The Weather Notebook: Nilometer

Nilometer
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Dave Thurlow, Host

The Nilometer on the Island of Rhoda Lithograph by David Roberts, R.A.

The world's oldest, continuous weather record comes from the Nile River in Egypt. There, Egyptians have been measuring the height of the river for more than 5,000 years. And, scientists now are finding that these records are unraveling some of the mysteries of El Niño. Hi, I'm Dave Thurlow and this is The Weather Notebook.

So advanced were the Egyptians in their record keeping that they developed a special instrument to measure the Nile waters, called a nilometer. The first nilometers were simply marks on the river bank; later, the Egyptians used marble scales, and then a well with water levels marked on it.

As with any other river, the height of the Nile is an important sign of the weather going on upstream, in this case, the highlands of Ethiopia. It so happens that El Niño tends to produce drought in Ethiopia. So, scientists are now looking closely at the nilometer records to see what they can tell us about how El Niño behaved way back when.

As best they can tell, El Niño came and went much as it does today: it typically lasted one or two years and returned every 4 to 7 years or so. Some of the multi-year stretches of the past where the Nile was very low may be tied to intense El Niños or El Niños that arrived in close sequence. In the last couple of decades, El Niños have become so frequent and strong that they're now a household word.

The nilometer data show that similar periods have occurred in the past, although things tended to return to normal after several decades. Perhaps the nilometer records assembled by the ancient Egyptians will help us pinpoint whether future El Niños are business as usual or a sign of climate change.

Thanks today to contributing writer Bob Henson. Funding for the show come from Subaru and the National Science Foundation.