Utah’s Great Salt Lake is now at a record low. The rivers that feed the big inland sea have been increasingly diverted to not only support drinking water and agriculture for a growing population, but also to water lawns and for other water uses. Underlying all this is a culture that doesn’t want to admit that they live in a desert.
History, and prehistory, teach us what happens when inland lakes dry up like this, and it isn’t pretty. At all.
In this series of articles, I’m going to do a deep dive into what happens over millions of years when big, inland endorheic lakes dry up. Normally, the whole drying and dust process happens over hundreds of thousands of years, but it can happen faster and with greater consequences when caused by human activity. Then, I’ll go into more detail about what’s happening to the Salt Lake, and what people can do to save the lake.
What Happens When Big Lakes Dry Up
The drying up of big inland seas and lakes is something the earth has seen before. For that reason, the consequences are pretty well understood. To explain this, let’s talk about a lake that started drying up 750,000 years ago, after staying full for over a million years.
Today, the Rio Grande runs from Colorado all the way to the Gulf of Mexico, draining into the ocean right next to the SpaceX facility in Starbase/Boca Chica, Texas. While its name implies bigness, it’s rather small compared to many rivers in the eastern United States. Compared to anything else in most of the regions it runs through, it’s still the biggest source of water — water that has been fought over for hundreds of years.
While the river feels permanent, it’s still pretty young. About 750,000 years ago, geologists tell us that the river didn’t reach the ocean. At that time, it had worked its way down from Colorado, breaking through and connecting drainage basins in northern and central New Mexico as it went, but ran into a big obstacle southeast of present-day El Paso, Texas.
Previously, the river had run into relatively mild obstacles, occasionally forming a small lake until the sheer weight of the water broke through, allowing the river to move on. This time, large mountains made of strong stone stood in its way, damming the river and forcing water to pile up. This lake ended up covering most of the region, and did so for at least a million years. Today’s El Paso, Ciudad Juarez, Las Cruces, Alamogordo, White Sands, White Sands Missile Range, and even Deming were all hundreds of feet underwater in a massive lake.
A screenshot from https://contourmapcreator.urgr8.ch/, showing the roughly approximate 4,250 ft. contour, considered by experts to be the minimum extent of the ancient Lake Cabeza de Vaca. Near where the lines are, you can see that the desert landscape is more red in color, so signs of this ancient lake still exist.
This lake, which geologists named Lake Cabeza de Vaca, had some massive weight to it. Time and pressure finally managed to break through the rocks and mountains southeast of El Paso, cutting deep canyons and forcing itself the rest of the way to the Gulf. The giant lake drained, and the Rio Grande cut itself a big, deep gash in the mud (after trying several different paths through the former lake). Today’s Mesilla Valley and the valley from El Paso to Fort Hancock are now fertile ground for agriculture, complete with water, but everywhere else the former lake used to be wasn’t nearly as nice for human habitation, unless another small river that once fed the massive flowed through the area.
The lake didn’t totally die when it broke through, though. The southwest portion of the ancient lake lived on during glacial periods (aka ice ages), forming Lake Palomas. During these wetter ice ages, several smaller rivers in New Mexico and Chihuahua fed the lake, forming a shallow inland salt sea that still fills up partially even today after particularly wet years. Another remnant, Lake Lucero, forms an intermittent lake bed next to White Sands National Park. There are a number of other small dry lakebeds in the area that do the same thing.
These little lake remnants don’t hold water consistently enough to hold their muddy bottoms in place. Lake Lucero’s white gypsum sands blow into great dunes, forming the nearby National Park. Other remnants created fields of dunes like Red Sands east of El Paso, or the Dunas de Samalayuca in Chihuahua.
While exploring those dune fields is a lot of fun, especially at Red Sands (they allow people to take vehicles out on the sands still), all of that airborne dust continues to form and blow away as ancient silt gets eaten away by the wind. This particulate matter ends up all over the North American continent, but more heavily affecting locals. Even worse, the blowing dust contains hazardous elements like arsenic and lead, which people end up breathing.
All of this makes people living in the area sick, causes automobile accidents during dust storms, and otherwise makes life a pain at times.
Nobody wants the biggest prehistoric lake to be full, as that would obviously flood out a number of cities, but having year-round lakes in a relatively small area would keep the dust situation under control. Even if the climate was just wet enough to temporarily flood the dry lakebeds every year consistently, the resulting salt flats would be able to keep the dust encased in mud beneath the surface and out of the air.
Unfortunately, past humans altered the climate with agriculture, redirected the flow of the rivers that fed the lake (for drinking and agriculture), and just generally didn’t give these little lakes and salt flats much of a chance to survive. Now, the descendants of these ancient humans are living with the consequences and can’t really go back to how things were, even as recently as the “Little Ice Age“.
Featured image by NASA, showing recent space imagery of the Great Salt Lake. Public Domain.
