At an age when my classmates were fascinated with dinosaurs or playing cowboys and Indians, I picked up a book called “Engineers’ Dreams” and was hooked. Thus began a lifelong interest in projects associated with engineering concepts aimed at improving our world.
The author, Willy Ley, has outlined some major civil projects, including the development of the Channel Tunnel linking Britain and France. Of course, the tunnel has been in use for 28 years. He also explored ideas for generating electricity. With solar and wind power in mind, each of its generation projects has seen significant development since.
Given my interests, I was drawn to a recent letter in The Desert Sun proposing to solve the water shortage in the Southwest by bringing in water from the Mississippi River.
This is not the first proposal to find water for the South West. Such a project, carried out more than 50 years ago, would have brought water from Alaska and Canada to supply the Columbia, Missouri and Colorado river systems. In addition to international political and environmental considerations, the proposal was sunk by an expected return on investment of about 5 cents for every dollar invested. I was wondering if the Mississippi water program would perform better?
Also, how could I save the feasibility of this scheme against the author’s assertion that two benchmark projects – the California Aqueduct and the Alaska Pipeline – represented much more difficult projects than he imagined. Putting together some facts challenged this assumption.
The proposed flow rate of 250,000 gallons/second is a lot of water. Converting it to a more normal engineering unit, that would be about 32,000 cubic feet/second (CFS). This happens to be about the same flow that passes through the Hoover Dam’s generating turbines at full capacity. In the original letter, this flow was correctly calculated as the flow required to fill Lake Power in one year. Even at today’s record low, Lake Power is not empty. Lower flows could reduce the cost and difficulty of the project while providing significant benefits.
The Alaska pipeline is a major project. It involved the construction, under difficult conditions, of a pipeline 48 inches in diameter and about 800 miles long. Peak capacity throughput is 2 million barrels per day, or about 100 CFS. So, for comparison, pumping the proposed volume of water from the Mississippi would involve a distance about twice as long for a flow rate about 320 times greater.
The California Aqueduct involves a peak flow of 13,000 CFS over a distance of approximately 450 miles. As proposed, this Mississippi diversion project would involve 2.5 times as much water over a distance almost four times as long.
One of the great challenges of the California Aqueduct is pumping water 1,926 feet high, which requires massive pumping equipment. Our Mississippi diversion program has a net elevation difference of 3,700 feet between New Orleans and Lake Powell, a terminus almost twice as high as the highest point of the California Aqueduct. This last difference is particularly significant as the 1,926ft drop to near sea level could, in theory, be used to generate power to offset the pumping power required. This option is not fully available for pumping at 3,700 feet.
The maximum elevations required to pump water are likely well above the net difference of 3,700 feet. If we don’t take into account the higher altitudes the water has to be pumped to, we still have to provide the energy to raise the water to 3,700 feet. Using the Hoover Dam Power Plant as a benchmark, this would require about 12,000 megawatts of pumping power.
The flux power requirement would require at least the equivalent capacity of approximately 5½ times the power output of the new Plant Vogtle nuclear facility in Georgia. Plant Vogtle has been valued at over $28 billion. For example, our water pumping program could result in a cost of $150 billion for power plants alone.
“Wait and say, what about wind power instead of nuclear? Surely that would be cheaper. Yes, it would be, but there are, of course, challenges. not reliably generate electricity 24 hours a day, 365 days a year, so the installed wind capacity would be greater than the current capacity of the 150 wind farms in Texas.
As a nation, we have apparently lost our appetite for big projects. I don’t think this one will overcome that reluctance.
John Homer is a retired professional engineer who works as a consultant on construction projects. He lives near Indianapolis and can be reached at [email protected]