Experts with ISA have studied the gulf between 1975 and 2018. The gulf sits along the northern Golestan and Mazandaran provinces southeast of the Caspian Sea.
ISA head Morteza Barari says that the once-thriving gulf has been desiccating since the past five years.
Satellite imagery shows that between 1975 and 1980, the gulf had the minimum amount of water, with its surface area between 317 to 340 square kilometers, Financial Tribune reported.
Since 1978, things became improved and the gulf reached its prime time in 1998, with surface area reaching 521sq.km.
However, the good times were short-lived. The gulf used to be fed by the Caspian Sea through a narrow link in its far-east tip.
However, with annual decrease of 3 to 4 centimeters in water level of the Caspian Sea, which is equal to 12 billion cubic meters a year, the water way linking the two water bodies began to dry a couple of years ago.
As such, the sea was no more able to feed the gulf and this turned the latter into a lake, fed only by occasional rainfall the volume of which is mercilessly low considering its water evaporation rate.
Satellite images show that the Gorgan Gulf surface area is currently less than 412sq.km.
Environmentalists note that the gulf is shallow, hardly four meters at its deepest, which makes it extremely vulnerable to dry climate and high evaporation that is 3 to 4 times higher than the rainwater inflow.
A member of the Caspian Sea National Research Center Homayoun Khoshravan said earlier a major desiccation has hit the far western part of the gulf, known as Miankaleh Wetland. "Barely 5% of the wetland remains," he told IRNA last summer.
Mapping and monitoring water surface bodies as the world`s most valuable natural resource has gained importance with the developing of remote sensing techniques.
Iran has been using satellite imagery for monitoring geological and environmental developments indicators, which can be used for improving management of water resources, farming and protecting the environment.