TEFE, Brazil (AP) – Just months after enduring floods that destroyed crops and submerged entire communities, thousands of families in the Brazilian Amazon are now dealing with severe drought that, at least in some areas, is the worst in decades. The low level of the Amazon River, at the center of the largest drainage system in the world, has put dozens of municipalities under alert.

The fast-decreasing river water level is due to lower-than-expected rainfall during August and September, according to Luna Gripp, a geosciences researcher who monitors the western Amazon’s river levels for the Brazilian Geological Survey.

As most of Amazonas state is not connected by roads, the main concern is the shortage of food, fuel and other goods normally transported through waterways. In Tefe, a city of 60,000 people by the Amazon River, large ships have not been able to arrive at the downtown port.

The situation is even more critical in the dozens of communities scattered through the region surrounding Tefe, affecting about 3,500 families. Many waterways, such as lakes and creeks, have dried up, eliminating access to the Amazon River and thus to nearby cities, which function as commercial hubs.

In the Sao Estevao community, the fishermen have postponed fishing pirarucu, the Amazon’s largest fish, because the boat to transport their catch to the city cannot dock. The legal fishing season runs until the end of November. If the water level does not rise soon, the seven-family community will lose a significant source of income, fisherman Pedro Canizio da Silva told The Associated Press in an audio message.

About six months ago, the community suffered losses due to a heavier-than-expected flood season.

“I lost my crops of banana and yuca. Moreover, caymans and anacondas got closer to us due to the flood and ate some of my ducks and chickens. The water underneath my stilted house almost reached the floor,” Mr. Canizio recalled.

In the Porto Praia Indigenous community, the nearby branch of the Amazon River has become a vast swath of sand that during the day becomes too hot to walk across. A motorboat trip to Tefe, normally 90 minutes long, now takes four hours, Anilton Braz, the local leader, told the AP, as the water is so shallow in some stretches that it is necessary to paddle instead of using the motor.

The local water source has become muddy and no alternatives exist, Mr. Braz said. “We fear our children will get sick with diarrhea and other diseases.”

The situation has led Tefe’s City Hall to declare a state of emergency to speed provision of aid to families, but so far help has been scant. “The mayor sent a little bit of food,” said Mr. Braz.

The local civil defense authority said 53 out of 62 municipalities have been affected by floods and drought in Amazonas state this year alone. The drier season, known locally as the “Amazonian summer,” usually lasts from June to December in this part of the rainforest.

In a region as vast as the Amazon, drought severity varies.

In Porto Velho, the capital of Rondonia state, the mighty Madeira River registered its lowest ever level since official records began in 1998. And in the Acre state capital Rio Branco, the Acre River, which cuts through the city, reached its lowest level since measurements started in 1967, according the Brazilian Geological Survey.

The drought in the Amazon River is not as extreme so far, although Coari, a city close to Tefe, is enduring its sixth worst drought since records began in 1975.