Why Lake Sevan is Turning Green: Clarification from the Ministry of Environment

Why is Lake Sevan turning green and what measures are being taken to address this issue? The Ministry of Environment has issued a clarification stating, "Dear citizens, the issue of the activation of blue-green algae in Lake Sevan is under the attention of the professional departments of the Ministry of Environment.

The bloom of algae (including cyanobacteria) in Lake Sevan is mainly due to the following factors:

• A large quantity of phosphorus and nitrogen compounds, which serve as nutrients,
• The high temperature of the water,
• A considerable intensity of light,
• The reduction of the hypolimnion layer in the Little Sevan due to the drop in lake levels, and its disappearance in the Large Sevan.

Due to the reduction and absence of the hypolimnion layer, there is an intense transition of phosphorus from the sediment layer to the water layer. The concentration of phosphorus in Lake Sevan continues to rise because the lake is overloaded with organic materials brought in by wastewater from human activities:

• Untreated municipal household wastewater, including wastewater from coastal resort areas,
• Agriculture and livestock,
• Submerged vegetation,
• Net-cage fish farming,
• Septic tanks not connected to the sewage network.

Currently, Lake Sevan is in the intensive blooming phase, and the lake corresponds to a mesotrophic state according to its trophic condition. As a result of this intense blooming, the concentration of phosphates decreases. Compared to June, the concentration of phosphate ions on July 15 has decreased by nearly 2 times. The absorption of phosphorus by the biological mass is ongoing, and when the concentration of phosphorus in the water almost approaches zero, the process will end. Observations indicate that this process will take 2-3 weeks.

The dissolved oxygen content in the near-bottom layer of Lake Sevan is observed at a range of 4-8 mg/L. The concentration of dissolved oxygen in surface and mid-layers is sufficient to sustain animal life (the minimum concentration is over 6 mg/L). The water temperature in the near-bottom layer at a depth of 60 meters is 4°C, while at a depth of 30 meters, it is 5-6°C, which is high and encourages the near-bottom layer to participate in water circulation. The water transparency has been observed at a range of 2-2.5 meters, which is very low.

We inform you that the Ministry of Environment is undertaking a series of measures and steps to address the problem of the activation of blue-green algae, which is one of the consequences of the disruption of the ecosystem of Lake Sevan:

• Regulation of industrial fishing for barbel in the lake
• Replenishment of fish stocks
• Development of the management plan for the Sevan basin
• Establishment of water quality norms for Lake Sevan (as per Government Decision No. 1211-N of July 22, 2021)
• Demolition of illegal constructions on the shore of Lake Sevan
• Reforestation of submerged and submerged areas
• Management of waste and garbage transport issues
• Implementation of the "Environmental Protection of Lake Sevan" (EU4Sevan) project, which prioritizes the following five outcomes:
• 1) Improvement of the monitoring system for Lake Sevan,
• 2) Capacity enhancement for implementing favorable and water-saving land use and agricultural practices,
• 3) Improvement of wastewater treatment capabilities, including natural solutions,
• 4) Increasing awareness and accessibility of information for the protection of Lake Sevan among adjacent communities, the private sector, and other stakeholders,
• 5) Improvement of the management system for the ecosystem of Lake Sevan.

Particularly, in the direction of wastewater management, the enhancement of the mechanical treatment plant in Gavar is planned, as well as the creation of a wastewater removal and joint treatment system for the communities of Vardenik and Tsovinar in the Lake Sevan basin. Dear citizens, we must systematically and persistently address the anthropogenic factors threatening the ecosystem of Lake Sevan, and as a derivative, gradually reduce and ultimately eliminate the natural phenomena stemming from them. Together, let us restore our national treasure, the ecosystem of Lake Sevan, and henceforth ensure its integrity under the responsible and caring attitude of all of us," the issued statement emphasizes.