigations due to the need to address tectonic and karstic challenges. These studies have been conducted since 1963. The primary objective of the dam’s planning was to regulate the hydroelectric potential of the Manavgat River and meet the energy demands of the Akseki Aluminium Industry.

The Manavgat River is fed by numerous karstic springs. The surface drainage area at the Oymapınar village measurement station is 715 square kilometres (km²), increasing to 929 square kilometres (km²) when including closed basins (poljes). Intense and deep karstification is particularly concentrated in the central section of the gorge where the synclinal axis intersects the river. This condition has also influenced the dam’s underground storage capacity.

Spillways

Oymapınar Dam is equipped with two spillways designed to safely discharge floodwaters. These spillways are located near the right abutment of the dam. Each spillway operates independently, and their combined capacity is rated at 3,000 cubic metres per second (m³/s). Each spillway is controlled by radial gates. This design is critical for ensuring the safety of the dam and downstream areas during potential extreme flow events.

Hydrological Conditions

Fluctuations in the flow regime of the Manavgat River are notable due to significant contributions from karstic springs. For instance, frequency analyses based on observations from 1940 to 1982 show variability in flood discharges. The lowest water levels occur in September and November, while the highest levels are recorded in December and March. Waters originating from Paleozoic sources exhibit distinct chemical composition and temperature differences compared to waters from Cretaceous and Miocene sources.