Area geography needs clarification

Jim Constantopoulos: Guest columnist

The July 18 CNJ article “What’s in a name?” was fun reading, but some of its sources lacked factual data.

Let me clarify some misconceptions and add some facts.

Portales is located in Portales Valley, an east-west trending valley that can be traced from near Fort Sumner to just north of Lubbock. The valley can be seen in aerial photographs, in satellite images and, of course, Google Earth.

As you drive into Portales along U.S. 70 from either Clovis or Elida, you can see Portales sitting in the valley. You can also see this from the Lovington Highway.

Along N.M. 467, the sand dunes mark the location of the north side of the valley, which can be seen in profile if you look south beyond Wal-Mart. So indeed, Portales does sit in a valley, but it is a stream valley, not a lake valley as quoted in the article.

Portales Valley was once occupied by the ancestral Brazos River, which had cut into the Llano Estacado in this area. What happened to the river?

During the Pleistocene, the Pecos River was migrating northward by what we call headword erosion. It eventually cut into the drainage basin of the upper Brazos and “captured” or “pirated” the stream. The sediments (mainly sand and gravel) transported by this stream and deposited in the valley served as an important aquifer for the Portales Groundwater Basin for many years.

While the Portales Valley may not look like a valley to most folks, many are surprised to learn about the elevation differences around here. The official elevation of Portales is 4,006 feet and for Portales Valley, the official elevation is 3,984 feet.

On the Portales quadrangle topographic map published by the United States Geological Survey, the lowest elevation reaches 3,950 feet about five miles southeast of Portales. Clovis is 262 feet higher than Portales at an elevation of 4,268 feet and Cannon Air Force Base is even higher at 4,285 feet. Melrose sits at an elevation of 4,413 feet, 407 feet higher than Portales.

So while it may be quite subtle, Portales is in fact located in a former stream valley containing sediments carried by the east-flowing Brazos River.