The Great Aquifer is Leaking

“Visit Nebraska. Visit Nice.” (more here)

Nebraska is nice, as the Nebraska Tourism Commission says, but why are they so modest? It’s more than nice—spectacular even. I especially like the immense vistas—maybe to the edge of the world! Maybe if I keep going I’ll float off to join the birds and the clouds, and we can sail across the beautiful blue Nebraska sky. Such thoughts cross my mind as I drive through open rolling country for miles and miles and miles.

It was Willa Cather who suggested that the Great Plains lead to the edge of the earth.

And something equally remarkable lies hidden from view. Cross Nebraska and you cross miles and miles of water-soaked consolidated sand just a few hundred feet below the surface—one of the most important aquifers in the world. Two-thirds of the water in this great aquifer—650 trillion gallons**—lies under Nebraska.

“Saturated thickness of the Ogallala Aquifer in 1997 after several decades of intensive withdrawals.” Note that the aquifer is most extensive and thickest (dark blue) in Nebraska (USGS via Wikimedia).

The Ogallala Aquifer is so-named because most of the water-bearing rocks belong to the Ogallala Group—named by geologist NH Darton after the town of Ogallala, Nebraska. It’s often called the High Plains Aquifer because it includes other rocks in addition to the Ogallala, but not many. Darton described the value of Ogallala rocks in his 1905 report about the central Great Plains:

“These great sand deposits, constituting the surface of the High Plains, contain a large volume of excellent water, which usually accumulates in the lower beds, where it is available for pump wells, generally at depths of about 200 to 300 feet. Such wells are numerous in the upland region of west Kansas, west Nebraska, and east Colorado, where they are the principal sources of supply.”

Rocks of the Ogallala Group consist of debris that was eroded off the Rocky Mountains during the Miocene Epoch (roughly 19 million to 5 million years ago), carried eastward by streams and wind, and deposited as far east as eastern Nebraska and south into Texas (Maher 2003). The coarse loosely-cemented sediments—mainly sand—make for porous rock that holds lots of water.

The Ogallala Aquifer underlies 111.4 million acres or 174,000 square miles. Often the water is just a few hundred feet down and easily accessible by wells, which is why it’s so important. It provides about 27% of the ground water used for irrigation in the United States (source). But as huge as it is, it’s being sucked down, mainly by agriculture. Replenishment can’t keep up with use. McGuire (2007) estimated that as of 2005, Ogallala water storage had declined by 9% since pre-development—on average. Locally the impact can be much greater. The need to conserve the Ogallala is now widely-recognized, but far from being achieved. For more, see the NRCS’s Ogallala Aquifer Initiative, and this interesting article from Scientific American about Ogallala depletion, and related changes and innovations in agriculture.

Water-level changes in the High Plains aquifer, predevelopment to 2005; modified from McGuire, 2007 (USGS). Red areas are most severe.

Back to Ogallala rocks … there’s another reason why they hold so much water. Not only are they porous, they sit atop older rocks that are rich in clay and volcanic ash and thus largely impermeable, thereby “sealing” the bottom of the aquifer. But sometimes it leaks.

Morning on the Niobrara River. Pale slope center of photo is the Valentine formation, the porous water-bearing basal unit of the Ogallala Group.

In carving their valleys, several Nebraska rivers have exposed the base of the Ogallala. Last month, I visited the Niobrara River to see the great aquifer. East of Valentine, the Niobrara flows through an unexpectedly deep narrow valley, revealing the contact between the porous Ogallala and underlying impermeable strata. Seeps and springs—“leaks”—mark the juncture.

Just east of Valentine, I stopped at the Fort Falls overlook on the Fort Niobrara National Wildlife Refuge, where there’s a clear view of the Ogallala base. Water seeps out at the contact between the water-rich Valentine formation and the impermeable Rosebud formation below, turning the Rosebud reddish-brown.

Shaded slope on a bright day makes for lousy photos, but still cool to see the Ogallala Aquifer!

Valentine formation (Ogallala Group) at top of slope, with grass and scattered trees; reddish brown layer in center of photo is the Rosebud formation (White River Group).

About 15 miles east of Valentine on Highway 12, a narrow road turns south, crosses rolling prairie for awhile, and then suddenly descends into the valley of the Niobrara, ending at a state park designated for the most spectacular leak in the Ogallala Aquifer—Smith Falls. At 70 feet, it’s the highest waterfall in Nebraska.

The substantial footbridge across the Niobrara is in its third reincarnation as a bridge. It was built in 1910 to cross Verdigre Creek; disassembled and moved in 1917; reassembled in 1922 as part of Nebraska Highway 14; disassembled and stored in 1993; and finally reassembled, renovated, and installed at Smith Falls State Park, opening in 1996.

A wooden walkway above the narrow canyon bottom leads to the falls.

This is the Rosebud formation, reddish brown when wet. Water comes from the Valentine above, out of view.

**McGuire (2007) reported 2.925 billion acre feet of water stored in the High Plains Aquifer in 2005. Roughly two-thirds of this lies under Nebraska (source)—on the order of 2 billion acre feet or 650 trillion gallons.

Sources (in addition to links in post)

Joeckel, RM et al. 2014. Architecture, heterogeneity, and origin of late Miocene fluvial deposits hosting the most important aquifer in the Great Plains, USA. Sedimentary Geology 311:75-95 http://dx.doi.org/10.1016/j.sedgeo.2014.07.002

Maher, HD, Jr., Egelmann, GF, and Shuster, RD.  2003.  Roadside geology of Nebraska.  Mountain Press Publishing Company.

Citizen Scientists Awake—We Have Wildflowers!

Laramie botanists are emerging from hibernation, hungry and irritable, in critical need of floral sustenance. But while other plant lovers are gaily posting colorful photos of spring flowers and lush foliage, we're desperately searching for any color at all.

NOAA’s extended forecast; the little pictures say it all.

I’m exaggerating, but barely. Wildflowers are just now appearing, and to see them we have to get out in between snow storms. Last Friday was sunny, so I grabbed my camera and drove up into the Laramie Mountains. Fortunately all the heavy wet snow from a few days before was mostly gone. I was intent on adding observations to my Plants of the Southern Laramie Mountains project in iNaturalist, which has lain dormant since last fall.

I didn't have to walk far to be rewarded. Pasque flowers (Pulsatilla or Anemone patens ssp. multifida) were common, as they usually are this time of year—in the field and on Facebook! But then who wouldn't be excited to come across large showy flowers when everything else is mostly brown and gray.

I found Oregon grape (officially creeping barberry, Mahonia repens) at the base of large granite boulders on a south-facing slope. Neat discovery—I didn’t know it bloomed so early. With flowers it's a good addition to my iNat project.

While on the ground photographing Oregon grape, I spotted spring beauty (Claytonia lanceolata). It is a beauty, but you have to look close as the flowers are only about a centimeter across.

In a sunny opening in the forest, three goslins caught my eye—luckily. I don't usually see them. Their downy brown and gold coats blend well with dead vegetation and litter.

What are goslins? The purplish patch above is a hint (click on image for a better view). Goslinweed is another name for pasque flower, because the buds look like goslings.

Source.

I wandered across a gentle south-facing slope with scattered low sagebrush. I was searching for Easter daisies, but brilliant yellow spots stopped me—sagebrush buttercups (Ranunuculus glaberrimus var. ellipticus). They're usually the first spring wildflowers I see in the Laramie Mountains, and are bright beyond bright in the dull landscapes.

Nearby were the coveted Easter daisies (Townsendia hookeri). Officially they’re called Hooker’s Townsend daisies, which raises the question: "Just exactly whose daisy is this?" In 1834, English botanist William Hooker named the genus for Pennsylvanian David Townsend, a civic-minded banker and respected amateur botanist. In 1957, American botanist John Beaman named the species for William Hooker.

And it gets more complicated. (Readers who aren't taxonomy geeks may want to skip this paragraph.) The Encyclopedia of Life calls T. hookerii “Nuttall’s Townsend daisy”—which lured me into further research. Strictly speaking, Nuttall's Townsend daisy is T. nuttallii. But T. nuttallii is usually lumped in with T. hookeri. Not here in Wyoming however. In fact one of our botanists, Robert Dorn, named it. T. nuttallii is restricted to limestone areas, and hasn't been reported from the Laramie Mountains. So I won’t worry whether the leaves are linear-oblanceolate (vs. linear), and whether the bristles of the pappus are of two lengths. This post illustrates vividly (nice photos) the challenges of our townsendias.

I collected a plant to add to my native xeric plants bed, next to what I believe are stemless Townsend daisies (T. exscapa). In 2013 I rescued them from a prairie in advance of road construction. T. hookeri and T. exscapa are hard to tell apart; the Flora of North America separates them based only on size of various floral parts—unfortunately. Distinctive characters are so much easier and reassuring!

A gasket scraper is an effective collecting tool for small compact plants in rocky soil.

Townsendia exscapa transplanted in 2013. They have thrived in the garden (next photo).

Hopefully these are two species, and hopefully I'll get a feel for their differences. Already I've seen a difference in “behavior.” When winter returned two days ago, the new arrival from the mountains duly opened its flowers in the morning, but the prairie daisies stayed shut all day.

Left, Easter daisy from Laramie Mountains (8000 feet elevation); right, Easter daisy from Laramie Valley (7000 feet). Photo was taken mid-afternoon on a cold gray day.

Yesterday was clear, and all the Easter daisies were singing in the sunshine.

But today ...

... only Frog Jolson keeps the music alive: