The water you drink today has likely cycled through Earth’s biosphere for millions of years, though scientists disagree on whether every drop has passed through a living organism. While some researchers calculate that the total volume of animal waste over geological time exceeds the planet’s water supply, hydrologists point to isolated groundwater and “juvenile” volcanic water as evidence that some supply remains untouched by biological processes.
Has every drop of water been inside a dinosaur?
According to Neil Donahue, a professor of chemistry and chemical engineering at Carnegie Mellon University, the answer is “emphatically yes” when using back-of-the-envelope calculations. Donahue estimates that if you assume chordates have maintained a consistent mass over time, these animals produce roughly 0.2 gigatonnes of urine daily. At that rate, it would take approximately 19 million years to “pee out” the entire volume of Earth’s oceans. Since the asteroid impact that ended the age of the dinosaurs occurred 66 million years ago, Donahue argues that modern and prehistoric animals have cycled more than the ocean’s total volume through their bodies.
Did you know? Earth holds approximately 1.4 billion gigatons of water, a figure provided by the U.S. Geological Survey that includes everything from polar ice caps to deep-crust groundwater.
Why is the “dinosaur pee” theory disputed?
David Kreamer, a professor of hydrology at the University of Nevada, Las Vegas, contends that the answer is no, arguing that water does not move through the global cycle at a uniform speed. Kreamer notes that significant portions of Earth’s water are effectively sequestered from the biological cycle. Glacial ice can trap water for hundreds of thousands of years, while deep groundwater reservoirs have remained isolated from surface life for tens of thousands of years.
Pro Tip: When evaluating environmental claims, look for the distinction between “global averages” and “residence time.” Water moves quickly through a cloud but stays in a deep aquifer for millennia.
What is “juvenile water” and where does it come from?
Not all water on Earth has participated in the surface water cycle. Kreamer describes “juvenile water” as moisture trapped deep within the planet’s crust that has never emerged to the surface in Earth’s history. This water is released into the atmosphere during volcanic eruptions when magma dissolves and expels it as steam or lava. Because this water reaches the surface for the first time during these geological events, it has never been processed by an animal, meaning it has never been “peed” before.
Frequently Asked Questions
- Is the water in my glass recycled? Yes, the Earth’s water cycle is a closed system. Most water molecules have been recycled through evaporation, condensation, and precipitation for billions of years.
- Can volcanic water reach my tap? Eventually, yes. Once juvenile water is released during an eruption, it enters the water cycle and can eventually reach rivers, lakes, or groundwater reservoirs.
- How much water is actually in the water cycle? The U.S. Geological Survey estimates Earth contains about 1.4 billion gigatons of water, distributed across oceans, ice, and atmospheric vapor.
What do you think? Does the idea of recycled water change how you view your next glass of water? Share your thoughts in the comments below or subscribe to our newsletter for more deep dives into the mysteries of our planet.
