The Caspian Sea, the largest inland body of water on Earth, is losing ground — literally. Since the mid-1990s, it has shed roughly 24,000 km² of surface area, an expanse close to the size of Sicily, and water levels have fallen by about two metres. New research using satellite imagery and ground-based hydrological data now gives us a clearer picture of why.
Climate change is part of the story. Rising regional temperatures have significantly increased evaporation from the sea’s surface. But evaporation accounts for only around 40% of the observed water loss. The remainder traces back to reduced river inflow — particularly from the Volga, which supplies roughly 80% of the Caspian’s water.
Dams, reservoirs, irrigation systems, industrial consumption, and canal diversions have collectively reduced the volume of water reaching the sea over several decades. Notably, rainfall over the Volga Basin has actually slightly increased during this period, which means the decline in inflow is a consequence of how the river system is managed, not a lack of precipitation.
The ecological consequences are already unfolding. The shallow northern Caspian — a vital zone for fisheries, migratory birds, wetlands, and sturgeon spawning grounds — is drying most rapidly. Rising chlorophyll levels in the water signal deteriorating water quality and growing risk of harmful algal blooms.
The economic stakes are equally real: ports, shipping lanes, and offshore energy infrastructure across the region all depend on the sea remaining at viable depths.
The lesson of the Aral Sea — once the world’s fourth largest lake, now largely a desert — is a stark reminder of how quickly these situations can spiral beyond recovery.
The five littoral states — Iran, Russia, Turkmenistan, Azerbaijan, and Kazakhstan — share both this sea and the responsibility for its future. The 2018 Aktau Convention was an important step, but what is urgently needed now is a binding, comprehensive framework covering water allocation, transparent monitoring, and ecological protection across the entire basin.
Concretely, this means open sharing of hydrological data, agreed environmental flow releases from upstream reservoirs, and coordinated limits on water diversion. The Caspian is not simply a shipping corridor or an energy asset — it is a shared natural system that underpins the livelihoods, food security, and long-term economic stability of the entire region.
The damage is real, but the sea has not yet crossed the point of no return. The window for effective action remains open — but it will not stay open indefinitely. /// nCa, 23 June 2026