Legislation that would protect glaciers, and possibly the frozen ground around glaciers, could threaten Chile’s multibillion dollar mining industry.

At issue is how to define glaciers and if mining near glaciers should be banned to protect the country’s water supply.

The key will be in the fine print of whether the final bill defines glaciers to include frozen areas around them and whether the protections would apply retroactively to mines already operating next to glaciers, The Associated Press reported.

“If it passes as a law with tough conditions it could harm not only the operation of current projects but also future projects,” said Juan Carlos Guajardo, head of the Chilean mining think tank CESCO. “Depending on the conditions, the scenarios would make mining activity very difficult in high mountain areas.”

Environmentalists point to the crucial role played by glaciers in protecting Chile’s water as reason enough to implement the wider definition. Glaciers are important because they act as natural dams, storing water for use throughout the year after the winter snow has melted. Even small glaciers can hold gigantic amounts of water that turn critical during warm months and especially in long dry spells.

In 2010, Argentina adopted a law that broadly defines glaciers — theoretically protecting not only the icy masses most people think of, but also “rock glaciers” and frozen groundwater on mountaintops where glaciers have melted away from the surface. The Argentine National Glacier Institute, which had a heavy hand in drafting Argentina's law, pushed the definition because it's believed most glacial water actually comes from such obscure but very significant water reserves, The Associated Press reported.

The Argentine law remains largely unenforced, but mining has still to develop in a big way there.

A similar law in Chile would have a much bigger impact on the world's copper and gold supplies. For now, the bill does not include protections on peri-glacial or permafrost areas and is far less punitive than Argentina’s law, but it could be amended to broaden the definition of glaciers. Chile has the largest number of glaciers in South America, from icy southern Patagonia to its most northern latitudes.

If Chile accepts a broader definition, it could severely hamper the Chilean industry's hopes to mine gold and copper from places where icy masses have retreated on the surface, exposing rich ore.