The Aquifer Is Not a River

The tap in a guesthouse in Dakhla runs warm and slightly sulphurous — the water comes up out of the ground at something close to bath temperature — and there is no river within two hundred kilometres of it. Kharga, the next oasis east, records well under a millimetre of rain in an average year — some years none measurable at all. Everything green in this part of Egypt, every date palm and rice paddy and alfalfa field, is standing on water that is pumped up out of sandstone, and that water fell out of the sky a very long time before it was needed.

The formation is called the Nubian Sandstone Aquifer System and it is the largest known store of fossil groundwater on earth: something in the order of two million square kilometres of saturated rock under Egypt, Libya, Sudan and Chad, holding a volume usually estimated at around 150,000 cubic kilometres. Isotope dating puts most of what has been sampled at tens of thousands of years old, and some of it a great deal older. It is, in the strict sense, not a renewable resource. It is a deposit.

Rain that stopped falling

The Sahara has been green more than once. Orbital wobbles shift the monsoon north on a cycle of roughly twenty thousand years, and during the wet phases the desert carried lakes, rivers, cattle herders and the rock art that expeditions still go to the Gilf Kebir to photograph — hippopotamus, giraffe, and at Wadi Sura the figures that look like swimmers. The most recent of those green phases ended around five thousand years ago, which is to say around the time the Old Kingdom was building at Saqqara. The water that soaked into the sandstone during the wet millennia is still down there. Almost nothing has gone in since.

The New Valley

Egypt has understood the arithmetic of its own population for a century: almost everyone lives on a few per cent of the land, in a strip along the Nile, and every scheme since Nasser has tried to move some of them off it. The New Valley Governorate was created in 1958 for exactly that purpose — it is the largest of Egypt's governorates, covering well over a third of the country, with perhaps a quarter of a million people in it. The plan was to drill into the aquifer, irrigate the depressions and relocate farming families out of the crowded valley. Wells went down, land was reclaimed, villages with grid-plan streets were built at Kharga and Dakhla, and the sums never worked. The land is thin, the summers are lethal, the market is a day's drive away, and a great many of the families who were moved out went home.

What did happen is that the pressure dropped. The oases were famous for artesian springs that ran on their own head of water — the Persians and the Romans tapped them, and Kharga still has underground aqueducts, the qanats at Ain Manawir, cut in the fifth century BC. Modern extraction has taken the head out of them. Wells that once flowed unaided now need pumps, the new boreholes go down a kilometre and more, and the ones drilled in the 1960s have had to be deepened since. None of this is disputed. The Egyptian ministry publishes the figures.

A river can be over-drawn and recover in a wet year. An aquifer that last filled in the Pleistocene has no wet year coming.

Siwa has the opposite problem

Five hundred kilometres northwest of Dakhla, Siwa is drowning in the same water. The oasis sits in a closed depression about eighteen metres below sea level with no outlet of any kind: what comes up out of its two hundred-odd springs, and what runs off its fields, has nowhere to go except the salt lakes on the basin floor. As irrigation expanded, those lakes grew and the water table under the palm groves rose with them. Salt came up into the root zone. Egypt grows more dates than any other country and Siwa is one of the places it grows them, so the loss of grove land to salinity is not a curiosity — it is the local economy. Drainage channels and evaporation ponds have been dug to move the problem around, and salt is now extracted commercially from the lakes, which is the sort of solution you arrive at when the alternative is no solution at all.

One tank, four taps

The aquifer does not stop at borders and nobody has agreed how to divide it. Libya broke ground on the same formation in 1984 and has been drawing from it since 1991, when the first water of the Great Man-Made River reached Benghazi — a network of buried concrete pipe carrying fossil water hundreds of kilometres north to the coast, and at the time of building described as the largest irrigation project in the world. Egypt, Libya, Sudan and Chad set up a joint authority for the aquifer — Egypt and Libya in 1992, Sudan joining in 1996 and Chad in 1999 — and in 2013 the four signed a strategic action programme covering monitoring and the sharing of data. It commits them to talk to each other about the numbers. It does not allocate a single cubic metre.

What a visitor actually sees

Very little of this is dramatic on the ground. You see alfalfa in a place with no rain, a spring on a tourist map that turns out to be a concrete tank with a pipe in it, irrigation stopping at a hard edge in the sand where the water and the diesel ran out. The clearest thing on the route is a building. Hibis temple at Kharga went up mostly under Darius I and is the most complete Persian-period temple standing anywhere, and in the twentieth century its stone began to crumble — salt crystallising inside it, drawn up out of a water table that irrigation on the reclamation around it had raised. There was a serious proposal to take the temple apart and move it somewhere drier; in the end the ground was drained instead and the temple stayed. It is worth the trip for the reliefs. It is also the one place on this route where the whole argument is legible at once: a monument put up by an empire that knew exactly how much water this depression had, being dissolved from below by one that decided there was more.