If you visit Peru, you will likely hear someone say: “It never rains in Lima”
LIMA is located in the great desert that runs along the Pacific Coast of South America
The coastal desert lies between the rugged Andes and the azure Pacific Ocean. From a distance, there appears to be nothing along the coast but stark, rugged hills of stone and sand in every imaginable shade of beige and brown. Erosion has draped many of the hillsides with cascades of brown rocks. These gradually make their way down the slope toward the sea, occasionally nudged along by the frequent earth tremors that occur here.
Once the rocks reach the shore, the pounding waves of the Pacific slowly grind them into sand, which the wind forms into crescent-shaped dunes. In parts of this vast desert, no rain has been recorded in 20 years, making it one of the driest spots on earth. But what makes this area so dry?
The Rain Shadow of the Andes
The answer has to do with the trade winds, which blow from east to west. As they encounter the high, saw-toothed ridges of the Andes Mountains, the winds are forced upward. Ascending to pass over the Andes, the winds cool, causing the moisture they carry to condense and fall as rain and snow, mostly on the eastern side of the range. Thus, the mountains cast a rainless shadow over the western slope.
Additionally, neither the cold Peru Current, or Humboldt Current, flowing northward from Antarctica nor the wind blowing in from the South Pacific provides much moisture. All these factors combined produce an extremely dry, though not hot, desert. Oddly enough, although rain is scarce, the humidity of the air is very high, especially during the Peruvian winter, from May to November. Where does this humidity come from?
In wintertime a blanket of low clouds hangs over the coast, and a heavy mist, which Peruvians call garúa, rolls in from the Pacific Ocean. During this season, months may pass without a glimpse of the sun, giving the region a chilly
The light winter drizzle is enough to wet the streets of Lima and also to bring life back to dormant desert plants on the high coastal hills. Large flocks of goats, sheep, and cattle take advantage of the green pastures that result. Moreover, since the early 1990’s, some towns in the desert have been using fog collectors
Still, moisture from the fog and clouds is not enough for wild vegetation to flourish year-round. Total precipitation in Lima is rarely more than two inches [50 mm] a year and comes mostly from condensation of the garúa. Therefore, the only green plants that thrive in the coastal desert are those that are irrigated by small rivers that bring life-giving water down from high in the snowcapped Andes. Viewed from the air, the little river valleys look like green ribbons lying across the desert.
Living Without Rain
To survive in such a dry climate, Peru’s ancient coastal cultures
As the early desert inhabitants learned, the desert soil is very fertile where there is water. Peru’s modern-day coastal irrigation projects provide the needed water to cultivate a variety of crops, including cotton, rice, corn, sugarcane, grapes, olives, and asparagus as well as other vegetables and fruits. At present, more than half of Peru’s population of about 27 million live along the narrow coastal strip.
When It Does Rain
Sometimes, however, rain does fall in parts of the desert, including Lima. Every few years, the cool Peru Current gives way to warmer waters that sweep over from the western Pacific. This phenomenon, known as El Niño, signals the imminent arrival of rain. Especially strong El Niños struck in 1925, 1983, and 1997/98. Understandably, desert dwellers, who are used to getting practically no rain at all, are ill prepared for torrential downpours and the ensuing floods.
One such flood struck Ica, Peru, in 1998. The Ica River inundated large areas of the city, and the mud-brick homes just melted away. Other parts of the desert benefited, soaking up the moisture and becoming lush pastures. The latest El Niño turned much of the Sechura Desert into a garden of green sprinkled with beautiful flowers.
The heavy rains also created a huge lake in the desert
Peru’s great coastal desert certainly adds to the wide variety of natural wonders found on our planet. Although it seldom rains here, through irrigation and proper use of precious water, this arid land has become a pleasant home for millions.
In the summer when temperatures climb to 70 or 80 [20 or 27°C.] degrees Fahrenheit, Lima residents shed their heavy clothes and enjoy the many fine beaches along the coast.
Wealth From Waste
For millenniums the cool, nutrient-rich seas off the west coast of Peru have provided food