IN NEWS: Land-Use Changes Linked to Water Pollution in Loktak Lake

ANALYSIS

A recent study by Nagaland University has underscored the mounting ecological stress on Loktak Lake, India’s largest freshwater lake in the Northeast, caused primarily by changes in land-use patterns across its catchment. Loktak’s ecological uniqueness—defined by its floating phumdis and the presence of the world’s only floating national park—makes the findings particularly significant.

Key Findings of the Study

1. Degradation Due to Human Activities
   • The study shows that expanding agriculture, settlement growth, and shifting cultivation (jhum) in Manipur’s upland catchments are directly deteriorating the water quality of rivers feeding Loktak Lake.
2. Comprehensive River Sampling
   • Field data were collected across nine major rivers: Khuga, Western, Nambul, Imphal, Kongba, Iril, Thoubal, Heirok and Sekmai.
   • These rivers form the primary hydrological input for the lake, making their ecological health crucial.
3. Land Use–Water Quality Relationship
   • Using LULC (Land Use Land Cover) mapsfrom the Manipur Forest Department, the study examined the influence of land categories such as agricultural land, settlement areas, degraded forests, jhum zones and dense forests on three key indicators:
     • Dissolved Oxygen (DO)
     • Biological Oxygen Demand (BOD)
     • Temperature
4. Most Polluted River: Nambul
   • The Nambul River emerged as the most polluted.
   • Its sub-catchment has 47% agricultural land and 11% settlements, leading to high organic pollution and depleted oxygen levels.
5. Jhum Effects: Khuga River
   • The Khuga River, despite higher forest cover, recorded the second-worst water quality due to 42% jhum cultivation in its sub-basin, causing sedimentation and nutrient loading.
6. Forested Catchments Show Better Quality
   • Rivers like Iril and Thoubal showed significantly better water quality, highlighting the protective ecological role of dense natural forests.
7. Environmental Implications for Loktak Lake
   • Loktak Lake already figures in the Montreux Recorddue to ecological degradation such as:
     • Declining fish populations
     • Increased pollution
     • Sedimentation
   • The study calls for:
     • Community-based land-use regulation
     • Stronger controls on agricultural run-off
     • Better waste-management efforts across settlements.

STATIC PART

Loktak Lake

• Largest freshwater lake in Northeast India.
• Known for phumdis—floating mats of vegetation and organic matter.
• Supports hydropower, fisheries, transport, and tourism.

Phumdi

• Floating biomass consisting of vegetation, soil, and decomposed organic material.
• Forms the substrate of Keibul Lamjao National Park.

Keibul Lamjao National Park

• World’s only floating national park.
• Habitat of the endangered Sangai (brow-antlered deer).

Ramsar Site

• Wetlands of global ecological importance.
• Require long-term conservation and sustainable management.

Montreux Record

• Register of threatened wetlands showing signs of ecological decline.
• A tool for prioritizing restoration and conservation actions.

Jhum Cultivation

• Shifting cultivation practiced on hill slopes.
• Causes soil erosion, deforestation, and increased sediment run-off into rivers.
  
  
  Updated – 27 October 2025 ; 08:02 PM | The Hindu