The Water Cycle

February 1, 2012 Maria

Winner for most artistic and mist-like arrows. (Source: National Geographic Society, Exploring Your World)

   Certainly everyone remembers their very first Water Cycle poster from elementary school. Typically, the poster featured a body of water, a land mass, and some clouds with three wide curving arrows showing how water moves (evaporates) from the ocean or lake, becomes (condenses into) clouds, which then rain or snow (precipitate) onto the land and then flow underground and/or back into the ocean or lake. Three arrow--ocean, cloud, land--right?--kind of like the plastics recycling logo.
   I am sure many of you are nodding your heads, happy to have remembered this much. And, I am sure many of you are shaking your heads and saying, "Ah, if it were only that simple!"
   Yesterday, I went in search of the water cycle illustration. I pulled several books from my book shelf, flipped to the index looking for "water cycle" or "hydrologic cycle." The first one I found (above) is the work of Robert Hynes and comes from my go-to geography books published by the National Geographic Society in 1989. The illustration is beautiful, misty, round, and feels fluid like a water cycle. However, it includes not three arrows but five. Or maybe two. Some of them are double headers. Naturally, because this is a product of the NGS, all you need to know is packed into a text block/caption adjacent to the illustration.
   Before reading that text, I went to my next favorite book and found another lovely misty scene (below) and was surprised to see that there were seven arrows and they did not move in the continuous cycle imprinted in my mind from grade school. Huh! I grabbed another book.

Pretty darn artistic, but the labels kind of ruin the mood. (Source: Ahrens, Meteorology Today)

That book was a college biology text book for a community-college class I signed up for fifteen years ago and then remembered I had two pre-schoolers at home and would have much homework, a lab, and an hour commute to the campus. I withdrew and kept the book--despite the fact that its water cycle looks more like a design for a water elevator (below). Rectilinearity aside, this illustration includes some enormous numbers--such as 425,000 cubic kilometers for the amount of water evaporated from the world oceans every year. Looking at water cycle maps without such numbers makes it easy to be lured into the notion that a big fat arrow is going to dump 425,000 cubic kilometers of water back on the earth. Do not be so lured. An estimated 385,000 cubic km of that evaporated ocean water falls as precipitation back into the ocean; and 111,000 cubic km falls onto land. That makes 496,000--not 425,000. The "extra" 71,000 cubic km of precipitation comes from evaporation from land plants (evapotranspiration).

(Source: Starr/Taggart, Biology: The Unity and Diversity of Life)

I reached for my least popular cloud book, Cloud Physics: A Popular Introduction to Applied Meteorology, which included an illustration I mistook for a water cycle diagram (below). It is not, but you can see my confusion.

A cascade impactor may move water, but it does not seem capable of producing clouds. (Source: Battan: Cloud Physics)

I almost missed this diagram (below) in my best-present-ever-from-my-husband-that-wasn't-butterfly-larvae book. The coastal landscape was unscenic, the clouds were not lovely, it was black-and-white, and the the cycle just didn't flow the way I wanted it to. This diagram resembles a cascade impactor (above).

(Source: Allaby, Encylopedia of Weather and Climate)

A few books on my shelf are too smart for me. There were no color pictures in it. Nor were there any diagrams that represented the water cycle. I did wonder if this equation (below) might be the water cycle in code, but decided to turn the page.

Huh? (Source: McIntosh/Thom, Essentials of Meterology)

And I saw this:

I really like this, but it is a diagram of the exchange of air in the troposphere. (Source: ibid)

And then this:

These caught my eye, but represent convergence, divergence, and vertical motion of something called "flow" I think that's air. (Source: ibid)

And then, from yet another book, this:

A little something from the HR Department? (Source: Barry/Chorley: Atmosphere, Weather & Climate)

Lastly, in a most wonderful book, I found a water cycle lacking in artistry, color, and clouds (!) but one that depicts with elegant simplicity my local, Puget Sound water cycle (below). In fact, the vantage point of the reader, the Olympic Mountains are on left, Cascades on the right, and where I live, right in the center. And it has a dizzying array of arrows--about two dozen of them. This water cycle gets under my skin. In a good way.

Source: Kruckerberg, The Natural History of Puget Sound Country

  At this point, dear reader, you are probably wondering where I am going with all this. Perhaps you are dreading a somewhat longish explanation (in words) of the water cycle according the Accidental Naturalist. No, this would be too much at the end of an already longish posting.
   What I want to tell you is that after my unplanned and exciting foray into The Water Cycle, my arrow counting, my analysis of straight and curving lines, I seem to have discovered the perfect way to organize my book on clouds.
   More on that in my next posting.

Note: All photographs of illustrations from books paid for or borrowed by the Accidental Naturalist.