The Water Cycle

Kids say the darndest things! This year “The Water Cycle” is being taught in Science at the high school, which came to my attention when a story was relayed to me the other night.


It had been raining, and the young man was quite anxious. “It’s raining!” he exclaimed. “Yes, yes it is,” his teacher agreed. Drawing closer, he whispered, “Do I smell like pee?” Backing up, his teacher stared at him. “What are you talking about? Of course not!”

The student went on to explain his thought processes. He fully understood the Water Cycle and its importance to Earth’s replenishing and sustainability of its water sources. Taking it a step further, he reasoned that all the animals urinate outdoors – dogs, cats, horses and cows, bears and raccoons, all the wild birds, even the insects and fish. Well (his eyes widening), all that urine must leach into the soil and evaporate just like water! Which meant it was now returning to earth and raining urine on his head.

Having never thought this through to this degree I stopped to ponder these ideas, searching for merit. His teacher, I might add, did no such thing. She told him the clouds filtered out impurities and the rain was clean and he could retake his seat. He was most relieved. I was impressed at her quick-witted response. This is where the scientist in me gets bogged down. This is why I’d be a lousy teacher.

So, the Water Cycle, in its simplest form, explains how water covers 71 percent of the Earth’s surface. This water cycles through several steps: It evaporates into the atmosphere, where it condenses into droplets that form clouds and later falls back to the earth as precipitation (rain, snow, hail, sleet), which is collected or returned to our oceans, lakes and land.

Next, urine from mammals is composed of about 95-percent water plus some other compounds, including urea. Urea contains nitrogen. This fact is very important to a different science lesson, the Nitrogen Cycle. Nitrogen is necessary for all life as the building block of protein, which both plants and animals need to grow. Nitrogen is the most important nutrient that plants get from the soil. The soil receives this nitrogen in two ways – nitrates come from animal solid waste like manure. From liquid waste like urine comes urea. Another way nitrogen is acquired is through decomposing into the soil.

Birds and reptiles are uricotelic (I wrote this whole story so I could prove I know that word), meaning their urine waste is in the more solid form of urates (that white stuff in the bird’s droppings) than liquid urine. It’s simply how their non-mammalian rudimentary kidneys function.

This is a very long-winded way of explaining that only the water from body wastes can evaporate into the air. All the “impurities” or other compounds are left behind to enrich our soil. Rainwater is essentially distilled water, free from impurities unless it picks up local air pollution/ dust or other debris as it returns as precipitation during the Water Cycle.

This is the most amazing win-win ever! So put on your galoshes and go splash in some puddles!

And have a great day!

Christine McFadden, DVM

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