From a socio-economic perspective, there are benefits and costs that result from the presence of water hyacinth. Some of them are linked to direct impacts and some are ecosystem related indirect impacts on fresh water bodies and their uses. The most direct impacts are to boating access, navigability and recreation; impede irrigation, access to fishing grounds and fish catch ability and act as prime habitat for mosquitoes.

Further, evapotranspiration from water hyacinth can exceed open-water evaporation rates and this can be a serious concern in water limited areas and small water bodies. Fish catch rates can be decreased because water hyacinth mats blocked access to fishing grounds, delayed access to markets and increased costs (effort and materials) of fishing. In addition to the direct socio economic impacts there are indirect impacts due to invasion of water hyacinth in fresh water ecosystems altering the fresh water ecosystem functions thereby affecting their uses. Water hyacinth can alter water quality by decrease of phytoplankton production, dissolved oxygen, nitrogen and phosphorous.

On the other hand, it can absorb heavy metals and other contaminants and therefore, water hyacinth is successfully used for industrial waste water treatment. The impacts of water hyacinth on ecological communities can alter productivity of the water body. Water hyacinth can greatly affect fishery if it induces changes in fish community composition, where the mats block breeding, nursery and feeding grounds for economically important species. There is evidence where decreased catch ability of certain overfished species can lead to increased fishery stocks which in the long-run could benefit a fishery and related human society. Water hyacinth provides habitat and food required for several harmful animals and other vectors of diseases like malaria and filariasis affecting human health and productivity. These socio-economic effects of water hyacinth are dependent on the extent of the invasion, the uses of the impacted water body, control methods and the response to control efforts. Large number of fresh water tanks in the dry zone of Sri Lanka provides multiple benefits to the people as source of irrigation, drinking water and aquatic fish and plants. Inland fish is one of major protein source for the people in dry zone. Dry zone water tanks have been invaded or under threat of invasion of water hyacinth can affect the functions of these fresh water tanks. Water hyacinth is extremely difficult to eradicate once established, incur an excessive cost for its eradication. The goal of most management efforts is to minimize economic costs and ecological damage. Recent literature on the management of water hyacinth focuses on techniques to remove the weed; however, little has been done to assess the full extent of benefits and costs that may occur in response to the establishment and management. Therefore our understanding of full-scale private and social benefits and costs of this invasive species is important to decide on the optimum level and efficient management of this non-native species.

Objectives
The main objective of this study is to assess the economic impacts of the spread and management of water hyacinth (Eichhornia crassipes) in fresh water tanks in dry zone of Sri Lanka.
Specific objectives

  1. To document the extent of the issue in terms of area, impact, and costs of management of water hyacinth in fresh water tanks in dry zone of Sri Lanka using secondary information.
  2. To quantify private and social costs and benefits of presence of water hyacinth in fresh water tanks in dry zone of Sri Lanka.
  3. To understand level of the voluntary control of water hyacinth by the communities in dry zone of Sri Lanka.
  4. To document the different management methods for control of water hyacinth and estimate the costs associated.
  5. To undertake benefit cost analysis for identified technical solutions/management methods.