City of Unley CEO Ray Pincombe says that an agreement has been reached with the Department of Transport, Energy and Infrastructure (DTEI), under which Unley Council will water the surviving trees on Greenhill Road's median strip, with funding provided by DTEI.

"The watering started on March 31, with 12,000 litres of recycled water sourced from Mawson Lakes," Mr Pincombe said.

In a further breakthrough, an agreement has been reached to source rainwater from the Adelaide Showgrounds at Wayville, using tankers, with up to ten waterings anticipated before the onset of winter.

"This is a matter of extreme urgency because a report from an aboriculture consultant has estimated that already 57 of the 158 trees along the median strip are dead, stressed or dying," Unley Mayor Richard Thorne said.

Mayor Thorne said it is now up to DTEI, which is responsible for the median strip including the trees, to decide how it plans to manage the strip in the future.

"Greenhill Road is an important boulevard for Unley as well as the southern part of inner-city Adelaide," he said. "Longer term it might be possible that Greenhill Road trees could be irrigated with recycled water from the adjacent Glenelg to Adelaide pipeline."

"The City of Unley is happy to discuss ways it can continue to work with DTEI to manage its media strip. Adelaide City Council has also indicated it could help where practicable."