In my business life I deal with drinking water and wastewater. In my personal life I advocate for the protection of inland lakes.

But I know the world of water is much bigger than that. In my own activities I barely touch on rivers. Trout streams. Wetlands. Stormwater. Oceans. And the reality is that all these — along with rain and snow from the sky — are components of the single entity called water.

That’s right. It’s all connected, every bit of it. We know about the natural water cycle — from evaporation, to rainfall, to the water resources on and under the ground. We also know about the urban water cycle, from ground or surface water, to treatment, to our household taps, and back to the source by way of wastewater treatment.

But better than thinking about those cycles is to consider water in all its forms and places. Thinking that way helps us see the bigger picture of the system in which we do our work.

Knowing watersheds

There’s the concept of watersheds. To understand it, picture a large, shallow bowl. Water falling anywhere on the bowl’s surface will run toward the low point at the center. In a landscape, hills and slopes form the sides of the bowl; water drains down to the lakes and streams at the bottom. A watershed includes all the lakes, streams and wetlands in the area being drained, and all the groundwater underneath.

A watershed can be large or quite small. For example, a small lake surrounded by hills might have a watershed of just a few square miles. On the other extreme, a river like the Mississippi has a watershed that encompasses a large share of a continent.

Getting back to groundwater, there’s a great deal more water beneath us than on the surface. For example, it has been estimated that the groundwater beneath my home state of Wisconsin would be enough to cover the entire state to a depth of 100 feet. In a bigger picture, scientists estimate that groundwater in the United States comprises at least 33,000 trillion gallons, about as much as the Mississippi River has emptied into the Gulf of Mexico over the past 200 years.

This water doesn’t consist of an underground lake. Instead, the water fills the spaces between the particles of sand and gravel. To observe what this is like, fill it with sand and then pour in water until the sand is saturated. That is how the groundwater exists.

Water on the move

The groundwater does flow, very slowly, from higher to lower elevations, obeying gravity. The surface of the groundwater is called the water table. It’s fed by rain and snow melted snow percolates down through the soil. The groundwater then gradually follows the slope of the landscape until it finds an outlet in a lake or stream.

It can take years or decades for a drop of water to travel from where it fell to a body of water. The slow, steady flow of groundwater is the reason streams run all year, even during drought. And most lakes are essentially places where a depression in the landscape causes the water table to be exposed. That is, looking out across your favorite lake, you are seeing the surface of the groundwater.

The level of the water tables changes year to year, decade to decade. In the simplest terms, its level depends on the amount of rain that falls and the amount of evaporation. So the water table will rise in wet years and fall during dry years. Eventually, much of the water that falls as rain or snow enters the groundwater system and ultimately finds an outlet in a stream. One stream flows into another, until a major river delivers it to the oceans.

So as we go about our jobs dealing with our specific water-related areas, it’s useful to remember how it all fits together. All the waters are connected, and in working to protect them, so are all of us.