Keeping the Water You’ve Got

In a dry climate, precipitation quickly moves away from our properties either by run-off or evaporation (or both).  The idea is to slow that water down, keep in on-site as long as possible to interact with our systems, then let it depart in a constructive manner.  Getting all available water deep into the soil to build a reservoir, then controlling it’s slow exit is key to establishing a system where precipitation exceeds evapo/transpiration.  The overarching principle is to begin high in the landscape to establish a groundwater “plume” that is nurtured and added to as it slowly progresses down slope, always at right angles to our contour lines.

Run-off

Heavy rains, snow/ice melts, and hard surfaces all create rapidly flowing surface water, i.e. run-off.  Although perhaps infrequent and unpredictable, it is in our best interests to observe and identify the situations and areas where run-off happens, then take permanent steps to slow and direct these surface water flows to where they are most needed and effective.  Swales are the classic Permaculture technique to slow and spread flowing surface water to allow its infiltration into the soil.  Other methods include gabions, pit-and-mound, and tankage (especially useful for roof water run-off).

Capillary Action or Wicking

In a dry climate we must pay particular attention to keeping water in the soil by minimizing evaporation due to dry winds, direct sun, and capillary action within the soil itself.  While gravity relentlessly pulls our water plume downhill at right angles to contour, evaporation at the surface of the soil can begin to pull water upwards due to capillary action which is essentially wicking between the tiny spaces between soil particles.  As a wetted surface dries out due to sun and wind evaporation, water is constantly pulled upward from below to continue the evaporation process.

Note that the term “soil” is used very loosely here … quite often dry climate soils have very little organic matter and are a homogeneous mix of sand/silt/clay which wicks very well!  The best way to break this cycle of wicking/evaporation is to apply a boundary layer substance that contains much larger spaces between particles.  Now as we pursue our soil building activities by adding organic materials and compost we establish this boundary layer, but watching our top layer of organics mummify (even as the soil beneath retains its moisture) is a painful sight.  So, to also retain moisture in our burgeoning, living topsoil, we apply copious quantities of mulch in the form of straw or chipped wood.  This carbon mulch is a sacrificial insulation layer that breaks any capillary action, provides shade and wind protection to the underlying soil, and breaks down slowly for extended protection.

Wind Protection and Shade

Use and construct any available cover.  Make constructed wind breaks also serve as shade for the rooting area of new plants.  A goal might be to establish windbreaks of hardy support species trees, shrubs, vines, and ground covers to shield a collection of micro-climates in which to grow less robust fruits, nuts, and berries.  Hybrid willows and poplars grow quickly to shelter locusts, pea shrub, and pines which will become the coppiced wood lot and established wind break.  The initial willow/poplar support species are relatively short lived and become ground-level wind breaks and carbon mulch upon their demise.  By continuous mulching, these boundaries become the perimeter of our “forest” and start the transition of bacteria-based grassland steppe into fungal-based woodlands … the first steps in creating a large “wet spot” forest sponge.

In this dry climate area, native plants congregate on the north, shady and wind protected side of basalt rock formations, which shed water and can effectively double the annual precipitation.  Constructed stone walls emulate this effect and further, provide mulch to help keep moisture in the soil while lending their thermal mass to moderate daily temperature swings.  Stone walls also capture detritus to accumulate dust and wind-blown organics materials to build soil and serve as habitat for insect predators and pollinators.

Stacked straw bales also provide excellent mulch and wind protection, plus slowly break down as a mulch reservoir.  Wooden fences, fabric strung around individual sapling deer fencing, rows of stacked brush piles, and earthen berms can all break wind (heh) to give newly planted trees and shrubs a chance to establish their root systems out of the direct blast and in the shade.  It is acceptable to put into service almost any wind barrier to deflect the direct laminar flow of unimpeded winds and create shade for new planting root areas.  Coupled with plenty of mulch and drip irrigation, wind break plantings will then have a much greater chance of success at the boundaries of the harsh evapo/transpiration environment found in dry climates.