2023-04-28 16:14:43
Read this story in English here.
The Catalan region of Spain is suffering from a prolonged drought, which has reduced reservoirs and led to restrictions on water use. Evidence of the drought stands out in satellite images of two large reservoirs in the region.
The Sau Reservoir (Pantà de Sau) and the Susqueda Reservoir (Pantà de Susqueda) are about 108 kilometers (67 mi) inland from Barcelona, and supply drinking water to the metropolitan area. The low water levels of the reservoirs can be seen in the image above, acquired by the Operational Earth Imager (OLI) aboard the Landsat 8 satellite on April 12, 2023. The image below was acquired by the OLI instrument onboard Landsat 8 in March 2021, when water levels in reservoirs were highest.
Dams built along the River Ter created these reservoirs in the 1960s, which have become a vital source of water for Catalonia’s residents and farmers.
“Seasonal droughts are typical of Catalonia’s Mediterranean climate, including in the Ter basin, which stretches from the Catalan Pyrenees to the Mediterranean Sea,” said Albert Ruhi, an ecologist at the University of California at Berkeley. “But in recent months, a lack of precipitation and a lack of snow cover has led to the driest spring since 1990 for the Ter river.” Ruhi, a native of Girona, a town just to the east of the reservoirs, studies the ecology of freshwater sources and how the River Ter is changing over time.
According to the Catalan Water Agency, the Sau reservoir (on the left) was at barely seven percent of its capacity on April 25, 2023. The Susqueda reservoir (on the right) had also decreased its water levels . That reservoir stood at 38 percent of its full capacity on April 25. Throughout Catalonia, reservoirs averaged around a quarter of their capacity.
You can see the brown edges of the exposed rock around the water in the reservoirs. These are the areas that were under water when the water level was near its capacity; this phenomenon is known as the “bathtub ring”. The drop in water levels in the Sau reservoir has exposed more than just rocks. The steeple of an 11th-century church and a nearby village, which have been submerged for almost the entire time since the dam was built, have become visible in recent months. The bell tower is occasionally exposed in times of little water; this year, the church is raised several meters above the water line. It should be noted that these elements are too small to be seen in these images.
Although much of Spain is experiencing drought this spring, Catalonia in the northeast has been particularly hard hit. During March and April, the region has received only about 14 percent of the expected rainfall based on 2009 to 2021 averages.
“The lack of spring rains and snow melt means that this year’s dry season will be twice or even three times as long,” Ruhi said. “This could lead to ecological impacts such as fish kills and algae blooms.”
In some places in Catalonia, officials have resorted to restricting water use among residents and farmers. In the small town of L’Espluga de Francoli, 97 kilometers west of Barcelona, household water supplies are disconnected every night between 10 pm and 7 am local time. Personal water consumption has been limited to 230 liters (61 gallons) per person per day in Catalan municipalities that represent almost six million inhabitants.
The lack of rain has been accompanied by high temperatures, and the year 2022 ranked as Catalonia’s warmest year on record. Between April 26 and April 28, 2023, forecasters expected temperatures in Spain to reach 40 °C (104 °F). Spain’s weather agency has warned that this could leave large regions of the country susceptible to wildfires.
NASA Earth Observatory images by Allison Nussbaum, using Landsat data from the US Geological Survey. Reporting by Emily Cassidy.
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