(General Studies-I (250 marks)Indian Heritage and Culture, History, and Geography of the World and Society)
(General Studies-III (250 marks)Technology, Economic Development, Biodiversity, Environment, Security, and Disaster Management)
A glacial lake outflow refers to the water that drains from a lake formed by the melting of a glacier. These lakes, known as glacial lakes, can be found in regions with current or past glacial activity. The outflow typically occurs when the water level in the lake rises high enough to breach a natural dam, which could be made of ice, moraine (rock and sediment deposited by the glacier), or bedrock.
they are common in the high elevation of glacierised basin. They are formed when glacial ice or moraines or natural depressions impound water.
There are varieties of such lakes, ranging from melt water ponds on the surface of glacier to large lakes in side valleys dammed by a glacier in the main valley.
These lakes normally drain their water through seepage in front of the retreating glacier. The moraine creates topographic depression in which the melt water is generally accumulated leading to formation of glacial lake.
When this lake is watertight, melt waters will accumulate in the basin until seepage or overflow limits the lake level.
The outflow can happen gradually or suddenly, depending on the stability of the dam and the volume of water. Sudden outflows, known as glacial lake outburst floods (GLOFs), can be particularly dangerous. GLOFs occur when the natural dam fails catastrophically, releasing a large volume of water in a short period. This can lead to significant flooding downstream, potentially causing damage to infrastructure, ecosystems, and human settlements.
Glacial lake outflows are an important aspect of the hydrological cycle in glaciated regions and can have significant impacts on local and regional water systems, sediment transport, and landscape evolution.
There are 2028 Glacial Lakes and Water Bodies having water spread area more than 10 Ha in the Himalayan region catchment which contributes to rivers flowing in India. Out of these 503 are glacial lakes and 1525 water bodies.
1169 Glacial Lakes / Water Bodies are located in the elevation zone from 4000 m to 500 m above sea level. Basin-wise details of Glacial Lakes / Water Bodies (having water spread area more than 10 Ha) in the Himalayan region catchment which contributes to rivers flowing in India are as follows
How is It Measured?
The Satellite images of Advanced Wide Field Sensor (AWiFS) of Indian Remote Sensing Satellite Resourcesat-1 were collected during the month May-November, 2009 of Himalayan region. Glacial lakes and Water Bodies were delineated based on the visual interpretation of above satellite imageries using ERDAS Imagine and Geographical Information System (GIS) software.
The inventory of glacial lakes /water bodies having water spread area more than 10 ha has been prepared and published in June 2011. The information in
inventory includes location of the lake (Latitude, Longitude and Elevation), name of lake (if available) and water spread area.
The Advanced Wide Field Sensor (AWiFS) is an optical imaging sensor used on Indian remote sensing satellites, such as the Resourcesat-1 and Resourcesat-2, operated by the Indian Space Research Organisation (ISRO). It is designed for medium-resolution Earth observation and is widely used for applications in agriculture, forestry, water resources, and land use planning.
Key Features of AWiFS:
Spatial Resolution:
AWiFS provides a spatial resolution of 56 meters (multispectral) and 70 meters (panchromatic), making it suitable for large-area monitoring.
Spectral Bands:
It operates in four spectral bands:
Band 2 (Green): 0.52–0.59 µm
Band 3 (Red): 0.62–0.68 µm
Band 4 (Near Infrared): 0.77–0.86 µm
Band 5 (Shortwave Infrared): 1.55–1.70 µm
Swath Width:
AWiFS has a wide swath of 740 km, enabling frequent coverage of large areas. This makes it ideal for monitoring large-scale phenomena like crop health, deforestation, and natural disasters.
Revisit Time:
Due to its wide swath, AWiFS can revisit the same area every 5 days, providing timely data for dynamic applications.
Applications:
Agriculture: Crop monitoring, yield estimation, and drought assessment.
Forestry: Forest cover mapping, deforestation monitoring, and biodiversity studies.
Water Resources: Monitoring water bodies, watershed management, and flood mapping.
Land Use/Land Cover: Urban planning, soil mapping, and environmental monitoring.
Disaster Management: Assessing damage from natural disasters like floods, cyclones, and earthquakes.
Advantages:
Wide Coverage: Large swath width allows for efficient monitoring of vast regions.
Frequent Revisits: High temporal resolution supports dynamic monitoring.
Cost-Effective: Provides valuable data for multiple applications at a lower cost compared to high-resolution sensors.
Comparison with Other Sensors:
AWiFS vs. LISS-III: AWiFS has a wider swath (740 km vs. 140 km for LISS-III) but lower spatial resolution (56 m vs. 23.5 m for LISS-III).
AWiFS vs. MODIS: AWiFS offers better spatial resolution (56 m vs. 250–500 m for MODIS) but with a narrower swath.
Significance:
AWiFS is a critical tool for India’s remote sensing capabilities, supporting national programs like crop forecasting, watershed management, and disaster response. Its data is also used globally, contributing to international Earth observation initiatives
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