Guajataca Lake by Norma Arbelo Irizarry | Wikimedia Commons

Reservoirs are manmade lakes created for the main purpose of storing water for domestic or industrial use, for agricultural irrigation, for producing electricity and for controlling floods during extraordinary rain events. There are no natural lakes in Puerto Rico. Our reservoirs, except for the one in Fajardo, were built in the mountainous region to retain the maximum volume of water in the smallest possible space, which is why our artificial lakes are deep and have steep shores. They are also located in geologically stable areas for seismic safety. The first reservoir, Carite, was built in 1913. Along with those of Patillas and Guayabal, in Juana Díaz (1914), it was the first irrigation system for the southern coast.

The water in the reservoir comes from rain and a river and its tributaries. During the course of the year, rainfall varies significantly, with a dry period that normally lasts from January to March or April, followed by intense downpours in May and June and a second period of intense rains from September through the end of the year. Reservoirs are the most important source of water on the Island. There are 36 main reservoirs owned by the Commonwealth of Puerto Rico, as well as several smaller private ones. Of the 36 public reservoirs, 21 are considered major ones because of their volume and variety of uses.

Importance of reservoir conservation

• Storage of water for domestic use and irrigation.
• Generate electricity.
• Help control flooding.
• Provide a refuge and habitat for aquatic animals (fish, shellfish and turtles); some lakes are designated as wildlife refuges.
• They are recreational sites for:
  • boating (kayaks, canoes and boats),
  • peace and relaxation.

Recreational and sport fishing also takes place on the artificial lakes or reservoirs. At the Department of Environmental and Natural Resources (DRNA) hatchery in Maricao, bass and seabream are raised and introduced into the reservoirs. There is also fishing for catfish, tilapia and peacock bass in almost all of them.

Threats to these resources
Erosion of land in the watersheds of the reservoirs produces sediment that builds up and reduces the capacity for storing water. At the same time, the accumulated effects of contaminants, including nutrients, and the presence of invasive aquatic plants, such as water lilies, water lettuce and bloodberry.

The presence of invasive animals, such as the suckermouth catfish, is another factor that affects the reservoirs, as it creates cavities that lead to erosion.

Withdrawing water faster than the safe rate for the reservoir is also a threat to its useful lifespan.

How do reservoirs affect other natural resources?

Reservoirs can have negative impacts on native flora and fauna, because the dam interrupts the migration of larva and immature animals to the estuary and back to the mountains. Native fish species need to be in contact with the estuaries for their reproductive cycle and the reservoirs interrupt those connections by blocking the water where the fish live. However, there are measures that can be taken in design and management to minimize the impact.

Protection

The DRNA regulates some aspects of the reservoirs through special laws, such as the New Wildlife Act. The Environmental Quality Board also has regulations applicable to the water quality. It also protects this resource through projects such as reforestation of watersheds and the presence of rangers.

References:

Departamento de Recursos Naturales y Ambientales (DRNA). “Los embalses de Puerto Rico”, Hojas de Nuestro Ambiente, 2006. http://www.drna.pr.gov/wp-content/uploads/2015/04/Los-embalses-de-Puerto-Rico.pdf. Consulted 1/1/2021.

Recursos de agua de Puerto Rico, Embalses, http://www.recursosaguapuertorico.com/Embalses-Principales.html. Consulted 1/1/2021.