Thirsty: Dates

At sunset in Ramadan, across a belt of the world from Morocco to Pakistan, the first thing that passes a billion lips after a day without food or water is a date. It is the fruit of the desert, sweet enough to keep for a year without a fridge, dense enough to be a meal, and old enough to be in the oldest texts of the region; the palm it grows on has been cultivated in Mesopotamia and the Gulf for at least five thousand years and was, for most of that time, the tree that made life in the oases possible, with its fruit, its shade for the crops beneath it, its trunk for the roof beams and its fronds for the baskets. The paradox is in the botany. The date palm grows in the hottest and driest places on Earth and it is one of the thirstiest trees there is.

A kilogram of dates carries about 2,300 litres of water, and this article is about why more than half of it is irrigation, which is rare among crops, what a palm drinks on a summer day, how the oases managed for three thousand years and why the water under them is going, and what happened to the groves of Iraq.

A tree with its feet in water

There is an Arab saying that the date palm likes its head in the fire and its feet in water, and it is accurate. The tree wants a summer of forty degrees and no rain to ripen the fruit, which is why it grows in the Gulf, the Sahara and the valleys of Iran and not in the wet tropics, and it wants a constant supply of water at the roots, because a crown of fronds in that heat transpires at a rate that a rainforest tree would recognise. The FAO's handbook puts the water requirement at 1,500 to 2,800 millimetres a year, which is the rainfall of the Amazon applied to a place that gets fifty, and a mature palm in a Gulf summer takes 150 to 300 litres a day. A hectare of palms, a hundred or so trees, drinks twenty to thirty thousand cubic metres a year. None of it is rain. All of it comes from a spring, a channel or a well.

That blue share is the story. Bananas are a tenth irrigation, maize a fifteenth, even the strawberries of Huelva on this site are a third; the date is more than half, and in the Gulf countries, where the green share is close to zero because there is no rain to count, it is nearly all. A kilogram of Saudi dates is two thousand litres of groundwater.

The oasis

For most of the palm's history the water came by gravity. The oases of the Sahara sit on springs where the aquifer meets the surface; the villages of Oman and the Emirates are watered by the falaj, a channel dug underground from the foot of the mountains and run for kilometres at a gentle slope to bring the mountain's water to the palms without a pump, the same system the Persians call a qanat and have built for three thousand years. In the Nile valley and in Iraq the groves stood along the rivers and were flooded from them. The water was limited by what the spring or the channel gave, the groves were sized to it, and the system lasted because it could not take more than arrived.

The pump ended that. From the 1960s the diesel pump and then the electric one let a farmer drill into the aquifer under the oasis and take what the spring had never offered, and the groves grew beyond anything the channels could have fed. Saudi Arabia planted tens of millions of palms on pumped fossil water, the same water it used to grow wheat in the desert until it stopped in 2016 because the aquifer was going, and the Emirates planted forty million by its own count along the roads and in the farms of Al Ain, where the falaj still runs but the trees drink from wells. The water under the Arabian peninsula fell as rain in the wet climate of the ice age, as the groundwater article on this site describes, and it is being spent on a timescale of decades. The palms will outlive it. A date palm bears for eighty years.

Egypt and the salt

The largest date country is one with a river. Egypt grows more dates than any other country, nearly a fifth of the world's, in the Nile valley and the delta and in the oases of the western desert, and its palms drink the Nile's water through the same canals as its rice and sugar, with the blue water counted against a river that Ethiopia, Sudan and Egypt are arguing over, as the Cairo article on this site describes. The oases of the western desert, Siwa, Bahariya, Dakhla and Kharga, are springs over a fossil aquifer that the government has tapped with deep wells for new farms since the 1960s, and the springs at Siwa, which fed the palms for three thousand years, now run into salt lakes because the wells have raised the water table and nowhere drains.

Salt is the oasis's other limit. A palm transpires pure water and leaves the salt of the irrigation water in the soil, and in a closed basin with no outlet the salt accumulates, as the irrigation article on this site explains in general; the date palm tolerates more salt than most crops, which is why it survived where others failed, and it has a limit, beyond which the fruit shrinks and the tree dies. The old oases drained their fields to a low point that became a salt marsh, and the new farms on pumped water, in Saudi Arabia above all, are salinising faster than the old ones ever did because the water from deep wells is saltier than spring water and the drainage was an afterthought. A grove of palms that drinks two thousand litres a kilogram and leaves the salt of every litre in the ground is a grove with a date on it.

Basra

Iraq was the date country for most of the twentieth century. The groves along the Shatt al Arab, the river that the Tigris and Euphrates become below their meeting, ran for a hundred kilometres on both banks in a forest of thirty million palms, watered by the tide that pushed the river's fresh water into the irrigation creeks twice a day, which is an irrigation system that needs no pump at all, and Basra's dates went to the whole world. The wars took the groves first: the front line of the war with Iran ran through them for eight years and they were cut, burned and mined. Then the river changed. Turkey and Syria dammed the Euphrates and Iran diverted the Karun, the flow at Basra fell, and the sea came up the Shatt al Arab behind it, so that the water in the creeks at high tide is now brackish for most of the year and in 2018 was salty enough that a hundred thousand people in Basra were treated in hospital after drinking it, as the TDS article on this site describes. The palms that survived the war are dying of salt. Iraq has fewer than ten million palms left, and Basra imports dates.

The Medjool and the Coachella

The date went west too. In the 1920s a plant collector carried offshoots of the Medjool, the large soft date of the Moroccan oases, to the United States after a disease had nearly wiped out the Moroccan groves, and planted them in the Coachella Valley of California, east of Palm Springs, where the climate is the Sahara's and the water comes by canal from the Colorado river. The valley now grows most of the world's Medjool on Colorado water that the river's other users, from Las Vegas to Mexico, are arguing over, and the Medjool has been planted back in Morocco, in Israel and Jordan along the Dead Sea, and in the Gulf, on water from wherever each place can find it. The trees in the opener of this article stand north of the Dead Sea on water pumped from the Jordan valley's aquifer, in a valley where the Dead Sea itself, as the Israel article describes, is falling by a metre a year because that water no longer reaches it.

What it teaches

The date is the product on this site that measures what a desert can afford. The tree is the right tree for the climate: it tolerates the heat, the salt and the sand, it needs no pesticide to speak of, and it has fed the oases for five thousand years on the water that springs and channels gave. The pump broke the limit, and the groves that stand on fossil water from Riyadh to Al Ain are, like the wheat that preceded them, a draw on a stock that does not refill, spent at two thousand litres a kilogram on a fruit that keeps for a year. The oasis knew how many palms the spring could feed. The question the Gulf has not answered is the same one, with the pump turned off.

Two thousand three hundred litres a kilogram, more than half of it from a well, and a tree that outlives the water it drinks.