An aquatic weed harvester, also known as a water mower, mowing boat and weed cutting boat, is an aquatic machine specifically designed for inland watercourse management to cut and harvest underwater weeds, reeds and other aquatic plant life. The action of removing aquatic plant life in such a manner has been referred to as "aquatic harvesting".

Overview

Water is an important resource and in many countries, waterways are increasingly clogged by aquatic plant growth. This is particularly so in tropical countries where warmer water means the plants grow more quickly, and increasing run-off of

fertiliser A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

s and effluent has exacerbated the problem. Irrigation ditches and pumps can become overgrown with vegetation, power station and factory water intakes can get blocked, boats can get hindered, fish stocks can be disrupted, and water moves more slowly, resulting in greater

evapotranspiration Evapotranspiration (ET) is the combined processes by which water moves from the earth’s surface into the atmosphere. It covers both water evaporation (movement of water to the air directly from soil, canopies, and water bodies) and transpi ...

and a greater risk of flooding. In some large irrigation projects in India, canals have become so overgrown with vegetation that water flow has been reduced to a fifth of its previous amount. In Bangladesh, floodwater has washed mats of

Rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

is the main aquatic plant grown for human food, but smaller areas of

watercress Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family Brassicaceae. Watercress is a rapidly growing perennial plant native to Europe and Asia. It is one of the oldest known leaf ve ...

and

water chestnut Water chestnut may refer to either of two plants (both sometimes used in Chinese cuisine): * The Chinese water chestnut ('' Eleocharis dulcis''), eaten for its crisp corm * The water caltrop The water caltrop is any of three extant species of th ...

are also cultivated. In their native environments, aquatic weeds are part of a balanced ecosystem, and it is mainly introduced species of water plant that become invasive and cause problems by congesting water bodies. The worst culprits, found in both temperate and tropical waterways, are floating plants such as

water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.water lettuce ''Pistia'' is a genus of aquatic plants in the arum family, Araceae. It is the sole genus in the tribe ''Pistieae'' which reflects its systematic isolation within the family. The single species it comprises, ''Pistia stratiotes'', is often cal ...

and ''

Salvinia ''Salvinia'', a genus in the family Salviniaceae, is a floating fern named in honor of Anton Maria Salvini, a 17th-century Italian scientist. Watermoss is a common name for ''Salvinia''. The genus was published in 1754 by Jean-François Séguier ...

'', fully submerged rooting plants such as ''

Hydrilla ''Hydrilla'' (waterthyme) is a genus of aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments (saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from ...

'' and

water milfoil ''Myriophyllum'' (water milfoil) is a genus of about 69 species of freshwater aquatic plants, with a cosmopolitan distribution. The center of diversity for ''Myriophyllum'' is Australia with 43 recognized species (37 endemic). These submersed ...

and rooting plants that reach the surface such as

cattail ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrush or reedmace, in American English as reed, cattail, or punks, in A ...

papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, '' Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'') can also refer to a ...

bulrush Bulrush is a vernacular name for several large wetland grass-like plants *Sedge family (Cyperaceae): **''Cyperus'' **''Scirpus'' **'' Blysmus'' **''Bolboschoenus'' **''Scirpoides'' **''Isolepis'' **''Schoenoplectus'' **''Trichophorum'' *Typhacea ...

and

reed Reed or Reeds may refer to: Science, technology, biology, and medicine * Reed bird (disambiguation) * Reed pen, writing implement in use since ancient times * Reed (plant), one of several tall, grass-like wetland plants of the order Poales * ...

Weed harvesting equipment

Weed cutting boats are developed to enable the maintenance of canals, lakes and rivers and to remove excessive aquatic life such as

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

and other plants that may negatively affect a waterway's

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

. Mechanical harvesters are large floating machines that have underwater cutting blades that sever the stems of underwater plants, gather the weeds and raise them on conveyor belts, storing the vegetation on board in a hold. Periodically this is discharged to a barge or an onshore facility. The harvested product can be

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...

ed, sent to a

landfill A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste materials. Landfill is the oldest and most common form of waste disposal, although the systematic burial of the waste ...

site or used in

land reclamation Land reclamation, usually known as reclamation, and also known as land fill (not to be confused with a waste landfill), is the process of creating new land from oceans, seas, riverbeds or lake beds. The land reclaimed is known as reclamati ...

. In developing countries aquatic vegetation may be harvested by hand or by net from the shore, cut and harvested by boat and lifted ashore by hand, crane, pump or conveyor system. The harvested vegetation may be used for the feeding of livestock. To reduce the high moisture content and to make it easier to transport, the weed can be chopped and pressed. Other uses to which the harvested vegetation can be put include ensiling the material for livestock fodder, adding it to the soil as a bulky organic fertilizer, manufacturing the raw material into pulp, paper or fibre, and

fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

it to produce

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

for energy production. Weed harvester 6520 from Berky

Advantages and disadvantages

Mechanical weed harvesters are effective at clearing aquatic weeds and the machines provide immediate relief from nuisance vegetation that interfere with navigation and recreation. Aquatic plants contain nitrogen, phosphorus and potassium that is bound in the vegetation, by removing the plants the nutrients are also removed. Removal of the biomass (plant material) prevents the build-up of muck and sediment on the bottom of the lake that occurs from the rotting weeds. Mechanical harvesters can also be used to improve the fishery by leaving behind aquatic vegetation for food and habitat. Aquatic weed machines are expensive and does require a capital investment and the process may need to be repeated several times in a growing season. Small fragments of weed may remain in the water and may spread to other locations thereby aiding in the dispersal of invasive species. However, a recent study by the Chautauqua Lake Association found that the harvesters lef
less than 1% of the loose plants behind
Some areas may be too shallow for the mechanical harvester and it may be unable to access restricted locations. Submerged tree stumps can damage the machine. Aquatic weeds can also be utilized as a source of

biofuel Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (E ...

. An alternative to mechanical harvesting is the use of herbicides, which are easy to apply and less expensive, but may have unwanted adverse impacts on the environment. While many aquatic herbicides have received EPA approval and are considered safe for aquatic environments, long term studies have found that aquatic herbicides can have major impacts on fish reproduction. Researchers at the University of Wisconsin-Madison found that fathead minnows exposed to concentrations of fluridone showed signs of endocrine disruption.

By region

Africa

Kenya Kisumu Harbour Hyacinths 1997ke09b21

In June 2015 in Uganda, use of the aquatic weed harvester was recommended by the country's

Ministry of Agriculture An agriculture ministry (also called an) agriculture department, agriculture board, agriculture council, or agriculture agency, or ministry of rural development) is a ministry charged with agriculture. The ministry is often headed by a minister f ...

to reduce

water hyacinth ''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.Lake Victoria Lake Victoria is one of the African Great Lakes. With a surface area of approximately , Lake Victoria is Africa's largest lake by area, the world's largest tropical lake, and the world's second-largest fresh water lake by surface area after ...

, which has caused a scarcity of fish in the lake. The scarcity of fish has negatively-affected the livelihood of locals who live in the lake's region. Additional types of machines were recommended to address the problem, which were the hydraulic harvester, take out elevator and

dredger Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...

India

Zoetermeer De Leyens Broekwegwetering Mowing boat (2)

In August 2015 in

Hyderabad Hyderabad ( ; , ) is the capital and largest city of the Indian state of Telangana and the ''de jure'' capital of Andhra Pradesh. It occupies on the Deccan Plateau along the banks of the Musi River (India), Musi River, in the northern part ...

, India, an aquatic weed harvester was used to remove algal weeds and trash from Hussainsagar Lake. An amphibious hydraulic excavator was also used. The work was performed to address pollution problems at the lake, which had accumulated significant algae and rubbish such as plastic bags and

plastic waste Plastic pollution is the accumulation of plastic objects and particles (e.g. plastic bottles, bags and microbeads) in the Earth's environment that adversely affects humans, wildlife and their habitat. Plastics that act as pollutants are catego ...

, food wrappers, and various garbage, some of which was floating atop the lake.

United States

Some U.S. companies manufacture aquatic weed harvesters. One such machine manufactured by a U.S. company can cut around one-half an

acre The acre is a unit of land area used in the imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imp ...

of weeds a day, and costs over $100,000.

Tampa, Florida Tampa () is a city on the Gulf Coast of the United States, Gulf Coast of the U.S. state of Florida. The city's borders include the north shore of Tampa Bay and the east shore of Old Tampa Bay. Tampa is the largest city in the Tampa Bay area and ...

used an aquatic weed harvester in 2013 to clear aquatic plant life from lakes in the area. In 2012 in

Leoni, Michigan Leoni Township is a civil township of Jackson County in the U.S. state of Michigan. The population was 13,807 at the 2010 census. Communities * Leoni is a small unincorporated community in the southeastern part of the township, east of Jackson, ...

, an aquatic weed harvester was used to remove

from Center Lake. The algae appeared to have roots, and other techniques such as attempting to kill it with chemicals were unsuccessful. The machine used collects algae and weeds that live at the bottom of the lake, removing them from the waterway.