Guest post by Sangeeta Deogawanka
February 2nd, designated as World Wetlands Day, has quietly slipped by with isolated events that speak of the lackadaisical attitude towards this rich ecosystem.
With 67,429 wetlands covering an area of about 5.5 million hectares, [Ministry of Environment and Forests (MoEF), 1990], the wetland systems in India are diverse, found in high altitude cold zones, the hot and humid coastal areas or occurring as scattered inland wetland systems.
While 80 % of the wetlands are distributed in the mangroves of Sunderbans and Andaman & Nicobar islands, the rest are found predominantly in the coastal areas of Orissa, Andhra Pradesh, Tamil Nadu, Karnataka, Kerala, Goa, Maharashtra and Gujarat.
Wetland management issues are surrounded by confusion and lack of proper wetland policy. Primarily because, wetlands fall under the jurisdiction of various departments like agriculture, fisheries, irrigation, revenue, tourism, water resources and local bodies, while the mangroves itself fall under forestry. This translates into lack of cohesion in both planning and management.
Though many of the larger wetlands have been mapped at 1:250,000 scale, there has been lack of uniformity in wetland mapping in India. The basis of characterisation used date back to 1970s. However, some recent initiatives using GIS (Geographic Information Systems) tools and software for mapping and analysis of wetland dynamics, is bringing hope for an effective wetland management. So far such work has been undertaken as isolated programmes by research institutes, University departments and individual researchers working on grants. Most of it is still not easily accessible. There is also lack of visibility, both in the technology used and the findings thereon. While the Wetland Working Group of the National Biodiversity Strategic Action Plan (NABSAP) has been taking this movement forward, the GIS Development initiative in publishing papers and findings related to wetland mapping is commendable.
Wetland policies aside, the Ramsar sites in India, currently 25, are well mapped and earmarked for conservation. While you can access all coordinates and attributes for the Ramsar sites, what about the rest of them spread all over the country? Even today, we have about more than 700 smaller and scattered wetlands not mapped, or without any data for prioritization.
Fortunately, the scientific community has not been waiting for Government policy initiatives. The past two decades have witnessed sustainable efforts in mapping these wetlands and compiling a resource base for conservation.
The mapping movement was started by the Salim Ali Centre for Ornithology and Natural History, with a GIS based Decision Support System for wetland conservation. With the support of the Institute of Remote Sensing, Survey of India, the National Remote Sensing Centre (Hyderabad), the State Remote Sensing Application Centre (Jodhpur) and various regional Remote Sensing Centres at Dehradun and elsewhere, wetlands are now being mapped using GIS techniques and Remote Sensing technology.
Some of the wetland mapping (given state-wise) are:
- Andhra Pradesh - (a)Kakinada Bay, using Orbital Remote Sensing data, (b) Rajahmundry wetlands
- Assam - Dhansiri River Channel, using topographic maps of the Survey of India (1914,1975) and Indian Remote Sensing satellite imagery (1990,1995, 2000)
- Bihar - Wetlands of East Champaran district, using IRS ID LISS III data, 2005
- Kerala - select wetlands, using IRS P6 (Resourcesat-1) LISS III datasets, Landsat TM data
- Madhya Pradesh - (a)Ramsagar reservoir, Datia District, using GPS Garmin 76 and satellite data of IRS-1D LISS-III of the year 2002, 2010, (b)Gwalior-Chambal region, using LISS III (2-7thMarch,2008) and Landsat TM (Oct2000) satellite imagery procured from NRSA, Erdas Imagine 8.6 software, Arc GIS 9.1 software, 2009
- Orissa - Samang Lake
- Punjab - Harike Wetland (a Ramsar site), using IRS-1A LISS-IONOSPHERE multidate data. 1997
- Tamil Nadu - (a)Pichavaram swamp, between Vellar and Coleroon estuaries along east coast, using IRS ID LISS III data, (b) Muthupet
- West Bengal - Sunderbans, using IRS IC/ID, LISS-III data of December, 1999, March 2001 in 4 bands (Green, Red, Near IR and SW IR) requisitioned from NRSA, ARC/INFO software.
The institutes involved were Survey of India, Institute of Remote Sensing, National Remote Sensing centre (Hyderabad) and State Remote Sensing application Centre (Jodhpur).
Using Geographic Resources Analysis Support System (GRASS), based on open source GIS, the Varthur Lake at Bangalore has also been mapped in a collaborative initiative of the Energy and Wetlands Research Group, Centre for Ecological Sciences and the Indian Institute of Science.
Why does one need geospatial tools for mapping wetlands?
Wetland mapping is the first step to monitoring this important part of the ecosystem. Wetland management helps reduce effects from floodwaters and storm surges, help recharge aquifers, filter sedimentation and pollution from upland drainage. From conservation point of view, coastal habitats can be monitored.
Status: Mapping of wetlands using geospatial tools, can be done accurately at minimal costs and manpower use. Monitoring at multiple spatial and temporal scales, support better understanding of the ecosystem for continuous assessment and analysis of future trends. Various geospatial tools are at disposal, from a range of GIS software to remote sensing data, to give an accurate picture of wetland status and study of trends.
Distribution: Mapping of wetlands using common attributes help to form a database of wetland distribution across the country. An inventory of wetlands in an area is vital to maintaining the ecological balances.
Monitoring of wetland dynamics
Geospatial tools when applied to wetland mapping help assess landscape changes, as well as monitor the pollution and siltation levels, weed infestation and aquaculture development.
Besides wetland change assessment, water quality analysis and modelling, mapping of surface water bodies, flood zonation mapping, irrigation & cropping patterns are also areas of application.
Study of wetland biodiversity, wetland ecology, conservation and restoration, seasonal monitoring and characterization, are possible with technology enabled mapping in an integrated multi-layered structure using remotely sensed data.
A classic example where proper wetland mapping and monitoring is in dire need, would be the Ramsar protected Wetlands in the East of Kolkata, which has been threatened time and again by human encroachment and land-grabbing builders. Mapping of boundaries when layered with socio-economic data, would facilitate constant monitoring and check on wetland profile. The significance of these wetlands cannot be understated, as excess monsoon run-offs is otherwise diverted downslope towards the Kolkata metropolis. So it is heartening to note that in February itself, a directive has been made by East Kolkata Wetland management Authority (EKWMA) for demolishing of illegal structures.
However, what we need is not isolated cases in wetland mapping, but a comprehensive national inventory base, with suitable codification, a master Geodatabase embedded with multi layered metadata.
A uniform methodology for codification, characterization and action plan needs to be evolved for creating a nationwide database of wetlands. Using IRS LISS III sensors for delineating turbidity, various aquatic vegetation and major geomorphological classes, comprehensive information can be recorded for spatial analysis with layers of metadata.
This would be the first step in forming an effective wetland policy. So kudos to the scientific and researching fraternity, who have taken up this task in a very precise and methodical manner! At the same time, the database needs to be presented in a uniform and comprehensive manner as in the U.S. National Wetlands Inventory, for a complete one-stop easily accesible resource bank on wetlands in India.
Some Web-GIS Applications used for wetland mapping in India are:
Google Maps API, PHP, PostgreSQL/ PostGIS (used for Kerala Wetland mapping)
GeoServer, OpenLayers, uDIG (used for Rajahmundry and Chennai wetlands)
DjVu technology (simple Maps on Inland wetlands of India)
ALOV map technology
Besides these open source software used, the OpenJump, SAGA GIS, Geocortex, ArcInfo, Erdas Imagine and ArcGIS are also favoured.
Case study: A study was carried out to demarcate the wetlands of east Champaran district of Bihar, using IRS ID LISS III data, in 2005. Data for both, pre and post monsoons, were analysed. Wetlands were qualitatively characterised based on turbidity and status of aquatic vegetation. Water logging problem in the study area was inferred from the seasonal variation of water spread during both the seasons. Three categories were identified, namely ponds/lakes, water logged areas and oxbow lakes. The study observed that the inland wetlands constituted 2.7 % of the study area, of which 1.8 % was subject to water logging.
Wetlands of India
Salim Ali Centre for Ornithology and Natural History
GIS Techniques for evaluating Wetland maps derived from Remotely Sensed Data.