Highlights

• The Bangalore Lake Information System (BLIS) provides comprehensive information about the lakes in and around Bangalore city.
• Documents lake biodiversity, which includes microalgae, zooplankton, ichthyofauna, macrophytes, and birds.
• Provides information on the physicochemical properties of lake water in and around Bangalore city.
• Provides spatial distribution of ecosystem services, habitat quality and biodiversity of lakes.
• BLIS will back sensible choices for protecting and managing urban waterbodies.

Lakes offer various societal services, such as provisioning, regulating, and cultural services. Numerous species, including fish, amphibians, birds, reptiles, insects, phytoplankton, and zooplankton, find home in lakes. Lakes have a critical role in controlling soil erosion, floods, microclimate variations, and biogeochemical cycles. Carbon storage in aquatic plants, microalgae, and lake soil prevents it from escaping into the atmosphere as carbon dioxide, thereby reducing global climate change. Lakes offer various recreational activities like walking, jogging, and exercise, as well as children's parks, and serve as a hub for sightseeing, fishing, hunting, boating, bird viewing, and photography. Lakes provide a platform for environmental research, education, and public awareness initiatives.

Greater Bangalore, spanning 741 square km and at an altitude of 920 meters, is divided into three watersheds: Hebbal, Koramangala-Challaghatta, and Vrishabhavathi. The region's undulating terrain has led to the construction of numerous tanks for traditional purposes like irrigation, drinking, fishing, and washing, largely due to Kempe Gowda's and Wodeyar dynasty visions. Para-state agencies such as BBMP, BDA, BWSSB, and PCB are custodians of Bangalore lakes, in collaboration with other departments such as Revenue, Fisheries, Minor Irrigation, Forest, Ecology and Environment Department, Citizens, and NGOs. 

A survey of lakes in Bangalore reveals a decline in ecosystems, with 98% being encroached and 90% being fed by untreated sewage or industrial effluents, highlighting the need for urgent action. Untreated domestic sewage discharge into lakes leads to water quality degradation, nutrient accumulation, oxygen depletion, algae growth, silt accumulation, lake depth reduction, groundwater contamination, odour problems, and loss of aesthetic value due to overgrowth of algae and aquatic macrophytes. Lakes across the world confront severe concerns such as pollution and mismanagement. Water pollution is mostly caused by urbanization, population growth, industry, and the discharge of household, industrial, and agricultural waste. Bangalore's lakes face threats from unfair macrophyte and microalgae growth, excessive plastic and solid waste, illegal building, damaged fencing, untreated sewage inflow from residences, flats, and industries, and filling neglected lakes. These issues contribute to the degradation of the ecosystem. 

The encroachment of lakes and construction activities in and around the lake catchment led to a decrease in the catchment area, a reduced ground water table, increased domestic sewage discharge, the generation of debris and solid waste, soil erosion, silt accumulation, deforestation, and a loss of interconnectivity among lakes. Land use changes cause hydrology issues, with unplanned urbanization leading to lake disappearance, floods, groundwater drops, heat islands, and increased carbon emissions. The decline of ecosystem goods and services, affecting economic growth and livelihoods, necessitates restoration and conservation strategies to maintain aquatic ecosystem health, biodiversity, and physical integrity.

Lake restoration is a crucial initiative aimed at recovering degraded or damaged lakes, as pollutants in these lakes can pose serious health and environmental issues. Lake rejuvenation involves various activities such as fencing, de-weeding, dredging, creating bird islands, afforestation, idol immersion tanks, sewage treatment plants, and fountains and aerators. These measures help prevent land encroachment, improve water quality, and reduce pollution. Additionally, they provide recreational opportunities, promote wildlife, and reduce heavy metal contamination. Implementing these measures can also enhance the self-purification capacity of lakes and support aquatic organisms. Bangalore city's restored lakes, categorized into good (10%), poor (37%), and very poor (53%), have largely become polluted, indicating inadequate decontamination and poor lake maintenance. Sewage and industrial effluents in Bangalore city cause water pollution, health risks, and environmental degradation. Regular monitoring and public awareness are needed to address these issues.

Lake ecosystem services refer to the benefits that human beings receive, directly or indirectly, from ecosystem functions. The Lakes of Bangalore provide provisioning, regulating, and cultural services, with a total ecosystem supply value of Rs. 36449 Lakhs per year, and a net present value of Rs. 93782 million. The monetary valuation of ecosystem services in lakes is crucial for sustainable management, requiring a well-organized database, water quality analysis, and biodiversity monitoring.

The Bangalore Lake Information System (BLIS) provides extensive information on Bangalore's lakes, including their physicochemical characteristics, ecosystem services, encroachment data, biodiversity, and assistance for ethical urban water management. Additionally, it helps to preserve and manage the ichthyofauna, macrophytes, birds, microalgae, and zooplankton found in urban waterbodies. The BLIS framework is a web application using Geoserver, PostgreSQL with the PostGIS extension, and Leaflet, utilizing OGC standards for spatial information and offering Web Map Service and Web Feature Service for interoperability. BLIS is a tool that helps with the efficient management of natural resources by fusing expert knowledge with GIS visualization. BLIS contains information on the geographical distribution of lakes, ecosystem services, habitat quality, and lake biodiversity in Bangalore to help with policy formulation, decision-making, and urban lake conservation.