Hot & thirsty: the struggle to supply Hong Kong with drinking water

After an unusually hot month of May, I've been thinking about Hong Kong's drinking water. I've never had to worry about water rationing, so I take it for granted there's water in the tap. That's only a recent luxury though, as Hong Kong struggled for many years to provide its residents with enough drinking water. I'm sure many readers will remember scenes like this.

Catching the rain

Hong Kong doesn't have any large rivers or natural lakes it can rely on for fresh water, so early residents relied on gathering rainwater from local streams then later from wells. The next development was to build reservoirs to catch more of the rain before it ran to the sea, and store it until it was needed.

Here's a look at how Hong Kong's reservoir capacity grew over the years [1]:

That's impressive, but of course the population [2] was growing at the same time. To see if the reservoirs kept up, let's see how much water storage capacity there was per person.

Those figures are better than I expected. I thought we'd see much greater drops in the numbers along the way, but they stayed fairly steady from the 1920s to the 1960s then jump up in the 70s and 80s when the Plover Cove and High Island reservoirs were completed.

What do the numbers mean?

Or, what's a cubic metre of water like?

It's not very big - it would fit under your dinner table. It is heavy though, as it weighs 1,000Kg which is a metric ton.

If you're going to drink it, it's the same amount of water as 1,000 one-litre bottles. So looking at 1980, when there were 113.8 cubic metres of water storage per person, that means 113,800 litres of water per person. If you had that much water to use over a year, that would be around 300 litres a day.

Here's how the other years' figures translate into daily amounts of water.

How much is enough?

That 1980 figure sounds like a lot of water. Imagine opening the door each morning and finding that Park & Shop had delivered 300 litre bottles of water to your door. Would we use it all by the end of the day?

A WHO publication on how much water is needed in emergencies [3] estimates 15-20 litres per person per day is needed in a refugee camp. That covers basic drinking, cooking and hygiene. The table above shows Hong Kong was still struggling to meet that number into the 1910s, showing just how limited the water supply was initially.

Once you move on from those very basic requirements, the amount of water used tends to rise as a country becomes richer. People move from a daily wash with a cloth and bucket to two showers a day. Or a new washing machine means a daily clothes wash, instead of the old weekly trip to the nearest stream.

Wash Day in the NT - 1953/54, by harryhktc

Another way to understand the figures is to compare them with the daily average consumption for a range of modern countries [4].

1. Our figures for Hong Kong in the 1920s-60s show around 40-50 litres per day. That's what someone living in Kenya or Bangladesh uses today.
    
2. In 1970 it jumped to 169 litres per day, similar to a modern-day usage in Peru or the Philippines.
    
3. Finally, the peak figure of 312 litres a day in 1980 is close to the daily usage in Norway or Spain today.

It seems like a 1980 Hong Konger shouldn't have used more water than a 2018 Spaniard, so why was there still water rationing into the 1980s?

Unfortunately there are several reasons why that reservoir capacity of 312 litres a day doesn't mean there were 312 litres a day flowing out of the taps.

1) Just because you build it, doesn't mean you'll fill it

Looking at the last ten years [5], around 260 million m³ of rainwater flowed into the reservoirs each year, or roughly half the capacity of our reservoirs. So instead of holding enough water to give you 312 litres a day, you could only plan to receive 156 litres a day.

2) Changeable weather

Next, each year's rainfall is different. Over the last ten years [5], the wettest year was 2016, pouring 385 million m³ of water into our reservoirs. But in dry 2011 they only received 103 million m³. A dry year like that would have cut the 1980s daily water allowance down to 62 litres a day.

3) Water isn't just for drinking

Hong Kong's industries also need water.

In the early years, companies were expected to take care of finding their own water. The Aberdeen Paper Mill needed plenty of water, and was built near a valley where they could build their own reservoirs. Over on the north side of the island the Taikoo sugar refinery, and later the Taikoo dockyard, both relied on a series of reservoirs they'd built on the surrounding hillsides to provide their water. You can see one of their reservoirs in this photo at the refinery from above - the reservoir is the light-coloured area near the centre of the photo.

Mt Parker Cable Car from top, by Admin

But by the 1980s those had all closed, and Hong Kong's industry relied on the public water supplies.

I haven't found figures showing how the water usage was split in 1980, but in 2003, domestic users consumed just over half of the drinking water [6]. So if we halve our dry 1980s year again, we're down to 30 litres a day per person, and it isn't hard to see why rationing was needed.

Why did rationing go away?

Hong Kong's population has increased by about half since 1980, and our per-capita water consumption has increased even faster, so why haven't we needed water rationing during the last thirty years?

Two saviours: The Dong river, and the Hong Kong toilet

In 2017/18, Hong Kong used a total of 1,269 cubic metres of water [8], supplied from from the following four sources.

Items 3 & 4 are the two big changes that let us avoid water rationing:

• Large, additional supplies of fresh water are delivered to Hong Kong by pipeline from the Dong river in Guangdong.
• We stretch our limited supply of drinking water by using sea water instead of fresh water to flush Hong Kong's toilets.

There were lots of numbers to wade through in this week's newsletter, so thank you if you've read this far. Are there any photos or memories of Hong Kong's water supplies that you can share with us in the comments below?

For my contribution, here's a letter from the new Hilton Hotel to a guest in July 1963. It proudly lets them know the Hilton had a supply of water from its own well, so guests could take a shower each day and avoid the once-in-four-days water rationing that the rest of the city faced.

References:

1. Reservoir capacities were calculated from the Chronology in the book Water for a Barren Rock, by Ho Pui Yin
2. Population figures come from The Population of Hong Kong and Wikipedia's Population of Hong Kong by year. I've used the closest year available, eg the figures from the 1901 census for 1900.
3. World Health Organisation: How much water is needed in emergencies
4. Average water use per day for countries around the world
5. Local Yield: https://www.wsd.gov.hk/en/core-businesses/total-water-management-strateg... 
6. An overview of water supplies in Hong Kong
7. HK Government book: Hong Kong 1981, a review of 1980
8. Hong Kong: The Facts - Water Supplies