How The Vanishing Lakes Of Bengaluru Can Be Restored
The number of lakes in Bengaluru has dropped drastically, and there is an urgent need to rejuvenate them.
Here are some recommendations:
Karnataka Chief Minister H D Kumaraswamy allocated Rs 50 crore for rejuvenation of the Bellandur lake in the budget presented on 6 July. The Government also plans to let out water from the lake for farming. The Kumaraswamy Government has also set aside Rs 10 crore to encourage farmers to grow soap nut to tackle the lake’s frothing caused by effluents containing soaps and detergents, saying it will offer entrepreneurial opportunity to farmers. Experts are, however, skeptical of this move. Here is a history on Bellandur lake and steps to revive it.
Taking advantage of Bengaluru’s topography, authorities had earlier created some 1,452 interconnected water bodies in the city’s current spatial extent of 741 sq km. These water bodies with a storage capacity of 35,000 thousand million cubic (TMC) feet, however, have reduced to an appalling 193 TMC due to the laxity and incompetence of the current decision-makers. Additionally, several lakes have been encroached upon with their interlinks being choked with storm water drains.
Lakes and water bodies or wetlands are one of the most productive ecosystems contributing to ecological sustainability, thereby providing necessary linkages between land and water resources. A valuation of ecosystem goods reveal that the productivity of tangible goods such as fish, fodder etc, stand at Rs 10,500 per hectare, annually. This highlights the vital role of wetlands in sustaining ecosystem goods and services and supporting people’s livelihood.
The quality and hydrologic regime (variations in the state and characteristics of a water body) of these lakes and wetlands is directly dependent on the integrity of its watershed. Bangalore being located on the ridge, forms three watersheds – Koramangala Challagatta valley, Vrishbhavathi Valley and Hebbal Nagavara Valley. Earlier rulers of the region, created interconnected lake systems taking advantage of the undulating terrain (Figure 1). In the last couple of decades, rapid urbanisation coupled with the unplanned anthropogenic (polluting) activities has altered the wetland ecosystem.
Urbanisation between 1973 and 2017 has resulted in an increase of 1,028 per cent concretisation or paved surface. This has impacted the natural resources leading to a decline in green spaces (88 per cent decline in vegetation), and wetlands (79 per cent), higher air pollutants and a sharp decline in the groundwater table. Geo-visualisation of likely land uses in 2020 and 2025 through multi-criteria decision making techniques (Fuzzy-AHP: Analytical Hierarchal Process) reveals a calamitous picture of 93 per cent and 98.5 per cent of Bangalore landscape filled with paved surfaces (urban cover) and a drastic reduction in open spaces, water bodies and green cover. This would make the region greenhouse gas (GHG) rich, water scarce, non-resilient and unlivable, depriving the city dwellers of clean air, water and pollution-free environment (Figure 2).
Changes in land use and land cover (LULC) in the wetland catchments influence the water yield and water quality of the lakes. Apart from drastic LULC changes, the inflow of untreated domestic wastewater, industrial effluents, dumping of solid wastes and rampant encroachments of catchment has threatened the sustenance of urban wetlands. This is evident from the nutrient enrichment and consequent profuse growth of macrophytes, impairing the functional abilities of the wetlands. Reduced treatment capabilities of the wetlands have led to the decline of native biodiversity, prevailing unhygienic conditions with mosquito menace, contamination of groundwater levels, affecting the livelihood of wetland dependent population. Decline in the goods and services of wetland ecosystems have influenced the social, cultural and ecological spaces as well as of water management. This necessitates a systematic lake rejuvenation paradigm and associated monitoring of wetlands to mitigate the impacts through appropriate management strategies.
A combination of LULC analysis in the catchment using remote sensing data acquired through the space-borne sensors facilitates identification of valley zones and wetland area. This in turn aids in maintaining records for encroachment and consequent action. Factors like nature of the catchment, wastewater quality and quantity influx, garbage dumping etc, related to water quality are the most important pressure driving the productivity of these rapidly disappearing wetland systems and are reasons for today’s dominance of exotic organisms with increasing heterogeneity of biotic components at an intermediate spatial and temporal scale. Nutrient (C, N and P) influx is the most significant reason for the present deterioration of these wetland and water bodies.
Sustainable catchment management practices with strategic control of untreated industrial and domestic effluents getting into these water bodies will be key for a sustainable city management plan. Recommended sustainable and low cost options for rejuvenation such as de-silting and de-weeding the water bodies, complete treatment of municipal and industrial wastewater, ban of ‘P’ use in detergents (phosphate based detergents), removal of encroachments, fencing and green belt around the water bodies, and growth of essential N-rich aquatic vegetation for the livelihood of dependent communities nearby and provision to retain the natural floating islands for in-situ bioremediation. Further, strategic planning needs to be adopted at the higher level for increasing consensus over optimal water usage, provisions for rain water harvesting, ground water recharge etc, and for fostering sustainable city management.
Recommendations For Rejuvenation Of Bellandur Lake
Decentralised optimal water management through:
- Rainwater harvesting by rejuvenating lakes. The best option to harvest rain water is through interconnected lake systems
- Treatment of sewage generated in households in each locality (opting the model functional since 2010 at Jakkur lake – STP (Sewage Treatment Plant) integrated with constructed wetlands and algal pond;
- Conservation of water by avoiding the pilferages (due to faulty distribution system)
- Ensuring water supply 24x7
- Ensuring all sections of the society get equal quantity and quality of water. Rejuvenating lakes in the region helps in retaining the rain water. Treating sewage and options to recycle and reuse would minimize the demand for water from outside the region.
Rainwater Harvesting Through Interconnected Lakes
Currently, the number of lakes in the Koramangala Challaghatta Valley is about 81, followed by the Vrishabhavathi Valley (56) and the Hebbal Nagavara Valley (46). Rejuvenation of lakes and re-establish interconnectivity among lakes (as in Figure 1) will help in retaining the rain water as well as groundwater recharge in a water scarce landscape.
Average annual rainfall in Bangalore is about 787 mm with 75 per cent dependability and a return period of five years (annual rainfall ranges from 750-850 mm). Catchment wise water yield analysis indicates about 49.5 per cent (7.32 TMC) of water yield in the Vrishabhavathi valley (including Arkavathi and Suvarnamukhi), followed by 35.2 per cent (5.2 TMC) in Koramangala Challaghatta valley and 15.3 per cent (4.2 TMC) in Hebbal valley and the total annual water yield in Bengaluru is about 14.80 TMC. De-silting lakes would enhance storage capacity and also help in the removal of contaminated sediments. This could be done sensibly through adoption of latest state of the art technology - wet dredging to remove deposited sediments. Domestic demand of water (at 150 lpcd) is 18-20 TMC per year (1,573 MLD). This means about 73 per cent of the city’s water demand can be met by efficient harvesting of rain water through lakes.
Decentralised Treatment Of Sewage
Quantification of sewage generated shows that about 16.04 TMC (1,258 MLD) of sewage is generated in the city. However, the model of decentralised harvesting of water and reuse of treated sewage is not an attractive proposition for the current breed of decision-makers with the colonial style of functioning/mindset. The financial gain is much higher in the case of mega projects (such as water diversion, river linking, etc.) compared to the decentralised models, which is the sole reason for the local administrators to degrade decentralised water harvesting structures and alienating local community.
The main reason for the deliberate and inefficient management of water resources is to maximise the net return for the ruling government themselves than the overall growth of the region with water security. The analysis illustrates that the city has at least 30 TMC (Bengaluru city) of water, which is higher than the existing demand (20.08 TMC, at 150 lpcd and 2016 population), if the city adopts the 5R’s (rejuvenate, retain, recycle, reuse and responsible citizens’ active participation with good governance).
Putting A Stop To Polluting Lakes With Untreated Sewage
Only treated sewage must enter the lake. Sewage treatment through integrated constructed wetlands (similar to Jakkur Model – Secondary Treatment Plant (STP) + Constructed Wetlands + Algae ponds, will remove nutrients, etc.) De-centralised treatment and reuse of treated sewage while shunning the path of senseless diversion of sewage from upstream to downstream regions and contaminating the surrounding ground water resources.
Re-establishing Interconnectivity of Lakes By Removing All Blockades
- To prevent stagnation of water and enhance aeration with movement of water, which will also help in optimising remediation.
- The decision-makers should implement the success model of lake interlinking in Bengaluru than river linking (to pilfer public money).
- Remove all encroachments without any fear, favour or political interventions (lake bed, storm water drains, buffer zone).
- Recover the area identified for setting up STP (40 acres as per RMP 2015) in the region between Agaram and Bellandur lakes and establish treatmant plant;
- Implementation of ‘polluter pays’ principle as per the water act 1974; zero discharge from industries
- Stop dumping solid waste and construction and demolition wastes in the lake bed, storm water drain
- Remove macrophytes (covered on the water surface) regularly
- Public Participation: decentralised management of lakes through local lake committees involving all stakeholders, and local stakeholders in the regular maintenance and management
- Regular surveillance through vigilant resident groups and network of education institutions
- Regular monitoring of treatment plant and lake water quality (physical, chemical and biological) and making available information to the public through the internet;
- Identify local NGOs for regular maintenance and management, install fountains (with music and LED) to enhance surface aeration and recreation value of the ecosystem
- Avoiding the introduction of exotic species of fauna (fish, etc.)
- Ban on the use of phosphates in the manufacture of detergents; will minimise frothing and eutrophication of water bodies
- Digitisation of land records (especially common lands – lakes, open spaces, parks, etc) and availability of this geo-referenced data with query based information system to public
- Planting native species of macrophytes in the buffer zone (riparian vegetation) as well as in select open spaces of lake catchment area
- Restrictions on the diversion of lake for any other purposes
- Ban on construction activities in the valley zones
- Good governance - single agency with the statutory and financial autonomy to be the custodian of natural resources with regard to ownership, regular maintenance and action against polluters (encroachers as well as those contaminate through untreated sewage and effluents, dumping of solid wastes)
- Effective judicial system for speedy disposal of conflicts related to encroachment. Reactivate KLCDA act and empower KLCDA with financial and administrative autonomy to maintain, monitor and sustainably manage lakes.
- Empower the local administration by eliminating land, water and waste mafia.
- Environment education at all levels will help in improving environmental literacy and also sustainable and healthy country with clean water, air, land.
Healthy youth would be an asset to the nation. Prudent management of natural resources through environmentally conscious citizen would help develop the country. There is an urgent need to shun the current path of development impinging on the sustenance of natural resources and health of the citizen; and stop unplanned irresponsible urbanisation in order to decongest Bengaluru.
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