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Aquatic Weed Harvester: Pukka Local.....made from scrap materials

Updated: Aug 9, 2021

Aquatic vegetations are part of the aquatic ecosystems and wetlands. Most often, they are considered as weed, if they are not fit for consumption or any other human activities. Aquatic weeds are useful if they are in the limited levels. The uses of aquatic weeds are as follows:

  • Cuts off excess light

  • Absorb nutrients and heavy metals

  • Provide space for hiding

  • Many varieties of fishes lay eggs on leaves and roots

  • Biofilm and periphyton grows on the submerged parts which a good food source for fishes and other organisms

  • Aesthetic beauty and adds value for tourism

If the tanks or lakes are unmanaged, if there is continuous influx of nutrients, aquatic weeds grow profusely and cover the entire waterbody. This affects the biodiversity and the ecosystem. There are three types of weeds namely submerged, emergent and floating weeds. Since, most of the catchment in Bangalore lakes is occupied for urban developmental activities, we see only floating and submerged weeds. Due to the influx of domestic sewage and other industrial wastes, most of the lakes dominated by Eichhornia, Pistia, Salvinia, Chara and other weeds. So, the fish production and productivity were reduced significantly in many of the lakes in Bangalore. In other parts of the country also, the issues remained the same with different magnitude.

Though, most of the institutes offer many of the chemical, biological ways of removal/managing the weeds, most them are not so, effective in larger waterbodies. Moreover, the common property resources have multiple stakeholders and pose management difficulties.

Dal lake in Srinagar, Jammu & Kashmir is one of the largest lakes in the country and major revenue earner for the state. Hundreds of house boats are operating for more than 40-50 years. Due to accumulation of large quantities organic load, it was completely infested with submerged and floating weeds. It affected the tourism significantly. Then, the Lake Development Authority, J & K purchased two weed harvesters which costed them Rs. 40 lakhs each. They have effectively cleared the weeds and managing the lake very well through periodic eradication of weeds using the harvesters. In spite of many such problems with many of the major lakes in the country, the competent authorities never copied the success stories.

The weed harvester at Dal Lake, Srinagar, J&K

The model which is operating at Srinagar has fitted with diesel engine with 10 feet of conveyor chain link with spikes which rotates and pulls the floating and submerged weeds and collects at the top. Once it is filled, the harvester comes to the shore and the workers drag it and fills it to the truck for safer disposal.

Commercial Weed Harvesters in the World

There are many global companies producing various types of weed harvesters; but they are exorbitantly costly. The cost may range from Rs. 40 lakhs to Rs. 4.5 crores.

Weed harvesters from European countries

Though, it was proposed to purchase such weed harvesters, many competent authorities never paid attention, resulting the severe weed infestation of many lakes particularly, the lakes which receives major organic load and sewage.

Hebbal Lake

Hebbal lake is one of the major lakes in Bangalore city with 40 Ha of water spread area. It was completely infested with flowing weeds, predominantly Eichhornia (Water Hyacinth). The weed was not cleared for more than five years. The fishing right is given to the Fisheries Cooperative Society. They were happy with the fish production for many years. But in the last two years, the fish catch was reduced significantly and they were unable to operate the nets due to the weed menace.

Hebbal lake completely covered with water hyacinth (from the airport side)

The team of fishermen were worried due to poor catch. They had approached the Department of Fisheries for financial support. But there were no such schemes. Earlier, there was a financial support from National Fisheries Development Board, Hyderabad. They used to give Rs. 6000/acre for weed removal. Whenever, situation become critical, people become creative. So, they have decided to design their own weed harvester. Few months ago, a team comprising Papanna, Lourdu Swamy, Arogyaswamy, Joseph and Govindaraj started looking for used car engines and such other scrap materials.

They collected the ambassador engine, axial box from Tata Sumo. They build the floating boxes using 2 mm iron sheets and fitted the engine and the propellor prepared by them. Since they do not know the science behind the surface area, buoyancy, propellor area, the model moved in the water but speed was too low.

Old Ambassador car engine and the propeller designed by the fishermen

Then they increased the propellor are using additional metal sheets and distribute the weight evenly. The front part was fixed with metal frame basin with spikes projecting in the front. When it in the water about 1.5 – 2 feet it will be submerged and it is enough to pull the floating weeds.

The weed aggregator pushes the weeds towards dyke and the Hitachi drags and piles it on the bund

The team of officers even went on the weed harvester observed its efficiency and suggested some of the modifications. However, the Fisheries Research and Information Centre, Hebbal (KVAFSU, Bidar) will take it forward by connecting the right organizations like RV College of Engineering, Bangalore, College of Agriculture Engineering, UAS, Bangalore, PES College of Engineering, Mandya to work on this model and come out with efficient and cost-effective model, so that it can be replicated at large numbers.

The man behind this innovation

Mr. Arogya Swamy aka Shanthappa, aged 53, a school dropout involved in fishing for more than a decade was facing lot of problems in catching the fish due to severe weed infestation at Hebbal lake. He was little familiar with metal fabrication and foundry work. But the team was not ready to invest on the new engine. So, he brought all the required materials and fabricated the propellor and weed aggregating basin of his own design. It costed Rs. 2.0 lakhs for the entire model. Using crane, the model was released to the lake. In the first trail itself, it moved and started pushing the weed. But everyone laughed at him because the speed was very slow. He reduced the weight by cutting unwanted parts, increased the propellor surface area and in the second time it worked better. They took three weeks to clear the weeds in an area of 80 acres and spent 7-8 lakhs. It worked out to be Rs. 8-10 thousand/acre. However, with suitable technical modifications, the cost of weed removal can be reduced significantly. FRIC, Hebbal is planning to recommend this innovation to Biotechnology Industry Research Assistance Council (BIRAC) for innovation award.

Present look of the Hebbal lake (North-West view)


Dr. Shivakumar Magada

Dr. K B Rajanna

Dr. Sruthishree C

Acknowledgement: Authors wish to thank Mr. Papanna, Arogya Swamy, Joseph, Lourdu Swamy and Govinda Raju, Members of fisheries cooperative society, Hebbal for their valuable inputs. We also thank the Mr. Dinesh Kumar, Joint Director of Fisheries, Mr. Chikkanna, Deputy Director of Fisheries, Mr. Nagendra Babu, Assistant Director of Fisheries, Department of Fisheries, Government of Karnataka for their valuable suggestions and their cooperation.

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