Lake Highlands. Criticism Ecological effects The Shasta Dam has had a severe negative effect on populations of Pacific salmon in the Sacramento River watershed ever since its gates were first closed in 1943. The massive structure completely prevents salmon migration from the lower reaches of the river to the Upper Sacramento, Pit, McCloud and other tributary streams. It is estimated that half of the best salmon habitat in the Sacramento basin lies upstream of Shasta Dam. Also, the dam caused temperatures in the river to rise because it released waters from higher elevations of Shasta Lake, which are warmed by the sun far more than the surface of the original river pre-dam. Warm waters are harmful to salmon, which prefer colder temperatures, and also impact other fish populations such as steelhead and wild California trout. In an attempt to save the plunging salmon populations, the federal government constructed the Coleman National Fish Hatchery on Battle Creek in 1942. The hatchery is situated approximately southeast of Redding, and produces 13,850,000 eggs per year – nearly 87 percent of which are for the fall chinook salmon run. Another remedy was carried out by the Bureau of Reclamation in 1991, with the installation of a gigantic facility called a TCD (Temperature Control Device) on the rear face of Shasta Dam. This structure enables dam operators to decide the depth of the reservoir from which the water feeding into the penstocks originates. As one progresses deeper into Shasta Lake, the water gets colder where it receives less sunlight. The TCD is equipped with fifteen openings called "shutters" arranged in rows along the back face of the structure. The rows lie , , and above sea level. (The crest of Shasta Dam is at an elevation of .) The system has shown significant success in reducing the temperature of the Sacramento River below the dam, although it does exhibit leakage. As for the health of the river overall, the dam has indirectly affected it by promoting the growth of cities and farms along it. However, construction of the dam also has had direct consequences to the morphology and vegetation zones along the river. By raising summer flows much higher than their natural average, and moderating the effects of most floods, the post-dam river supplies an even amount of water to the riparian zone each year, and resultantly vegetation has encroached on the river channel. The