Five months of the most torrential rains in a century have turned Peru's northern desert into a swampy tangle of jungle vegetation and newborn rivers, leaving this once prosperous provincial capital held together by a fragile overland supply route to the Pacific coast and the belief that by May, the worst would be over.

By last week, both the lifeline and the hope of many residents here had disappeared. Dark squalls blowing in from the Pacific this month cut all roads linking Piura to the rest of Peru, creating acute shortages of food, medicines, drinking water and fuel.

The rains, the first to be registered in Piura in May since 1891, were the most demoralizing yet of a seemingly endless disaster.

"We've reached the breaking point," said Victor Navarro, head of civil defense in Piura province. "Without work, food or water and the power company on the verge of closing, this situation is going to explode."

So far, the most violent demonstrations have been provided by the rain itself. More than 98 inches of it--350 times the normal annual rainfall--have hit northern Peru since December.

In Piura, the country's richest agricultural region, it is estimated that 80 percent of this year's crops has been lost, depriving as many as 300,000 of the department's million residents of any source of income.

Here in the province capital, lagoons of rain water and raw sewage stretch for blocks. Boys rescue stalled vehicles from the mud for tips. Unable to drain, the stagnant water, which has attracted a plague of insects, rats and toads beyond even a biblical punishment, has also spread skin diseases and potentially fatal intestinal disorders.

Many families continue to live in homes that have been flooded for months. The less fortunate have watched their brick and adobe houses melt in the deluge.

"You try to rebuild little by little, and one night your house is washed away," said Carlos Morales, a furniture painter who lives with his family of eight in a home nearly dissolved by the rain. "We thought this would be over by April. An earthquake would have been kinder."

The cause of this year's rains has been linked to "El Nino," a warm-water current, named for the Christ child, that periodically visits the west coast of South America in late December. In normal years, cold water carried north by the Humbolt Current keeps temperatures down along Peru's coast and makes the fishing grounds among the richest in the world.

This year, meteorologists say, El Nino has arrived with unprecedented force, encouraged by the slacking of the winds that usually stall the current far to the west. In addition to bringing rain, the warm water has killed millions of fish and sea birds off Peru, crippling the country's important anchovy industry.

As Peru's north is inundated, its southeast is suffering from drought that is also attributed to El Nino. The four-month-old drought has damaged crops and livestock of farmers in the Puno region--which even in normal times ranks among the poorest in the country.

The effects of El Nino extend far beyond Peru. Some scientists have given it credit for the mild winter enjoyed by the eastern United States this year, and others have blamed it for the recent drought in Australia.

While responsibility for the rains here has been assigned to El Nino, blame for the shortage of aid in Piura has fallen squarely on the democratic government in Lima. When President Fernando Belaunde Terry made a surprise one-day tour of the affected zone last week, his second in five months, he was met here by an angry crowd of students, housewives and businessmen.

"The government is completely unprepared to deal with a disaster of this scope," said Lily Cuculiza de Shaeffer, head of the Red Cross in Piura. During the past two months, disease aggravated by malnutrition has tripled the infant mortality rate.

Last week, Belaunde promised local leaders that the government would come up with $400 million in aid for the region, half of it financed by international lenders.

Taking a longer view, the government also plans to import nearly 20,000 cattle from Panama to take advantage of the blooming desert.