'We may have to evacuate Tehran': The catastrophe threatening Iran (drought, no water)

[nitpicked]

1. Cities have been abandoned in the past before

6th/7th century BC:

https://eos.org/articles/megadrought-helped-topple-the-assyrian-empire#:~:text=And%20the%20fall%20of%20the,after%20its%20abandonment%2C%20Weiss%20said.

Around 2,700 years ago in what is now northern Iraq, the Assyrian Empire was at its zenith, dominating the cultural and political landscape of the Fertile Crescent. But within a few years, the empire collapsed, leaving the once thriving capital of Nineveh abandoned for nearly 200 years. The cause of this catastrophe is an enduring mystery, but a climate record preserved in a cave formation now is revealing that the timing of the empire’s rise and fall coincided with a wet period followed by a 125-year-long megadrought.
(snip)

The new study relies on a limestone stalagmite called a speleothem recovered from the Kuna Ba cave in northeastern Iraq, about 300 kilometers southeast of the modern city of Mosul, just across the Tigris River from the ruins of Nineveh. By tracking the ratios of oxygen and uranium isotopes, which are sensitive to variations in precipitation and temperature, the team was able to reconstruct a high-resolution record of nearly 4,000 years of paleoclimate history for the region.

Researchers then aligned the precipitation records with archaeological and written cuneiform records and found a remarkable correlation: The rise and zenith of the Assyrian Empire, from 920 to 730 BCE, occurred during a period of higher-than-average rainfall, deemed the Assyrian megapluvial, that lasted from 925 to 725 BCE. And the fall of the empire, between 660 and 600 BCE, falls within the peak drought period that lasted from 675 to 550 BCE. This 125-year megadrought helps explain why Nineveh was not resettled for over a century after its abandonment, Weiss said.
(snip)

((And earlier
https://www.ncei.noaa.gov/sites/default/files/2021-11/6%20Drought%20and%20the%20Akkadian%20Empire%20-Final-OCT%202021.pdf

Around 4,300 years BP, Sargon of Akkad united city-states of
Mesopotamia (present-day Syria and Iraq) into the world's first
empire. The empire consisted of two distinct regions: productive
rain-fed agricultural regions in the north and the irrigated alluvial
plain between the Tigris and Euphrates Rivers in the south. The
Akkadian Empire flourished for about 100 years until, at 4,170 ±
150 years BP, it suddenly collapsed (Weiss et al. 1993). The city of
Tell Leilan in the northern region was abandoned and covered with
one meter of windblown silt (Weiss et al. 1993). Refugees from
the north moved to the southern lowlands. Eventually, about 300
years later, the north was resettled, but the preceding events had
destabilized the region and altered the political structures.
For some time, researchers attributed the collapse to political
disintegration and invasion by hostile groups. Some paleoclimate
records indicate that a catastrophic drought also occurred around
this time and suggest that climate factors beyond the control of the
empire played a role in its demise.

In a deep-sea sediment core collected in the Gulf of Oman,
there are distinct peaks of the minerals calcite and dolomite
that begin at 4,025 ± 125 BP and last for about 300 years
(Cullen et al. 2000). These minerals are transported to
the Gulf of Oman as dust from the dry, windswept regions
of Mesopotamia. Scientists interpret these peaks as
coming from an abrupt drying of the Tigris and Euphrates
floodplains. In the sediment cores, there is a volcanic ash
layer (tephra) observed in two adjacent samples spanning
the start of the mineral peaks. The geochemical composition
of this tephra matches that of another tephra preserved at
Tell Leilan from the time of the collapse. This correspondence
makes it very likely that the increase in windblown silt and the
collapse of the Akkadian Empire happened at the same time.

This comparison of data from Gulf of Oman marine sediments and archeological findings shows
the synchrony of the collapse of the Akkadian Empire with severe climatic changes, including
the abrupt onset of drought as indicated by dust deposition (Cullen et al. 2000).
(snip)

The cause of the abrupt drought around 4,200 years BP is still
unknown. One suggested cause is a cooling of the North Atlantic. The
modern instrumental record shows that droughts in Mesopotamia
occur when North Atlantic sea surface temperatures are anomalously
cool. Another possibility is that changes in tropical sea surface tem
perature in the Indian Ocean and western Pacific initiated droughts
across the Middle East, India, and East Africa.
(snip)