A lake so crystal clear and blissfully cerulean that you’re sure you’ve died and went to heaven: Ice Lake in June. Ice Lake is in the San Juan Mountains, one of the most beautiful natural areas I've been in. But over the years, these mountains have been gutted for their trove of natural resources: ore and water.
The quest for ore split open the flanks of the San Juan mountains when the Spanish descended during mid-1800's Gold Rush. Before then, the native Ute people didn't have a need for subsurface exploration. Mining equipment, most of it abandoned, is still sprinkled amongst the green and gold hill slopes, and quirky legacies of the mining era, like musky saloons, still stand in towns like Silverton.
The San Juan Mountains' ore crystallized over millions of years, and then was mostly taken in a few decades. The ore sat within Precambrian and Paleozoic-Cenozoic sedimentary and volcanic rocks, which have been both ravaged by mining pits, and sculpted into elegant spires and cirques by glaciers during the Last Glacial Maximum ~20,000 years ago. These relict glacial landforms make the mountains so breathtaking and hold lakes like Ice Lake.
Aside from ore, the San Juan Mountains are the source of another, increasingly important resource: water. Precipitation in the mountains is the ultimate water source, but sediment deposits in alpine lakes hold valuable information on the history of drought, fires, and temperature in the mountains, which can help us predict water availability during future climate changes.
The Paleoclimate Dynamics lab group at Northern Arizona University studies lake sediment in the San Juans. My buddy Charles did his Masters project on paleoecology in the San Juans: he gathered lake cores in sub-alpine San Juan lakes like Ice Lake, and studied layers of pollen and charcoal to gain insight on past environmental and climate changes.
Charles’ lake cores recorded the Medieval Climate Anomaly, which is a period of global warming ~900-1250 years ago that can be used as a proxy to think about current global warming. Pretty cool – but first you have to get the cores, and there was a miscommunication regarding the promised mule team.
“We were supposed to get a team of pack animals to carry our stuff, 3 and a half miles up and over a 1,200-foot pass to the lake, and there was no way we could carry thousands of pounds of coring equipment and a steel raft frame. So instead, Ethan [another student] and I went and ended up coring about seven different lakes and getting short cores. We hiked all the stuff up carrying 100 pounds of shit and brought the cores out, trying to keep it steady and not shake up the cores.”
They eventually figured out a system and got the longest “short core” they could, which was about 6 feet long.
“I went August 2017 with Scott and we did a vegetation survey and ID’d every plant we saw. You want to know what the modern vegetation is like since you’re [studying plant] pollen. You assume the pollen at the top is the same as modern vegetation. You see fluctuations in pollen throughout the whole core. You make inferences about how the climate changed through time based on pollen percentages.”
Their findings had implications for the future of the Southwest: they found that during the Medieval Climate Anomaly the climate was especially arid, there were many fires and drought. Because the elevation was similar and because we expect temperature changes to be similar too, we can relate those findings to the upcoming warming climate today. We can also expect more drought.
“The policy takeaway is we are probably fucked for sure. There won’t be enough water for all the agricultural needs in the region.”
By “the region” Charles means everywhere that the Colorado River supplies water to, which is the entire Southwest, including California and all of the Imperial Valley, a major agricultural center.
The Colorado River is born in the Rock Mountains and runs to the Gulf of California: Rivers of the San Juan Mountain including the Animas, Piedra and La Plata rivers are tributaries to the San Juan River, which is a tributary to the Colorado River. A hundred years ago or so, the Colorado River Compact divided the Colorado River into an upper and lower basin, allocating its water to the constituents of those basins for the future. The issue is, they signed away 100 percent of the water they thought they had, but they actually only had 60 percent of that. It had been a “wet” time, and the river was running higher than usual. They basically counted their chickens before they hatched.
Forty million-plus people rely on Colorado River water in California, Arizona, Nevada, and parts of New Mexico. Most of that water is shipped away to municipalities, which is an issue for the Imperial Valley because of the agriculture there.
“Once that water gets cut, we’re fucked.”
Hiking around Ice Lake now, it's hard to imagine such drought, but just a peek into the geologic past will show you how quickly and dramatically things can change.
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