Space & Innovation

Where Does Water from Snow and Rainfall Actually Go?

Only about a quarter of precipitation ends up in the oceans. Where does the rest go? Continue reading →

Here's a question that matches the old "If a tree falls in a forest and no one hears it, does it make a sound?" question. But this one is less abstract. If rain or snow falls on land, where does it eventually go?

If your answer is that it turns into runoff that ends up in waterways and eventually flows into the oceans, you're only partially right. Only about a quarter of the precipitation over land does that. So what happens to the rest?

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University of Utah researchers have the answer, and even some precise numbers.

In an article in the journal Science, they report that of the remaining water, most of it - 64 percent - is exhaled back into the atmosphere by plants, in a process called transpiration. Based upon previous studies, another 27 percent lands on leaves and evaporates, and the rest evaporates from soil (6 percent) or from lakes, rivers and streams (3 percent).

The findings actually were a bit of a surprise, because previous research suggested that even more of the water - as much as 80 percent - was accounted for by plant transpiration.

The researchers used hydrogen isotope ratios of water in rain, rivers and the atmosphere from samples and satellite measurements to come up with their numbers.

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"It's important to understand the amount of water that goes through each of these pathways," one of the study's authors, University of Utah hydrologist Stephen Good, explained in a press release. "The most important pathway is the water that passes through plants because it is directly related to the productivity of natural and agricultural plants."

The researchers also found that of the precipitation that seeps down into the Earth's groundwater, most moves through the soil so quickly that it isn't available for plants to use. Only 38 percent of the water ends up being involved in moving nutrients, fertilizers or contaminants, or in affecting biological processes.

Some rainfall lands on plant leaves and then evaporates back into the atmosphere.

It might sound a bit cramped, but there's an entire world of organisms that can call a drop of water their home. And, up close, they look practically out-of-this-world. Each year, the Nikon Small World competition sets out to collect some of the best microphotography. Take a look at some of this year's most stunning images of creatures that live in water. This photo from Dr. Jan Michels of Christian-Albrechts-Universität zu Kiel in Kiel, Germany shows Temora longicornis, a marine copepod, from its ventral view at 10 times magnification.

SEE MORE PHOTOS: It's a Nikon Small World After All

This microphotograph shows the diatom Melosira moniliformis at 320 times its size.

This algae biofilm photographed up-close makes what's usually referred to as "pond scum" look like art.

This Philodina roseola rotifer was alive and well when this microphotograph was taken.

This microphoto shows a water flea flanked by green algae.

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Warfare in a water droplet! This microphoto shows a Hydra capturing a water flea at 40-times magnification.

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One of the ultimate human pests -- the mosquito -- begins life as larvae, here shown suspended in a single droplet of water.

Ever wonder what sex between two freshwater ciliates looks like magnified at 630 times its actual size? Now you know!

This freshwater water flea is shown at 100 times its actual size.

Closterium lunula, a kind of green alga, is shown here. This particular specimen came from a bog pond, according to the photographer.

While it may resemble a visitor from outer space, this is what a zebrafish embryo looks like under a microscope, three days after being fertilized.

This microscopic crustacean appears yellowish-orange because it is mounted in Canada Balsam with crystals and other artifacts.

A white-spotted bamboo shark's embryonic pectoral fin makes for a stunning image under a microscope.

SEE MORE PHOTOS: It's a Nikon Small World After All