Wetlands, as the term implies, are 'Wet' lands that exist because the inflow of water exceeds the outflow for brief to extended periods of time during the growing season. Inland wetlands receive water from precipitation, snow melt, river outflow, surface overland flow, ground water discharge, lake seiches and seepage from streams, lakes, ponds and irrigation systems. Most natural wetland functions are a result of or closely related to wetland hydrology. Wetland food chain, fish and wildlife habitat value, nutrient cycling, socio-economic values, heritage and even aesthetic values are tied to the source, velocity, frequency, timing and quantity of water.

The fact that lakes occupy such a small fraction of the landscape belies their importance as environmental systems and resources for human use. They have intrinsic ecological and environmental values. Besides, humans use lakes for many commercial purposes including fishing, transportation, irrigation and industrial water supply, and lakes function as receiving waters for wastewater effluents.

They moderate temperatures and affect the climate of the surrounding area. By storing water they help regulate stream flow, recharge ground water aquifers and moderate droughts. They provide habitat to aquatic and semi aquatic plants and animals, which in turn provide food to many terrestrial animals, adding to the diversity of the landscape.

The myriad ways in which humans use lakes, along with numerous pollutant generating activities of society, have stressed lake ecosystems in diverse ways, frequently causing impairment of lake quality for other uses. Stresses to lakes arise from easily identifiable point sources such as municipal and industrial wastewater, non-point degradation like urban and agricultural run-off within a lake's watershed, and the most insidious long-range atmospheric transport of contaminants. Major degrading factors include excessive eutrophication due to nutrient and organic matter loading; siltation due to inadequate erosion control in agricultural, construction, logging and mining activities; introduction of exotic species; acidification from atmospheric sources and acid mine drainage; and contamination by toxic (or potentially toxic) metals such as mercury and organic compounds such as poly-chlorinated biphenyls (PCBs) and pesticides. In addition, physical changes at the land-lake interface (eg. draining of riparian wetlands) and hydrologic manipulations (eg. Damming outlets to stabilise water levels) also have major impacts on the structure and functioning of these ecosystems.

Lakes have played a major role in the history of Bangalore and served as an important water source for drinking and irrigation. Wetlands of Bangalore occupy about 4.8% of the city's geographical area (640 sq.km) covering both urban and non-urban areas. The spatial mapping of the water bodies in the district revealed that the number of waterbodies has decreased from 379 (138 in north and 241 in south) in 1973 to 246 (96-north and 150-south) in 1996. This overall decrease of 35.09% was attributed to urbanisation and industrialisation. The tanks were reclaimed for various purposes such as residential layouts, commercial establishments, sport complexes, etc. At present only 30% of the lakes are used for irrigation. Fishing is carried out in 25% of the lakes surveyed, cattle grazing in 35%, agriculture in 21%, mud-lifting in 30%, drinking in 3%, washing in 36% and brick-making in 38%. This highlights the need for appropriate conservation and management measures.