This publication by Space Applications Centre (SAC), Indian Space Research Organisation (ISRO) is an outcome of the project on National Wetland Inventory and Assessment (NWIA) and deals with the updated database and status of wetlands, compiled in an atlas format. Increasing concern about how our wetlands are being influenced had led to formulation of the project entitled to create an updated database of the wetlands of India.
What is Wetlands?
Wetlands defined as areas of land that are either temporarily or permanently covered by water exhibit enormous diversity according to their genesis, geographical location, water regime and chemistry. They are one of the most productive ecosystems and play crucial role in hydrological cycle. Utility-wise, wetlands directly and indirectly support millions of people in providing services such as storm and flood control, clean water supply, food, fiber and raw materials, scenic beauty, educational and recreational benefits. Thus, their identification and protection becomes very important.
Categories of Wetlands
The wetlands have been categorised under nineteen classes and mapped using satellite remote sensing data from Indian Remote Sensing Satellite: IRS P6- LISS III sensor. The results are organised at 1: 50,000 scales at district, state and topographic map sheet (Survey of India reference) level using Geographic Information System (GIS). This publication is a part of this national work and deals with the wetland status of a particular State/Union Territory of India, through text, statistical tables, satellite images, maps and ground photographs.
This is the first time that high resolution digital remote sensing data has been used to map and decipher the status of the wetlands at national scale. The methodology highlights how the four spectral bands of LISS III data (green, red, near infra red and short wave infra red) have been used to derive various indices and decipher information regarding water spread, turbidity and aquatic vegetation. Since, the aim was to generate a GIS compatible database, details of the standards of database are also highlighted in the methodology.
The results and finding are organized in three sections; viz: Maps and Statistics, Major wetland types, and Important Wetlands of the area. The Maps and Statistics are shown for state and district level. It gives details of what type of wetlands exists in the area, how many numbers in each type, their area estimates in hectare. Since, the hydrology of wetlands are influenced by monsoon performance, extent of waterspread and their turbidity (qualitative) in wet and dry season (post-monsoon and pre-monsoon period) are also given.
Some important findings
Excluding rivers, wetlands cover some 10 million hectares, or a little over three percent of the country’s geographical area.
Of this 10 million hectares, reservoirs account for about 2.5 million hectares, inter-tidal mud flats for 2.4 million hectares, tanks for 1.3 million hectares, lakes/ponds for 0.70 million hectares, mangroves for some 0.47 million hectares and corals for about 0.14 million hectares.
Objective of the Project?
The main objective of the project were wetland mapping and inventory at 1:50,000 scale resolution by analysis of digital satellite data of post and pre-monsoon seasons, creation of digital database in GIS environment and preparation of state-wise wetland atlases.
State wise distribution of wetlands
Lakshadweep has 96.12 per cent of geographic area under wetlands
Andaman and Nicobar Islands (18.52 per cent),
Damand and Diu (18.46 per cent)
Gujarat (17.56 per cent) have highest extent of wetlands.
Puducherry (12.88 per cent)
West Bengal (12.48 per cent),
Assam (9.74 per cent) are wetland-rich States.
States like Mizoram, Haryana, Delhi Sikkim, Nagaland and Meghalaya the extents of wetland is less than 1.5 per cent.
The inventory said, India has long coast line and large area under coastal wetlands like inter-tidal, mudflat, lagoon and creek.
The inventory has also mapped high altitude lakes lying above 3,000 meter elevation. The Indian Himalayas cover almost 18 per cent of India’s land surface and is spread over six states, which have 4703 lakes above 3,000 meter elevation.
This includes 1996 small lakes. The total area of these lakes is 1.26 lakh hectares.