Water isn’t just water. That is, a stream might seem like a single, cohesive flow, but it’s really a confluence from different sources. Each flows through different paths, carries different chemicals and nutrients, and has different properties.

In the GIF above, the reddish stuff is groundwater, mixing with blue-er (cooler) surface water. Groundwater is everything from droplets suspended in the tiny spaces between dirt particles to sprawling reservoirs comparable in size and volume to the world’s largest lakes. It is constantly flowing out of, and into, surface water, bringing with it every class of human-generated runoff—from fertilizers to pharmaceuticals. So if you care about the origin of those strange silhouettes you and your friends saw shambling through the gloomy wetland near the chemical factory—or any water you drink, ever—then you should be aware of your groundwater.

“Groundwater, like all water, is a finite resource,” says John Lane, head geophysicist at the USGS Office of Groundwater. Like the water in streams and rivers, groundwater comes primarily from snow and rain. “Although it is renewable at some level, we are also using it at a prodigious rate,” says Lane. “It can also be contaminated, and it is being affected at some level by sea level and climate change.”

Thermal infrared image of groundwater discharge revealing differences in water temperatures.

Difference is, once it seeps into the earth, groundwater moves very slowly. Lane and his crew are like water detectives, trying to figure out where groundwater comes from, and where it goes. And a lot of that detective work begins where the groundwater enters the surface system. These points of re-entry can be hard to find. “You can’t see it with a naked eye,” says Lane.

But you can with a thermal imager. “Groundwater is pretty stable, and tends to approach the mean annual temperature of its region,” says Lane. For instance, in New England, where he is based, groundwater is around 55˚F. In the summer, it will be cooler than surface water; in the winter, warmer. So Lane and his co-investigators hit the field—in boats, cars, and mud boots—with an infrared camera.

Once you’ve identified the groundwater discharge location, you can do all kinds of detective work. Lane is a geophysicist, so he’s predominantly interested in the sediment structures, fractures, and different underground strata through which the groundwater moves. Other experts, like hydrologists, will try to figure out where the water came from. “There are certain age dating techniques that you can use to give you an idea of that water’s past life,” says Lane.

You can also use the thermal imager to trace contamination. “If you find a focused discharge site, you can get samples before the water dilutes and find the true concentration of its chemical constituents,” says Lane. And with some educated trudging and drilling, scientists can figure out from whence the cocktail chemicals, nutrients, and other additives came from. Because how else are they going to figure out how to rid the swamp of those chemically-mutated monsters?

Go Back to Top. Skip To: Start of Article.

Source link