As we examine the Earth around us, we see many “cycles.” These are predictable pathways that see certain kinds of matter changing from one form to another – and eventually returning to some original form, only to begin the journey over again.
Perhaps the best example of such cycles is the hydrologic cycle. Liquid water on the surface of our planet is transformed (primarily by solar energy) into gaseous water in the atmosphere. Later, this gas cools and condenses to form liquid water, which returns to the surface as precipitation. It is important to note that the quantity of water in the hydrologic cycle does not change! Only the location and the form (solid-liquid-gas) of the water change.
How do humans fit into this cycle? Don’t we consume water? Doesn’t this mean that the Earth will eventually run out of water?
Actually, we humans – like all the other animals and plants, microscopic and larger – are a part of the hydrologic cycle. We don’t really “consume” water. Instead, we change the water’s location and form for a time. We drink liquid water. Most of this water leaves our bodies as gaseous water, in every breath that we exhale. We also return water to the cycle through sweat, urine, tear drops, and feces, but exhalation is the main route of return.
What about water used for irrigation? Some of the water applied to crops or lawns evaporates and goes right back into the cycle. Some percolates beyond the plants’ roots, and eventually flows into a surface water location. But most of it is “consumed” by the plants. And, just like animals, the plants eventually “transpire” the water back into the atmosphere.
What about the water we use in our homes? When the water “goes down the drain,” it doesn’t leave Earth. It makes its way through our sanitary sewer systems and travels on to our wastewater treatment plants. These plants remove contaminants from our sewage, and leave clean water behind. Most of that water goes into streams or oceans, and thus goes right back into the hydrologic cycle. We just rented it for a short while.
Could we extend our rental period a bit? Sure! By “recycling” or “reclaiming” treated wastewater, we could use the water for a second purpose, before it returns to the hydrologic cycle. In fact, ALL water is recycled! Because it is part of an endless cycle, we are drinking the same water that the dinosaurs drank, and swam in, and – well, you know.
So what could be more “natural” than water recycling? It’s what our Earth has been practicing for countless eons. The “Toilet-to-Tap” label that was placed on water recycling a few years ago is a rotten bit of politician-speak, that tries to deceive the public about the natural reality of water recycling. There should be zero tolerance for such deceit.
But the hydrologic cycle is not the only cycle that we witness on our planet. In future blogs, we’ll examine the carbon and nitrogen cycles, too. And let me give away the ending on these: the amounts of carbon and nitrogen on our planet remain constant, just like the amount of water! Are you listening, Mr. Gore?