Climate change is causing glaciers in the Bolivian Andes to melt at an alarming rate, according to a recent study, posing serious risks to the millions of people who rely on the glaciers for drinking water, hydropower and irrigation.

Researchers used satellite images to measure change in glacier area and published their findings earlier this month in The Cryosphere.

The findings are alarming: The glaciers covering the Bolivian Andes have shrunk by nearly half since the 1980s, and the melting ice has left behind at least 25 unstable glacial lakes capable of causing sudden and catastrophic floods.

The glacier loss will also affect the 2.3 million people in La Paz and El Alto, which the study’s authors say get around 30 percent of their water from glacial supplies during the dry season. Outside of these cities, the melted water is also an important source of drinking water and hydroelectric power for rural mountain villages.

“Most glaciers will be gone or much diminished by the end of the century – so where will the water come from in the dry season?” said Simon Cook, a lecturer at the Manchester Metropolitan University in the U.K. and lead author of the study, in a press release.

“Big cities like La Paz are partially dependent on meltwater from glaciers,” he said. “But little is known about potential water resource stress in more remote areas. Much more work needs to be done on this issue.”

Bolivia has struggled with water scarcity for years. The problem captured international attention in 2000 when the World Bank encouraged the Bolivian government to sell the public water system to the Bechtel Corp., granting the company control over the city’s water for four decades with an average annual profit of 16 percent.

The deal caused monthly water bills to skyrocket for low-income households. Mass public protests framed water privatization as a violation of basic human rights and successfully forced the Bolivian government to cancel the contract in what was later known as Bolivia’s ‘Water Wars.’

The country’s water supply has since remained in public control, and nongovernmental organizations such as Water for People have developed local initiatives to increase access to clean water in rural parts of the country.

President Evo Morales’s administration has also made repeated promises to attain 100 percent coverage of drinking water and basic sanitation by 2025.

Deputy Minister of Water and Sanitation Ruben Mendez reported Friday that drinking water coverage has reached 84.7 percent – among the best coverage per capita in Latin America. In rural areas of the country, Water for People estimated that access now hovers around 76 percent.

Still, some experts are concerned that Morales’s goal is will not be reached amid increasingly severe droughts, which have been exacerbated by El Niño. This year’s drought is considered to be the worst drought of the last quarter century and one of the three worst in the last 65 years. In response, the Bolivian government has allocated $6.9 million to provide water-starved households and farmers with water, seeds, forage and balanced food for livestock.

The drought has also contributed to the loss of Bolivia’s second-largest body of water, Lake Poopo, which was officially declared evaporated last month. Huffington Post reported hundreds, if not thousands, of people have lost their livelihoods and been displaced after years of rising temperatures and under-regulated mining activity.