3 Gorges Dam Update – 27th July 2020

Dam capacity is at 8% prior to the start of the flood season. Outflows are limited to 40,000 m3/s and water level last seen at 162m. The design limit is 175m and the dam overflows at 185m. And a quip about keeping time.

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Dam design capacity is at 8% prior to start of flood season.

This is the 3 Gorges Dam update for 27th July 2020 by The Rembau Times.

You can find out the latest most up to date reading from http://3gd.mooo.com  , including live footage of the 3 Gorges Dam.

Capacity in 2018

We want to first start by looking at the capacity of the dam in a normal year – say 2018. Prior to the start of the flood season proper, which is at the end of July, the dam operators have managed to lower the water level to about 150m in anticipation of the incoming seasonal floods called the Plum rains. Design capacity is the measured as the

1 – Water Level/ Design Capacity in m, 175m  

In 2020, prior to the start of the August month, the dam only has half of the remaining design capacity remaining or 8%. The inflows recorded over the past several days were in the order of 60,000 m3/s. The remaining capacity started last week at the dangerously low level of 6% but managed to gain a bit back to 9% over the next several days as the outflows of 40,000 m3/s was higher than the peak inflows of about 37,000 m3/s. However all that changed on the 26th and the 27th when the peak inflows started to hit 60,000 m3/s, with the average inflows hitting 40,000 m3/s.

The key point to note is that at this point in theory, the dam should be doing everything it can to discharge all the water to avoid overflowing. The 3 Gorges dam spillway capacity is at 116,000 m3/s so if they wanted to do reduce the water level dramatically, they can do so by opening the spillway.

However opening the spillway comes with 2 costs.

The first cost is to cause a widespread flooding in Wuhan.

The second cost is that with that much of water discharged, cavitation damage is a real threat as had happened in the Glen Canyon dam.  Cavitation is the process whereby water “boils” to become water vapour due to low pressure and then explodes violently as it escapes the low pressure zone and reaches normal pressure. As the water bubbles explode, they send pressure shock waves which can destroy concrete and bend steel rebar.  In the Glen Canyon incident in the early 1980s, the damage was of the order of thousands of cubic feet of concrete per minute!

That is perhaps why the water discharge level at the 3 Gorges Dam is now rate limited at 40,000 m3/s.

Other matters: Rembau Standard Time

Readers may have noticed that sometimes we use the term “Rembau Standard Time” in our reporting. This will probably lead us into a 5 min discussion on how computers store time.

In our earlier days, we once encountered a really horrible thing. A programmer had decided to store timestamp information as text e.g. “28th July 2020: 09:49 AM” in a database (Microsoft SQL) when designing a particular system. Yes, it was a Windows based program.

Actually, UNIX has a really nice way of representing dates and times using the timestamp concept. A timestamp is a really long number, e.g. 1595102446 represents the date 18-Jul-2020 20:00.

Of course there is a catch here. 18th July by whose definition? Is it 18th July in Qingdao China or Quebec, Canada? Is it 20:00 in Balochistan, Pakistan or Burgundy, France.

Python has a really nice way to fix this last ambiguity, a parameter called _tzinfo. You can specify this last parameter, by specifying the tzinfo parameter as being anything from Africa/El_Aaiun to Brazil/Acre.

Thanks to Evan Sikorsky, we get a nice picture of all timestamps available.

World Timezone segmentation By Evan Siroky – https://github.com/evansiroky/timezone-boundary-builder, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=58166594

What can I say, it was probably late at night in the early 1990s and I was tired … so I invented GST (Gulf Standard Time)

Paul Eggert, computer scientist

Computer scientist, Mr. Paul Eggert is literally keeping time on our behalf. He is the inventor of Gulf Standard Time, of which some Gulf Countries are unhappy about

 

It is our intention that Rembau Standard Time be recognised as a bonafide option within the world timezone database, currently maintained by Mr. Paul Eggert. While we respect and thank Mr. Eggert for his tireless work in keeping time on our behalf, we must protest that an area as politically important as Rembau, should be given its own timezone.

 


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1 COMMENT

  1. My 20 year struggle with dates finally ends today. Python is really fantastic, takes care of converting between time zones, day light savings time, holding precision until fractional second. Example in the data feed we have the name : UTC + 8:00. Used to look at it and say ‘er…what..’ Not any more.
    Enjoy the prawns.

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