To store the energy contained in 1 gallon of gasoline requires over 55,000 gallons to be pumped up 726 feet (CCST 2012).
As a thought experiment look at what it would take generate all of America’s 4,058 TWh electricity, where Power = height of dam * cubic feet/second (cfs) water * turbine efficiency (~60 to 90%) / 11.8 (converts feet and second units into kilowatts).
Given that the 550-foot high Grand Coulee dam produces an average of 18 TWh a year with 50,000 cfs, at 90% efficiency, we’d need 225 more of them, using a grand of 58.4 billion cubic yards of water flowing through each dam, equal to 110 Lake Michigan’s, the world’s 6th largest fresh water lake.
You’d also have a hard time finding enough cement. The Grand Coulee used 11,975,500 cubic yards of concrete, so 225 would need 4 billion tons (2.7 billion cubic yards * 1.5 tons/cubic yard). Cement is 10 to 20% of concrete, so you’d need 3 to 6 times more cement than what America produces every year (USGS).
Using hydroelectric power to balance intermittent energy has many problems on downriver ecosystems, stranding fish in pools, and harming other aquatic life. In California, hydro units also have very limited amount of water available in the fall and winter months, so they are not available as a regulation resource during a number of months (CEC).
Adding more hydropower or pumped hydro storage is difficult because “”it requires two proximal large reservoirs with a sufficient amount of water surface and pressure elevation between them. Suitable geologic formations are rare and tend to be found in remote off-grid locations, such as mountains, where construction is difficult or restricted (SMUD AB2514).
CEC. June 2010. Research evaluation of wind generation, solar generation, and storage impact on the California Grid. Prepared by KEMA, Inc for the California Energy Commission.
CCST. April 2012. California’s Energy Future: Electricity from Renewable Energy and Fossil Fuels with Carbon Capture and Sequestration. California Council on Science and Technology. (height of Hoover Dam)
USGS. 2011. Cement production. United States Geological Society. 127,200,000 long tons converted to 142,464,000 short tons (2,000 lbs)