IN NEWS

Chilika Lake Facing Gradual Reduction in Depth Due to Heavy Siltation

ANALYSIS

Chilika Lake, Asia’s largest brackish water lagoon and a designated Ramsar Site, is witnessing a gradual reduction in depth due to continuous accumulation of muddy soil and sediment inflow. The issue was highlighted in the Odisha Assembly by the state forest department, raising concerns regarding the long-term ecological sustainability of the lake ecosystem. The problem is significant because Chilika is one of India’s most ecologically productive wetland ecosystems and supports fisheries, migratory birds, biodiversity conservation and tourism-based livelihoods.

Increasing Siltation and Declining Depth

According to the Odisha government:

• Around 8 lakh metric tonnes of muddy soil enter Chilika every year.
• The forest department extracted nearly 3,26,716 cubic metres of muddy sludge over the last five years.
• The lake’s minimum depth has reduced to 0.38 metres, while the maximum depth remains around 6.2 metres.

Continuous sediment deposition is gradually filling the lagoon basin, reducing water depth and affecting the hydrological dynamics of the wetland.

Causes Behind Sediment Accumulation

The major causes contributing to siltation include:

• Sediment inflow from rivers draining into Chilika.
• Catchment degradation and soil erosion.
• Reduced flushing capacity of the lagoon.
• Changes in tidal exchange with the Bay of Bengal.
• Expansion of marshy and weed-dominated zones.

Studies indicate that Chilika’s tidal prism and self-cleansing ability have weakened significantly over the years. Research also suggests that changing geomorphology and repeated opening and closure of lagoon mouths have altered sediment dynamics and salinity patterns.

Ecological Consequences of Shrinking Depth

Reduction in lake depth can have multiple ecological impacts:

Impact on Fisheries

• Disturbance in fish migration routes.
• Alteration in salinity balance.
• Decline in habitat suitability for fish, prawn and crab species.

Threat to Biodiversity

Chilika supports:

• Migratory birds
• Irrawaddy dolphins
• Aquatic vegetation
• Brackish water biodiversity

Shallowing of water bodies may alter wetland habitats and increase eutrophication risk.

Decline in Water Flushing Capacity

Reduced depth weakens:

• Natural water circulation
• Sediment removal mechanisms
• Salinity regulation

Experts have warned that the lagoon’s natural cleansing capacity has weakened considerably.

Government Measures and Restoration Plans

The Odisha government stated that the Chilika Development Authority (CDA) monitors water quality through 17 monitoring stations. To restore the lagoon ecosystem:

• A Detailed Project Report (DPR) is proposed with assistance from IIT Madras.
• Eco-restoration proposals include:
  • Desilting critical channels
  • Bathymetric surveys
  • Hydro-sedimentological studies
  • Tidal mouth management
  • Dredging operations

Importance as a Migratory Bird Habitat

Despite ecological stress, Chilika continues to remain one of South Asia’s most important migratory bird habitats.The lagoon functions as:

• Wintering ground for ducks, gulls, terns and shorebirds.
• Refuelling site for migratory birds travelling from:
  • Southern India
  • Russian Arctic
  • China
  • Mongolia

Bird diversity has shown improvement since 2023:

• 196 bird species were recorded in 2025 compared to 187 species in the previous year.

Ramsar Significance of Chilika Lake

Chilika was India’s first Ramsar Site and is globally recognised for its ecological richness.The lagoon is vital for:

• Fisheries-based livelihoods
• Wetland biodiversity
• Migratory bird conservation
• Coastal ecological stability

The Ramsar Convention earlier placed Chilika under the Montreux Record due to ecological degradation, though subsequent restoration efforts improved its condition.

STATIC PART

Chilika Lake

Chilika Development Authority (CDA)

Ramsar Convention

Important Ecological Terms

Updated – 03 December 2025 ; 12:59 AM |Times of India News Source