You stand at the base of the dam and the dam is the largest thing you have ever stood next to. The dam is a wall across a river and the wall across a river is the most audacious act of construction because the wall says to the river you will stop here. The river does not want to stop. The river has never stopped. The river has been flowing since before there were people and the before there were people is the river's seniority and the river's seniority does not matter to the dam. The dam says stop. The river stops. The water backs up. The lake forms. The lake is not a lake. The lake is a reservoir and the reservoir is the dam's product and the dam's product is stored energy waiting to fall.

The Hoover Dam holds back the Colorado River and the holding back the Colorado is the bet that the desert can be a city. The dam was built during the Depression and the building during the Depression meant the dam was a jobs program and the jobs program killed ninety six workers and the killing of ninety six workers built a wall seven hundred and twenty six feet tall in Black Canyon between Nevada and Arizona. The concrete in the Hoover Dam is still curing. The concrete was poured in blocks and the blocks were cooled with refrigeration pipes because the concrete generates heat as it cures and the heat would have taken one hundred and twenty five years to dissipate without the cooling. The Hoover Dam made Las Vegas possible. The dam made Phoenix possible. The dam made Los Angeles possible. The dam took a river that ran through the desert and turned it into electricity and irrigation and swimming pools and the turning a desert river into swimming pools is the American twentieth century in one sentence.

The Three Gorges Dam in China displaced one point three million people and the displacing one point three million people is the cost of electricity for sixty million. The dam is the largest power station in the world and the largest power station in the world sits across the Yangtze River and the Yangtze is the third longest river in the world and the putting a dam across the third longest river in the world is the scale of ambition that only a government with absolute power can execute. Thirteen cities were submerged. One thousand six hundred factories were drowned. The Three Gorges Dam drowned history. The Yangtze gorges that inspired a thousand years of Chinese painting are underwater and the underwater paintings are the cultural cost that does not appear on any balance sheet. The dam generates twenty two thousand five hundred megawatts. The dam cost twenty eight billion dollars. The dam is the arithmetic of sacrifice.

The Johnstown Flood of eighteen eighty nine killed two thousand two hundred and nine people because a dam failed. The South Fork Dam above Johnstown Pennsylvania was owned by a hunting and fishing club whose members included Andrew Carnegie and Henry Clay Frick and the club did not maintain the dam and the not maintaining the dam killed a town. The dam broke after heavy rain and twenty million tons of water hit Johnstown in ten minutes and the ten minutes killed more Americans than any other single event until the Galveston hurricane. The Johnstown Flood is the proof that a dam is a promise and the promise is that the wall will hold and the wall holding is the difference between a reservoir and a catastrophe. The distance between a lake and a flood is the thickness of a dam wall.

You drive across the dam and the driving across the dam means you are driving on top of the wall that holds back the water and the water on one side is higher than the road and the road being lower than the water is the vertigo. You look over the edge and the edge drops seven hundred feet and the seven hundred feet of drop is the energy. The water wants to fall. The dam will not let the water fall except through the turbines and the falling through the turbines is the conversion and the conversion is kinetic energy becoming electrical energy and the electrical energy becoming light in a city a hundred miles away. The dam. The wall that makes electricity from gravity. The wall that makes cities from rivers. The wall that bets against the water and the water waits. The water is patient. The water has been patient for longer than the dam has existed. The dam will fail eventually. Every dam fails eventually. The river will win. The river always wins. But not today. Today the dam holds.