water

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Max

why does water move in circles?

from MichaeL and Aaron

Joined: 27 Mar 2004 Posts: 43

Hi Michael and Aaron,

Wow - this is an amazingly good question! In some ways the answer is fairly easy, but in other ways it is very difficult.

Since it is the "water cycle", there really is no beginning or end. But let's start at an important part of the cycle which is PRECIPITATION (rain and snow). Imagine that it is raining in Salisbury, Vermont. The rain may fall at your house or at the school or wherever. Some of the water will EVAPORATE or be TRANSPIRED (this is when water is evaporated from plants), but eventually much of that water will reach Otter Creek. As some of you taught me, the water in Otter Creek eventually reaches Lake Champlain, and the water in Lake Champlain eventually flows into the St. Lawrence river. And as you know, the water in the St. Lawrence
River eventually flows into the Atlantic Ocean. Of the PRECIPITATION that fell on Salisbury, about half will reach the Atlantic Ocean by the St. Lawrence River, and the other half will be returned to the atmosphere by EVAPOTRANSPIRATION (evaporation plus transpiration) before reaching the Atlantic Ocean.

The water that originally fell in Salisbury may stay in the ocean for days, or weeks, or years, or even thousands of years, but eventually it will be evaporated from the ocean and returned to the atmosphere. Then the water vapor (clouds, etc) can move in the air with the winds. Maybe it will blow back to Vermont and fall again as precipitation on Salisbury, or maybe the winds will take the water vapor to Russia, or Africa, or just about any other place on Earth. But eventually it will fall as rain or snow again, thus completing the water cycle (not really a "circle", but instead a "cycle").

Sometimes when I drink a glass of water, I like to imagine where that water has been in the past. Maybe it has been in China or the Pacific Ocean or Russia or maybe it was inside a dinosaur thousands of year ago! Or it could have been in a glacier or a wooly mammoth or maybe all of these places! So to me, the history inside a glass of water, or inside a lake or flowing down the Otter Creek is lots of fun to imagine. You can be sure that some of the water "molecules" inside a glass of water have been all around the earth many many times. And of course after you drink the water the cycle will continue!

Excellent question!

Max