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More and more Caribbean villages are collecting rainwater in concrete cisterns like this one in the Philippines.

Areas of the Caribbean and Latin American benefit from cistern projects that provide potable water

In recent decades, many countries in the Caribbean and Latin America have made strides in potable water infrastructure. The use of desalination has spread to the point that some in the public think of rainwater harvesting (RWH) as old-fashioned. But the Caribbean Environmental Health Institute (CEHI) believes rainwater is still a vital water resource that shouldn’t be relegated to the dustbin of history. The lowlands of Caribbean Central America from the Mosquito Coast inland, are also typically rich in rainfall, and the Global Water Partnership, an international network created to foster an integrated approach to water resources management, is promoting RWH there as well.

On some of the smaller islands like the Grenadines and some of the Bahamian islands, rainwater is still the only source of fresh water, and on drier islands like Antigua, Barbuda, the Bahamas, and the U.S. Virgin Islands, rainwater harvesting is widespread despite general access to municipal potable water.

Many issues contribute to water scarcity in the islands. Infrastructure damage from hurricanes often leaves municipal water supplies down for considerable lengths of time. Additionally, agricultural, population, and industrial growth all demand more water while simultaneously polluting existing groundwater and surface water supplies. An estimated 85% of the Caribbean’s wastewater is discharged untreated directly into lakes, streams, rivers, and the sea. Many municipal grids also do not reach outlying communities, and the cost of water is often too high for low-income residents.

Safe Rainwater Collection System

Addressing these water concerns in Caribbean communities, sociologist Cecelia A. Green and environmental engineer Farah Nibbs recently detailed their collaboration in the development of rainwater storage tanks with built-in filters for the Caribbean region. Considering that as much as 63 inches of rain falls on Puerto Rico from May to December, and Dominica can receive up to 15 inches per month during the fall, a low-cost method of collecting rainwater from rooftop catchments and storing it safely is a great benefit.

Green and Nibbs’ residential tanks — typically with a capacity of 200 gallons — use a biosand filtration stage that removes molds, bacteria, or protozoa from the rainwater. The process removes “up to 96.5 percent of bacteria and up to 99 percent of viruses from rainwater. By the time the kitchen tap is turned on, the water is clean and safe for drinking.”

The tanks are built with Ferrocement. This building material uses low-cost components — sand, rebar, chicken wire, Portland cement — that are readily available in the Caribbean to create a durable cistern tank that can withstand high winds, as well as earthquake tremors.

Central America

Adjacent to the Caribbean, another new, low-cost RWH system has been deployed in the Central American nations of El Salvador and Honduras. The system stores collected rainwater in 25,000-liter polyethylene bags that hold the equivalent of five tanker trucks. The bags, which cost $1,400, can supply a family for 15 days, although their current subsistence usage rations water to considerably more people. The initiative, which was launched in 2017, was promoted by the Global Water Partnership. Funding from Australia and from the Ford Foundation got the project started, and local organizations and governments provide operational support. Expansion of the program is slated to continue.

With abundant rainfall in the Caribbean and Central American lowlands, a widespread application of rainwater harvesting and storage could considerably ease water stress and provide a more water-resilient future for the regions.

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