The Don Pedro Dam, since 1971 also known as the Old Don Pedro Dam, was a dam across the Tuolumne River in Tuolumne County, California. The structure still exists and is flooded underneath Don Pedro Reservoir, which is formed by the New Don Pedro Dam.

Don Pedro Dam
Old Don Pedro Dam and reservoir, circa 1925
Official name	Old Don Pedro Dam
Location	Tuolumne County, California
Coordinates	37.7125°N 120.4020°W / 37.7125; -120.4020
Opening date	1924; 98 years ago (1924)
Dam and spillways
Type of dam	Concrete thick arch/gravity
Impounds	Tuolumne River
Height	283 ft (86 m)
Length	1,000 ft (300 m)
Width (crest)	16 ft (4.9 m)
Width (base)	170 ft (52 m)
Reservoir
Creates	Don Pedro Reservoir
Total capacity	290,400 acre⋅ft (358,200,000 m3)
Power Station
Turbines	4
Installed capacity	30 MW

Construction

It was a solid concrete gravity dam that was 283 ft (86 m) high, 1,000 ft (300 m) wide, 16 ft (4.9 m) thick at the crest, and 170 ft (52 m) thick at the base. It was completed in 1923 where the Tuolumne River had carved a narrow gorge with walls of solid rock about a mile (2 km) below Don Pedro Bar. The reservoir created by this dam contained 290,400 acre⋅ft (358,200,000 m³) of water when full, 14.3% of today's capacity.

A 15 megawatt power plant was part of the dam's original design, and two more 7500 kilowatt generators were added in 1926 for 30 megawatts total, just 15% of today's capacity. The old dam still exists about 1.5 mi (2.4 km) upstream from the new 1971 dam, and since the old dam topped out at just 580 ft (180 m) above sea level it is now under some 250 ft (76 m) of water when the new reservoir is full.

References

• Dwight H. Barnes. "Chapter 12: The First Don Pedro". The Greening of Paradise Valley, The First 100 Years of the Modesto Irrigation District. Modesto Irrigation District. Retrieved November 7, 2010.
• Richard W. Amero (June 30, 2000). "Lessons from Hetch Hetchy". Retrieved November 7, 2010. {{cite journal}}: Cite journal requires |journal= (help)
• Sukhwant Virk; Josh Hinkey (August 31, 2007). "Don Pedro Dam: General Information". University of California, Davis. Archived from the original on June 10, 2010. Retrieved November 7, 2010.
• Department of Water Resources (2009). "Station Meta Data: Don Pedro Reservoir (DNP)". California Data Exchange Center. State of California. Retrieved November 7, 2010.

External links

• Turlock Irrigation District
• Modesto Irrigation District
• USGS Hydrologic Data