Pump up the jam, pump it up?

I am as of late fascinated with the concept of pumped hydro power stations. It’s a ridiculously simple concept. You put a big artificial lake on top of a hill and use off-peak or excess power to pump water up the hill. Then during peak times you run water back down the hill to feed hydroelectric generators.

Pumped hydro solves a lot of the issues inherent in “green” energy like wind and solar, namely that they suck for base load. But if you have a bunch of wind farms and solar installations in West Texas, and then you have cisterns on top of the mesas (you need a closed loop since it’s so dry out there), you can potentially use the system as a whole for base load. Which is crazy.

But it gets me to thinking about Addicks and Barker reservoirs. Those dams aren’t doing so great. The Corps doesn’t let them get full anymore because of the risk of failure. Back in the old days – when they were built – the idea was that we were going to concrete and straighten all the Bayous which would get more water to the sea, faster. In practice that sort of thinking turned out to be back asswards; straighter bayous just backed up that much faster, and modern hydrology is all about adding meanders and benches and various other places for water to stack up.

But what if you just piped that stuff?

You could run a pressurized storm pipe from Addicks and Barker south, and either outfall it to the Brazos, or else run it all the way out to Chocolate Bay – that way you wouldn’t just be relocating the flood to Lake Jackson. Basically like a freeway bypass. Maybe call it the Grand Floodway, or something.

4 thoughts on “Pump up the jam, pump it up?”

  1. If you are proposing piping the water as a supplement to Addicks and Barker Reservoirs, you would probably need to handle about 2500 cfs in that pipe in case of a flood. Peak record flow at Buffalo Bayou at W Belt is about 5000 cfs; peak flow with Addicks, Barker in place at Buffalo Bayou in downtown is about 10000 cfs. So you wouldn’t need to handle the whole flow of course, but enough to provide relief to downstream areas. At a maximum of 20 ft/s, you’d need a pipe 12.6 feet in (inside) diameter. That’s a pretty big pipe! And you’d of course have to worry about erosion corrosion due to all of the sand and grit in the floodwater. This would not only reduce the lifetime of pipe (if you had to use it several times per year, for instance), but decrease its capacity since a rougher surface would increase friction losses. Remember that other liquids which are transported long distances by pipeline have very little sediment. I think the cost to build a pipeline with a minimum 30 ft ROW for 20 miles would be very, very high.

    But if you’re proposing it as an alternative to the reservoirs, you would need much more capacity. The record flow for Buffalo Bayou at downtown was from the 1930s, and it was 40000 cfs, before urbanization (and before the reservoirs). This could easily be higher today without the benefit of the reservoirs.

    I like your idea about the cisterns though. It’s low tech, the technology is available today (compared to the batteries they propose for these windfarms), and doesn’t generate toxic waste, like most battery-based solutions would generate.

  2. I hadn’t considered the scouring effect of sediments in a pressurized environment. Over a long distance (say, Barker to Chocolate Bay), it would be interesting to compare the cost of a traditional gravity pipe with periodic lift stations versus a pressure pipe with some kind of prefiltration to remove most of the suspended solids.

    As far as sizing, I would think you’d set it up for relatively continuous operation, primarily to drain the reservoir faster during routine events. Hence you always have full capacity when the 2-year or the 5-year storm shows up. Your 2500 cfs pipe carries more than the base discharge rate (2000 cfs). A 60″ pipe (using your velocity assumption) would carry 390cfs, which is still a 20% increase. A bank of three gets you 1175.

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