Oker Dam, Dam in Goslar, Germany

Oker Dam is a water barrier in the Harz mountains of Lower Saxony that holds back a large reservoir spanning across the landscape. The structure includes the dam wall itself, a broad water surface, and technical installations for power generation and water management.

Construction began in 1938 and was completed in 1956 following devastating winter floods that affected downstream towns in 1946. The project aimed to prevent such flooding disasters in the future.

The reservoir has become a focal point for local leisure, where residents and visitors engage in swimming, fishing, and recreational boating throughout the year. These water-based activities are woven into how people spend their free time in the Harz region.

The area is accessible via walking trails and roads with several vantage points along the water. Visitors should plan visits according to seasonal conditions and weather, as water activities and accessibility vary throughout the year.

The spillway works by siphon effect: two groups of four pipes, each 1.5 m² in cross-section, sit at 416.60 m above sea level and together pass about 120 m³/s. It has operated only twice, in 1981 and 1994.