Arequipa: Weather & Water

This is our 2nd post on Arequipa, where we look at the causes of its desert weather and its water challenges.

Unique Location – Weather

Even though it’s over 60 miles (100 km) from the Pacific Ocean, Arequipa’s weather is dominated by the impact of the Humboldt Current (sometimes called the Peru Current). The Humboldt Current carries cold water up from the southern tip of Chile to northern Peru. It creates what is called an “upwelling”. Upwellings occur when cold, nutrient-rich water is brought to the surface of the ocean. The Humboldt Current is one of the major upwellings of the world, and supports a huge amount of marine life. (It has been estimated that 18-20 percent of the fish caught in the world from oceans come from the Humboldt Current!)

Another thing the cold Humboldt Current does is cool the air above it. Cooler air can’t absorb as much moisture as warmer air. The result is that part of northern Chile and southern Peru is one of the driest areas in the world, called the Atacama Desert. There are some weather stations in the Atacama Desert that have never recorded any rain. Arequipa is at the northern tip of this desert, so it gets very little rain and a LOT of sun – more than 300 days of sun every year.

Arequipa Map

On the other side of Arequipa (and the Atacama Desert) are the tall Andes Mountains. The mountains act as a barrier to keep out clouds and rain. The far side (east side) of the Andes Mountains can actually be very wet, and is where the Amazon river and rainforest begin. So Arequipa, and the Atacama desert, are sandwiched between the Humboldt current and the Andes.

For us, after arriving from the Costa Rican rainforest, the weather was boringly wonderful: brilliantly sunny every day, and cool at night. (I think being a weather forecaster in Arequipa must be an easy job. Put in your forecast of “Sunny, High of 73°F (22°C), Low of 52°F (11°C)”, go on vacation for 9 months, and come back for the 3-month rainy season.)

Sun & Water

Since we’re traveling with an environmental focus, we were happy to see some solar panels on rooftops. Given the amount of sun in Arequipa, solar power seems like it makes a lot of sense. However, everything we saw seemed to be only for hot water heaters. It seems like even more solar energy could be used (especially with 300 sunny days a year!). Here’s a picture of a solar hot water heater visible from our rooftop (the silver tank, in the middle of the picture, with the black solar panel below it).


Given the lack of rain in Arequipa, where does its water come from? It is a big issue. There is one river, the Rio Chili, that provides all the water for Arequipa. It also provides irrigation for agriculture and water for industry. In this photo below, these green farming areas are huddled next to the Rio Chili. Behind and all around this narrow strip of green, everything is brown.


The Rio Chili starts high up in the mountains, and for most of the year, outside of the short rainy season, it’s fed only by melting snow and glaciers. The problem is, with climate change causing warming temperatures, there is less and less snow in the mountains, and the glaciers are disappearing at an alarming rate. We heard that El Misti used to have a white skirt that reached far down the mountain for most of the year. Now, as you can see from the following picture, there is hardly any snow visible on the top — at best, it looks like a bit of gray hair.


There are a lot of discussions going on about water in Peru, given the high percentage of the country that depends on water from Andes glaciers. We read about a new water law encouraging everyone to conserve existing water. This is great, and absolutely necessary. But there are almost a million people living in Arequipa. With only one relatively small river providing water, it’s hard to imagine what will happen to this beautiful city as the impacts of climate change continue to be felt.

Glaciers and mountain snow provide a kind of storehouse of water that is gradually released during the long dry season. At the current pace of climate change, many of the glaciers in the area could be gone this century. Then, where will the water come from?

Additional Link

Humboldt Current info on Wikipedia

Study Guide

  1. What is the Humboldt Current?
  2. How does the Humboldt Current impact Arequipa’s weather?
  3. Where does the water in the Rio Chili come from?

Note – All images taken by Larry Kraft except for Humboldt Current diagram, which was provided by a US government employee to Wikipedia, and is in the public domain.

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