Diamond Lake (Oregon)

Diamond Lake
Lake with Mount Thielsen in the background
Location	Douglas County, Oregon
Coordinates	43°09′31″N 122°09′03″W / 43.15861°N 122.15083°W / 43.15861; -122.15083Coordinates: 43°09′31″N 122°09′03″W / 43.15861°N 122.15083°W / 43.15861; -122.15083
Type	natural, eutrophic
Primary inflows	Silent Creek, Short Creek
Primary outflows	Lake Creek
Catchment area	55 square miles (140 km2)
Basin countries	United States
Max. length	3.5 mi (5.6 km)
Max. width	1.5 mi (2.4 km)
Surface area	3,040 acres (12.3 km2)
Average depth	24 ft (7.3 m)
Max. depth	52.5 ft (16.0 m)
Water volume	77,100 acre feet (95,100,000 m3)
Residence time	1.6 years
Shore length1	9 mi (14 km)
Surface elevation	5,183 ft (1,580 m)
References
1 Shore length is not a well-defined measure.

Diamond Lake is a natural body of water in the southern part of the U.S. state of Oregon. It lies near the junction of Oregon Route 138 and Oregon Route 230 in the Umpqua National Forest in Douglas County. It is located between Mount Bailey to the west and Mount Thielsen to the east; it is just north of Crater Lake National Park.

The outlet of the lake is at its north end. From there, water flows via Lake Creek into the North Umpqua River and ultimately to the Pacific Ocean.

Diamond Lake was named for John Diamond, for whom Diamond Peak is also named. He saw the lake in 1852 while on the summit of Diamond Peak. Diamond was a pioneer settler of Coburg, Oregon, and part of a party opening a road between the Middle Fork Willamette River and Idaho as an immigration route.

An adjacent post office named Diamond Lake, Oregon, was established in 1925 and ran until 1956, when it was changed to a summer-only office.

Although rainbow trout are not native to Diamond Lake because the lake lacks the required spawning habitat, large populations of aquatic insects make it ideal for fish. After treating the lake to remove rough fish in 1954, the Oregon Department of Fish and Wildlife (ODFW) stocked the lake with a Canadian strain of rainbow trout and later added local strains in about 1970. Stocked trout grew rapidly in the lake, and before other species began competing successfully with trout, anglers caught 10-pound (4.5 kg) rainbows regularly, and the average catch weighed more than 1 pound (0.45 kg). However, in 1992 a non-native species, tui chub, was detected in the lake. These fish, illegally introduced to the lake, quickly multiplied and negatively affected the sport fishery. The water became murky, the insect population dropped dramatically, and the trout population declined.