Water Hazard is an ongoing architectural research project by moss.  We are studying water related issues to become better stewards of this most precious resource.  Below is the latest dispatch.

If you have been airborne over our country’s midsection, or just looked at a Google aerial you probably noticed the green circles that dot the otherwise brown scrub.  What are those?  Some kind of large scale version of Connect4?  An extreme close up of A Sunday Afternoon on the Island of La Grande Jatte? Nascent efforts of an uncreative UFO crop circle team? Only when you’re at ground level do you find the culprit for those irrigated green discs.  The story of the green circles and the remediation efforts inside.

“There were those in the 1830’s that thought the Louisiana Purchase had been as waste of $15 million – that the whole billion acres would remain as empty as Mongolia or the Sahara.”[1]  There is a reason this newly acquired expanse was once called the Great American Desert.  The area is considered semi-arid, receiving about 10-20 inches of precipitation annually, putting it on par with San Diego, CA (10.8” per year), another irrigated desert.  Before westward expansion, the dry, dusty territory was filled with tall prairie grasses and buffalo.  With the Homestead Act came farmer’s, who fooled by some exceptionally wet years, planted sorghum and wheat until the soil literally blew away when the climate returned to historic norms, resulting in The Dust Bowl.  A lesson learned?  Nope.

Through a clever bit of rebranding, a shortage of arable farmland elsewhere, the transcontinental railroad, and, most significantly, the discovery of ground water, the Great American Desert became the High Plains.  Since then its been taken for everything its worth.  You see, the area sits atop one of the most coveted and plentiful (at least it used to be plentiful) underground water reserves in the world, the Ogallala Aquifer.

% Share of aquifer by state (3)

Stretching from South Dakota to West Texas, the Ogallala accounts for roughly 30% of groundwater extraction for irrigation in the U.S.  It is estimated that 253 million acre-feet of water has been extracted for irrigation purposes since mechanized agriculture took hold in the 1950’s, which means the proverbial well may run dry in a couple of decades, relegating the High Plains to a permanent dust bowl. [4]

The amount of water that is on the planet now is the same as it was when dinosaurs roamed.  Unfortunately, it is always on the move, changing forms and levels of salinity.  The main problem with High Plains water (and most groundwater, for that matter) is that the extraction of groundwater is occurring far more rapidly than it can be recharged.  From 1949 to 2001 withdrawals have increased 10-fold, topping out at 21 million acre-feet of water in 2005 [2], far more than can be replenished naturally, to the point that some areas of the aquifer in West Texas and the Oklahoma Panhandle have already gone dry.  The natural recharge rate of the aquifer in the High Plains is only about 1 inch per year.  Considering the pre-development 200-400 feet of saturation depth had been there since the Ice Age, time is not on the aquifer’s side.  Based current water usage you would think we are still foolish enough to believe 1920’s lore that the aquifer was inexhaustible.  Er… Oh.

Ideally, when rain falls it percolates through soil and rock to replenish the aquifer below.  Our current mechanized method of agriculture is fatally flawed, something I covered here, but for the purposes of water recharge, the planting of annual crops is the main culprit for the dessication.  The crops typically grown in the breadbasket, corn and soybeans (curiously, neither of which is used to make bread) have a shallow root structure and are annuals, two qualities that are highly disadvantageous for capturing rainwater.  Exacerbating the problem is the typical form of irrigation in the Plains, center pivot irrigation.

Center pivot irrigation systems came into prominence in the 1960’s, named so because the motorized overhead irrigation structure pivots around a center point, which is what creates the liter of lush green circles throughout the High Plains.  Aside from the inefficiency of irrigating from the top down (most water evaporates before it can reach the roots of the plant), the center pivot leaves four wedges of unused and unproductive land on the fringes.  A scan of aerial imagery shows one wedge is usually used for houses, barns, and outbuildings, but the other three remain vacant.  If a typical 160 acre farm has a growing disc of 125 acres, 35 acres remain unused, enough to feed 29 people, if you assume it takes 1.2 acres to satiate one adult.

I drew this on a plane once

So after 5 circle farms you have wasted enough land to account for an entire 160 acre farm.  No good.  What if the unused wedges were planted with a perennial edible, or better yet, and indigenous fruit orchard?  Not only would this make use of the wedges, but it would help to retain soil, recharge water (since its roots are deep and remain in tact during the winter), produce a greater variety of food, and help mitigate water runoff and soil erosion.  Here’s what it might look like.

[1] Cadillac Desert, by Marc Reisner, 1980

[2] USGS study, by V.L. McGuire, 2007

[3] Data from USGS, 1997, infographic by moss

[4] USGS change in saturation level map, by V.L. McGuire, 2007

Previous Water Hazard study