Land: A Critically Important Medium for Storing Water (Revised and Expanded)

Ricardo Aguirre, PE, BC.WRE, CFM,

Director of Land Management and Water Security

WEST Consultants, Inc.

Natural methods to store runoff are often superior to technological methods and are essential to addressing water scarcity in much of the world.

Background

The Tier 1 Water Shortage declared for the Colorado River for the first time ever in 2021 has intensified the focus on water scarcity. Responding to historic drought, low runoff conditions in the Colorado River Basin, and water shortage at Lake Mead, one of the Colorado River’s main reservoirs, this declaration signifies a reduction in water available to Lower Colorado River Basin States. This heightened focus on water scarcity is particularly evident in Arizona, as shown by the numerous articles that detail the issues and describe possible solutions. Unfortunately, discussion of these issues, including by decision-makers, tends to focus on costly technology-only solutions rather than a comprehensive natural approach that meaningfully addresses the threat of water scarcity for current and future generations.

In particular, the administrators charged with handling water scarcity fail to model their solutions on the natural patterns supporting watershed health for millennia or to capitalize on the land as a critically important medium for storing water. Innovative agricultural researchers and practitioners have documented these concepts for decades, but their findings have not broken into the mainstream discussion. For example, indicators of degrading watershed health have been documented for at least 150 years, since roughly the Industrial Revolution, signaling a correlation between the rise of technology and the decline of watershed health.

150 Years of Declining Watershed Health

Edward Beale was chosen in 1857 to survey a military wagon road from New Mexico to California (Figure 1) along today’s Interstate 40. Beale made frequent journal entries during his journey, noting the continually flowing streams and large expanses of tall, nutrient-rich green grasses that often impeded his progress. According to Along the Beale Trail: A Photographic Account of Wasted Range Land (Lockett, 1940), the land in that area has severely degraded since Beale’s survey.

In 1875, William Hornaday (Smithsonian Institution Archives), an American zoologist, conducted expeditions throughout the Western States during which he observed massive bison herds, some so large that it took them five days to cross. The bison were a part of a vast diverse network of grazers and predators that included antelope, horses, elk, deer, wolves, coyotes, wildcats, and bears.

Research chronicled by Dan Flores in American Serengeti (Flores, 2016) reveals that the grazers Hornaday observed, and their predators, co-evolved with the grasses Beale observed. According to Flores, the landscape that supported the volume of wildlife during the mid-1800s was a “complex ecology at least 20,000 years old” “far from the empty ‘flyover country’ of recent times” (Flores, 2016).

Reductionism and Mechanized “Solutions”

Reasons for the accelerated decline of watershed health since the Industrial Revolution include ranchers’ misunderstanding of the unique ecology of the Western States causing overgrazing and partial rest, the Federal killing program in the nineteenth and twentieth centuries, industrial agriculture, and the Industrial Revolution’s civil infrastructure boom of highways, railroads, dams, canals, and cities. This human intervention eradicated the migratory patterns established by those past grazers and their predators that were supported by and coevolved with the Western States’ former grasslands. This accelerated decline led to the 1930’s Dust Bowl and the desertification we see today.

The tools of science and technology born from the Industrial Revolution have greatly influenced how humans see the world and created the belief that those tools answer today’s environmental problems. Mechanical and technological advancements have transformed fields like information technology, transportation, construction, utilities, and space exploration, generally for the better. However, applying mechanical approaches to nonmechanical systems like agriculture, health, erosion, wildlife, rangelands, forests, and water security not only fails but advances the existential threats to humanity.

Civil infrastructure, especially the infrastructure affecting drainage (e.g., roads, bridges, culverts, railroads) exemplifies this problem. Because civil engineering projects are land-connected projects, practically all civil infrastructure affects how water drains over a landscape. The Santa Cruz River north of Tucson, Arizona, presents a telling example of this. In the late 1800s, the river was a perennial watercourse that meandered through a widespread mesquite bosque consisting of diverse wildlife with groundwater at or near the surface in the surrounding area (Figure 2).

Today, the Santa Cruz River is a dry riverbed with no upstream dams. It has been straightened and channelized, often with concrete fortified embankments to allow development to encroach onto the floodplain. The river is now prone to flooding beyond its embankments, especially during the more intense monsoonal episodes following long drought periods. Further, the surrounding hardscapes and dead, compacted soils no longer infiltrate stormwater. This reality, combined with pumping, has led to groundwater depths in the area now exceeding one hundred feet.

In the agricultural realm, the industrial farming practices of tilling and applying pesticides and fertilizers have had similar effects on how and whether land stores water (Plowman’s Folly: Faulkner, 1943). These practices reduce soil organic matter, i.e., soil carbon, which leads to soil compaction at the plow depth and a direct reduction of soil water-holding capacity. Exploring the sequential effects of applying nitrogen fertilizer alone, as warned by Sir Albert Howard in the 1940s and University of Illinois researcher Richard Mulvaney (Philpott, 2010) today, shows how it proliferates soil organisms that feed on organic matter. Initially thought to be good, new evidence demonstrates that that practice causes an eventual collapse of the soil structure after the soil organic matter has been consumed and soil organisms die. The result again is compaction and increased runoff and erosion.

Because mechanized farming practices kill soil life and dead soil cannot hold water, farmers are compelled to increase their irrigation rates, which continues the cycle of adverse effects on long-term water security. Water infiltration is a function of compaction and surface soil salinity, indicators of the level of soil organic matter. The inability of dead soil to infiltrate water will lead to evaporation, causing salts to be left behind, furthering the soil’s inability to infiltrate water. This gives rise to the need for yet more irrigation, according to Pillar of Sand author, Sandra Postel (Postel, 1999).

Unlike the compartmentalized, centralized, and one-dimensional approaches to handling the flow of water and use of land of civil engineering and industrial farming that represent a reductionist mindset, nature manages water as a holistic, complex, decentralized, and three-dimensional cycle. As such, superimposing the industrial land development practices of civil infrastructure on previously functioning watersheds has resulted in the threat to water security we see today.

Solving Water Scarcity By Mimicking Nature

According to the research conducted by Judith Schwartz in Cows Save the Planet (Schwartz, 2013), for every one percent of increased soil carbon the land can retain up to an additional 60,000 gallons of water per acre. Dr. David Johnson’s research, (Figure 3: Center for Regenerative Agriculture and Resilient Systems, 2020) equates one percent to 40,000 gallons of water per acre, still quite significant. According to Dr. Elaine Ingham (Soil Food Web School, 2020), however, soil organic matter (soil carbon makes up 58% of soil organic matter, Edwards, 2021) must be at a minimum of three percent to start prompting an effective water and nutrient cycle (soil types and other factors may cause variations). Unfortunately, most arid soils in the Southwest have degraded to below three percent soil organic matter.

Using animal impact and herd effect can increase the carrying capacity of the land in the form of water and plants to achieve watershed health and provide long-term water security for future generations. The megafauna observed and documented around 150 years ago present a clear example for humans to follow to achieve this effect, but relatively few have been willing to change their livestock management practices accordingly. Those who have attempted to mimic predator-prey grazing patterns through adaptive grazing management have had differing levels of success. Both those who have had success and those who have not have been criticized in scientific studies that have been misapplied, poorly performed, ill-conceived, and often misunderstood.

For example, research by Oldeman and Engelen in 1991 suggests that livestock overgrazing caused as much as 20 percent of the world’s pasture and range to lose productivity and that the global grass-eating livestock herd, which in 1991 numbered about 3.3 billion, was unlikely to increase much, if at all. Assuming the research was sound, one could reason that it provided both sufficient evidence and a cause for concern that the degraded grasslands were caused by overgrazing. It is easy to blame the degradation on the livestock rather than on the livestock management practices used. However, the growing body of literature shows that the management of livestock, not the livestock themselves, is the key to changing this dynamic.

Land management practitioners from varying climates and soil conditions around the world, including the Southwest, have established a proven track record (see Figure 4). These practitioners have demonstrated that accurately mimicking the predator-prey relationship induces the conditions of animal impact (dunging, urinating, salivating, and trampling) and herd effect (a behavioral change that affects soils and plants when many animals are bunched closely together, for short periods with longer rest periods, to protect themselves from predation). Animal impact and herd effect evolved with soils and vegetation to create watershed health in erratic rainfall environments like the Southwest. This is the key that enables restoration of grasslands on healthy soils of high water holding capacity.

Conclusions

Can humans use land management to achieve the water-holding capacity in the soil necessary to address a Tier 1 water shortage? To accomplish that worthy goal will require a practical and disciplined approach to land management that vigilantly looks for signals to adjust to willingly and without delay. Practitioners willing to dedicate themselves to the level of discipline required to accurately mimic nature will also need to remain focused despite detractors, remaining focused on the landscape’s feedback.

The combined research of Schwartz, Johnson, and Ingham indicates that 80,000 gallons of water, or approximately 3 inches of rainfall per acre, is retained when the soil organic matter is above that crucial 3 percent level necessary to prompt watershed function. The largest storms in the Southwest during the year are monsoonal, providing up to 3 inches of rainfall in a very short period. In other words, an area that receives 12 inches per year, on average, could retain practically all the rainfall throughout the year. In a watershed with healthy soil, a single acre of land could store approximately 326,000 gallons of water a year; with a per capita demand of 100 gallons per day, that acre could support the water demands of 9 people. Scaling up to the volume of water for large watersheds consisting of hundreds of square miles reveals the potential of land as a credible medium for storing water. If the soil organic matter increases to five, seven, or even ten percent, it is clear how healthy grasslands historically supported all those bison!

Learn more about Ricardo's work with regenerative land management and how land management and other forms of engineering with nature can replace traditional water resources engineering in Ricardo's appearance on the Engineering with Nature Podcast.