Phewa Lake is one of the most popular lake of Nepal. It is the second largest lake of Nepal and only Nepalese lake to have temple at its centre. It is very important from religious, cultural and water resources point of view. Tall concrete buildings around the Phewa Lake have been decreased its beauty to a great extent. People still wash clothes at its bank; by stealing the eyes, hoteliers and restaurants owners don’t mind throwing rubbish into the lake. As a result, the lake is being polluted from all sides. Over the last three decades, regular silt and garbage depositing at the bottom of the lake has reduced its depth considerably. On top, hyacinths have only added more woes to Phewa Lake, making things only bad to worse. These obnoxious weeds do spread rapidly and cover a larger area in no time.

Water hyacinth is a free-floating perennial plant that can grow to a height of 3 feet. This highly adamant hyacinth was first seen in Phewa Lake in 1990. Soon after then, it started spreading rapidly, damaging tourism, fishery, and the natural existence of the lake itself. It creates all kinds of problems by clogging waterways and shipping the passages. It thrives on the water surface and spreads far quicker than we can imagine of. It has the capacity to reduce a huge lake into a marsh only if adequate action is not taken in time. Moreover, dead leaves and roots of hyacinths sunk below and deposit there. Phewa Lake has already been reduced to 12 thousand Ropani reducing 0.18sq. km area in every two years. Due to regular silt deposit and hyacinths encroachment, the bank of the lake has turned marsh. Taking the advantage, some unscrupulous local people of the area have started paddy plantation on the encroached land. Little is known about the effects of water hyacinth on water-bird communities; however, increases in macroinvertebrate and fish abundance and diversity suggest a potentially positive interaction with water birds when water hyacinth is at moderate density.

There are several popular control mechanisms for preventing the spread of, or eradication of, water hyacinth. Various campaigns and programs are conducted in regular interval to remove weeds from field. The most effective methods so far found to control these plants include draining ponds completely, then removing and chopping up the plant (away from the pond, as even a small can regrow into large one. Chemical control method is the least favored due to the unknown long-term effects on the environment and the communities with which it comes into contact. Physical control, using mechanical mowers, dredgers or manual extraction methods, is used widely but is costly and cannot deal with very large infestations. It is not suitable for large infestations and is generally regarded as a short-term solution. Mechanical removal of water hyacinth is seen as the best short-term solution to the proliferation of the plant. However, for such large area it might be difficult to achieve target. Biological control is the most widely favored long-term control method, being relatively easy to use, and arguably providing the only economic and sustainable control. Several Insects and fungi has been identified as a control agent of water hyacinth. Some varieties of Moth, Weevil and Fungi has been proved to be effective in controlling high incidence of water hyacinth.

Water hyacinth has many practical uses. It can be used in making papers, fibre board, ropes, yarn, charcoal briquetting and is also used for water purification and biogas production. We can establish commercial production of such items which will utilize water hyacinth and check its population at regular interval.

References:

https://bhupendralimbu.com.np/2019/09/29/impacts-of-environmental-change-a-study-of-fewa-lake/

https://www.gardeningknowhow.com/ornamental/water-plants/water-hyacinth/water-hyacinth-control.htm

http://library.uniteddiversity.coop/Water_and_Sanitation/water_hyacinth_control.pdf

https://water-hyacinth.com/solution.html