Many are still without power in Puerto Rico.
More than 15 inches (nearly 40cm) of rain fell on the surrounding mountains after the Category 4 Maria left the island on Wednesday afternoon, swelling the reservoir.
The entire US territory remains without power, cellphone service is spotty, drinkable water is scarce, buildings have been destroyed, roads have washed away and a dam might collapse after the storm hit Wednesday.
Dominica Prime Minister Roosevelt Skerrit said, "It is a miracle there were not hundreds of deaths". Evacuation to the U.S. mainland is the only option for some patients. The unity that we needed in Puerto Rico is there now, because when catastrophes like this hit we don't look other ways. The reservoir can hold about 11 billion gallons of water for drinking, irrigation and power generation.
Today, AP employs the latest technology to collect and distribute content - we have daily uploads covering the latest and breaking news in the world of politics, sport and entertainment. "Seven or eight cities depend on that lake to drink".
Supplies first will go to a staging area in Miami, volunteers said.
"We essentially bring a base in a box", Lt. Col. Steven Campbell said. With roads blocked and phones dead, officials said, the situation may worsen. "Do not attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order", the alert said. But Public Affairs Secretary Ramon Rosario Rosario said in a statement that the dam's "fissure was big and it will collapse at any minute".
Many who live near the dam are being evacuated by buses.
He says hysteria is starting to spread and the hospital is at capacity and people are going to start dying.
Rossello went to Isabela to urge the mayor to evacuate three neighborhoods. "The risk is life". "We're 24 hours post-hurricane warning and right now our efforts are to make sure we have everybody safe, that we can rescue people". A representative for Judge Laura Taylor Swain, the lead judge in Puerto Rico's bankruptcy, could not immediately be reached. Both New Orleans and Puerto Rico, pre-storm, had lots of natural affordable housing - housing that's "affordable" because it's old and dilapidated, though livable.
Hurricane Maria maintained a category 3 status Saturday morning, slowly moving north and away from the Bahamas with maximum sustained winds of 115 miles per hour. Rossello couldn't say when power might be restored.
Delta, which was also expected to restart some of its San Juan operations Saturday, reported an "unfavorable assessments of airport and area infrastructure".
"The destruction in Puerto Rico is unprecedented and we expect health needs to rise quickly".
"There is now great need existing in Puerto Rico and the surrounding islands, and all those who have been impacted by hurricanes Irma and Maria are in our thoughts and prayers", church leaders said in a statement.
Carol Veniez said her daughter is in a risky situation, and will likely never go back to Puerto Rico once her family makes it to North Carolina.