Many people consider the well of Zam-Zam to be a miracle. As you know the story, I won’t repeat it here, but it popped out of nowhere just for Hajar and her son who were starving in the desert left alone by Ibrahim. “Musa” wrote on my blog:

How can you explain the zam zam well that feeds millions of people everyday and was even scentifically tested by western scientists? Over 5,000 years the well hasnt dried up, zam zam well is a miracle indeed.

The reality is that there is nothing special about this well. It’s simply monitored carefully so that it doesn’t dry up.

If it truly was unlimited, why doesn’t Saudi use it to convert their desert into an oasis?

Zamzam Studies and Research Center (ZSRC) in Saudi Arabia explains quite clearly that they carefully monitor the water levels and only allow as much as can safely be taken so that the well does not dry up. Not only that, it’s refilled by rainfall.

A threshold water level in the well is maintained. If the water level goes below this level the pumping is stopped, water level is allowed to recover, and then pumping is resumed. The annual discharge from the well is restricted to around 500,000 m3. However, this limit can be modified if hydrological condition so permit. For example, due to last year ‘s high rainfall the augmented aquifer recharge allowed proposed production increase by about 92000 m3 for the year 1432 AH.

Source: Zamzam Studies and Research Centre

There you have it. The water levels are carefully monitored and refilled by rainfall. According to weather data published online, Rainfall in Riyadh is about 100mm per year. The surrounding areas also get similar amounts of rainfall. In California, the wettest areas get six times the rainfall as the drier areas. They transfer the water via aquaducts to support the farming industry. As well, the article also states:

In order to manage demand water from Zamzam well is pumped, treated, and stored in underground storage tanks on a continual basis.

Is the water even good for you? There was a BBC study that raised some fears about the quality of zam-zam water:

In May 2011, a BBC London investigation found that water taken from taps connected to the Zamzam Well contained high levels of nitrate, potentially harmful bacteria, and arsenic at levels three times the legal limit in the UK, the same levels found in illegal water purchased in the UK. Arsenic is a carcinogen, raising concerns that any who regularly consume commercial Zamzam water in large quantities may be exposed to higher risks of cancer.

Source: Contaminated ‘Zam Zam’ holy water from Mecca sold in UK (BBC) CORRECTION this water was sold and tested in UK and we do not know if it’s actual zamzam or something else. Most likely zamzam water is tested and filtered carefully as the original article below states

There was a statue of Jesus in India that used to drip water from its feet. Pilgrims would go and collect the water and even drink it. So an author by the name of Sanal decided to look into it, he found out that the source was bad plumbing and ultimately a leaky toilet. Most of the time, these things can easily be explained if you just look into it. Don’t just take such claims as miracles until you really research them.

Original article in full archived here: Zamzam Studies and Research Centre (Saudi Arabia) – This article explains in detail how they monitor and maintain this supply.

Also,

The reason why Zam-Zam hasn’t dried up is because beneath Saudi Arabia is an ancient aquifer – glacial water from the last Ice Age trapped under the sand, thanks to quirks in its geology. This aquifer has made it possible for Saudi to become the world’s 6th biggest producer of wheat. It is possible that the Zam-Zam is fed by this aquifer, which some estimates put it as big as Lake Erie. But the aquifer water is being drawn down so fast that it is deying up: hence the controls on Zam-Zam. (What California can learn from Saudi Arabia’s water mystery)

In conclusion, there is nothing special about the zam-zam well any more than any other well in the world.