Environment / Reservoirs of Puerto Rico
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Guajataca Lake
Reservoirs are man-made lakes, whose main purpose is to store water for domestic and industrial consumption, irrigation of agricultural fields, production of electric power, and flood control during extraordinary rain. In Puerto Rico, there are no natural lakes. Our reservoirs, except for the one in Fajardo, were built in mountainous areas to retain the maximum volume of water in the smallest possible surface area; therefore, our artificial lakes are deep and their banks have a precipitous decline. They are located in areas with geological stability to ensure seismic safety. The first reservoir was built in 1913: Carite, together with the one in Patillas and Guayabal in Juana Diaz (1914) made up the first irrigation system on the south coast.

The water in reservoirs comes from rain, a river, and its tributaries. Throughout the year, rainfall varies significantly, with a dry season that normally runs from January to March or April, followed by heavy downpours in May and June, and a second period of intense rainfall from September until the end of the year. Reservoirs are the most important source of water in Puerto Rico. On the island, there are 36 major reservoirs owned by the Commonwealth of Puerto Rico as well as several smaller private ones. Of the 36 public reservoirs, 21 are considered major in terms of volume and diversity of use.

Importance of Conservation
Reservoirs perform a variety of important functions. For example they:
Store water for domestic use and irrigation.
Generate energy.
Serve as a refuge for birds and habitat for aquatic fauna (fish, shrimp and turtles); some lakes are designated as wildlife shelters.
Are recreation areas for:
navigation (kayaks, canoes and boats)
recreational and sports fishing: The DNER fish farm in Maricao reproduces sea bass and black sea bream which are later introduced in our reservoirs. In addition, you can catch catfish, tilapias and Peacock Bass in almost all reservoirs;
contemplation and recreation
they help control flooding

Threats to this resource
The following constitute a phenomena that threaten the functionality of our reservoirs.
1-Land erosions in the hydrographical basin of reservoirs, which produce sediments that reduce their water storage capacity.
2-The accumulation of pollutants, including nutrients.
3-The presence of invasive aquatic plants such as hyacinth, water lettuce and pokeweed.
4-The presence of invasive exotic animals, such as plecostomus which create cavities in lake slopes leading to erosion.
5-Extraction of water at a higher rate than what is safe for the reservoir.

Effects of reservoirs
Reservoirs could have a negative impact on native flora and fauna because dams interrupt migration of larvae and juveniles towards the estuary and from these to the mountains. Species of native fish need to be in touch with the estuaries during their reproductive stages, and reservoirs disrupt these connections because they store water where the fish are established. However, there are design and management measures that are used to minimize the impact.

The DNER regulates some aspects regarding reservoirs through special legislation, such as the Wildlife Law of the Commonwealth of Puerto Rico. The Environmental Quality Board has regulations that apply to water quality and protects this resource through projects such as reforestation of hydrographical basins and the presence of guards.

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