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Diamond Valley Bass

Diamond Valley Bass
Southern California anglers can hardly contain their excitement as the region's largest water reservoir prepares to open. And wait till you hear what's swimming in its depths!

By Richard Alden Bean

Diamond Valley Reservoir is a big deal not only for its size, cost of construction and value as a water supply but also for the impact this body of water promises to make on angling in southern California.

First known as the Eastside Reservoir project, later Domenigoni Reservoir and finally as Diamond Valley Reservoir, the newest lake in southern California was made by building long dams at the mouths of two valleys southwest of Hemet. Blocking the Diamond and Domenigoni valleys, creating the largest reservoir in southern California - one that will hold 800,000 acre-feet of water when full.

Early planning had this reservoir completed in 1999. That turned out to be a bit optimistic. While the basic construction was done by 2002, much of the recreational development that goes with this large lake is still to be completed. It represents the only new body of water in southern California since the California Aqueduct system came on line in the early 1970s and ushered water to the region's other manmade water storage facilities - lakes Castaic, Silverwood, Pyramid and Perris.

Some numbers to provide perspective on the enormity of the Diamond Valley project: The reservoir has a surface area of 4,500 acres, making it the largest reservoir in southern California. It's four and a half miles long, more than two miles wide, and its bottom ranges from 160 to 260 feet deep. When you combine all that with a maximum elevation of just 1,756 feet above sea level, it isn't a difficult stretch for anglers to see this as yet another year-round, multi-tiered fishery. Diamond Valley's waters will be cold enough and deep enough for trout, and it will also be warm enough to host bass and panfish.

Photo by Ron Sinfelt

With a project cost of nearly $2 billion, Diamond Valley almost doubles southern California's surface storage capacity. Its 800,000 acre-feet are the equivalent of 269 billion gallons of water. (As a rough estimate, 1 acre-foot of water can be visualized as a football field 1 foot deep in water.) More important, an acre-foot of water supplies the interior and exterior water needs of two south state homes for a year.

Three dams were needed to create Diamond Valley. All are earth/rock fill, rather than concrete. The West Dam measures 285 feet high, 1.7 miles long (9,100 feet) 1,200 feet wide at the base and 40 feet wide at the crest. The East Dam is slightly smaller at 185 feet high, 2 miles long (10,500 feet) 800 feet wide at the base and 40 feet wide at the crest. On the north side of the lake, the Saddle Dam is 130 feet high, (above the lowest point on the ridgeline), a half-mile long (2,300 feet) and 720 feet wide at the base. It is basically a small gap filler between two hills. More than 110 million cubic yards of earth and rock were required for what is known as the largest earth and rock fill project in the United States. Excavation began in 1995. Dam construction began in late 1996.

Water for Diamond Valley comes from two systems. The first is the Colorado River Aqueduct, in which water is delivered through the San Diego Canal into the reservoir's forebay. Water is pumped from the forebay into the reservoir. The other is water from the California State Water Project from Lake Silverwood, fed into the reservoir by gravity, through a 45-mile inland feeder, 12 feet in diameter, that connects with the nine-mile-long Eastside Pipeline.

According to the Metropolitan Water District, which owns the reservoir, Diamond Valley secures six months of emergency storage in the event of a major earthquake and provides additional water supplies for drought protection and peak summer needs. Cynics and critics of the project believe the reservoir was created to accommodate further development of real estate in Riverside and northern San Diego counties, which would be a financial boon to developers who supported Governor Pete Wilson when the plans were approved.

Whatever the reason for Diamond Valley's creation, it can't help but be a winner with southern California anglers and promises to become one of the state's hottest new fisheries. Because of a program run by Department of Fish and Game biologist Mike Giusti, Diamond Valley has swimming in its depths Florida-strain largemouth bass, Florida bluegill, redear sunfish, crappie, smallmouth bass, channel catfish, blue catfish and rainbow trout. Silverside minnows and shiners were stocked as forage for the game fish, and it's likely that threadfin shad will find their way into the lake as well.

Giusti is also hoping to get his hands on kokanee salmon for Diamond Valley. He noted that the Mohave Hatchery has capacity to raise the fish, and Project Kokanee would initially pay for them. Project Kokanee is a private group dedicated to preserving and expanding kokanee fisheries in California. Kokanee would not interfere with any other sport fish. Indeed, they probably would provide some exceptional fishing for a species that most southern California anglers never see.

Walleye and lake trout have also been briefly considered for stocking at some point in Diamond Valley, but it's unlikely either will be introduced. These species would bring new fisheries to southern California and, in the case of walleye, to the state. Giusti says there is reason to believe walleye would do well here, and the lakes' depth and cool temperatures at its lowest reaches are indications that lake trout might well survive here.


One fish that has not been stocked and is not wanted is the striped bass, although the species is prevalent in the aqueduct system that feeds water into Diamond Valley. Equipment has been installed to keep them out, although it's also possible they will show up there some day. Lake Skinner, another MWD reservoir, is just a few miles to the south, and it swarms with striped bass, as does the remainder of the California Aqueduct. Time will tell, of course, but most anglers suspect that striped bass ultimately will find their way into this big reservoir.

"As far as striped bass go, we definitely don't want to stock them, and I would like to keep them out for an extended period of time," Giusti said. "But eventually they will probably get into the lake. I hope we can keep them out for at least 20 years. I just drafted a letter that, if they allow me to do it, will permit us to use an electric barrier that will kill any fish that passes through it. Standard screen designs won't work because of the volume of water, but we are looking at an electric barrier. I would like to crank up the amperage so it kills the few fish that might get in there."

The primary fishery consists of the various

species of black bass. Bass fishing is probably the most popular angling sport in southern California, or at least the one with the most organized voice. Bass anglers early on made it clear to the DFG they wanted bass in Diamond Valley. A rearing pond, built in what is now the lake bottom, gave bass and other warmwater species a chance to start growing many months before the lake began to fill.

Broodstock bass to 8 pounds were released in the pond, and there was a spawn of those fish in 1999. When the first water began to enter the new reservoir the lake level crested the pond and that year's spawn of fish moved out to feed in the now larger lake. In a year, those original spawned bass were in the 12- to 15-inch range and weighed from 2 to 3 pounds. That rapid growth hasn't stopped, and when the lake opens to general fishing, the bass angling public is in for a nice surprise.

Giusti likes to point out that the "Golden Ruler" used by bass anglers to estimate weights indicates that a 13-inch bass should weigh 1.1 pounds and a 15-inch fish should weigh around 2 pounds. And that is true at most places. At Diamond Valley, a 13-inch bass weighs right at 2 pounds and 15-inchers tip the scales at 3 pounds. The 8-pound broodstock bass weighed 12 pounds two years ago.

Giusti said that the year-class fish for 2000 are all 10-inchers, and he estimates the bass population in Diamond Valley is already around 300,000 fish. "The sampling I've done out there is unreal," said Giusti, who has been taking scale samples from 25 bass per month to chart growth rates. "Four of us on the electrofisher, which is not the best boat to be fishing from, boated 300 bass in three and a half hours of fishing. Three casts in a row I caught two fish on a the same jerkbait."

Good as the prospects for bass are, the trout fishing should be nearly as good. The first trout plants involved subcatchable-sized rainbows and were stocked at rates of six to 15 fish to the pound. By the following year, those trout were in the one to 1 1/2-pound range. "That gives you some idea of the growth rates were going to see, at least initially," said Giusti.

It remains to be seen what the panfish situation will be like. Diamond Valley is a big lake, and quite deep over much of its area. A lot of the panfish action is going to be dependent on the growth of aquatic vegetation, and it's unknown what kind of periodic water treatments the lake will get. If the conditions are right, the Florida-strain bluegill and the redear sunfish should grow to surprising sizes, as they have in Lake Perris, which regularly turns out 2-pound bluegill and even larger redear.

The catfish situation is even more interesting. With the stocking of channel cats, the lake should swarm with these tasty critters. And blue catfish, which attain great size, are likely to add an immediate trophy dimension to the catfish fishery. The average channel cat usually weighs less than 10 pounds; the state record is just 52 pounds. Blue catfish, on the other hand, grow at least twice that big. The current state-record blue is a 101-pounder from San Vicente Reservoir in San Diego County.

The unknown in this mix is the smallmouth bass. Smallmouths have been successfully introduced in many parts of the Colorado River, but haven't done as well as had been hoped in southern California lakes. Pyramid Lake has load of small bronzebacks, and attempts to introduce them into Big Bear Lake have not been particularly successful. If smallmouths do work out in Diamond Valley, it will be an outstanding fishery for the lower half of the Golden State.

Along with the smallmouth and the Florida-strain largemouth, anglers might expect to see the introduction of spotted bass at some point. Spots have set a number of world records in California in recent years.

It wasn't just fish that were "stocked" in Diamond Valley. Giusti and a crew from the DFG developed extensive habitat improvements, which added fish-friendly bottom structure features. In addition to bass structure in the form of rock piles and such, there are also spawning "condos" for channel catfish, and structures that will aid in the shelter and growth of juvenile fish of all sorts.

That's the good news. The bad news is that the lake opening keeps slipping. When this article was first assigned, the opening was supposed to be in March 2003. Then the MWD announced an opening date of July 4, and now it looks very much like it might be Labor Day before the lake is open to boats and angling.

The MWD has severely restricted the types of motors allowed on Diamond Valley. One the one hand, the regulations will keep the hordes of personal watercraft riders away from the lake, which is good for anglers. The regulations - intended to protect drinking water supplies from contaminants - also ban all older two-stroke boat motors. Only the newest injected two-stroke engines and four-stroke outboards will be allowed to use Diamond Valley Reservoir. Without those regulations as well as the removal of MTBE from California's gasoline supplies, boating on the lake would have been impossible.

The MWD is not going out of its way to open shoreline areas to foot traffic, which means Diamond Valley is pretty much a boater's lake.

The 4,500-surface-acre Diamond Valley Reservoir is between Temecula and Hemet off Highway 79 at Newport Road in the Domenigoni/Diamond valleys, about four miles southwest of Hemet. The visitor center is on Newport Road at the east side of the lake. Take Highway 79 to the new Domenigoni Highway. Go east seven miles to State Street, turn right, go about one mile to Newport Road and turn right.

At the time this article was written, fishing regulations for Diamond Valley had not been approved, but the DFG will probably shoot for a five-fish 15-inch minimum on largemouth bass, a catch-and-release only policy for smallmouth bass, and general regulations for the trout and panfish angling. Lake use and boat launch fees had not been set at press time.

The initial launch facility will be at the Marina Cove near the East Dam. Quarry Cove Marina will be developed later. Original plans for Diamond Valley included camping and several small fishing lakes in addition to the main lake, and a number of shopping and dining areas, and a golf course. An Internet search on Google will reveal dozens of sites concerning Diamond Valley Reservoir. You can also get information from the Diamond Valley Information center at 1-800-211-9863.

A good angler's topographic map of Diamond Valley is available from Fish-n-Map, 8535 W. 79th Ave, Arvada, CO 80005; (303) 421-5994;

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