Holistic Management® Framework – Water Cycle

The Water Cycle
Apparently there is only a finite amount of water on Earth which constantly cycles from the atmosphere to the surface and back. Of course, much of this water is seawater, too salty for most plant and animal use until it evaporates and returns as snow or rain. Some is captured in aquifers or icecaps for long periods of time before rejoining the cycle. However, the majority of water is constantly on the move from atmosphere to surface to atmosphere.

Because water is rapidly becoming a major limiting factor in agriculture, industry, and cities, it is important that one understands the cycle and how it becomes available for use. The basic cycle can be seen in Figure 1. It describes the various paths water follows upon falling on the land as fog, rain, snow, hail, etc. Some evaporates directly, some runs off into streams, rivers, lakes, and on into the sea before evaporating again. Some penetrates the soil where some attaches to soil particles and becomes available for plant use. Another portion penetrates deeper into underground supplies where it remains until it is pumped, flows into a river, seeps, springs, or bogs, or is tapped by deep-rooted plants.

The time water spends in the soil is of critical importance in the growth and reproduction of plants and therefore animals, including humans. It is extremely important that we understand this stage of the water cycle.

All water that penetrates the soil will be strongly attracted to drier soil particles, which is why there is, after a short time, no sharp division between wet and dry only a gradient of wetter to drier. It keeps moving until all has adhered to soil particles or it reaches an underground reservoir. To remove the final film of water from a soil particle it usually takes drying in the sun or in an oven. That is because as water is removed the soil particle’s attachment to the remaining water becomes stronger. On the other hand, the hold a particle has becomes weaker the more water it holds.

Plants take in water and nutrients dissolved in by their root hairs. As long as their ability to draw the water is stronger than the hold the soil particles have, they can keep drawing. As less and less water is held by the soil particles the less the plant is able to absorb and it slows its growth rate. It this continues long enough the leaves wilt or curl to conserve the moisture it does have left. However, there are many things one can do to conserve more moisture in the soil and extend the time plants can grow strongly before wilting.

To sustain the maximum amount of life, except in wetlands and deserts, an effective water cycle must be created. Plants make maximum use of precipitation, little evaporates from the soil, any water that does run off does so slowly and carries little organic matter away. There is a good air-to-water balance allowing plants to absorb water easily, since most plants need roots surrounded by oxygen as well as water to grow.

A non-effective water cycle is the opposite of this. A great deal of water is lost through direct evaporation, and that which does soak in is difficult for plants to absorb due to lack of a good air-to-water balance. Soils become waterlogged when too much moisture is received due to an impervious layer of subsoil preventing downward movement. Water displaces the air and then only plants adapted to this lack of oxygen can grow. The same effect can take place when the soil becomes capped, that is sealed with a crusty layer which eventually lets some water penetrate but not air.

When forming your holisticgoal, it is critical that you describe how the water cycle must function on your property in the future in order to sustain your production on the land. If you do not directly manage land, it is still important that you understand the difference between and effective and non-effective water cycle as it pertains to your community and to assist in deciding policies that lead to effective water cycling.

Effective Water Cycles
While knowing the normal average rainfall for an area gives one an idea of what types of plants and animals might be found there, the average is usually not this year’s precipitation, especially in more brittle environments. One year is wetter, the next drier, and even if the average does fall it may be distributed very differently that the last year of average rainfall. Creating an effective water cycle tends to make what rain does fall more effective.

Effective rainfall is that which soaks in and becomes available to plant roots, insects, and microorganisms or that replenishes underground supplies with very little subsequently evaporating from the soil surface. This means that the cycle must direct most water either out to the atmosphere through plants or down to underground supplies. It is very difficult to create an effective water cycle in the more brittle environments, usually less than half of the rain received is used effectively. Since it takes approximately 600 tons of water to produce one ton of vegetation, it follows that one must not waste what does fall.

In less brittle environments, effective water cycles tend to be more common due to the difficulty in creating and maintaining vast areas of bare soil. However, where large quantities of organic matter has been removed and especially in croplands that are often left bare, absorption rates are low and there can be a great deal of runoff and, possibly, surface evaporation rates.

Capping
The characteristics of the soil surface are extremely important in determining whether a water cycle is effective or not. Rain drops falling on bare and exposed soil tends to destroy the soil crumb structure ( Crumb structure refers to the presence of aggregated soil particles held together by “glue” provided by decomposing organic matter). The amount of damage is determined by the size and velocity of the drops. As raindrops impact bare ground, they force organic and lightweight material to wash away, while the heavier fine particles settle and seal, referred to as a cap, the soil.

This cap reduces water penetration, oxygen penetration, and carbon dioxide leaving the soil. The air imbalance can lead to plants not being able to absorb nutrients, even when abundant in the soil because the microorganisms are negatively affected by the imbalance. After the initial cap is formed a number of microorganisms and fungi increase its strength. This in turn leads to less water and air penetration and carbon dioxide exiting.

Soil cover, in the form of low-growing plants and dead, prone plant material (litter), protects the soil surface making it more difficult for raindrops to cap the soil or wash away. In less brittle environments, soil cover maintenance is rarely a problem, except in cropped land, while in more brittle environments maintaining soil cover is difficult to maintain due to the wide spacing of plants.

Creating an Effective Water Cycle
The most important factor in an effective water cycle is management that maintains soil cover, followed by organic matter, aeration, and drainage. What are the management tools available to either advance or destroy an effective water cycle? In less brittle environments, only technology – herbicides, machinery – repeated used can destroy soil cover, whereas as little as one application can destroy it in more brittle environments. Three tools – rest (partial or total), fire (periodically), and overgrazing (the tool of grazing misapplied) have exposed millions of acres of forests, rangelands, and national parks soils in the more brittle environments. Since these three are used extensively in almost all more brittle environments, there is little wonder the incredible amount of bare soil exists.

In less brittle environments, rest can restore soil cover and therefore increase the effectiveness of the water cycle. In more brittle environments, the tool of animal impact can provide the amount of soil cover needed. Animals can be used to trample down old standing vegetation or crop residues creating littler, while the trampling also breaks the soil capping, preparing a seedbed for new plants to germinate.

Aeration, organic matter, and drainage all depend on soil cover, but only if there is sufficient soil cover. They are also affected by root structure, if roots are healthy, they help aerate the soil, provide organic matter, and pump more water upward into the plant. Roots are damaged by overgrazing in any environment, or overgrazed and over-rested in more brittle environments. They are also affected by soil organisms, including earthworms, bacteria, fungi, and millions of other microorganisms.

The advantage of having an effective water cycle is that floods and droughts are fewer and less severe, even in areas of erratic rainfall. Floods that do occur tend to rise and subside slower, with clear floodwater, as there is less soil and debris in them. Droughts are far less severe because moisture from the year before will have been stored in the soil and what does fall will penetrate more easily. With an effective water cycle far more water is available over a longer time period so that plants begin growing earlier, more profusely, and longer into the growing season, even in moderately long dry spells. In addition far more water is available for springs and streams. While we may not be able to double the amount of rain we receive, we can double the effectiveness of what we do receive.

Noneffective Water Cycles
In areas of noneffective water cycles, droughts are more frequent and severe due to higher surface evaporation and runoff, plants begin growing later and then in spurts leading to lower production; i.e. in rangelands or croplands lower forage or crop yields. Floods are also more likely and more severe, the greater amount of bare ground the higher the rate of runoff – possibly more than half the water received. And the amount of evaporation lost from bare ground is equally astonishing. And in the more brittle environments of the world it is the soil evaporation rates that lead to the majority of water shortages. A number of large cities located in more brittle environments around the world are nearing the point where their and their surrounding countryside’s lack of effective water cycles may doom them as cities.

The outcomes of noneffective water cycles can be summarized so: Increased runoff leading to more frequent and severe flooding; decreased water penetration and increased evaporation losses with more frequent and severe droughts; less forage and/or crop production; slower plant growth; falling underground supplies; unstable rivers; silted dams and eroding catchments; detrimental effects on other ecosystem processes.

The signs of a noneffective water cycle do not require special equipment to recognize: bare soil; litter banks caught against vegetation; signs of water flow, exposed grass roots, silt deposits, coarse pebble layers on the bare surface; formerly year-round streams/rivers now only periodic, perhaps not at all during dormant or dry seasons; lowering water levels in wells and springs.

Water Cycles in Cities
Urban dwellers rarely think about the water cycle except in times of flooding or water rationing and/or rising water bills. By increasing the effectiveness of the water cycle in urban areas, we can decrease the amount that needs to be pumped, transported, or wasted.

Most cities give little chance for raindrops to penetrate the soil, they are covered with impermeable materials, metal, concrete, asphalt, etc. This leads to incredible amounts of runoff, which is most likely contaminated by chemicals and/or heavy metals from lawns, roads, and factories. This water is then channeled to storm sewers dumped into streams, rivers, or seas, thereby contaminating them and destabilizing river banks, adding silt to the flow to farms and towns downriver.

If instead of city planners tapping underground reservoirs, lakes, rivers, etc., what if they enacted building codes that more closely mimicked the natural water cycle how much closely? Roofs that capture rainwater and store it in cisterns; paving and road materials that allow immediate penetration and absorption of water; roads and parking lots treated with oil-eating bacteria; and other current or developing technologies that would enable water to be used where it falls. Sooner or later we will be forced to mimic nature’s water cycle in cities, why not start now when the price will not be exorbitant as in the future when more will have to be done to correct the problem.

The importance of the water cycle in the proper functioning of landscapes and, as we have learned, cityscapes, can not be understated. Floods, droughts, pollution, silting of dams, and many other consequences occur when the water cycle is ineffective. As landowners or managers, or even as community members with no direct control of land other than perhaps your yard, it is imperative on all of us to make sure that we do everything we can to create effective water cycles in our own environments. The dividends we collect in the future will be enormous.

Savory, Allan and Jody Butterfield. 1999. Holistic Management, A New Framework for Decision Making (Washington, D.C: Island Press), 104-119.

By: Mike Everett
Consultant and Instructor