How much has the Caspian Sea water level changed since the 1st century BCE?

Based on archaeological, geological, and historical evidence, the water level of the Caspian Sea has fluctuated by at least 23 feet (7 metres) since the 1st century BCE.1

These long-term changes are primarily driven by climatic shifts that alter the balance between water gains—such as river influx and precipitation—and water losses through evaporation. Human activity, including the construction of reservoirs on the Volga River for irrigation and industry, has also influenced these levels over time.1