Moving Water and Earth

Long after the downtown mills have disappeared, the St. Anthony Falls Laboratory remains a thriving concern, a solid, homely building recently adorned with bright banners to announce its presence to the public. The new director, in a reversal of Straub’s expatriate thirst for knowledge of fluid mechanics, arrived from Greece via the University of Iowa and Georgia Tech. “I received congratulatory emails from colleagues all over the world—New Zealand, Australia, Japan, Europe—when I announced that I would take the job here,” said Fotis Sotiropoulos, who accepted the directorship last year. He likes to point out that the lab’s reputation in the international scientific community stands in stark contrast to its anonymity here in the Twin Cities.

Besides building grand models exploring how rivers could be mastered and contained with locks and dams, the lab has been long involved in such pedestrian pursuits as standardization; staff measure, for instance, the rate of flow through a specific culvert design—not exactly the sort of work that seizes the imagination. But recently the lab’s scope has broadened to consider questions of sustainability. One of Sotiropoulos’ interests—exploring new ways to create electricity from tidal power—is an example. He envisions “windmills under water” moored at the bottom of New York’s East River, which could help make the city the world’s first green-powered metropolis. It’s a long hope, to energize this most profligate country’s largest city with the power of nature, but the thought of exporting engineering expertise generated by the Falls of St. Anthony—a brilliant post-industrial use of flow—would have greatly pleased the man who was the first and longest custodian of that power source.

 

Hydroelectricity was not on the mind of William De La Barre when he arrived in Minneapolis in the late 1870s, though the first hydroelectric plant in the country opened here a few years later. De La Barre was dispatched to the Mill City as an air-filtration salesman after the massive explosion of a flour mill owned by Cadwallader Washburn triggered a chain reaction that leveled most of the city’s milling capacity. Impressed by the enterprising young Austrian immigrant, Washburn engaged him to help rebuild and improve his enterprise. De La Barre could not have lucked into a better patron than Washburn, who would eventually control the rights to nearly every ounce of flow that passed over the falls.

Water power has two components: flow and head. The Mississippi’s flow is high when spring snowmelt swells the river, and generally dwindles toward an annual nadir in the early months of winter; production of flour and lumber in Minneapolis, fueled by flow, would slow correspondingly. But De La Barre spotted an obvious means of improvement: The mills were underutilizing head, the distance that the water falls before moving turbines. If Father Hennepin, first beholding the falls, was contemplating the vertical distance from the point where water first spilled over the limestone ledge to the relative calm after the river resolved its way through the field of boulders below, his seemingly exaggerated fifty-foot estimate was spot-on. De La Barre persuaded Washburn to redesign the canal that brought the river to his mills, and each turbine was set deeper into the underlying sandstone; new tailraces (the channels that bring diverted water back to the river) also relocated the outflow farther downstream. The result: The power supply to the Minneapolis mills was ingeniously doubled, and the milling season was extended.

De La Barre worked vigorously well into his eighties, and his tenure as the city’s water czar lasted until the 1930s. Convinced that “only eternal vigilance would keep the falls in existence,” he countered the competition from coal-generated steam power, which had begun to satisfy a growing municipal demand for electricity and allowed the mills to wean themselves from the mechanical power of the river. De La Barre successfully advocated for a series of headwaters reservoirs—Leech, Winnebigoshish, and Pokegama—that would store water to mitigate the river’s seasonal impotence, and this adaptation converted the falls into a steady source of hydroelectric power. The turbines of St. Anthony Falls, once used to pulverize wheat and saw logs into lumber, now spawned electricity giant Northern States Power, today’s Xcel Energy.

 

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