Friant Dam - Expansion

Expansion

Because of its relatively small storage capacity relative to the average annual discharge of the San Joaquin River – 520,528 acre feet (642,062 dam³) versus 1,790,000 acre feet (2,210,000 dam³) – Friant Dam often has to release excessive amounts of water that could be otherwise used for irrigation or power generation, also causing downstream damage. From 1981 to 2011, an average of 450,000 acre feet (560,000 dam³) was spilled each year because the reservoir was unable to contain it. The USBR has proposed increasing the height of Friant Dam by up to 140 feet (43 m), nearly tripling the reservoir's storage capacity to 1,390,000 acre feet (1,710,000 dam³). A smaller 60-foot (18 m) raise would increase storage capacity to 860,500 acre feet (1,061,400 dam³), while a 25-foot (7.6 m) raise would increase storage capacity to 652,500 acre feet (804,800 dam³). The increase in height would also allow for the generation of between 4.7–30.4 MW of additional power.

Another proposal to increase storage in the upper San Joaquin River basin is Temperance Flat Dam, which would be located in the San Joaquin River canyon upstream of Friant Dam and impound between 460,000 to 2,775,000 acre feet (570,000 to 3,423,000 dam³) of water. The proposed dam would stand 415 to 840 feet (126 to 260 m) high above the river, and it would capture most of the floodwater that would otherwise be spilled from Friant Dam. However, Temperance Flat has come under heavy controversy because it would flood a large scenic section of the San Joaquin River gorge, negatively affect wildlife in the river and inundate two upstream hydroelectric power plants, causing a net loss in power generation. The water supplied from such a dam would be very expensive, ranging from $1000-1500 per acre foot (area farmers currently pay about $60 per acre foot). Raising Friant Dam would likely produce similar increases in the cost of irrigation water.