Puerto Rico is experiencing a historic drought that’s led to water rationing following the driest month on record in July.

Yet one ready-made solution is barely being tapped: the normally copious rainfall. Anywhere from 30 to 169 inches of precipitation falls on the territory annually, but the government doesn’t require US citizens in Puerto Rico to install catchment systems to take advantage of the free resource—unlike some other island states. As climate change increases the odds of more intense droughts on the island, that type of decentralized infrastructure may be just what Puerto Ricans need in an emergency.

“One of the best unused reservoirs of water in Puerto Rico are the roofs of the houses,” says Fernando Abruña, a partner at local firm Abruña & Musgrave Architects.

The drought has exacerbated a water crisis that was already in motion due to ruptured water pipes and other decrepit infrastructure. For the past week, Puerto Rico governor Jenniffer González has ordered municipal governments to shut off water two days at a time for people in the northeast to conserve local supplies, leaving 180,000 households with limited access. The problems began well before that, though: Many families have been without consistent water for more than 100 days.

While the drought is a factor, the biggest issue isn’t a lack of water, says environmental lawyer Ruth Santiago, but rather the government’s mismanagement of it.

“Even with the climate crisis and these droughts, we still have abundant water,” says Santiago, who works with the local group Comité Diálogo Ambiental (the Environmental Dialogue Committee). “We could be harvesting rainwater right now,” she says as a storm erupts mid-conversation.

The most resilient harvesting systems rely on gravity, using gutters to divert rainwater from a roof to a canister that connects to indoor pipes like a faucet or showerhead. Bigger systems can help collect water to cool power plants and other industrial uses.

Abruña, who is also a fellow with the American Institute of Architects, estimates the island could gather 30 billion gallons of water a year if just 1 million households used rainwater collection technology. The average resident uses 62 gallons a day, amounting to just over 72 billion gallons of residential water use a year.

The Puerto Rico Aqueduct and Sewer Authority loses about 60 percent of the island’s drinking water before any arrives at customers’ homes due to leaking pipes and failing infrastructure. The ongoing emergency was caused, in part, by a series of ruptures in the 72-inch Superaqueduct water pipe, a main artery that services major cities on the northern coast. Repairing and updating the island’s aging water distribution system is most urgent, Santiago says, but rainwater harvesting is a cost-effective solution that can be quickly implemented.

The practice is not widespread in Puerto Rico, where the government has prioritized centralized grids fed by freshwater, but these systems are popular in other island communities. Roughly 90 percent of homes in the US Virgin Islands have a cistern to collect rainwater, and the territory has building codes that require many new developments to include this infrastructure. (Barbados has similar codes.) In Hawaii, Honolulu County even offers a limited number of free rain barrel installations to residents.

“There is nothing that can help the Caribbean region as quickly and as reliably as rainwater harvesting,” says Farah Nibbs, an assistant professor at the University of Maryland Baltimore County’s Department of Emergency and Disaster Health Systems, noting governments should treat it “as part of the national water supply.”

She also says governments should help cover the costs to avoid putting onerous “economic and financial burdens on households.” Yet in Puerto Rico, the government offers no incentives or financial assistance. That’s left small organizations attempting to meet demand.