Big Cliff Dam  Big Cliff Dam is a concrete gravity dam on the North Santiam River in the western part of the U.S. state of Oregon. The dam spans the Linn County–Marion County border in the Oregon Cascades. The dam's primary functions are flood control, power generation, irrigation, fish habitat, water quality improvement, and recreation. It is one of 13 dams created by the U.S. Army Corps of Engineers under the Willamette Valley Project which was authorized by the Flood Control Act of 1938. It was constructed between March 1949 and May 1953 at the same time as Detroit Dam. Big Cliff is river distance below Detroit Dam at river mile 47 of the North Santiam River. Big Cliff smooths river flow resulting from power generation fluctuations of Detroit Dam, a practice known as river re-regulation. Big Cliff Reservoir, primarily known as Big Cliff Lake, has daily depth variations of up to . Big Cliff can generate up to 18 megawatts of power. The dams' operators try to keep the water temperature in the range for ideal fish habitat by mixing water from the top of Detroit Lake with water from the bottom.