Science Briefs

April 14, 2013 

Index for forecasting droughts questioned

For decades, scientists have used sophisticated instruments and computer models to predict the nature of droughts. With the threat of climate change looming large, the majority of these models have steadily predicted an increasingly frequent and severe global drought cycle. But a recent study from researchers at Princeton University and the Australian National University suggests that one of these widely used tools – the Palmer Drought Severity Index – may be incorrect.

The PDSI was developed in the 1960s as a way to convert multiyear temperature and precipitation data into a single number representing relative wetness for each region of the United States. The PDSI, however, does not originally account for potential evaporation, which depends on solar radiation, wind speed and humidity.

The new model developed by Justin Sheffield, a hydrologist at Princeton and the lead author of the study, is producing different numbers.

The report was published in www.earthmagazine.org. eurekalert.org

Irrigation from African mountains harms oases

For more than 40 years, snowmelt and runoff from Morocco’s Atlas Mountains has been dammed and redirected hundreds of kilometers to the south to irrigate oases farms in the arid, sub-Saharan Draa Basin.

But a new study by American and Moroccan scientists finds that far from alleviating water woes for the six farm oases in the basin, the inflow of imported water has exacerbated problems by dramatically increasing the natural saltiness of their groundwater.

Researchers from Duke University and Ibn Zohr University in Morocco measured dissolved salt levels as high as 12,000 milligrams per liter at some locations – far above the 1,000 to 2,000 milligrams per liter most crops can tolerate.

Dissolved salt levels in the groundwater of the three southernmost farm oases are now so high they endanger the long-term sustainability of date palm farming there.

“The flow of imported surface water onto farm fields has caused natural salts in the desert soil and underlying rock strata to dissolve and leach into local groundwater supplies,” said Avner Vengosh, professor of geochemistry and water quality at Duke’s Nicholas School of the Environment. “Over time, the buildup of dissolved salt levels has become irreversible.” eurekalert.org

Dinosaurs were strong swimmers

A Canadian researcher has identified some of the strongest evidence ever found that dinosaurs could paddle long distances.

Working together with an international research team, University of Alberta grad student Scott Persons examined unusual claw marks left on a river bottom in China that is known to have been a travel route for dinosaurs.

Alongside easily identified fossilized footprints of many Cretaceous era animals – including giant, long-neck dinosaurs – researchers found a series of claw marks that Persons says indicates a coordinated, left-right, left-right progression.

The report was published this month in the journal Chinese Science Bulletin.

“What we have are scratches left by the tips of a two-legged dinosaur’s feet,” said Persons. “The dinosaur’s claw marks show it was swimming along in this river and just its tippy toes were touching bottom.” eurekalert.org

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