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Arkavathy basin in Karnataka

Reviving the Arkavathi river using nature-based solutions

WWF-India offers a range of community-engaging solutions to monitor and restore wetland health in the Arkavathi river basin in Karnataka

Arkavathi, a major tributary of Kaveri river, originates at Nandi hills, 60 km north of Bengaluru and feeds into Kaveri, 90 km south of Bengaluru.

One third of Bengaluru city falls within its 4,150 sq. km river basin.

The river cascades through a network of tanks and lakes that are losing their water-holding capacity.

Half of the river is critically polluted, as per the Central Pollution Control Board. Two reservoirs – Hesaraghatta and Thippagondanahalli (TG Halli) – built to cater to the city’s growing water needs, have remained dry for years.

Twenty years ago, these tanks and lakes were connected. Built-up area covered just 20 percent of the river basin.

Despite large-scale agriculture, including cultivation of commercial crops, farmers could rely on surface water for irrigation.

Since then, rapid urbanisation has degraded the river’s catchment area. By 2020, built-up area doubled as Bengaluru city expanded towards Kempegowda airport.

Cultivation of exotic, water-intensive crops, has sucked the river basin dry. Irregular monsoons, a result of climate change, are no longer able to recharge water bodies that are fast disappearing.

Instead of flowing from one to another, the river basin is now a bed of scattered fragments.

As surface water runs dry, groundwater dependence has increased, leading to drilling of unauthorised borewells.

Close to the river source, rural Bengaluru relies heavily on groundwater for irrigation and domestic use.

As per the Central Ground Water Board, both urban and rural Bengaluru districts have over-exploited groundwater levels.

For over two decades, groundwater has been overexploited in Bengaluru

To learn about the state of Arkavathi, WWF-India conducted a hydrocensus survey in the river’s headwater region, where elevation offers a natural advantage. Revival of upstream wetlands has a direct effect on water bodies downstream.

The survey recorded groundwater quality of 125 borewells, in a 650 sq km study area, from Nandi hills to Hesaraghatta reservoir. It found that average groundwater depth had dipped to 400 feet, increasing the risk of water contamination.

Damage to this region’s ecosystem has affected people’s livelihoods. “We treat water like gold”, said Naveen Kumar, an affected farmer. “Earlier water was available at 300 feet, today our borewells run dry at even 1,300 feet below ground level”, he continued.

WWF-India also compiled health scorecards for 41 wetlands in this region. The health of each wetland was ranked from A to E on four parameters – area, hydrology, biodiversity and governance – recommended by the Ministry of Environment, Forest and Climate Change (MoEFCC).

Wetlands in upper Arkavathi are in poor health

Percentage of wetlands surveyed in headwater region of Arkavathi basin, rated based on four health parameters:

The health grades given to the lakes, starting from best to worst.
A
B
C
D
E
Ratings for 41 wetlands in the headwater region of Arkavathi basin, based on their scores on wetland health cards compiled by WWF-India.

The headwater region refers to the study area between Nandi hills and Hessarghatta reservoir.

The four parameters i.e. Area, Hydrology and catchment, Biodiversity, Governance, are based on the MoEFCC template for wetland health assessment.

Source: WWF India

The health cards revealed deeper concerns behind the state of the wetlands in the region. Out of 41 wetlands, half were ranked D or below, indicating low to very low health. Remaining wetlands too were in a poor state, and ranked C.

All the surveyed wetlands in the region were ranked “very low” on governance and management. None of them were notified as wetlands, which is essential to mobilise state efforts for their protection.

Five wetlands – Nagarakere, Chikkatumakurukere, Kanchiganallakere, Shivpurakere, and Mutturkere – performed the worst, and were ranked E.

There are several causes for the poor rank. Illegal encroachments, untreated sewage water, and water-weed infestation obstruct river flow and stress the Arkavathi ecosystem. These stressors reduce water-holding capacity of wetlands, affect biodiversity, and outweigh any source of potential recharge, such as regular rainfall.

A wetland ecosystem under threat

Factors that stress the Arkavathi ecosystem outweigh sources of potential recharge

The Arkavathi river basin is a network of water bodies connected by channels like stormwater drains and water canals

The Arkavathi ecosystem has several components:

  • Wetlands: These hold and absorb excess rain, acting as a source of freshwater.
  • Channels from the river: These regulate natural inflow and outflow of excess water and prevent flooding
  • Groundwater recharge: Water percolates through soil in healthy wetlands, keeping groundwater levels recharged.

The stressors which harm the Arkavathi basin include: First - Water-intensive plantations: Exotic water-thirsty crops interfere with the water systems. Second - Borewells: Borewells drill deeper in search of groundwater for irrigation, poking holes into water-holding layers

Third - Urbanisation and encroachment: Urban settlements and man-made structures obstruct water channels and prevent natural drainage of water.

Fourth - Untreated sewage release: Two-thirds of sewage water dumped in Arkavathi is untreated due to limited capacity of sewage treatment plants.

Fifth - Weed infestation: Aquatic weeds multiply in polluted water, suffocate aquatic life, and create silt-beds that reduce lake depth and water holding capacity

  1. A combination of these stressors has shrunk the water bodies and degraded wetland health in the Arkavathi basin

Source: Restoration of Polluted River Stretches, Central Pollution Control Board

In its five year long wetland restoration project, WWF-India is deploying nature based solutions that are sustainable and low in cost. These measures rely on community mobilisation, like the wetland mitra programme, that has more than a thousand registered volunteers. Wetland mitras, or friends of the wetland, are trained to conduct wetland health assessments, organise cleanliness drives, and monitor borewells.

Installing rafts with aquatic plants, commonly known as floating islands, is another nature-based method of maintaining healthy wetlands. These islands clear out pollutants from the water, and become home for a variety of aquatic and bird life.

De-weeding water channels and repairing bunds to regulate water storage, are other affordable solutions being implemented in the upper Arkavathi region to naturally reverse wetland degradation.

Wetland restoration initiatives by WWF-India

Excessive water-weed growth clogs streams and chokes aquatic life. If not removed, water plants anchor down to form a bed of silt. Before de-weeding, Yelahanka Puttenahalli.
Excessive water-weed growth clogs streams and chokes aquatic life. If not removed, water plants anchor down to form a bed of silt. Before de-weeding, Yelahanka Puttenahalli.
Regular de-weeding to unclog water inlets and outlets. After de-weeding, Yelahanka Puttenahalli.
Regular de-weeding to unclog water inlets and outlets. After de-weeding, Yelahanka Puttenahalli.
Installation of floating islands, which are artificial platforms for aquatic plants to grow, absorb nutrients and purify surface water.
Installation of floating islands, which are artificial platforms for aquatic plants to grow, absorb nutrients and purify surface water.
Floating islands become a thriving habitat for birds, insects, fish, and microbes. A bird perches on the floater, Madiwala.
Floating islands become a thriving habitat for birds, insects, fish, and microbes. A bird perches on the floater, Madiwala.
Wetland mitras (friends of the wetland) and local residents carrying out cleanliness drives, clearing out waste in Bashettihalli wetland.
Wetland mitras (friends of the wetland) and local residents carrying out cleanliness drives, clearing out waste in Bashettihalli wetland.
Training programmes for wetland mitras on using the Wetland Health Assessment (WHA) tool, for monitoring and reporting wetland health.
Training programmes for wetland mitras on using the Wetland Health Assessment (WHA) tool, for monitoring and reporting wetland health.
Monitoring borewell in Doddaballapura district, to check for depth, water levels, temperature and water quality indicators such as pH and TDS.
Monitoring borewell in Doddaballapura district, to check for depth, water levels, temperature and water quality indicators such as pH and TDS.
Solar-powered floating fountains installed at Nagarakere to aerate water, provide oxygen to aquatic life, prevent excessive bacteria growth, and contribute to a healthy wetland ecosystem.
Solar-powered floating fountains installed at Nagarakere to aerate water, provide oxygen to aquatic life, prevent excessive bacteria growth, and contribute to a healthy wetland ecosystem.
Training farmers to not use pesticides, which contaminate water and disrupt the microbial balance of wetlands.
Training farmers to not use pesticides, which contaminate water and disrupt the microbial balance of wetlands.

In the past, some of these solutions have helped to turn the ecosystem around. The Bashettihalli wetland, which ran dry for thirty years, is one such success story. Community efforts led by WWF-India have restored the wetland’s catchment area and its connection with upstream Arkavathi wetlands.

Community-led nature-based solutions revived the Bashettihalli wetland

Restoration efforts increased the wetland’s water holding capacity by 60 percent

This animation illustrates the deforestation in a specific region from 2002 to 2022.

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Source: WWF Analysis
Satellite image of Bashethalli lake taken on February 2024 Satellite image of Bashethalli lake taken on April 2019

April 2019

February 2024

Between 2016 and 2019, specific measures in Bashettihalli wetland included removal of 190,000 cubic metres of silt, same as the volume of water in fifty Olympic swimming pools. The planting of over a thousand native saplings restricted water-guzzling plants to just a tenth of the area. The program also carried out activities to de-weed and repair lake bunds. From the start of 2019, its impact became noticeable. About 5 sq km of catchment area was restored and Bashettihalli’s water storing capacity increased by 60 percent. Ground water quality improved, with levels rising by at least 100 feet.

These findings were reflected in Bashettihalli’s health rank, which moved up from E to D. These measures pave the way to rejuvenate other wetlands in the Arkavathi basin.

Source of maps:
Global Land Cover and Land Use Change, 2000-2020 (GLAD), OpenStreetMaps

Design, development and production by Revisual Labs

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