The Amateur Naturalist

The summer monsoon rains during the past several weeks have brought many of the temporary streams in our area to life. 

Why have some streams been flowing but others have remained dry? Why have some flowed for only a short time? Rain water is a primary consideration, but it is the level of water in the ground below and around a stream that has a major influence on whether a stream will have flowing water on a continuing basis.  

The ground around a stream may contain sufficient water so that some of the water is always coming to the surface. Water then flows continuously whether the ground water is high or low. The stream then is perennial since it always receiving water either from the ground below or from the rain above.

An ephemeral stream, in contrast, has ground water that is always below the bottom of a stream bed. Water now always leaves a stream to enter the ground, percolating farther below. An ephemeral stream is filled initially by rain water but this water goes from the stream into the surrounding soil. An ephemeral stream therefore exists for only a short period of time. It also may flow for a short distance before its water goes underground.

An intermittent steam has characteristics of both perennial and ephemeral streams. Its ground water may be below a stream bed for part of the time but then rise high enough so that it starts to provide water in a stream. The stream then may continue to flow for a longer time or greater distance after rain water no longer is available. However, the stream eventually disappears as water percolates farther under ground. 

Based on ‘Temporary Streams’ by Owen T. McDonough

Pajarito Canyon provides an example of an intermittent stream. Google Maps indicates that it is a permanent stream. However, a very dry stream bed greets a person at the start of the hiking trail leading up the canyon from West Jemez Road. The sandy and gravelly stream bed provides a clue as to where any water has gone.  However, the stream changes its character if one observes it after hiking a few hundred yards up the canyon. Water can be heard bubbling in the distance and a flowing stream appears. The stream becomes delightful when a person reaches a small waterfall with wild flowers growing above it.

The stream is dry at the start of a hike, but then a flowing stream appears. Photo by Robert Dryja

A small waterfall is located further upstream. Photo by Robert Dryja

But now a surprise occurs. The flowing water disappears a short distance farther upstream from the waterfall. With a little exploring, a spring will be found at this point. The flowing water of the Pajarito Canyon stream exists for about 150 feet from its start to its finish.  Its water emerges from the ground near the waterfall but then percolates back into the ground a short distance later.  A permanent stream occurs much further downstream as it leaves White Rock Canyon.

The Pajarito Canyon stream may become longer and exist for more time if the summer rains continue to provide additional water. Repeated visits in coming weeks should see the character of this stream change. The plants and animals that live adjacent to it also will be changing.