The Water Cycle: Water's Journey from Land to Sky & Back Again

Posted Tuesday, February 23, 2021

Would you believe that your last drink of water could have once been used by a dinosaur?

Water on earth today has been here for millions of years. Because of the water cycle (hydrologic cycle), water moves from the earth to the air to the earth again. It changes from solid to liquid to gas, over and over again.

What is the water cycle?
The water cycle keeps the amount of total water on the globe constant. Water evaporates. Water from oceans, lakes, rivers, ponds, puddles, and other water surfaces evaporates to become clouds. The clouds make rain, snow, or sleet that falls to earth to make rivers and streams, some of which seeps into the ground to form groundwater. All of this water flows to the ocean to start the cycle over again. Before returning to the ocean, some water is taken for drinking water and then is discharged as wastewater. The cycle is never-ending.

Precipitation creates runoff that travels over the ground surface and helps to fill lakes and rivers. It also percolates or moves downward through openings in the soil to replenish aquifers under the ground. As we all know, some places, such as the Pacific Northwest, receive more precipitation than others. These areas are usually close to oceans or large water bodies that allow more water to evaporate and form clouds. Other sites receive less. Often these areas are far from water or near mountains. As clouds move up and over mountains, the water vapor condenses to form precipitation and freezes. Snow falls on the peaks.Water Cycle

What if the water cycle stopped?
Without it, all life on earth would end. Without this never-ending cycle, plants would die. Underground sources would soon be emptied. While rivers, lakes, and oceans would overflow and flood large areas of land. The whole ecologic cycle would end.

Pollution of water sources
Water can be polluted with human and/or chemical wastes. Even deep underground aquifers can be contaminated from the surface. For example, oil thrown on the ground or in the sewer can pollute water and is very hard to remove.

Everyone must do their part to keep water sources clean.
Public utilities must clean water very carefully. We test water and measure pollutants to make sure the water is safe. We can measure tiny amounts of contaminants in bodies of water—parts per million, parts per billion, and even parts per trillion. The water that we deliver to people must meet strict rules of purity. It is hard to imagine but:

  • One part per million would be equal to one drop in 10 gallons.
  • One part per billion would be equal to one drop in 10,000 gallons.
  • One part per trillion would be equal to one drop in 10 million gallons.

At Skagit PUD, we are committed to providing you the safest and most reliable drinking water possible. Annually, we produce a water quality report for each of our eight water systems. The report explains where your water comes from, what it contains, and how it compares to Environmental Protection Agency (EPA) and state standards. Copies are available on our website and at our Mount Vernon office.


Evaporation – liquid water becoming gas
Transpiration – evaporation of water from plants
Condensation – water vapor becoming a liquid
Precipitation – rain, snow, sleet, or hail
Aquifer – large underground water source
Percolation – movement of water through the soil