6 minute read
Invisible Water
Groundwater resource management and agriculture in Union City
For a handful of small communities @TravelNewMexico in the farthest corner of northeastern New Mexico, something remarkable has happened beneath their feet. Their story involves a perhaps unlikely team––farmers, ranchers, and geologists––and illustrates how a lot of hard work, as well as a lot of heartache and fear, has led to some big changes in traditions that had been passed on for several generations. The story of the groundwater of Union County serves as one example of an ongoing community-based effort for figuring out how to manage an invisible but most valuable resource—one that determines much about the fate of the land we live on, and of our families.
In much of New Mexico, water used for livestock, crops, residences, and communities comes from deep underground, and yet many in New Mexico know very little about this precious resource. For example, generations of agricultural producers on the eastern plains of New Mexico have relied on groundwater to grow crops and raise cattle due to a lack of surface water. At first, small hand-dug wells and windmills drilled with small auger rigs were the primary way to retrieve this water. After the Dust Bowl, center pivots became more mainstream as a form of crop irrigation, and they are often seen as being a more efficient means of watering than ditch or row watering. For cattle ranching, windmills are still in service in some areas, although wells are slowly being converted to solar-powered pumps in many places. No matter how it is delivered to the surface of the land, the primary water source in the region is groundwater from the aquifer.
A common conception in northeastern New Mexico is that most producers are sitting above the Ogallala aquifer and, therefore, “oceans of water” lie beneath our feet. If one looks at Union County from above, the majority of the county is rangeland, with three areas of center pivot irrigation: near Gladstone on the west side of the county, around Sedan southeast of Clayton, and around Seneca northeast of Clayton. But this geographic distribution of irrigated farmland raises an interesting question: If there are oceans of water beneath the ground, why then is irrigated cropland confined to these small patches? After all, it may take three hundred fifty gallons a minute to drive a center pivot, but if all that water exists, should we not be able to farm everywhere? Recent geohydrology work in Union County has begun to dismantle this idea of the Ogallala as the primary aquifer for the area and to raise concerns about the groundwater resources available for production in the county.
Generally speaking, most land owners have an idea about the state of their groundwater. Some know there is trouble brewing because they or their neighbors have had to lower pumps in wells or wells have gone dry. For most of the history of deep-well irrigation in the area, very little solid data has been available for most of northeastern New Mexico. But things began to change in 2005 when the Office of the State Engineer designated the last administered groundwater basin in New Mexico: the Clayton groundwater basin. Now that policy would be put into place to begin to regulate use of groundwater, many residents of Union County grew concerned about the state of that invisible, precious resource. Recognizing how little most of Union County knew about our groundwater resources, the Northeastern Soil and Water Conservation District (NESWCD) decided to learn more about our aquifers. District Board members taught themselves to measure static water levels to USGS standards and teamed up with geologists to learn more about what groundwater resources were really there and what the potential lifetime for these aquifers could be.
The Union County Hydrogeology Project, launched in 2007, included annual water level measurements and, eventually, water chemistry and isotope analyses, as well as geologic mapping. By 2012, Union County was deep in the heart of the worst drought the area had ever seen, with barely measurable precipitation that year. Water level measurements from 2007 through 2013 showed the water table dropping rapidly around Sedan and Seneca with some wells showing declines of up to ten feet a year. In 2013, the release of water level measurement data as well as geology, chemistry, and isotope data began to bring into focus the true story of the groundwater resources for the county. And the story was grim.
A critical part of understanding how to manage groundwater as a resource is to determine the relationship between discharge and recharge. For a well, the basic hydrologic cycle would ideally see a balance between discharge (use of the well by pumping water) and recharge (snow and/or rainfall percolating down to the local water table). If there is far more discharge than recharge, the water table declines and eventually wells go dry. Tritium, a useful marker of modern precipitation, is an isotope of hydrogen that occurs naturally in the upper atmosphere. On its own, it is not a significant component of the groundwater system, but during the testing of atomic bombs in the 1950s, large quantities of tritium were released into the atmosphere. This man-made tritium makes its way down into the water table as rain and snowmelt percolates down through the soil. If the water drawn from a well has measurable tritium in it, it means that post-1950s precipitation was able to meander down to the water table. Well water with little to no measurable tritium indicates that recharge is happening very slowly, if it is happening at all. Effectively, the net use of water via wells is far greater than the net replenishment of the resource.
Unfortunately, the majority of wells studied in Union County have little to no tritium in the water, suggesting the recharge part of the hydrologic cycle is very slow or simply not happening. When this information was shared directly with producers, a sea-change occurred. In January 2015, the district’s geology team went through its annual water level measurements and discovered something unusual: The wells around Sedan that had been dropping significantly, up to ten feet per year, had declined less than a foot over the past year. Startled by this change, the geology team went knocking on doors to ask local producers what they had observed during the year.
A remarkable story emerged. After learning more precisely what was happening with their groundwater, the majority of producers around Sedan had shifted their crop management strategy. Many switched from higher grade corn varieties to low grade silage corn that had a much shorter growth season. Others changed to hay varieties and some areas were reverted to grassland through the USDA’s Conservation Reserve Program. Overall, these changes appear to have led to a net slowing of the water table decline. This change in crop strategy has not been easy for local farmers and has created financial strain for these families to some extent, but the sacrifice was made to preserve the ability of the land—and now the groundwater—to sustain these families for at least another generation or two.
Kate Zeigler measures static water level in an old, abandoned irrigation well northwest of Sedan. Keeping track of water levels over several years shows the short- and long-term behavior of local water tables.
Photo by Randy Podzemny.
Barbara Podzemny stands on an outcrop of Ogallala Formation in a creek bottom south of Clayton. Mapping the outcrop exposures of Ogallala helps with understanding the characteristics of this rock unit as an aquifer.
Photo by Kate Zeigler.
It is not only the farming families who have made major changes. Their ranching counterparts have implemented similar strategies by turning wells off religiously when cattle move out of pastures, rather than letting the windmills pump water for wildlife or for maintenance. Some ranch families began converting windmills to solar powered pumps or submersible pumps on timers, thereby controlling the flow of groundwater more carefully. In subsequent winters, the pattern held––wells continue to decline, but on average by less than a foot or two each year, a huge change. Even in 2019, with new families starting to work in the area, neighbors have shared the information that has come out of the efforts described here and conservation efforts continue. With the current understanding of how slow (or nonexistent) recharge is for these aquifers, it is unlikely that we will be able to level out consumption versus recharge for these areas, but the care taken for the use of every drop of water lengthens the time a family has to find alternatives. Ideas that have circulated include aquaponics, and one exploratory project in Alamosa, Colorado, seeks to explore the local geology even more to experiment with shallow targeted recharge efforts that include engineering ditches and/or ponds in “sweet spots” on the landscape to allow more snowfall and/ or rainfall to work its way down to the local aquifer.
The traditions built into ranching and farming families are strong and carry over multiple generations. One of the strongest lessons passed down is “take care of the land and the land will take care of you.” Producers in Union County have carried that lesson to include their groundwater resources as something to be taken care of along with their soil, their crops, their grass, their cattle, and their communities. The impact of Union County’s efforts has rippled out and there are now groundwater resource management studies being conducted on range and crop land in seven area counties. Groundwater is a tricky resource—it is one of the most precious components of a ranch or farm, but it is the easiest to overlook. The joining of forces between producers and geologists has helped these families and communities take care of their groundwater to prolong this land’s ability to provide for future generations.
By Kate Zeigler and Barbara Podzemny
