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The Blue Nile is oldest of the Nile's two main tributaries, but before our research nobody knew for certain when it began to flow from its headwaters high up in the Ethiopian Highlands, to its delta in the Egyptian Mediterranean, more than 4000 kms downstream? Estimates ranged from over 30 million, to less than one million, years ago. 

It’s been a long and bumpy research journey to find out. The project started, literally, with a bump. A rather big bump. Having just arrived in New Zealand for my sabbatical, I was awoken in the early hours by a terrifying shaking. It was, what came to be known as, ‘the Christchurch Earthquake’. Aftershocks continued for months, keeping everyone on edge.

So finally I retreated, for some peace, to the beautiful University of Canterbury’s field station in Kaikoura, a wonderfully serene beachside location overlooking the mountains on South Island’s east coast. And it was there that the idea for the Nile project was conceived, and a successful proposal for funding was written, as I sat quietly watching the seals play in the water.

My idea was simple. Oil companies have drilled thousands of metres deep into the Nile delta in the Mediterranean, collecting sand samples deposited by the river over millions of years. The Ethiopian headwaters of the Nile contain sand with zircon minerals of a distinctive age, not found anywhere else in the Nile’s drainage basin. So if we could identify the oldest Nile delta sands that contain evidence of these distinctive zircons derived from Ethiopia, we'd know when the river was first connected all the way ‘from source to sink’.

The concept might have been simple, but the practicalities were less so. Challenge 1 was obtaining sand samples from the Nile delta. The only people who have access to such samples are oil companies, and data-sharing with academics is not something that necessarily comes easily to them. Whilst they need to protect their commercial interests, academics need to be able to publish their findings. It took a long period of negotiations, including several blind alleys, before agreement was reached with BP Egypt and samples finally arrived in Lancaster.

Challenge 2 was fieldwork. Before analysing the Nile delta sediments we first needed to prove our hypothesis that the headwaters are the only place in the Nile catchment that contain zircons of this distinctive age. If zircons of the same age were also found further downstream, then we couldn't prove that these zircons in the delta came from the headwaters.

And so began the logistical headaches of trying to gain access to the various regions through which the Nile River flows: Rwanda, Uganda, Ethiopia, Sudan and Egypt. Wonderful countries all, but not known, for the most part, for their ease of field logistics, particularly when it comes to permits.

For the first field season, to Uganda and Rwanda, I was joined by colleague Eduardo Garzanti from the university of Milan-Bicocca. I remember that trip mostly for its wildlife – elephants, giraffes, hippos, but more worryingly, crocodiles that like to sunbathe on sandy river banks which are also where the best samples are usually located. We took turns to collect the sample whilst the other person kept look-out, armed with our trusty spade. Quite what we planned to do with the spade if attacked by a croc was unclear, but luckily we never had to find out.

On my next trip, to Ethiopia, I was joined by my PhD student Laura Fielding. We were lucky enough to be there over the festival of Timket (Epiphany) which the Ethiopian Orthodox Church celebrates in an explosion of colour and exuberance as the Arc of the Covenant is paraded through the streets accompanied by a vast noisy crowd. It is also the country I remember for our guide’s insatiable appetite for eating raw goat meat at every opportunity, and for our driver’s continual refusal to stop the car and let us collect samples; the latter made for somewhat fraught working conditions until we parted ways.

Next up was Sudan, by which time we were also joined by Laura’s co-supervisor Ian Millar from the British Geological Survey. Sudan stands out as the country in which I first experienced tear gas. I was watching the Whirling Dervishes Ceremony at the mosque in Khartoum, mesmerised, when the military arrived with their heavy handed crowd-control technique, bringing the display to an abrupt halt.  It was an inauspicious start, but things improved, and I warmed to the country and its so welcoming people.

Our most challenging field work was in Egypt, by which time we had also added Frank Darius, an ecologist and experienced Egyptian desert traveller, from the Technical University, Berlin, to our team.

The first trip took us deep into the Eastern Desert to sample the Red Sea Hills. The second required us to spend over a week crossing the Great Sand Sea of the Saharan Western desert to reach the Libya-Sudan border. The latter took us into an area so remote that the Egyptian authorities required us to take a security entourage of three extra vehicles. Over this convoy presided our multi-faceted guide extraordinaire, Mahmoud: a desert chef who whipped up Michelin Star dinners; a fixer of sticky situations, like when our security detail had inexplicably failed to inform the Military of our presence in the area; and a mechanic who could keep the vehicles on the road with little more than a ball of string and duct tape.

The vehicles were our modern day ‘ships of the desert’; far from the nearest road, they were our lifeline in this huge sand sea, As well as driving in them, we spent considerable time under them (for shade, where none else existed) or out of them (pushing them or digging them out of the relentless sand, or waiting whilst they were being fixed…. again).

And in between all the field work, Laura and Ian were plugging away in the lab, analysing the material we brought back. First results were good and confirmed our initial hypothesis; zircons of the specific age we were looking for were indeed only found in the Nile headwaters.

With that confirmed, the acid test was to see if zircons of the same age could be found in the Nile delta sediments. Many hundreds of zircon analyses later and we found what we were looking for – we found zircons of the same age as those of the Ethiopian headwaters, in Nile delta sediments laid down 30 million years ago. Success! We had proved that the Nile has been flowing more than 4000 kms from source to sink for 30 million years.

So then came the last part, writing up the paper for publication. The paper was accepted by the journal Earth and Planetary Science Letters, and subsequently picked up by New Scientist who thought it of sufficiently broad interest to report to the general public – a gratifying finish to a great project.