ENVIS Technical Report: 25

ECOLOGICAL ASSESSMENT OF LENTIC WATER BODIES OF BANGALORE

WETLANDS

Wetlands are, ‘lands that are in transition between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water.’ Thus, wetlands serve as a vital link between land and water. Wetlands differ due to variations in water regime, fauna and flora, climate, soils, and topography, and are classified into the major categories of marshes, fens, bogs, swamps, and shallow open water.

Ramsar Convention (http://www.ramsar.org) defines Wetlands as ‘areas of marsh or fen, peat-land or water, whether artificial or natural, permanent or temporary, with the water that is static or flowing, fresh, brackish or salt including areas of marine water, the depth of which at low tide does not exceed 6 m’. This definition evolved with the perspective of conservation and restoration of degrading wetlands worldwide. Mangroves, corals, estuaries, bays, small creeks, flood plains, sea grasses, lakes, etc. are all covered under this definition.

Wetlands can be virtually found in every continent, country and state across the Arctic tundra wetlands in Alaska and peat bogs in Appalachians to riparian wetlands in the arid west. In India, wetlands are distributed in different geographical regions ranging from the cold arid zone of Ladakh to the warm arid zone of Rajasthan, the tropical monsoonal central India to the wet and humid zone of southern peninsula. Most of the wetlands in India are directly or indirectly linked with major river systems like the Ganga, Brahmaputra, Godavari, Narmada, Tapti, Krishna, Cauvery, etc. A few of them which are Ramsar sites and of international significance are Dal lake in Srinagar, Kolleru in Andhra Pradesh, Chilka lake in Orissa, Wulur in Jammu and Kashmir, and the backwaters of Cochin.

In many areas of the world wetlands have been drained, filled in, or considered useless land. In Southeast Asia existing wetlands have been modified or new wetlands have been created to allow for rice culture, and these paddy fields have fed billions of people over the centuries. The decline in wetlands is global and a large percentage of wetlands have been lost consistently every year due to manifold reasons.

Functions and values of wetlands

Wetlands and lakes are an essential part of human civilization; meeting many crucial needs for life on earth such as drinking water, fish and shellfish production, water quality improvement, sediment retention, aquifer recharge, flood storage, transport, recreation, climate stabilisers and so on. Wetlands are also used to treat wastewater in many places. In addition, wetlands are globally important as natural sources of methane as a green house gas, to the atmosphere as this trace gas plays an important role in the regulation of climate. Wetland sediments are valuable because they preserve a long-term record of environmental conditions and the sediments in peat bogs are used in gardens. Wetlands due to their above listed biological, ecological, hydrological, social, cultural and economic values form an important component of the environment. The values of wetlands though overlapping, are thus inseparable. Some of the important functions of wetlands are discussed below.

Wetlands - natural water purifiers: Wetlands act like a water filtration system and improve the water quality by removing contaminants, excessive nutrients, and suspended particles.  Wetlands help in filtering the pollutants and soil runoff from upstream sources, which helps keep rivers, bays, and oceans clean in the downstream. In this way, healthy wetlands help mitigate the negative effects that human and farm waste, and some by-products of industrial pollution generate. Wetlands act as natural water purifiers, filtering sediment, nutrients and absorbing many pollutants in surface waters. In some wetland systems, this cleansing function enhances the quality of groundwater supplies as well.

Groundwater recharge and discharge: Wetlands act like giant sponges, storing, then slowly releasing groundwater, melted snow, and floodwater. The extent of groundwater recharge depends on the type of soil and its permeability, vegetation, sediment accumulation in the lakebed, surface area to volume ratio and water table gradient (Ramachandra T.V., Kiran R., and Ahalya N, 2002 ²¹).

Flood control and stream flow maintenance: Wetlands help control inland flooding and forestalls wave erosion along shorelines; because urban buildings and pavements release water runoff quickly, wetlands downstream from urban areas perform valuable flood control services. Wetlands along rivers and streams store excess water during rainstorms. This reduces downstream flood damage and lessens the risk of flash floods. The slow release of this stored water to rivers and streams helps keep them from drying up during periods of drought.

Wetlands as carbon sinks: Although wetlands occupy only a small portion of the world’s area, they are estimated to contain 10-14% of the carbon. Wetland soils such as histosols, may contain upto 20% carbon by weight and of course peats are more carboniferous. Their draining and conversion into agricultural land releases large quantities of carbon dioxide to the atmosphere, thus contributing to the carbon dioxide problem. Their plants and rich soil may provide one buffer against global climate change, by storing carbon instead of releasing it into the atmosphere as carbon dioxide.

Role in biogeological cycles: Wetlands play an important role in atmospheric and natural cycles (biogeological cycles). Nitrogen, phosphorus, sulphur, iron, magnesium and water cycles are all closely tied to the different layers of oxidation in wetlands. The ability of wetlands to transform nutrients and metals, particularly the ability to store phosphorus and transform nitrogen and sulphur to gases suggests that they play an important role in reducing nutrient concentrations in natural waters. Further, artificial wetlands may be used to treat nutrient laden waters produced by human activities. However, overloading a wetland with nutrients, beyond its threshold, impairs its ability to perform basic functions. Wetlands can slow eutrophication by the absorption of eutrophic parameters - phosphorus and nitrogen, thereby reducing algal growth, and excessive aquatic vegetation. Nitrogen fertiliser runoff from farms has overwhelmed the capacity of some wetlands to filter pollutants, creating "dead zones" in areas such as the Gulf of Mexico, where algal blooms are fueled by this and other nutrients have run riot and displaced a once thriving diverse oceanic ecology.

Shoreline and stream bank stabilisation: By absorbing the energy of storm waves and slowing the water currents, wetland vegetation serves as a buffer against shoreline and riverbank erosion, thus reducing sedimentation. Coastal wetlands help to blunt the force of major storms. Mangrove wetlands reduce flooding, coastal erosion, and property damage.

Wildlife habitat: Wetlands filter sediments and nutrients from surface water and support all life forms through extensive food webs and biodiversity. Wetlands provides habitat for many species of amphibians, reptiles, birds, and mammals that are uniquely adapted to wet environments. Upland wildlife such as deer, elk, and bear commonly use wetlands for food and shelter. Essential nesting, feeding, spawning, breeding grounds, and migratory route refuges are provided by the wetland ecosystem.  Wetlands are particularly vital to many migratory bird species. They provide habitats and support diverse ranges of biodiversity (e.g., in one square metre of coral reef, there can be up to 3000 species) Wetlands in a sense are biodiversity laboratories. For one, the diversity of conditions in wetlands set the environmental parameters that allow for, even encourage, the evolution of novel survival strategies. For example, many bog species have special adaptations to low nutrient levels, waterlogged conditions, acidic waters, and extreme temperatures. Wetlands are also home to many threatened and endangered species. Freshwater and marine life including trout, striped bass, pike, sunfish, crappie, crab, and shrimp rely on wetlands for food, cover, spawning, and nursery grounds.

Recreation – education: Many wetlands contain a diversity of plants and animals that provide beautiful places for sightseeing, hiking, fishing, hunting, boating, bird watching, and photography. Wetlands provide countless opportunities for environmental education, research and public awareness programs.

Wetland products: Wetland products include fish, timber, housing materials such as reeds, medicinal plants, the provision of fertile land for agriculture (sediments), water supply for domestic, arable, pastoral or industrial purposes, energy resource (fuel wood, etc.), transport, recreation, tourism, etc. By supporting diverse human activities, large wetlands play a particularly important role in the subsistence and development of thousands of people. Direct economic benefits include water supply, fisheries, agriculture, energy resource, wildlife resource, transport, recreation and tourism, supporting a vast diversity of flora, fauna and cultural heritage. Indirect benefits are improved water quality (including drinking water) by intercepting surface runoff and removing or retaining its nutrients, processing organic wastes, reducing sediment before it reaches open water, flood control and other cultural aspects. (Ramachandra T.V., Kiran R., and Ahalya N, 2002 ²¹)

Threats and loss of wetlands

Throughout the subcontinent, wetlands are degrading rapidly at a rate, which is unacceptable. Despite the government’s acceptance of the fact that these invaluable natural resources need to be conserved, wetland loss and degradation continue unabated. Wetlands have been lost and degraded in many ways that are not as obvious as direct physical destruction or degradation. Wetland loss and degradation can be due to conversion of wetland to non-wetland areas as a result of human activity or impairment of wetland functions as a result of human activity.

Habitat degradation on account of accelerating pollution, drainage, weed infestation, siltation and successive droughts has claimed the premature departure of many migratory birds. Apart from habitat loss, silt, chemicals, fertilisers and pesticides pouring into the waters from intensively cultivated land is another major cause of wetland degradation. Vast amounts of spongy wetlands have been drained to get a little extra land for agriculture, urban development, etc. Reclaimed land has soon become worthless lowering the water table, negating the very purpose of producing a good crop. Many wetlands are being drained, filled, cultivated, built upon, denuded and are buckling under the pressure of growing human numbers and the rising tempo of developmental activities.

Apart from pollution, the other major problems include the hydrological manipulations of wetlands in the form of flow alterations and diversions, disposal of dredged or fill material, sewage inflows, encroachment for developmental activities and construction of dykes or levees impacting wetland quality, species composition and functions. Wetlands near urban areas are under increasing developmental pressure for residential, commercial and industrial facilities. Urban areas in addition to altering the natural drainage patterns increase paved surfaces and reduce the land cover which in turn leads to increased amounts of surface runoff resulting in floods and water logging after rainfall. Increased runoff brings with it various substances that degrade water quality, such as fertilisers, chemicals, grease, sediment and oil, etc.

Although the debate over the rate of loss of wetlands is academically interesting, it is not especially important since we know that wetlands are being destroyed at a rate that is incredible. Historically, the pattern has been one of progressive wetland loss; especially in the developed world where a wide range of other land uses compete for wetland area. The largest threats today, however, are in the developing world where uncoupling of the traditional linkages between human communities and ecosystem functioning are likely to result in irretrievable losses.

Implications of losses and mismanagement of wetlands

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 developmental projects and improper use of watersheds have all caused a substantial decline of wetland resources in the country (Prasad S.N, Ramachandra T.V., Ahalya N., Sengupta. T., Alok Kumar, Tiwari A. K., Vijayan V. S.and Lalita Vijayan, 2002 ²²).

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  million ha of wetlands in India, 40.9 million ha are under rice cultivation (MoEF, 1993).

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, local medicine, 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 of India's 4240 sq. km of mangrove forests occurs 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 (prawns). Important ecosystem functions such as buffer zones against storm surges, nursery grounds and escape cover for commercially 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.

Hydrological alteration: Alteration in the hydrology can change the character, functions, values and 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 sq. km of irrigated land has increased to 4550 sq. km in 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 arid soils. India has 32,000 ha of peat-land remaining and drainage of these lands will lead to rapid subsidence of the soil surface.

Inundation by dammed reservoirs: At present, there are more than 1550 large reservoirs covering more than 1.45 million ha and more than 100,000 small and medium reservoirs covering 1.1 mi11ion ha in India (Gopal, 1994). By impounding the water, the hydrology of an area is significantly altered and allows for harnessing moving water as a source of energy. While the benefits of energy are well recognised, it also alters the ecosystem.

Alteration of upper watersheds: Watershed conditions influence the wetlands. The condition of the land where it precipitates, 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 water-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.

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, fertilisers and herbicides.

Groundwater depletion: Draining of wetlands has depleted the groundwater recharge. Recent estimate indicate that in rural India, about 6000 vi1Iages are without a source for drinking water due to the rapid depletion of groundwater.

Introduced species and extinction of native biota: Wetlands in 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 salvinia (Salvinia molesta) have threatened the wetlands and clogged the waterways, competing with the native vegetation. In a recent attempt at prioritisation of wetlands for conservation, Samant (1999) noted that as many as 700 potential wetlands do not have any data to prioritise. Many of these wetlands are threatened.

Conservation of wetlands

Gradually rising awareness and appreciation of wetland values and importance in the recent past have paved way to the signing of many agreements, of which Ramsar convention signed in Iran in 1991 is the most important. Wetlands conservation in India is indirectly influenced by an array of policy and legislative measures. Some of the key legislations are given below ²³:

• The Indian Fisheries Act - 1857
• The Indian Forest Act - 1927
• Wildlife (Protection) Act - 1972
• Water (Prevention and Control of Pol1ution) Act - 1974
• Territorial Water, Continental Shelf, Exclusive Economic Zone and other
• Marine Zones Act - 1976
• Water (Prevention and Control of Pollution) Act - 1977
• Maritime Zone of India. (Regulation and fishing by foreign vessels) Act 1980
• Forest (Conservation Act) - 1980
• Environmental (Protection) Act - 1986
• Coastal Zone Regulation Notification - 1991
• Wildlife (Protection) Amendment Act - 1991
• National Conservation Strategy and Policy Statement on Environment and I Development - 1992
• National Policy And Macro level Action Strategy on Biodiversity-1999

India is also a signatory to the Ramsar Convention on Wetlands and the Convention of Biological Diversity. Apart from government regulations, development of better monitoring methods is needed to increase the knowledge of the physical and biological characteristics of each wetland resource, and to gain, from this knowledge, a better understanding of wetland dynamics and their controlling processes. India being one of the mega diverse nations of the world should strive to conserve the ecological character of these ecosystems along with the biodiversity of the flora and fauna associated with these ecosystems.

Convention on Wetlands (Ramsar, Iran, 1971) ²¹

The Convention on Wetlands is an intergovernmental treaty adopted on 2 February 1971 in the Iranian city of Ramsar, on the southern shore of the Caspian Sea. Thus, though nowadays the name of the Convention is usually written "Convention on Wetlands (Ramsar, Iran, 1971)", it has come to be known popularly as the "Ramsar Convention". Ramsar is the first of the modern global intergovernmental treaties on conservation and wise use of natural resources, but, compared with more recent ones, its provisions are relatively straightforward and general. Over the years, the Conference of the Contracting Parties (the main decision-making body of the Convention, composed of delegates from all the Member States) has further developed and interpreted the basic tenets of the treaty text and succeeded in keeping the work of the Convention abreast of changing world perceptions, priorities, and trends in environmental thinking.

The treaty – The Convention on Wetlands of International Importance especially as Waterfowl Habitat – reflects its original emphasis on the conservation and wise use of wetlands primarily to provide habitat for water birds. Over the years, however, the Convention has broadened its scope to cover all aspects of wetland conservation and wise use, recognising wetlands as ecosystems that are extremely important for biodiversity conservation in general and for the well-being of human communities. For this reason, the increasingly common use of the short form of the treaty’s title, the "Convention on Wetlands", is entirely appropriate. The Convention entered into force in 1975 and has 150 Contracting Parties. More than 1590 wetlands have been designated for inclusion in the List of Wetlands of International Importance, covering some 134,030,385 hectares. UNESCO serves as Depositary for the Convention, but its administration has been entrusted to a secretariat known as the "Ramsar Bureau", which is housed in the headquarters of IUCN–The World Conservation Union in Gland, Switzerland, under the authority of the Conference of the Parties and the Standing Committee of the Convention. The implementation of the Convention on Wetlands is guided by its mission statement, which is” The Convention's mission is the conservation and wise use of all wetlands through local, regional and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world". To mark the date of the signing of the convention on wetlands, 2nd February of each year is observed as World Wetlands Day (WWD). It was celebrated for the first time in 1997 and the beginning was quite encouraging. Each year a theme is suggested for the day. Last year in 2002, it was ‘Water, Life, Culture’. In year 2003 the theme was ‘No Wetlands – No Water’. This theme was chosen in honour of the UN’s International Year of Fresh Water (IYF). This is to strengthen the UN’s efforts and also to be the first to initiate the IYF celebrations. As a part of conservation strategy a data book called Montreaux Record is kept of all those wetlands, which require international help for conservation. The inclusion of a site in this list makes it eligible for global package for conservation. Each year an award known as ‘International Ramsar Convention Award’ is given to the best conservation efforts and it carries a cash prize of $ 10,000 and a commendation ²⁵.

Conservation and Restoration of Wetlands -The ecosystem approach

Wetlands are an integral part of a watershed; and everything is connected to everything else on this earth. The ecosystem is interactive and there is a continuous interaction between adjacent ecosystems and their components. What happens at one level eventually impacts the other levels. We need to understand the causes and long-term solutions to our environmental problems. The fragmented approach of finding quick fix solutions, although convenient, obscures the essential unity of many processes taking place, ignoring the functional linkages that are vital to natural ecosystems. An ecosystem approach assigns a role to all the components in a larger ‘whole’, where the individual components contribute to the overall structure. The approach recognises the interrelationships between land, air, water, wildlife, and human activities. This can be evidenced by this simple example of how the air pollution catapulted by the spiralling consumption of fossil fuels has led to the contamination and acidification of lakes and waterbodies which in turn has led to the death and extinction of many aquatic organisms. Thus, to understand a lake ecosystem, the view must be as large as the watershed, the air shed, the landscape and eventually as large as the biome or the planet (Gene.E Likens ²⁶).

Lack of ecosystem approach in the management of natural resources has led to the current chaos.  The water systems should be studied and managed as part of the broader environment through a systems approach. A true systems approach recognises the individual components as well as the linkages between them, and that a disturbance at one point in the system will be translated to other parts of the system. Sometimes the effect on another part of the system may be indirect, and may be damped out due to natural resilience and disturbance. Sometimes the effect will be direct, significant and may increase in degree as it moves through the system. (Ramachandra T.V ²⁷).

The ‘ecosystem approach’ emphasises the management of the watershed along with the waterbody to ensure the sustainable use and management of water resources. In this direction, restoration of catchments with natural vegetation and maintenance of the green belt around the cities to prevent the runoff contaminated with silt and pollutants, reuse and recycling of water through appropriate use and practices becomes essential. 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'. Since, wetlands are a common property resource, it is an uphill task to protect or conserve the ecosystems unless the principal stakeholders are involved in the process.

Wetlands in India

India has a rich variety of wetland habitats. Most of the wetlands in India are directly or indirectly linked with major river systems such as Ganga, Cauvery, Krishna, Godavari and Tapti. Wetlands distributed from the cold arid Trans-Himalayan zone to wet Terai regions of Himalayan foothills and Gangetic plains extend to the floodplains of Brahmaputra and swamps of northeastern India including the saline expanses of Gujarat and Rajasthan. Along the east and west coasts they occur in the deltaic regions to the wet humid zones of Southern peninsula and beyond, to the Andaman and Nicobar and Lakshadweep Islands. India also shares several of its wetlands with Ladakh and the Sunderbans deltas with Bangladesh. These wetland systems are directly or indirectly associated with river systems of the Ganges, Brahmaputra, Narmada, Tapti, Godavari, Krishna and Cauvery. Southern peninsular India has very few natural wetlands, although there are a number of man-made water storage reservoirs constructed virtually in every village known as ‘tanks’ providing water for human needs and nesting sites for a variety of avifauna ²⁸.  The total area of wetlands (excluding rivers) in India is 58,286,000 ha, or 18.4% of the country, 70% of which comprises areas under paddy cultivation. The country's wetlands are generally differentiated by region into eight categories (Scott, 1989): the reservoirs of the Deccan Plateau in the south, together with the lagoons and the other wetlands of the southern west coast; the vast saline expanses of Rajasthan, Gujarat and the gulf of Kutch; freshwater lakes and reservoirs from Gujarat eastwards through Rajasthan (Kaeoladeo Ghana National park) and Madhya Pradesh; the delta wetlands and lagoons of India's east coast (Chilka Lake); the freshwater marshes of the Gangetic Plain; the floodplain of the Brahmaputra; the marshes and swamps in the hills of north-east India and the Himalayan foothills; the lakes and rivers of the montane region of Kashmir and Ladakh; and the mangroves and other wetlands of the island arcs of the Andamans and Nicobars ²⁹.

A survey conducted by the Ministry of Environment and Forests (MoEF) in 1990 showed that wetlands occupied an estimated 4.1 million hectares of which 1.5 million hectares were natural and 2.6 million hectares were man-made (excluding paddy fields, rivers and streams) and mangroves occupying an estimated 0.45 million hectares. About 80% of the mangroves were distributed in the Sunderbans of West Bengal and Andaman and Nicobar Islands, with the rest in the coastal states of Orissa, Andhra Pradesh, Tamil Nadu, Karnataka, Kerala, Goa, Maharashtra and Gujarat. A preliminary inventory by the Department of Science and Technology, recorded a total of 1193 wetlands, covering an area of about 3,904,543 ha, of which 572 were natural (Scott and Pole, 1989 ³⁰). A Directory of Indian Wetlands published by WWF and Asian Wetland Bureau in 1995 records 147 sites as important of which 68 are protected under the National Protected Area Network by the Wildlife Protection Act of 1972.

A Directory of Wetlands in India (1988) gives information on the location, area and ecological categorisation of wetlands of our country. Efforts to conserve wetlands in India began in 1987 and the main focus of governmental efforts is on biological methods of conservation rather than adopting engineering options. Chilka lake and Keoladeo Ghana national park were the first two Ramsar sites in India. Later in 1990 Harike lake in Punjab, Wulur lake in Jammu and Kashmir, Loktak lake in Manipur and Sambhar lake in Rajasthan were included. Recently, eleven wetlands in India have been categorised for seeking international assistance to save them from distress situation. These include Point Calimere in Tamil Nadu, Astamudi, Sasthamkolta lake and Vembanad wetlands in Kerala, Kolleru lake in Andhra Pradesh, Bhitrakanika mangroves in Orissa, Pong Dam lake in Himachal Pradesh, East Calcutta wetlands in West Bengal, Bhoj wetlands in Madhya Pradesh, Tsomoriri in Jammu and Kashmir and Deepor Beel freshwater lake in Assam..

Chilka lake was on Montreaux Record of Ramsar due to adverse changes in its ecological character caused by pollution and other anthropogenic pressure was removed from the list in 2002. Subsequently, it bagged the International Ramsar Conservation Award.

Status of Wetlands in Bangalore

Bangalore, capital city of Karnataka is the sixth largest metropolis in the country.  Bangalore urban with a population of more than five million consists of three taluks namely Anekal, Bangalore North and South. The city apart from being the political capital of the state is also a very important commercial centre housing some of the major industrial establishments, multinationals and software giants.

The district supports about 9.41% of the state's total population and 27.41% of the total urban population of the state. The urban agglomeration is spread between North and South taluks of Bangalore covering an area of about 151 sq. km. with an average population density of 16,399 individuals/ sq. km (census, 1991).

Bangalore District is located in the heart of south Deccan of Peninsular India. It is situated in the southeastern corner of Karnataka state (12°39’ – 13°18’ N latitude and 77°22’ – 77°52’ E longitude) with a geographical area of about 2,191 sq. km (Bangalore rural and urban districts) at an average elevation of 900 m above the mean sea level. The climate of the district has agreeable temperature ranging from the highest mean maximum of 36.2° C in April to lowest mean maximum of 11.4° C in January. It has two rainy seasons from June to September and from October to November coming one after the other but with opposite wind regime, corresponding to south-west and north-east monsoons. The mean annual rainfall of about 900 mm with a standard deviation of 18.7 mm was recorded from the year 1875 to 1976 (Srinivasa et al, 1996) (Ramachandra T.V., Kiran R., and Ahalya N, 2002 ²¹).

Wetlands of Bangalore occupy about 4.8% of the city’s geographical area (640 sq. km) covering both urban and rural areas (Krishna et al., 1996). Bangalore has many man-made wetlands but no natural wetlands. They were built for various hydrological purposes to serve the needs of irrigation and drinking water supply. The vast majority of the wetlands in Bangalore occur on the outskirts of the city in the rural fringe. Studies on lakes of Bangalore during the past decade show that 35% tanks were lost owing to various anthropogenic pressures. (Ramachandra T.V., Kiran R., and Ahalya N, 2002 ²¹). The number of man-made wetlands has fallen from 379 in 1973 to 246 in 1996 and further reduced to 81 at present (Lakshman Rau et al., 1986 ³¹)

Bangalore – ‘the garden city’, once sported a large number of lakes, ponds and marshy wetlands, which ensured a high level of groundwater table and a pleasant climate. Urbanisation and anthropogenic stress in Bangalore city has led to the discontinuity of the drainage network due to loss of wetlands. Many lakes and ponds have already disappeared due to various developmental activities and pressures due to unplanned urbanisation and expansion. The remaining lakes are dying fast, as they are filled with solid waste materials and sewage. The present trends in decrease in the water quality and number of waterbodies are the result of unplanned development of the city, resulting in vast tracts of wetlands being cleared. Recent studies on lakes in Bangalore show that nearly 40 percent of lakes are sewage fed, 13 percent surrounded by slums, and 35 percent showed loss of catchment area. Lakes situated on the city outskirts are facing problems due to brick kilns contributing to the declining water quality. (Ramachandra T.V., Kiran R., and Ahalya N, 2002 ²¹).

Need for ecosystem quality assessment of Waterbodies

Burgeoning human populations coupled with agricultural and industrial developments increase the pressure on water requirements. The restoration, conservation and management of these water resources require a thorough understanding of what constitutes a healthy ecosystem. Monitoring and assessment provides basic information on the condition of our waterbodies. Monitoring can be conducted to (EPA ³²):

• Characterise waters and identify changes or trends in water quality over time;
• Identify specific existing or emerging water quality problems;
• Gather information to design specific pollution prevention or remediation programs;
• Determine whether program goals -- such as compliance with pollution regulations or implementation of effective pollution control actions -- are being met; and
• Respond to emergencies, such as spills and floods.

Some types of monitoring activities meet several of these purposes at once; others are specifically designed for one reason. The information thus collected influences the legislative, economic and social practices adopted by society to improve and maintain the quality of the natural environment.