Thursday, July 21, 2022

1979 New Melones Dam and 300mw Hydropower in California


The nameplate (sustainable) capacity with its two units is 300mw. Its maximum capacity is 380mw. [usbr-performance] "The net head of the project is 146m [480']. The project generated 524.292 GWh of electricity." [power-technology] Judging from the data in the usbr-performance link, the 524.292 GWh is a per-year average over 10 years from 1998 to 2007.

"The primary function of New Melones Dam and Lake is flood control. Of the 2,400,000 acre-feet capacity, 450,000 acre-feet is reserved for flood control purposes. The remaining capacity is used for a number of purposes including the satisfaction of preexisting water rights, fisheries enhancement, water quality improvement and electrical generation."

The reservoir has inundated a 1926 dam that exists 3/4 mile upstream from this dam. That dam was a 183' arch dam that was 211' (64m) tall. It was built by two of the irrigation districts that supply water to the foothills, Oakdale and South San Joaquin. Those two districts still receive water from this reservoir. [usbr-project, Plan tab and usbr-history]
The original reservoir stored 112,500 acre-feet of water. (The current reservoir stores 2,400,000 acre-feet of which 450,000 is reserved for flood control. [usbr-project])
usbr via wikipedia

Construction began in July 1966. The reason why it took over a decade to build this dam is that about a decade was spent in the courts. "The battle over construction of New Melones Dam was a signal at the end of the era of large dam construction. The controversy focused on the loss of a popular stretch of recreational white water, inundation of archeological sites, and flooding of the West`s deepest limestone canyon." [WaterBoards, p1] "National attention focused on the long and bitter fight, which involved court challenges, a 1974 state ballot initiative and a river rafter who chained himself to a rock to prevent the filling of New Melones Reservoir. The struggle between environmentalists and water developers lasted from the early 1970s until the Stanislaus Canyon finally flooded in 1982 and 1983 during a high runoff year." [WaterEducation]

So was the controversy because of the inundation of the Iron Canyon or the shores of Melones Lake or both?
1962 New Melones Dam @ 24,000

On the above map, note that the powerhouse is close to the lower-left corner. It was far enough downstream from the old dam that today it is downstream of the new dam.
Jonny Rogado posted
Old Melones Powerplant

Jonny Rogado posted
New Melones Hydro Powerplant
Dennis DeBruler: It has a nameplate capacity of 300mw and a "maximum operational capacity" of 380mw.
Comment on Jonny's post

Comments on Jonny's post

Screenshots from the video in the comment. It doesn't do a very good job of catching the variety of the output flow hitting the river water.




The comment about the road culvert helped me identify the outlet structure. 

This is the top of a 55' diameter, 620' tall surge protection shaft. [WaterBoards, p5]

I could not find the spillway until I found this reference.

The spillway is a drop shaft into the original diversion tunnel. It has a crest is at 1088', and it has a capacity of 126,000cfs @ 1123.4'. (Normal pool is 1050'. The capacity of the outlet works is 8300cfs @ 1088') [usbr-dam, Details tab]

As we close fossil-fuel and nuclear power plants, we are loosing an important renewable resource.
NewsData, paycount 3
Drought conditions in the West as of June 15, 2021. U.S. Drought Monitor

At 625', it is the second-largest earthen dam in California. (Oroville, which is 742' high, is the largest.) "The hope was that the new, much larger dam would provide an expanded supply of water that could be used to flush toxins out of the San Joaquin River Delta and compensate, to some extent, for the fact that little or no water from the San Joaquin River reaches the Delta." But there is now so little water that even basic needs such as city water supply, electricity. irrigation and recreation are becoming hopes. [CalaverasEnterprise] Keeping fish eggs cool is another need that is in jeopardy. [CalaverasEnterprise-tulloch]

UnionDemocrat, Shelly Thorene, paycount 5
The reservoir was down to 54% in June 2021. That is when the two irrigation districts sold water to other irrigation districts.

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