Lluta River (Chile, July 2012), from the Earth Observing-1 satellite.
The Lluta River runs through the Atacama Desert, which is the driest place on earth, with less than a millimetre of rain per year. About 24km west of this photo is the town of Arica, which has the lowest precipitation of any city in the world – 0.8mm per year, about 75 less than California's Death Valley.
A few types of cacti can survive in the Atacama, and some other drought-tolerant species. In the canyons, however, there is far more vegetation. The canyons were carved by the Lluta and San José Rivers, both of which have their headwaters in the east (at the foothills of the Andes) and flow into the Pacific Ocean. To the north-east is the stratovolcano Tacora, and glaciers on this volcano provide enough water for the Lluta to flow year-round. Few rivers in the area can do this.
Along the bottom of the Lluta and Apaza Valleys there are blocks of green colour from irrigation, carried out by residents of the small farming villages in the canyon bottoms. However, despite the seemingly-lush fields, the Lluta Valley has major problems with water quality. This is because the Lluta River is quite saline and acidic, and also has dangerously high levels of arsenic, boron, sulphate, and other unwanted substances that flow into the river from natural geothermal springs and upstream mining operations.
Because of this, the Lluta can only be used to irrigate pastureland and a few tolerant crops (such as onions and potatoes). Those living in the area struggle economically, and rely on bottled water from the Chilean government.
The scarps (steep slopes) forming the Lluta Valley's walls make it difficult to reach the valley floor from the plateau. One of the few access points is Route 11 near the village of Churina. The slope on the southern wall was lessened because of the complicated network of drainage channels that join the river from the east, and the lower gradient made it easier to build the road.
A few kilometres to the east is a massive amphitheatre-shaped scarp caused by the Lluta Collapse, and the water running off it created the distinct drainage pattern. The Lluta Collapse happened about 2.5 million years ago, making it one of the oldest-known landslides in the world, and it displaced 25 cubic kilometres of material.
The San José River, a few kilometres south of the Lluta, carved the Apaza Valley. Its clean waters can support a wide variety of high-quality crops, particularly olives.
