Groundwater, Soil Health and Land Management: A Complexity of Linkages

By Kate Zeigler, Ph.D., CPG
Zeigler Geologic Consulting, LLC

In northeastern New Mexico, we don’t get many tourists who stop by to look at the scenery … in part, that’s because we don’t have much to look at if you’re a tourist, since a big photo op for folks is live water. Which we ain’t got much of. So, when we think about the vast open spaces of the High Plains, how do our agricultural producers make a living out here? Because there is so little surface water, farming and ranching rely primarily on groundwater resources and we are at the mercy of increasingly unpredictable weather patterns. An oft- forgotten corner of the American Southwest, this little patch of New Mexico didn’t have much data at hand to understand how groundwater resources worked until the Northeastern Soil & Water Conservation District formed an alliance with a team of geologists. From this sprang a regional effort to gather data on the groundwater resources and figure out how to manage every precious drop.

Effectively, what we now know is that the aquifer systems beneath the High Plains are more complicated than we anticipated. Two wells a half mile apart may not be drawing from the same pool of groundwater (so please don’t shoot your neighbor for “stealing” your well water). Changes in thickness, variations in rock types, ancient topography filled in with yet other deposits, volcanoes, and many other geologic phenomena have created a series of “bathtubs”. Word to the wise is to manage each well as its own resource and assume it’s probably not recharging in your life time. Take care of the groundwater and the groundwater will take care of you.

As this effort to understand groundwater resources has built, so have parallel efforts to understand the soils of the region, which are equally critical. Both efforts are far behind where they need to be – the world, weather, economics, all are changing much faster than we can gather and analyze data. When we think about where water goes on and under the land, we all know our basic hydrologic cycle: precipitation falls on the land and some flows away along creeks and rivers. Some water ponds in low spots and some sinks quickly down into the ground. Evaporation and evapotranspiration mobilize some of that precious moisture back up into the atmosphere and off we go again! But … what’s happening to that water that left us when it sank below the surface? Water goes where pressure, gravity, porosity, permeability, etc. guide it, not where you want (or expect) it to go.

The soil is the primary interface that moisture moves through in its subterranean voyage. Soil scientists understand this realm well in terms of texture, chemistry, plant interaction, etc. But many of us are beginning to realize that we don’t always understand the intricacies of how water moves through soil. Are our soils helping get water down to replenish aquifers? Is that water traveling sideways until it escapes into streams and springs? Sucked up by thirsty plants and released as evapotranspiration? Also, as droughts lengthen and deepen, horrible feedback loops develop. As plants die off, bare ground expands. Our rains now seem to come in short, high-intensity events that cause significant erosion and water runs off the land so fast that it can’t percolate down. Soil moisture and unconfined aquifers suffer as a consequence.

How will understanding and influencing soil health help with water cycling? Soil scientists will tell you that a healthy soil not only produces better forage, but it retains water better. And as more vegetation grows, erosion is slowed down. Sheetwash is buffered by the plants, and the water slows and has a chance to percolate downwards. This water may never make its way all the way down to the local aquifer – many aquifers in the region are isolated from the world above by bedrock shale layers that prevent (or greatly slow down) the downward migration of precipitation to the water table. But more water held in the soil can potentially revive seeps and springs, and fatten up those perennial pools that occur in our rocky little creeks.

Landscape health is critical, but there are trade-offs. The short-term economics of the tasks needed to help soil or groundwater can seem overwhelming. Every operation needs to consider the short-term economic pain of paying for things that will help the soil versus the long-term payback of a healthy, functional ecology. And no two operations will tackle this balance the same way. Every ranch, every farm is unique. Broad-brush “fix-its” should always be tweaked to fit the operation.

Ground cover, be it litter or living plants, is essential for cooling the surface and minimizing evaporation. Established photo points can help document change over time in different pastures or fields. Use exclosures to see what happens when you don’t let the cattle graze an area for a while. Use the myriad phone apps available for quick interpretation of your forage and soils. Manage your groundwater: learn which of your wells may be able to recharge in good years. Rely on your non-recharging wells in bad years – treat them like a noninterest-bearing savings account. Rotational grazing techniques move the cattle, so move your water too! Storage tanks and pipeline systems are expensive in the short term, but can pay off enormously in the long run.

For too long, scientists have nerded their way along, noses pressed to the plant, the dirt, the rock. For too long, agricultural producers have done their best to take care of their land using methods that made sense at the time. It’s time for producer and scientist to saddle up together (and it’s gonna be a long ride …). Landowners are the stewards – they know the land better than any scientist ever will. But the combined work of both can catapult us much further in our work to help this landscape. And let us take care of the land, so the land can take care of us.

Dr. Kate Zeigler is owner and senior geologist at Zeigler Geologic Consulting, LLC, a small woman-owned business located in Albuquerque. Born in Montana and raised in Texas, she came to New Mexico in 1999 to continue her studies of geology. She earned her Bachelors from Rice University and her M.S. and Ph.D. from the University of New Mexico. Once finished with school, Kate went on to become a consulting geologist and found her calling in using her skillset to provide information about groundwater resources to agricultural producers and rural communities. In addition, she serves on the executive boards of the New Mexico Water Dialogue, El Llano Estacado RC&D Council, the New Mexico Geological Society Foundation, and the New Mexico Chapter of the American Institute of Professional Geologists.