From Headwaters to the Sea
by Bill Schlesinger
Just outside of our townhouse in North Carolina lies a shallow, linear depression that is mostly filled with autumn leaves. Come rain, this drainage way carries water downslope to Sandy Creek, a tributary to the Neuse River. Normally dry, but occasionally flowing, such a stream is known as an ephemeral or headwater stream—the origins of all big rivers that dump into the sea.
When they are full of water, ephemeral streams extend the total length of rivers reaching the sea. In a very real sense, during rainstorms rivers grow upstream. The total length of streams in the U.S. is five times longer in high vs. low flow conditions. The difference is greatest in the Great Plains, and lower in mountainous regions of the eastern and western regions of the country. Nearly the entire length of streams in the desert Southwest may consist of ephemeral streams that are dry arroyos for most of the year and raging torrents of water after rainstorms.
Even though ephemeral streams are seldom wet and certainly not navigable, they are all part of the network of drainages that carry water to the sea. One recent account suggests that 55% of the flow of major rivers in the United States derives from ephemeral streams. This is why the recent Supreme Court decision (Sackett vs. the EPA) exempting ephemeral streams from protection is most unfortunate. The Sackett ruling allows someone to dump a toxic chemical into a dry drainage knowing full well that later in the year the deposit will make its way down to a perennial stream. After all, all water flows downhill.
Stream ecologists recognize a watershed as the entire area that is drained by a single river. Watershed studies have a rich history in hydrological and ecological sciences. This is a system-wide approach to environmental management that should form the basis of the Clean Water Act, enforced by The Environmental Protection Agency. Rather than the cuts now imposed on it, the EPA needs the full scientific wherewithal for holistic management of U.S. rivers. Anything less, leaves populations downstream vulnerable to mischief upstream at a time when our water resources are most precious. This is not the time to “unburden” the corporate world from regulations that protect our environment.
References
Brinkerhoff, C.B. et al. 2024. Ephemeral stream water contributions to United States drainage networks. Science 384: 1476-82
Messager, M.L. et al. 2021. Global prevalence of non-perennial rivers and streams. Nature 594: 391–397
Prancevic, J.P., H. Seybold, and J.W. Kirchner. 2025. Variability of flowing stream length across the U.S. Science 387: 782-784.
