Map of Lake Nicaragua

source: worldatlas.com

History

Historical state of Lake Nicaragua: Indigenous tribes of Nicaragua most likely used the lake as a water supply for consumption and cleaning, as well as a food supply. The cities on the eastern shore of the lake have long been used as ports to the Caribbean Sea, as the San Juan River connects the lake to the sea. Before the use of chemicals in agriculture and the development of industry, the ecological state of the lake was very good.

source: http://www.vereinerde.com/

Human Impacts

The main negative impact people have on Lake Nicaragua is through pollution. Many large cities send their residential and industrial sewage to the lake. Even cities that are far away from the lake dump their sewage into rivers that lead to the lake. In 1981, MARENA (Ministry of the Environment and National Resources) found in a study that 70,000 pounds of raw sewage were being dumped into the lake a day. During this time, the Sandinista government was putting no money into the sewage and water infrastructure. However, between 2002 and 2007, ENACAL (Nicaraguan Water and Sewage Enterprise) invested 162 million dollars into the country’s water and sanitation systems.

Nicaraguan investment per capita in water supply and sanitation

Source: Unidad Pública de Inversiones; Data on population and deflators: World Bank World Development Indicators database

            The most infamous resident of Lake Nicaragua is the Bull Shark. Originally thought to be an endemic species of Lake Nicaragua, the Lake Nicaragua shark (as it is often called) recently was found to be nearly identical to Bull Sharks in other locations and to have entered the lake via the San Juan River. Because of the sharks’ aggressive nature, fisherman hunted these sharks to near extinction during the time of the Somoza Dynasty’s rule in Nicaragua (1936-1979). Today, the sharks are known more as legends due to how rare they are. The last media report of a sighting was in the year 2000. As far as wildlife in general, the dual-volcanic island of Ometepe was recently named an UNESCO Biosphere Reserve. The island has hundreds of species of birds as well as the more than 40 species of fish that reside in the lake. In addition to the bull shark, another notable marine animal that occupies the lake is the sawfish. The lake is inhabited by 16 species of cichlid fish. The cichlid population began to drop due to an attempt to increase fishing yields in the 1980s with the introduction of the farming of African tilapia fish. In 1995, cichlid were estimated to account for 58% of the lakes biomass, but this figure has likely to have dropped do to heavy fishing of these species as well as competition with the tilapia.     

Future Prospects

The current pollution of the lake, while certainly not a positive addition to the ecosystem, is not a huge problem. In comparison to Lake Managua, where mercury pollution has greatly contaminated the ecosystem, the pollution in Lake Nicaragua is not noticeable. However, if the agricultural production and industry continues to expand without changing the way sewage and contamination is dealt with, pollution of the lake is likely to worsen. Lake Nicaragua will become cleaner as the nation develops. Currently Nicaragua is the poorest country’s in the region, but small strides have been made toward improving the sewage infrastructure and will hopefully continue to be made in the future. One issue of concern in relation to wildlife in and around the lake is the possibility of harnessing the potential energy of the water flow from the lake to the San Juan River via hydroelectric technology. Proposed plans to construct a dam would reduce average flow rate by as much as 36%. The construction of a dam would undoubtedly affect wildlife and plants in the San Juan River-Lake Nicaragua basin as well as sediment composition. 

What should be done?

The best way to prevent the further contamination of Lake Nicaragua is for the country to invest in the development of its sewer and water infrastructure. However, given the poverty in the country this is going to be very difficult. The overall advancement of infrastructure in the area will help advance the country and make the development of sewage infrastructure more likely. Despite the possible ecological effects, the development of hydroelectric power sources would help develop the country. Also, due to the large surface area of still water, the Lake creates strong winds that blow to towards the pacific. The potential for wind power is great, and would help further the development of the country.

Sources:

McCary, Jeffrey K. “Tilapia Status in Nicaraguan Natural Water.” Springer Science  and Business Media. 2006

McKaye, Kenneth R. “African Tilapia in Lake Nicaragua: Ecosystem in transistion.” BioScience: Vol. 45.1995. University of California Press.

Montenegro-Guillén, Salvador. “Lake Cocibolca/Nicaragua”. 2006. Worldlakes.com

Thorson, Thomas B. “The Status of the Lake Nicaragua Shark: an Updated Appraisal.” University of Nebraska- Lincoln. 1976. http://digitalcommons.unl.edu/

Thorson, Thomas B. “The Impact of Commercial Exploitation on Sawfish and Shark Populations in Lake Nicaragua.” 1982. 

Water Resources and Freshwater Ecosystems- Country profile: Nicaragua. World Resources Institute. http://earthtrends.wri.org/text/water-resources/country-profile-135.html