Research papers.
WETLANDS OF INDIA
Energy home

S. N. Prasad, T. Sengupta, Alok Kumar, V. S. Vijayan and Lalita Vijayan
Salim Ali
Center for Ornithology and Natural History,Coimbatore-641 108.

T. V. Ramachandra and N. Ahalya
Center for Ecological Sciences, Indian Institute of Science, Bangalore-560 012.

A. K. Tiwari
Regional Remote Sensing Service Center, Dehradun, Uttarachal-248 001.

CONTENTS
Introduction
Distribution of wet lands in India
Diversity of aquatic vegitation and avifauna in wetlands
Diversity of fishes in wetlands
Threat to wetlands is a threat to ecological balance
Acute wetland losses
Chronic wetland losses
The most seriously threatened wetlands in India
Wetland management - Current status
Protection laws and government initiatives
National wetland strategies
Use of Remote Sensing and GIS in wetland management
Interconnectivity of wetlands
Classification scheme of inland wetlands
Criteria for identifying wetlands of international importance( Ramsar Convention)
Classification of wetlands in the Indian subcontinent (Gopal et at., 1995)
Proposed classification of Inland wetlands in the Indian subcontinent(Anon, 2000)
Conclusion

INTRODUCTION

Wetlands are defined as lands transitional between terrestrial and aquatic eco-systems where the water table is usually at or near the surface or the land is covered by shallow water (Mitch and Gosselink, 1986). The value of the world's wetlands is increasingly receiving due attention as they contribute to a healthy environment in many ways. They retain water during dry periods, thus keeping the water table high and relatively stable. During periods of flooding, they mitigate floods and trap suspended solids and attached nutrients. Thus, streams flowing into lakes by way of wetland areas will transport fewer suspended solids and nutrients to the lakes than if they flow directly into the lakes. The removal of such wetland systems because of urbanization or other factors typically causes lake water quality to worsen. In addition, wetlands are important feeding and breeding areas for wildlife and provide a stopping place and refuge for waterfowls. As with any natural habitat, wetlands are important in supporting species diversity and have a complex of wetland values.

The present review is aimed at providing, in a nutshell, the distribution of wetlands, the value of wetlands, the causes and consequences of the loss of wetlands. The review attempts to provide a glimpse of the use of modern spatial technology tools, viz., Remote Sensing/GIS for obtaining an assessment, description and monitoring of inland wetlands. The review also gives a methodology for an ongoing nationwide attempt at evolving a conservation area network or a protected area network of inland wetlands.

DISTRIBUTION OF WETLANDS IN INDIA

India, with its annual rainfal1 of over 130 cm, varied topography and climatic regimes, supports and sustains diverse and unique wetland habitats. Natural wetlands in India consists of the high-altitude Himalayan lakes, followed by wetlands situated in the flood plains of the major river systems, saline and temporary wetlands of the arid and semi-arid regions, coastal wetlands such as lagoons, backwaters and estuaries, mangrove swamps, coral reefs and marine wetlands, and so on. In fact with the exception of bogs, fens and typical salt marshes, Indian wetlands cover the whole range of the ecosystem types found. In addition to the various types of natural wetlands, a large number of man-made wetlands also contribute to the faunal and floral diversity. These man-made wetlands, which have resulted from the needs of irrigation, water supply, electricity, fisheries and flood control, are substantial in number. The various reservoirs, shallow ponds and numerous tanks support wetland biodiversity and add to the country's wetland wealth. It is estimated that freshwater wetlands alone support 20 per cent of the known range of biodiversity in India (Deepa and Ramachandra, 1999).

Wetlands in India occupy 58.2 million ha, including areas under wet paddy cultivation (Directory of Indian Wetlands). The majority of the inland wetlands are directly or indirectly dependent on the major rivers like Ganga, Bhramaputra, Narmada, Godavari, Krishna, Kaveri and Tapti. They occur in the hot arid regions of Gujarat and Rajasthan, the deltaic regions of the east and west coasts, highlands of central India, wet humid zones of south peninsular India and the Andaman and Nicobar and Lakshwadeep Islands.

Table 1. Area Estimates of Wetlands of India (in million ha)

Area under paddy cultivation 40.9
Area suitable for fish culture 3.6
Area under capture fisheries (brackish and freshwater) 2.9
Mangroves 0.4
Estuaries 3.9
Backwater 3.5
Man-made impoundments 3.0
Rivers, including main tributaries (28,000 km)
Canals and irrigation channels (113,000 km)
Total Area of Wetlands(Excluding Rivers) 58.2
(Source: Directory of Asian Wetlands, IUCN, 1989).

Indian wetlands are grouped as:

(I) Himalayan wetlands:
Ladakh and Zanskar
Pangong Tso, Tso Morad, Chantau, Noorichan, Chushul and Hanlay marshes
Kashmir Valley
Dal, Anchar, Wular, Haigam, Malgam, Haukersar and Kranchu lakes
Central Himalayas
Nainital, Bhimtal and Naukuchital
Eastern Himalayas
Numerous wetlands in Sikkim, Assam, Arunachal Pradesh, Meghalaya, Nagaland and Manipur, Beels in the Brahmaputra and Barak valley
(II) Indo-Gangetic wetlands:
The Indo-Gangetic flood plain is the largest wetland system in India, extending from the river Indus in the west to Brahmaputra in the east. This includes the wetlands of the Himalayan terai and the Indo-Gangetic plains.
(III) Coastal wetlands:
The vast intertidal areas, mangroves and lagoons along the 7500 km long coastline in West Bengal, Orissa, Andh,ra Pradesh, Tamil Nadu, Kerala, Karnataka, Goa, Maharashtra. and Gujarat. Mangrove forests of Sunderbans, West Bengal and Andaman and Nicobar Islands. Offshore coral reefs of Gulf of Kutch, Gulf of Mannar, Lakshwadeep and Andaman and Nicobar Islands.
(IV) Deccan:
A few natural wetlands, but innumerable small and large reservoirs and several water storage tanks in almost every village in the region.

Wetlands provide many services and commodities to humanity. Regional wetlands are integral parts of larger landscapes; their functions and values to the people in these landscapes depend on both their extent and their location. Each wetland thus is ecologically unique. Wetlands perform numerous valuable functions such as to recycle nutrients, purify water, attenuate floods, maintain stream flow, recharge ground water, and also serve to provide drinking water, fish, fodder, fuel, wildlife habitat, control rate of runoff in urban areas, buffer shorelines against erosion and offer recreation to the society. The interaction of man with wetlands during the last few decades has been of concern largely due to the rapid population growth- accompanied by intensified industrial, commercial and residential development, that further leads to pollution of wetlands by domestic, industrial sewage, and agricultural run-offs, such as fertilizers, insecticides and feedlot wastes. The fact that wetland values are overlooked has resulted in threats to the source of these benefits.

Wetlands are often described as "kidneys of the landscape" (Mitch and Gosselink, 1986). Hydrological conditions can directly modify or change chemical and physical properties such as nutrient availability, degree of substrate anoxia, soil salinity, sediment properties, and pH. These modifications of the physicochemical environment, in turn, have a direct impact on the biotic response in the wetlands (Gosselink and Turner, 1978). When hydrological conditions in wetlands change even slightly, the biota may respond with massive changes in species composition and richness and in ecosystem productivity. Traditional limnological methods of assessment of water quality are time consuming and uneconomical, but using remote-sensing data assessment of water quality and productivity in surface impoundment is both cost-effective and fast. The indicators useful for such an assessment include suspended materials visible to the human eye, which include suspended inorganic material, phytoplankton, organic detritus and dyes.

DIVERSITY OF AQUATIC VEGETATION AND AVIFAUNA IN WETLANDS

Aquatic biodiversity is dependent on the hydrological regime and geological conditions; efforts are being made to conserve the biodiversity found in wetlands; streams and rivers. The goal of this effort to conserve this irreplaceable biodiversity is to minimize its loss through sustainable management and conservation practices. The first step in conservation of biodiversity is to assess the diversity of natural resources present and identify those, which are important and most irreplaceable (Groombridge and Jenkins, 1998). Awareness of the unique nature of biodiversity, and the plethora of factiors contributing to the decline in habitat quality and species populations has been growing in the past decade.

In India, lakes, rivers and other freshwaters support a large diversity of biota representing all almost all taxonomic groups. Algae in open waters represent the floristic diversity and macrophytes dominate the wetlands. It is difficult to analyze the algal diversity in India with reference to different habitats, endemicity to India, as well as the changes that occur due to anthropogenic disturbances. From an ecological point of view, the diversity of species present in the wetlands is an indication of the relative importance of the to aquatic biodiversity issue as a whole.

The total number of aquatic plant species exceeds 1200 (Gopal, 1995): Wetlands are also important as resting sites for migratory birds. Aquatic vegetation is a valuable source of food, especially for waterfowl. In the winter, migratory waterfowl search the sediment for nutritious seeds, roots and tubers. Resident waterfowl may feed on different species of aquatic vegetation year-round.

DIVERSITY OF FISHES IN WETLANDS

The Indian fish fauna is divided into two classes, viz., Chondrichthyes and Osteichthyes. The Chondrichthyes are represented by 131 species under 67 genera, 28 families and 10 orders in the Indian region (Kar el al, 2000). The Indian Osteichthyes are represented by 2,415 species belonging to 902 genera, 226 families and 30 orders, of which five families, notably the family Parapsilorhynchidae is endemic to India. These small hill stream fishes, include a single genus, viz., Parapsilorhynchus, which ,contains 3 species. They occur in' the Western Ghats, Satpura Mountains and the Bailadila range in Madhya Pradesh only. The fishes of the family Psilorliynchidae with the only genus Psilorhynchus are also endemic to the Indian region. Other fishes endemic to India include the genus OZytra and the species Horaichthys setnai belonging to the families Olyridae and Horaichthyidae respectively. The latter occur from the Gulf of Kutch to the Trivandrum coast. The endemic fish families form 2.21 per cent of the total bony fish families of the Indian region. 223 endemic fish species are found in India, representing 8.75 per cent of the total fish species known from the Indian region and 128 monotypic genera of fishes found in India, representing 13.20 per cent of the genera of fishes known from the Indian region.

THREAT TO WETLANDS IS A THREAT TO ECOLOGICAL BALANCE

Wetlands are one of the most threatened habitats of the world. Wetlands in India, as elsewhere are increasingly facing several anthropogenic pressures. Thus, the rapidly expanding human population, large-scale changes in land use/land covers, burgeoning development projects and improper use of watersheds have all caused a substantial decline of wetland resources of the country. Significant losses have resulted from its conversion threats from industrial, agricultural and various urban developments. These have led to hydrological perturbations, pollution and there effects. Unsustainable levels of grazing and fishing activities have also resulted in degradation of wetlands.

The current loss rates in India can lead to serious consequences, where 74% of the human population is rural (Anonymous, 1994) and many of these people are resource dependent. Healthy wetlands are essential in India for sustainable food production and potable water availability for, humans and livestock.

They are also necessary for the continued existence of India's diverse populations of wildlife and plant species; a large number of endemic species are wetland dependent. Most problems pertaining to India's wetlands are related to human population. India contains 16% of the world's population, and yet constitutes only 2.42% of the earth's surface. The Indian landscape has contained fewer and fewer natural wetlands over time. Restoration of these converted wetlands is quite difficult once these sites are occupied for non-wetland uses. Hence, the demand for wetland products (e.g. water, fish, wood, fiber, medicinal plants, etc.) will increase with the increase in population. Wetland loss refers to physical 'loss in the spatial extent or loss in the wetland function. The loss of one km2 of wetlands in India will have much greater impacts than the loss of one km2 of wetlands in low population areas of abundant wetlands (Lee et aI., 1996). The wetland loss in India can be divided into two broad groups, namely acute and chronic losses. The filling up of wet areas with soil constitutes acute loss, whereas the gradual elimination of forest cover with subsequent erosion and sedimentation of the wetlands over many decades is termed as chronic loss.

ACUTE WETLAND LOSSES

1. Agricultural conversion

In the Indian subcontinent due to rice culture, there has been a loss in the spatial extent of wetlands. Rice farming is a wetland-dependent activity and is developed in riparian zones, river deltas and savannah areas. Due to captured precipitation for fishpond aquaculture in the catchment areas' and rice-farms occupying areas that are not wetlands, the downstream natural wetlands are deprived of water. Around 1.6 million ha of freshwater are covered by freshwater fishponds in-India. Rice-fields and fishponds come under wetlands, but they rarely function like natural wetlands. Of the estimated 58.2 miIlion ha of wetlands in India, 40.9 mi11ionha are under rice clirtivation (MoEF, 1993).

2. Direct deforestation in wetlands

Mangrove vegetation is flood-and salt-tolerant and grows along the coasts and is valued for fish and shellfish, livestock fodder, fuel wood, building materials, localmedicine, honey, bees wax and for extracting chemicals for tanning leather (Ahmad, 1980). Alternative farming methods and fisheries production have replaced many mangrove areas and continues to pose threats. Eighty percent ofIndia's 4240 km2of mangrove forests occur in the Sunderbans and the Andaman and Nicobar Islands (Government of India, 1991). But most of the coastal mangroves are under severe pressure due to the economic demand for shrimps. Important ecosystem functions such as buffer zones against storm surges, nursery grounds and escape cover for commercia11y'important fisheries are lost. The shrimp farms also caused excessive withdrawal of freshwater and increased pollution load on water, like increased lime, organic wastes, pesticides, chemicals and disease causing organisms. The greatest impacts were on the people directly dependent on the mangroves for natural materials, fish proteins and revenue. The ability of wetlands to trap sediments.and slow the flow of water is reduced.

3. Hydrological alteration

Alteration in the hydrology can change the character, functions, values arid 'the appearance of wetlands. The changes in hydrology include either the removal of water from wetlands or raising the land.-surface.elevation, such that it no longer floods. Canal dredging operations have been conducted in India from the 1800s due to which 3044 krn2'of irrigated'iand has increased to 4550 kl112in 1990 (MoEF, 1994). An initial increase in the crop productivity has given way to reduced fertility and salt accumulations in soil due to irrigated farming of aridsoils. India has 32,000. ha of peat-land remaining and drainage of these lands wi11lead to rapid subsidence of the soil surface.

4. Inundation by dammed reservoirs

At present, there are more than 1550 large reservoirs covering more than 1.45 millioi1'lia and more than 100,000 small and medium reservoirs covering 1.1 mi11ionha in India (Gopal, 1994). By impounding.the water, thebydroIogy oran area is significantly altered and allows for harnessing moving water as a source of energy. While the benefits of energy are well recognized, it also alters the ecosystem.

CHRONIC WETLAND LOSSES

1. Alteration of upper watersheds

Watershed conditions influence the wetlands. The condition of the land where precipitation falls, collects and run off into the soil will influence the character and hydrological regime of the downstream wetlands. When agriculture, deforestation or overgrazing removes the w~ter-holding capacity of the soil, then soil erosion becomes more pronounced. Large areas of India's watershed area are being physically stripped of their vegetation for human use.

2. Degradation of water quality Water quality is directly proportional to the human population and its various activities. More than 50,000 small and large lakes are polluted to the point of being considered 'dead' (Chopra, 1985). The major polluting factors are sewage, industrial pollution and agricultural runoff, which may contain pesticides, feliilisers and herbicides.

3. Ground water depletion

Draining of wetlands has depleted the ground water recharge. Recent estimate indicate that in rural India, about 6000 vi1Iagesare without a source for drinking water due to the rapid depletion of ground water.

4. Introduced species and extinction of native biota

Wetlands iri India support around 2400 species and subspecies of birds. But losses in habitat have threatened the diversity of these ecosystems (Mitchell and Gopal, 1990). Introduced exotic species like water hyacinth (Eichhornia crassipes) and sal.vinia (Salvinia molesta) have threatened the wetlands and clogged the waterways, competing with the native vegetation. In a recent attempt at prioritization of wetlands for conservation, Samant (1999) noted that as many as 700 potential wetlands do not have any data to prioritize. Many ofthese wetlands are threatened.

THE MOST SERIOUSLY THREATENED WETLANDS1N INDIA

Dal Lake, Logtak Lake, Wular Lake, Salt Lakes swamp, Harike Lake, The Sunderban, lheelsin the vicinity of Haldergarh, Chilka Lake, Dahar and Sanj lheels, Kolleru Lake, Southern Gulf of Kutch, Estuaries of the Karnataka coast, Gulf of Khambhat, Kaliveli Tank and Vedayanthhtu Estuary, Khabartal, The Cochin Backwaters, Dipor Bheel, Wetlands in the Andaman and Nicobar Islands

WETLAND MANAGEMENT - CURRENT STATUS

Wetlands are not delineated under any specific administrative jurisdiction. The primary responsibility for the management of these ecosystems is in the hands of the Ministry of Environment and Forests. Although some wetlands are protected after the formulation of the Wildlife Protection Act, the others are in grave danger of extinction. Effective coordination between the different ministries, energy, industry, fisheries, revenue, agriculture, transport and water resources, is essential for the protection of these ecosystems.

PROTECTION LAWS AND GOVERNMENT INITIATIVES

Wetlands conservation in India is indirectly influenced by an array of policy and legislative measures (Parikh and Parikli,1999). Some Ofthe key legislation is given below :-

NATIONAL WETLAND STRATEGIES

National wetland strategy should encompass (i) Conservation and coI\aborative managen1ent, (ii) Prevention of loss and promotion of restoration and (iii) Sustainable management. These include :

(1) Protection

The primary necessity today is to protect the existing wetlands. Of the many wetlands in India, only around 68 wetlands are protected. But there are thousands of other wetlands that are biologically and economicallyimpOliant but have no legal status.

(2) Planning, Managing and Monitoring

Wetlands that come under the Protected Area Network have management plans but others do not. It is important for various stakeholders along with the local community and the corporate sector to come together for an effective management plan. Active monitoring of these wetland systems over a period of time is essential.

(3) Comprehensive Inventory

There has been no comprehensive inventory of all the Indian wetlands despite the efforts by the Ministry of Environment and Forests, Asian Wetland Bureau and World Wide Fund for Nature. The inventory should involve the flora, fauna, and biodiversity along with wetland direct and indirect values. It should take into account the various stakeholders in the community too.

(4) Legislation

Although several laws protect wetlands there is no special legislation pertaining specially to these ecosystems. Environment Impact Assessment is.needed for major development projects and highlighting threats to wetlands need must be included and appropriate measures to be formulated.

(5) Coordinated Approach

Because Wetlandsare common property with multi-purpose utility, their protection and management also need to be a common responsibility. An appropriate forum for resolving the conflict on wetland issues has to be set up. It is important for all the relevant ministries to allocate sufficient funds towards the conservation of these ecosystems.

(6) Research

There is a necessity for research in the formulation of a national strategy to understand the dynamics of these ecosystems. This could be useful for the planners to formulate strategies for the mitigation of pollution. The scientific knowledge will help the planners in understanding the economic values and benefits, which in turn will help in. setting priorities and, focusing the planning process.

(7) Building Awareness

For achieving any sustainable success in the protection of these wetlands, awareness muong the general public, educationaland corporate institutions must be created. The policy makers at various levels, along with site managers,need to be educated.Beca!Jsethe country's wetlands are shared, the bi-lateral cooperation in the resource management needs to be enhanced.

USE OF REMOTE SENSING AND GIS IN WETLAND MANAGEMENT

Remote sensing data in combination with Geographic Information System (GIS) methods are'effective tools for wetland conservation and management. The application encompasses water resource assessment, hydrological modeling, flood management, reservoir capacity surveys, assessment and monitoring of the environmental impacts of water resources projects and water quality mapping and monitoring (Jonna, 1999).

1. Flood zonation mapping

Satellite data are used for interpretation and delineation of flood-inundated regions, flood-risk zones. Temporal data helps us to obtain correct ground information about the status of ongoing conservation projects. IRS lC/D WiFS data having 180 km spatial resolution and high temporal repetitiveness has helped in delineating the zonation of flooding areas of large river bodies, thus helping in the preparation of state-wide and basin-wise flood inventories.

2. Inventory and monitoring of irrigation and cropping pattern

Remote-sensing data pave the way for an economic methodology to inventory, monitor and manage water bodies due to improving spatial, spectral and temporal resolution. Satellite data in association with the geographical information systems provide a cost and time-effective tool to identify, map, inventory and monitor cropping patterns, crop production and condition, irrigation status and to help in the diagnosis of poorly performing irrigation patterns. Indian IRS-l A and lB satellites data have been used to inventory irrigation systems, cropping patterns, water logging, tank irrigation, watershed delineation, silting during post-monsoon, temporal changes in the water-spread and irrigated areas. These inventorying data are used as inputs to formulate conservation and management plans for development of land and water resources.

3. Water quality analysis and modeling

Remote sensing data are used for the analysis of water quality parameters and modeling. Water quality studies have been carried out using the relationship between reflectance, suspended solid concentration, and chlorophyll-a concentration. In the near infrared wavelength range, the amount of suspended solids content is directly proportional to the reflectance. Due to spatial and temporal resolution of satellite data, information on the source of pollution and the point of discharge, as well as the inflow of sewage, can be regularly monitored.

Using IRS LlSS II data Sasmal and Raju (1996) monitored the suspended load in estuarine waters of the Hoogly, West Bengal in a GIS environment. In this study, band 4 of the data set was found to show a wider range of digital classes, indicating a better response with depth than the rest of the bands. Landsat TM and IRS -lA fdata were used to estimate sediment load in Upper Lake, Bhopal (Raju et aI., 1993). This study showed a high relationship between the satellite as well as ground truth radiometric data and total suspended solids. Different image processing algorithms are also used on the Landsat. MSS dataset to delineate sediment concentration in reservoirs (Jonna et ai., 1989). Qualitative remote sensing methods have. been used for real time monitoring of inland water quality (Oitelson et aI., 1993), Airborne sensors have also been used to study the primary productivity and related parameters of coastal waters and. large water bodies (Seshmani et ai., 1994).

4. Mapping changes in river courses

Hazra and Bhattacharya (1'999) studied the changes in the river course of the Ganga -   Padma River over space and time to delineate the vulnerable zones for environmental management, using visual interpretation techniques to identify and delineate. various geomorphological and geological features. The results indicate the river will shift along its course due to natural calamities and in some places due to anthropogenic interferences.

5. Delineation of extinct river courses

Because ofits sensitivity to moisture and penetration capabilities in arid regions, satellite remote sensing also helps jn displaying anomalies in the terrain that are caused by the pattern ofvegetation/water bodies, sand-dunes, lithology, drainage courses, salt lakes, topography - and slopes, natural breaks, etc., which help in creating a conceptualized model ofthe extinct rivercourse. Hence, it proves an effective tool for the study ofthe course ofthe ancient river Saraswati (Sharma et al., 1999) more than any other method.

6. Water resource management

GIS and remote sensing were used for the development ofwater resources in the Sai- Gad sub-watershed ofAlmora District, Uttar Pradesh (Mohan et al., 1999). Various thematic maps on the hydro-geomorphological characteristics, elevation, slope, drainage, surface water bodies and land-use have been generated and integrated for the Action Plan for Water Resources Development.

For the evaluation ofhydro-geochemical conditions ofthe Niva River Basin, Chittoor district in Aridhra Pradesh, drainage maps ofthe basin were prepared and the imagery data were interpreted using standard interpretation keys such as colour, tone, texture, and pattern ofdrainage, shape and topography. The results revealed that the underground potential of the basin is moderate to good (Rao, 1997). 

The drainage pattern ofJharia coalfield, Bihar, India as observed on IRS-l A LISS II image shows that the region is drained by 11 streams, which eventually drain into the river Damodar (Srivastava, 1997). It is thus helpful in conducting environmental impact assessment.

Use ofsatellite remote sensing data coupled with aerial photo-interpretation greatly aid in planning ground water exploration and help in locating the sources by identification ofgeomorphological units. Air-borne and space-borne data were used for the qualitative evaluation of ground water resources in Keonjhar District, Orissa (Das et al., 1997). The study revealed the importance of hydrogeomorphological mapping from remotely sensed data in groundwater targeting in the structurally complex terrain of the district. Resistivity soundings and exploratory digging further corroborated the study.

Remote sensing, geophysical, DBTM (Digital Basement Terrain Model) and GIS were used for sustainable utilisation of water resources of the Alaunja watershed, located on the 'Chotanagpur' plateau of Bihar (Kumar, 1999). The study helped in the prioritisation of water resource development in the watershed, i.e., delineation of the area suitable for groundwater/surface water utilisation.

With the development of highly precise remote sensing techniques in spatial resolution and GIS, the modeling of the watershed has become more physically based and spatially distributed to enumerate interactive hydrological processes considering spatial heterogeneity. A distributed model with an SCS curve number method called the Land Use Change (LUC) model was developed (Mohan and Shresta, 2000) to assess the hydrological changes due to land use' modification. The model developed was applied to the Bagmati River catchment in the Kathmandu valley basin, Nepal. The study clearly demonstrated that integration of remote sensing, GIS and spatially distributed model provides a powerful tool for assessment of the hydrological changes due to land-use modifications.

7. Habitat mapping using microwave remote sensing

Microwave remote sensing tools have an important role to play in applications relating to wetland monitoring and mapping. In optical remote sensing, the visible and infrared part of the electromagnetic spectrum is used to characterize objects of interest. However, during monsoon season, the suitable atmospheric windows for acquisition of optical data are limited to cloud-free periods. This is a major lacuna for wetland applications, because wetlands are highly seasonal and dynamic systems compared to terrestrial ecosystems. The radar imaging system overcomes many of these limitations by providing increased canopy penetrations and day and night acquisitions nearly independent of weather conditions (Ramsey, 1995; Ramsey and Laine, 1997). His therefore imperative to use radar data for a better understanding of the dynamics of wetland ecosystems as well as their assessment, monitoring and management. There are also several advantages to using microwave data. Microwave sensors have a unique sensitivity to the moisture content of earth material. They are also highly sensitive to textural properties of vegetative cover. Therefore, they can be used to discriminate between grasses, aquatic vegetation, forest and crop cover. In this way the surrounding people can use them to identify the encroachment inside a national park for agricultural activities.

Identification of different habitats is also an important activity for wetland monitoring and management. Studies indicate that Synthetic Apeliure Radar data are far superior to optical satellite data in the delineation of open water, habitat and aquatic vegetation. Although radar remote sensing can play an important role in wetlands, .sofar very little work has been carried out and there is huge potential to explore and exploit the different capabilities of radar data for wetland research. High Incidence Angle Radar data have been used to delineate the open water habitat with aquatic vegetation critical for waterfowl in wetlands The study of Keoladeo Ghana National Parkin Bharatpur has shown that radar data are 3 to 4 times better in delineating the extent of open water, aquatic vegetation categories and also localities of high soil moisture content (Srivastava et at., 2001). This information will be of great significance in formulating Habitat Suitability Index (BS) models for a variety of faunal species.

THE INTERCONNECTIVITY OF WETLANDS

The interconnectivity of wetlands and changes in it over a period of time were documented for large areas of Bangalore urban and rural districts by Deepa and Ramachandra (1999). From a landscape perspective, it is vital that studies on interconnectivity are given emphasis. The results are of crucial significance in designing conservation preserves of wetlands.

WETLAND MAPPING - A Status Review

Wetlands playa vital role in maintaining the overall cultural, economic and ecological health of the ecosystem; their fast pace of disappearance from the landscape is of great concern. The Wildlife Protection Act protects few of the ecologically sensitive regions whereas several wetlands are becoming an easy target for anthropogenic exploitation. Surveys of 147 major sites across various agroclimatic zones identified the anthropogenic interference as the main cause of wetland degradation (The Directory of Indian Wetlands, 1993). 'The current spatial spread of wetlands under various categories is shown (Parikh and Parikh, 1999).

The National Wetland Committee of the Ministry of Environment and Forests (MOEF), Govt. of India, has recommended a number of proactive steps. Accordingly, twenty-two sites were declared tentatively as wetlands of National and International Significance for long-term conservation. The Committee recommended a nation-wide inventory of wetlands to be undertaken under the guidance of the National Wetland Committee with the support of the Standing Committee on Bioresources (SC-B) "of the National Natural Resource Management System (NNRMS) and MOEF. The Space Application Center (SAC), Ahmedabad, of the Indian Space Research Organization (ISRO) had undertaken, in collaboration with various state remote sensing application centers, a nation wide mapping of inland wetlands. This was done on a reconnaissance scale and was completed in 1997. The study recommended mapping at a larger spatial scale as wetlands below 56 ha in size could not be delineated.

The Space Application Center (SAC) has mapped the wetlands at 1:250000 scale on the mainland as well the islands. Using the visual interpretation of coarse resolution satellite data the states of Sikkim, West Bengal, Goa, Punjab, Haryana, Himachal Pradesh, Chandigarh, Delhi, Andaman, Nicobar, Lakshwadeep, Dadra and Nagerhaveli were mapped at 1:50000 scale. However, in the rest of the country, only wetlands of 56.25 ha and above in size could be mapped. It is known that a vast majority of wetlands in number, extent and conservation importance is below 50'ha in size (for example, those in the Indo-Gangetic plains and in the Deccan peninsula). Thus, the inventory covered only a small number of wetlands: moreover, the conservation values are not known for those wetlands even whose inventory has now been obtained. The data merely indicate locations of wetlands, and the classification of wetlands on 1:250,000 scale is only geomorphologicin nature (such as Oxbow Lakes, Playas, Lakes, Ponds,etc.,) and has no other factual biological conservation value. By itself, the information will only be partly useful for conservation of wetlands. This estimate is likely to be twice as large if we include wetlands of size 50 ha or less (Das et aI., 1994) for Etwah and Mainpuri districts of U.P.

Requirements and information needs for wetland mapping

Past research on wetland conservation in the country has shown conclusively that microwetlands or satellite wetlands around a bigger wetland act as a constellation of habitat mosaics for resident and migratory waterfowl (Vijayan, 1990). This is of special importance for inland wetland habitats in the flyways of migratory birds in the Indo-Gangetic plains and in the Deccan peninsula. Often, the size of these micro-wetlands is much smaller than 50 ha. Therefore, there is a great need to map wetlands of sizes smaller than 50 ha.

Thus, the objective is to develop an inland wetland inventory for the entire country. This will be carried out by means of available data and by also fresh data generation using modern spatial technologies. Thus by using digital remote sensing data for wetland mapping and analysis, information at any scale of all wetlands will be available according to the management and conservation requirements. Realizing the importance of wetlands, the Ramsar Convention in 1971 has urged the member countries to designate noted wetlands as Ramsar Sites or Wetlands of International Significance.

This has been recognized by many conservationists (e.g., Choudhury, 2000) and a wetland conservation strategy should therefore have an extensive basis of participatory processes. A hierarchical watershed- based approach will have a positive impact in not only reversing the chronic cases of wetland resource depletion but also helping design a network of wetland conservation preserves. These preserves would strive to not only conserve precious aquatic biodiversity but also help serve as a refuge for important economically useful wild plants and animal genetic resources.

ONGOING PROGRAMME OF WETLAND CONSERVATION

The program output is expected to aid in evolving a National Inland Wetland Conservation Strategy. The strategy includes policy, administrative and monitoring measures.

CLASSIFICATION SCHEME OF INLAND WETLANDS

The classification scheme proposed by Gopal et al. (1994) on inland wetlands in the Indian subcontinent is a mix of hydrological and biological (aquatic plants diversity) factors. However, from a practical conservation planning perspective, the immediate need of the hour is to produce a reasonably detailed classification based on a mix of habitats and aquatic vegetation. The merits of such a classification lie mainly in its utility to both managers and academicians. Such a scheme is possible with extensive state-of-the art spatial technologies and careful1ychosen field information and data. The current sensor resolution of course would permit aquatic vegetation classification at species assemblages level, if not at species level. However, for the reasons of wider usage and lower costs, it is nevetiheless possible to use the 20 m resolution sensors of the IRS series of Indian remote sensing satellites. Hence the modified classification system should be adopted for classification of inland wetlands using remote sensing data.

A proposed methodology

For classification of inland wetlands using remote sensing techniques, Band 4 of IRS 1C LISS III image data is to be density sliced for the separation of water bodies. The threshold values for water mask are to be obtained interactively. A bit map is to be generated for the water bodies. This mask will be used for further classification of water bodies into turbidity patterns and aquatic vegetation. Although the density slicing of band 4 provides acceptable results in most of the cases, it may some times, lead to confusions with non-water classes. A major class of confusion is the shadow due to terrain. Such anomalies can be removed through stratified density slicing and through contextual refinements.

The normalized Difference Vegetation Index (NDVI), which minimizes effect of the shadow, can also be used for separation of water bodies, as the wetland areas fall in a lower NDVI zone than terrestrial vegetation. However, NDVI may also exhibit confusing results, because many other non-vegetated classes like snow, barren land, etc., nmy exhibit NDVI values comparable to these of a water body. However, an interactive integration of band 4 and NDVI will clearly separate water bodies. .

Turbidity patterns

Turbidity patterns are best reflected by the band 1of IRS 1C, LISS III image data. The higher the DN value in band 1, the higher is the turbidity. The turbidity classification is a subjective one as it is impractical to relate the quantitative values for turbidity (which are dynamic according to the season) with the reflectance. Thus, determination of the threshold for different turbidity levels needs to be carried out by examining the major (large-sized) water bodies in the area.

Aquatic vegetation

Aquatic vegetation needs to be classified within the water body mask that is generated using band 4 of IRS LISS III data. The NDVI {generated as: (IR-)/(IR+R) where, IR is DN value in Band 3 and R is DN value in band 2 of IRS IC LISS III is to be obtained for water bodies. The NDVI values are subjectively divided into vegetation levels, i.e. nil, poor, moderate and high vegetation coverage. After country wide mapping of inland wetlands, some selected wetlands of each state which are prioritized due to their biodiversity values are to be considered for detail mapping. Table 3. Extent of Wetlands in India (Parikh and Parikh, 1999)

Area of Wetlands in India
Million hectars
Area under wet paddy cultivation
40.9
Area suitable for fish culture
3.6
Area under capture fisheries
2.9
Mangroves
0.4
Estuaries
3.9
Backwaters
3.5
Impoundments
3.0
Total Area
58.2

 

CRITERIA FOR IDENTIFYING WETLANDS OF INTERNATIONAL IMPORTANCE (RAMSAR CONVENTION)

A wetland is identified as being of international importance if it meets at least one of the following criteria that were approved at the Fourth Meeting of the Conference of Contracting Parties to the Ramsar Convention at Montreux, Switzerland, 1990.

Criteria for representative or unique wetlands

A wetland should be considered internationally important if

General criteria based on plants or animals

A wetland should be considered internationally important if

Specific criteria based on waterfowl

A wetland should be considered internationally important if

CLASSIFICATION,OF WETLANDS IN THE INDIAN SUBCONTINENT
(Gopal et at., 1995)

(I) INLAND WETLANDS

A. Freshwater wetlands

a. Woody vegetation

i. Permanently flooded (or waterlogged)

Myristica swamp (Myristica sp.) Sub-montane hill valley swamp (Bischofia, Alstonia, Salix) Creeper swamp (including cane brakes) (Magnolia, Eugenia, Calamus)

ii. Seasonally flooded

Eastern seasonal swamp (Machi/us gamblei,. Elaeocalpus sp.) Barringtonia swamp (Barringtonia acutangllla) Syzygillm cllmini swamp (Syzygium cllmini) Seasonal low swamp forest (Cepahalanthlls occidentalis) Eastern Dillenia swamp (Dillenia indica, Bischofia javanica) Riparian fringing forests (Tamarix dioica,Terminaliasp.)

(II) Alder forests (Alnus nepalensis) Saline wetlands

a. Woody vegetation

i. Permanently flooded (or waterlogged) There are none

ii. Seasonally flooded (or waterlogged) Saline scrubs (e.g., Rann of Kutch)

b. Herbaceous vegetation (submerged or other halophytes)

i.. Permanently flooded (or waterlogged) Saline high-altitude lakes (littoral zones   only)

ii. Seasonally flooded (or waterlogged) Saline lakes (e.g., Sambhar, Pachpadra, Deedwana) Riverine blue pine forests Wet Bamboo brakes (Bambusa, Neohouzeaua)

C. Herbaceous vegetation

i. Permanently flooded (or waterlogged) Submerged and/or floating leaved

Cattails (mainly Typha angustata) Reeds (Phragmites karka, P. australis, Arundo donax) Tall Emergent (other than reeds and cattails) (e.g., Ipomoeafistulosa) Tall sedges (Scilpus, Cyperus, Eleocharis)

ii. Seasonally flooded(or waterlogged) Submerged and/or floating leaved

Cattails (Typha elephantina) Reeds (Phragmites kafka, Arunda donax) Tall Emergent (other than reeds and cattails) (e.g., lpomoeafistulosa) Tall sedges (Scilpus, Cyperus, Eleocharis)   Short sedges and grasses (Kyllinga. Eleocharis, Fimbristylis Paspalum, Echinochloa) Wet meadows (mostly forbs, Cynodon) Tall grasses (Vetiveria, Erianthus, Saccharum).

PROPOSED CLASSIFICATION OF INLAND WETLANDS IN THE INDIAN SUBCONTINENT (Anon, 2000)

(1) FOREST

A. Dense

B. Open

(2) ARABLE

(3) WASTELAND

(4) WETLAND  

A. Ponds/Tanks/Lakes

B. .Reservoirs

C. Waterlogged

D. Oxbow lakes / Cutoff

a. Turbidity Low

b. Turbidity Medium

c. Turbidity High

1. Aquatic vegetation poor coverage

2. Aquatic vegetation moderate coverage

3. Aquatic vegetation high coverage.

(5) ROADS

(6) MAJOR HABITATION


 

CONCLUSION

                      It is noteworthy that even a small country like UK could designate 161 wetlands as Ramsar Sites, India being a mega-diversity country, so far managed to delineate a mere six sites to date. There is obviously much ground to be covered in our conservation efforts for wetlands. In addition, a paradigm shift in our conservation ethic is also a strong need of the hour. This shift is necessary and perhaps mandatory due to the very nature of the resource being conserved and 'protected'. Because wetlands are a common property resource, It is an uphil1 task to protect or conserve the ecosystems unless the principal stakeholders are involved in the process. The dynamic nature of wetlands necessitates the widespread and consistent use of satellite-based remote sensors and low-cost, affordable GIS tools for effective management and monitoring.