High salt levels ‘endangering oaeses farming’

High salt levels in the sub-Saharan Draa Basin are endangering the farming of oases, experts have said.

For more than 40 years, snowmelt and runoff from Morocco’s High Atlas Mountains has been dammed and redirected to the south in order to irrigate these oases farms which were struggling to survive in the arid desert.

However, a new study has found that instead of alleviating water woes for the six farm oases that reside in the basin, the inflow of this water has dramatically increased the natural saltiness of the groundwater, thereby exacerbating the problem.

Dissolved salt levels in the groundwater of the three most southernmost farm oases are now incredibly high. So high, in fact, that they put the long-term sustainability of the date palm farming there at risk.

Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment, explained: "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.”

"Over time, the buildup of dissolved salt levels has become irreversible."

The team of scientists found this out by identifying the distinctive geochemical and isotopic signatures of different elements in the water, like oxygen, strontium and boron. Elements residing in low-saline water have different stable isotope signatures, or ‘fingerprints’, than those in high-saline water.

Nathaniel Warner, study leader, explained that using these ‘fingerprints’, the team is able to track the nature of the salinity source.

While the practice of importing freshwater to promote crops is common throughout the world, he emphasised that this is a short term solution at best.

The expert underlined the importance of tackling this problem as future climate change models predict significant drops in precipitation in the Southern Mediterranean and Northern African regions in the coming years.