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| Fig. 1: The location of the proposed Cedar Grove reservoir in Kings Canyon National Park, (Courtesy of the U.S. National Park Service) |
Today, the Kings River has the longest drop in an undammed river in the United States. [1] This means it has the most untapped potential for hydroelectricity of any river in the country. Over a century ago, several parties fought to dam the Kings River. They lost. The story behind the struggle for Kings Canyon National Park is long and complicated. It involves messy politics, massive amounts of money, and competing desires to protect the environment. [2] The triumph of Kings Canyon National Park demonstrates a victory of environmental preservation over human use. But was it worth it?
Let us estimate the amount of power that could be produced by a dam on the Kings River.
The Kings River currently has several dams on it. The largest is the Pine Flat Hydroelectric Plan, which generates 165 MW. [3] However, the Middle and South Forks of the Kings River remain undammed because they are in Kings Canyon National Park. In the 1940s, these forks were initially excluded from Kings Canyon to leave room for the possibility of building a dam. [2] One of the proposed dams was at the Cedar Grove at about 36.78994, -118.66977, seen in Fig. 1. [4] This location was annexed to Kings Canyon National Park in 1965, preventing the river from ever being dammed here. [2] We will now determine the energy that would be produced with a dam at Cedar Grove.
Hydroelectricity works by transforming the mechanical energy of water flowing in a river into electrical energy. A dam is built on a river, creating a reservoir on the upriver side of the dam. Inside the dam] are turbines. Some water is allowed to flow through the dam, rotating the turbines as it flows. The turbines then act like motors in reverse, generating power.
The main factors that affect the amount of energy a dam produces are the head, or difference in water surface elevation on the upriver and downriver sides of the dam, and the water flow rate through the dam.
The energy stored in the system is
The power generated is the rate that the energy is changing over time. So, we can calculate the power generated using
where ρ is the density of water, g is the acceleration due to gravity, h is the head, Φ is the flow rate, and η is the efficiency of the dam. The density of water is 1000 kg/m3 and the gravitational constant is 9.8 m/s2. We used the Randell Report, which initially investigated the possibility of placing a dam at this location, to determine the head is about 610 m (2000 feet). [4] We averaged USGS data on location from the year October 1954 to September 1955 to determine the flow rate is 479 ft3/s (13.57 m3/s). [5] We will assume the efficiency is η = 0.9, which is common for hydroelectric systems today. [6] Thus, we find this dam would generate
or 73.1 MW.
One dam on the Kings River could produce 73 MW. Over the period 2015-2024, the average residential customer consumed 10.64 MWh of electricity in one year. [7] Thus, this dam could power about 59,385 homes.
However, we must discuss some assumptions made in determining this number. We assumed the flow rate through the dam was equal to the average flow rate at the dam location over a one year period in the 1950s. However, the flow rate may have changed in the intervening 80 years due to differences in precipitation, melting glaciers, increased infrastructure, and more. Further, even within the period we examined, the flow rate varied by over 4000 ft3/s. [5] The flow rate decreases drastically in late summer; so much so that it is likely no power could be generated. In addition, we assumed a very efficient dam, which would cost more money and resources to build. We also assumed an ambitiously large dam with extremely high head, which may not be possible.
Another factor to consider is that water has value outside of generating electricity through hydropower. For example, dams severely decrease the flow of water, thereby reducing the amount of water that can be used for irrigation downstream. The Kings River currently provides irrigation for over one million acres of farmland in some of the most agriculturally productive counties in the country. [8] Further damming the Kings River would change the irrigation landscape and potentially hinder the agricultural production abilities of the vital California central valley.
Thus, while this was a worthwhile exercise, we cannot fully understand the impact of a dam at Cedar Grove through only simple theoretical calculations. Further, we cannot answer the question of whether it was worth it to preserve the Middle and South Forks of the Kings River without considering the qualitative impacts. This a question that involves considering irrigation to farmland, cost of building the dam, cost of maintaining the dam, other uses of the water flowing through the Kings River, and, above all, the unquantifiable benefits that come from an undammed river.
The ability to walk beside a free-flowing river and feel the connection as the blood pumps through your veins in much the same way. The sweet taste of freshly melted glacier on parched lips. The bite of cold as you bathe in icy waters after a long day in the sun. These factors are unquantifiable, but impactful enough that people have fought, and continue to fight, for Kings Canyon for decades.
© Maya Mandyam. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] P. Houston, "Kings River to Get Federal Protection in Compromise Bill," Los Angeles Times, 2 Apr 87.
[2] W. C. Tweed and L. M. Dilsaver, Challenge of the Big Trees: The Updated History of Sequoia and Kings Canyon National Parks (George F. Thompson Publishing, 2017).
[3] J. F. Taylor, "Pine Flat Hydroelectric Project License Amendment Water Quality Certification,"U.S. Federal Energy Regulatory Commission, December 2022.
[4] R. R. Randell, "Report to the Federal Power Commission on the Storage Resources of the South and Middle Forks of Kings River, California," (U.S. Government Printing Office, 1931).
[5] "Surface Water Supply of the United States, 1955. Part II, Pacific Slope Basins in California," U.S. Geological Survey, Water-Supply Paper 1395, 1958.
[6] "Reclamation: Managing Water in the West - Hydroelectric Power," U.S. Bureau of Reclamation, July 2005.
[7] "Electric Power Monthly, October 2025," U.S. Energy Information Administration, October 2025, Table 5.1 and Table 5.7.
[8] "Kings River Handbook," Kings River Conservation District, September 2009.