It is not uncommon for the extraordinary to quickly become the ordinary. Consider cell phones, tablet computers (or just computers in general), hybrid cars, heart transplants, drone aircraft, digital cameras, Amazon.com, Facebook…the list is long and varied. Most of these are considered “ordinary” by today’s standards, but each was little more than an idea in someone’s brain a decade or two ago, and all were considered extraordinary when they debuted. What was cool and unusual yesterday is commonplace today. But even something that might become commonplace can remain extraordinary if we only see it once in a while. My recent weekend excursion is a perfect example…
I live in a medium-sized city on the Eastern edge of the Pacific Northwest in the United States. My wife was born and raised here, so she is well-acquainted with the local sites, sounds, and events. I’m a transplant, but have lived in the area for almost 15 years — nearly a native resident by some standards. Three large reservoirs, one flowing into another in a canyon above our city, store drinking and irrigation water. The Army Corp of Engineers, along with other federal and local water officials, manages the reservoirs. Spring is a particularly busy time for them as they regulate reservoir levels with runoff from melting snow packs and spring rains. It’s not an exact science, but the result is, in select years, an extraordinary spectacle — the Rooster Tail.
The Rooster Tail is, in short, a method for releasing water from the lower of the three reservoirs to reduce erosion in the river bed below the dam (its main purpose) while simultaneously putting on a spectacular and extraordinary show. Released water, under natural pressure from deep in the reservoir, is gravity fed through a 6 foot diameter outlet. Rather than letting the water fall naturally into the riverbed, the outlet diverts the water into a high arc that spreads the water over a large area and resembles…you guessed it… a rooster’s tail.
As we watched the Rooster Tail from across the river, my mother in-law asked if I was, perhaps, looking at the arc of water through my “engineering filter”. She was spot-on. I was indeed watching the Rooster Tail and wondering about all of the details that made it work: size of the outlet, location of the inlet at the base of the dam, diameter of the inlet versus that of the outlet, volume of water exiting the outlet, amount of pressure pushing the water from the base of the dam, etc. Accounting for lots of variables, and making lots of engineering calculations and decisions, went into a process that at a high level is really as simple as “open the valve and let the water out”. And that is what engineers do when we practice our engineering art. Our goal is often to abstract the operation of a complex system up to the “open the valve and let the water out” level, thereby hiding the myriad details of system operation from the user. Sometimes we can make our calculations and decisions using pencil, paper, and a decent scientific calculator. But many times system questions and calculations are too complex to analyze at a pencil and paper level – that’s where multi-physics modeling and simulation shine. With a capable modeling language and robust number-crunching simulator, it’s amazing what a simulation can tell you about your system — all from the comfort of your office.
There are a bunch of engineering details about the Rooster Tail that I don’t know. But thanks to a brief information sheet handed out by the Army Corp of Engineers, I know that water leaves the outlet at a rate between 11,250 and 18,750 US gallons per minute (GPM). If you’re not a hydrologist, these figures may not mean a lot to you, so think of it in another way. The Summer Olympics held in London are coming up fast on the world’s calendar. If you’re a fan of swimming competitions (and even if you’re not) take a minute to notice the size of the pool where the main swimming events are held. The typical Olympic pool holds around 660,000 US gallons of water. At 11,250 GPM, the Rooster Tail can drain an Olympic pool in just under a minute – barely enough time for the 100 meter male and female freestyle world record holders to complete the race (disregard the minimum water depth required for swimming). Crank the Rooster Tail up to its upper limit of 18,750 GPM, and the pool is drained dry in less than 36 seconds – just long enough for the 50 meter freestyle world record holders to show their stuff. The Rooster Tail moves an impressive of water in a very short time.