Imagining water

Bill Maher’s Real Time show this weekend was good, and featured, among others, the brilliant George Will. I’ve always been a fan of Will, even though his politics are a bit right of mine. What I appreciate is his intellect and his objectivity. When he has an opinion, he can explain it in perfect logic – something I aspire to. And on this show, from vaccinations to wokeness to economics, I tended to agree with Will.

But the thing that really struck me about the show was the “New Rules” segment, which concluded with a diatribe about the two Americas. Not the division in politics, but the division in water. Maher showed a graphic of the continental US, in which the left half of the country is a parched wasteland and the right half a flooded mess. A bit overstated, but basically true.

It struck me how much that graphic looks exactly like a picture of the Big Island of HI. The western half of the island is very dry and the eastern half is very wet. And that’s increasingly what our evolving climate is doing to the United States – the 70 million-ish people west of the Rockies are living in an area with less and less rainfall, no sustainable access to drinking water, aquifers and reservoirs drying up, and the 260 million-ish people east of the Rockies are drowning.

Thinking like an engineer (here’s a problem, what’s the solution?), are we going to move 70 million people to the water or are we going to move water to the people? Maher maintains that moving water from the east to the west is entirely feasible, a no-brainer given that we move oil thousands of miles in pipelines.

But is it? The first thing that I thought of is scale – that’s a LOT of water we’re talking about. Ignoring agriculture and industry, we would need about 100 gallons of water per person per day. That’s 7 billion gallons piped in every day.

And we shouldn’t ignore agriculture, because agriculture is 80% of total water use in California. If 7 billion gallons = 20%, then the total need is 35 billion gallons per day. Let’s round that up to 40 billion gallons to account for the non-CA agricultural needs.

Now…is that feasible? Doing some rough math, it turns out that the CO river, one of CA’s main water sources today, provides about 14 billion gallons of water per day to the west. So we would need about three more CO river-sized new sources of water from the east to the west. And because we have to traverse mountains (notably the Rockies), the water will need to be pumped (gravity is not our friend here) and very likely contained in pipes (to facilitate pumping under pressure).

These will be some big-ass pipes and the power needed to pump the water is…gigantic. Using this as my conversion / equation source, the power needed to pump 25 billion gallons over the Rockies (through passes averaging about 6,000 feet) is about 700 GWh, assuming 70% efficiency in the overall pumping system.

The largest solar farms on Earth today generate about 2 GW of energy continuously and require about 50 square kilometers, so we would need 350 of these to power our new water source. That’s 17,500 sq. km of new solar farms, about the size of the state of New Jersey (excluding water).

That’s actually smaller than I would have thought, and PV efficiency keeps increasing, so that might not be a limiting factor. There’s a LOT of empty land west of the Rockies.

The size and number of pipes needed for the new water source are also a scale problem. A hypothetical 10-foot diameter water pipe can transport about 90,000 gallons of water per minute or 130 million gallons per day, and our daily need for 25B gallons (in addition to the existing CO river) means we would need 192 of our hypothetical 10-foot diameter pipes. That’s 192 new very large pipelines running from the wet eastern US to the dry western US. I suppose it’s doable, but it’s a bigger project than anything we’ve ever done (384K miles of pipeline), including the entire interstate highway system (47K miles of highway). Sounds pretty expensive.

Using this as a rough estimator, the cost of our 192 hypothetical 10-foot diameter pipelines, running 2000 miles each, would be $4 trillion – a big number, but not really a limiting factor. We’re talking about spending that kind of money in today’s US budgets.

The point of all this is to try to decide if Maher’s assertion that building pipelines to supply water to the west is actually feasible. My conclusion is that yes, it is. Even if my estimates are off by a factor of 2 (100%), it’s doable.

But that doesn’t mean that we should dive in and start building. First we’d want to do a few other things and attack the demand side of the equation, like:

  • Change the way our toilets work, as that is the single largest per person use of water in the US
  • Invest in desal plants on the west coast – desal combined with small nukes or PV (to power the pumps) makes a lot of sense
  • Stop growing stupid crops in a desert, like rice, hay and almonds – move that production east, to where the water actually falls from the sky

After working through this, I’m encouraged. We can make the western US a great place to live again if we invest in some VERY large engineering / terraforming projects. That’s certainly a better use of tax dollars than the Forever War. And the projects sound like fun.