Diamond Valley Lake is a man-made off-stream reservoir located near Hemet, California, United States. It is one of the largest reservoirs in Southern California and one of the newest. It has a capacity of . In terms of surface area, it is the largest lake wholly within Riverside County and the Inland Empire. The lake nearly doubled the area's surface water storage capacity and provides additional water supplies for drought, peak summer, and emergency needs.
The Metropolitan Water District of Southern California (MWD) began the $1.9 billion construction project in 1995. Filling of the lake, by way of the Colorado River Aqueduct, began in and was completed in . The lake is served by the Inland Feeder.
The lake features three earth fill dams, two located on either side of the valley and one on the north rim. Construction of the dams used nearby materials, and was one of the largest earthworks projects in the United States. Excavation of core materials for the dams resulted in many paleontological finds, all of which are displayed at the Western Science Center at the lake's East end. The lake is open to boating and fishing, along with hiking and other recreational activities around the lake.
Geography
Diamond Valley Lake is located within the Domenigoni/Diamond valleys, between the Domenigoni Mountains and Rawson Mountains, southwest of the city of Hemet. The site was chosen because of its location between the cities of San Diego and Los Angeles, and because of the raw materials located on-site for the construction of the three dams. The location was also chosen because of its proximity, about , to the existing Colorado River Aqueduct that originally supplied the lake with water.
Construction
Planning for the lake began in 1987. The main goal was to meet Southern California seasonal, drought and emergency needs. MWD chose the current site because of its geographic location, and began construction planning in 1993. Construction of the lake was the largest construction project by the MWD since building the Colorado River Aqueduct.
At its peak in 1997 and 1998, the reservoir construction project employed an average of 1,800 people. At times, more than 1,900 people labored in building the reservoir's three dams. From start to finish, about 5,000 people were employed by the construction project.
Dams
Construction of the three dams was completed in 1999, requiring the excavation of of foundation material. The earth fill dam project required about of sand, clay and rock. Much of the materials needed were obtained from the project area. Core materials were obtained from the silty and clayey sandy alluvium in the floor of the reservoir and the rock fill came from the bedrock highlands of the reservoir's south rim. Design and construction of the dams took into consideration the threat of earthquakes with the San Jacinto Fault Zone, located about from the reservoir, and the San Andreas Fault, located about from the reservoir. In 2001, four of the twelve pumps were converted to hydroelectric turbine generators capable of producing 3 megawatts of power each. If all the pumps were converted, the entire facility could produce up to 40 megawatts of power.
Water is pumped from the pumping station, located just outside the west dam, through a long, diameter pipe and into the lake via the I/O tower. At peak rate, water flowed into the lake at per second. Filling of the lake finished in 2003.
The reservoir was initially filled to its capacity of in 2003. Water from the Colorado River Aqueduct stopped being used due to the threat of the Quagga mussel, an invasive species that has already contaminated other Southern California lakes served by the aqueduct. In 2009, the lake began being filled with water provided by the Inland Feeder after nearly two years without a source. The water replenished much of what was lost after drought conditions required the MWD to tap into the lake. By March 2016, an extended drought had dropped storage to .
Paleontological finds
thumb|A [[Paramylodon|Paramylodon harlani on display at the Western Science Center]]
During excavation, bones and skeletons were found from extinct mastodons, mammoth, camel, sloth, dire wolf and long-horned bison.
Paleontologists from the San Bernardino County Museum in Redlands, California uncovered thousands of fossils in the Diamond and Domenigoni valleys that will add immensely to the store of public knowledge about the region. Collectively, these animal fossils are named the Diamond Valley Lake Local Fauna.
The paleontological finds of mammoth, mastodon, bison, and other Pleistocene Epoch species from Diamond Valley Lake provide a unique snapshot on inland southern California during the Ice Ages, and bridge a massive information gap between fossil deposits at La Brea Tar Pits in Los Angeles, California and Ice Age sites in the Mojave Desert. Unofficially, the Diamond Valley Lake area is often referred to as the "Valley of the Mastodons". Fossils from the Diamond Valley Lake site comprise a classic late Pleistocene assemblage, which includes the following extinct animals: However, these fossils were later identified as a new species Mammut pacificus.
In North American paleontology, mastodons are thought to have been solitary forest-dwelling browsers. The abundance of mastodons in the fossil record from the site suggests that, during the last Ice Age, the Diamond Valley Lake site was more wooded or forested than today.
Stocking of the lake with fish began before the reservoir was filled, with a small rearing pond being placed on the bottom of the valley. The lake has several species of freshwater fish; largemouth bass, smallmouth bass, bluegill, crappie, rainbow trout, striped bass, channel catfish, and shad. It was discovered that a small population of flathead catfish were accidentally introduced. It is considered one of the best fisheries in California.
thumb|700px|center|The East Dam and recreation park of Diamond Valley Lake. The aquatic center and Western Science Center can be seen at the far right.
Much of the area around the lake remains undeveloped and empty. Original plans included large recreation areas on both the eastern and western end of the lake complete with golf courses, campgrounds, swimming lakes, water parks and other amenities. The MWD still plans on building the additional recreation facilities, but lack of funding and lack of support from developers has prevented them from doing so.
Gallery
<gallery mode=packed>
File:DiamondValleyLakeHemetPoppies.jpg|A view of Diamond Valley Lake and California Poppies
File:DiamondValleyLakeTrail.jpg|A trail around Diamond Valley Lake
File:DiamondValleyLakeViewSanJacinto.jpg|A view of the San Jacinto mountains from Diamond Valley Lake
File:DuamondValleyLakeChaparral.jpg|Chaparral and a rocky outcrop at Diamond Valley Lake
</gallery>
See also
- List of dams and reservoirs in California
- List of lakes in California
- List of largest reservoirs of California