Water follows the path of least resistance. Over countless years, rivers and streams change course, reshape the earth, and leave a bit of history behind. That history is seen in the sediments dropped along the way and reflected in the progress made possible by its mere presence.

It’s the presence of water that makes life possible at all.

But it’s not always what a waterway leaves behind that matters. Sometimes it’s what the water continues to carry with it that matters most. This would certainly ring true for pollutants like insecticides, pesticides, and herbicides used in commercial farming applications. Applied in one location, such chemicals can find their way into rivers and streams and end up a world away.

Select a river or stream close to the Lab and trace its flow as far as you can. Does it reach the ocean? If you were to drop a message in a bottle (signifying the transportability of chemical agents) and toss that thing in the water how many states, or people, would it pass along the way? Use the USGS Streamer Interactive Map to trace the flow downstream to confirm your assessment.