Three years ago a drought lowered the height of the Mosul Reservoir in Iraqi Kurdistan and briefly revealed a city that archaeologists think might be Zakhiku, a center of the Bronze Age Mittani Empire. Now, the dry conditions have returned, presenting a major threat to the people of Iraq, but benefiting archaeologists by giving them a second chance to explore the important site.

Drought in southern Iraq has been less noticed worldwide than heatwaves in India and Pakistan, but it has been severe enough to force the release of large amounts of water stored upstream in the Mosul Reservoir. The possibility that the Mosul will run dry before the drought ends is a terrifying one, but in the meantime, the water level has dropped so much that ancient treasures are being revealed.

During the previous reduction in reservoir levels, a German-Kurdish team found a large palace, complete with murals preserved on the walls. The palace had at least two periods of usage, one around 3,400 years ago, and would have sat 20 meters (66 feet) from the Tigris River's eastern bank. It was clearly a center of Bronze Age power, and historians suspected it was the city of Zakhiku, referred to in sources from 3,800 years ago.

Subsequently, however, wetter weather saw the reservoir retake the palace. This year, when drought revealed the site again, archaeologists sprung into action, putting together a team within days and securing funding from the Fritz Thyssen Foundation with a speed government funding agencies could not match.

Already the city has been largely mapped, revealing several large buildings beside the palace. These include immense fortifications and what appear to be a storage complex and factories – it seems the Mittani empire knew more about the benefits of urban planning and concentrating industrial uses together than some of their successors.

"The huge magazine building is of particular importance because enormous quantities of goods must have been stored in it, probably brought from all over the region," said Professor Ivana Puljiz of the University of Freiburg in a statement. Dr Hasan Qasim of the Kurdistan Archaeology Organization added: "The excavation results show that the site was an important center in the Mittani Empire."

Although the reservoir submerged the complex for most of the last 40 years, the mud-brick walls are remarkably well preserved. The archaeologists attribute this to an earthquake in 1350 BCE, which brought down the upper walls and protected those below.

More than 100 cuneiform tablets from shortly before the earthquake have been found in ceramic vessels, added to the 10 found during the previous excavation. Once translated, these could give important insights into the city's life.

Plastic sheeting has been placed over the site to preserve newly exposed areas through future inundations.

The Mittani Empire lasted from around 1600 BCE to 1260 BCE, and at its peak covered much of modern-day Syria and northern Iraq – a huge area by ancient standards. Eventually, it was overrun by the Hittites from the north and Assyrians from the south. However, it is little known today partly because the only Mittani cities that have been explored are small ones from the empire's periphery. Zakhiku, close to the core, could change that; if the drought lasts.

Unfortunately for the people of Iraq, rising global temperatures are likely to bring drier conditions to the region. The height of the reservoir will wax and wane, but the suspected Zakhiku is likely to be exposed more often. That won't necessarily mean more opportunities for archaeologists, however. Droughts are destabilizing: The hardship induced by a drought played a major part in plunging neighboring Syria into a decade-long civil war. Science is unlikely to flourish if such conditions extend into Iraq for long.