THE AMERICAN WAY:
PAST & PRESENT

Last year, the State governments of Arizona and Nevada, of the United States of America, reached an unprecedented accord.  The remotely populated Nevada, consumes only a mere fraction of its allocation of Colorado River water, and its powerful western neighbor, ever-thirsty California, threatens to bleed the excess for good.  Meanwhile, Nevada’s not-so-powerful southeastern neighbor, Arizona, cries out for help because, its recent population-boom severely depleted its groundwater levels.  The neighborly accord, allows Arizona to feed today, its dry aquifers, with the surplus water of Nevada who, in turn, will take out the same quantity from the River, above its quota, as its demand increases.  An extraordinary act for all these western States, given their appalling pasts, of voracious groundwater extraction.

However, the indigenous peoples of America have always nourished the mother earth, with the vital liquid, before consuming the same.  The arid, Pacific coastal belt, has sustained large settlements, over thousands of years, because the ancient engineers knew, how to recondition the dry environment, to support all life forms –its fauna and its flora.  They augmented ground infiltration of water, by slowing down the surface runoff, and exploited the groundwater, by moving their cultivating fields closer to it, although, specific techniques depend on local topography and the availability of resources. 

Many ancient North American desert farmers, kept their valley plots covered, with fist-sized pebbles ('gravel mulch gardens' - Cordell, 1984), which, among other benefits, also help slowdown the runoff.  The Papago farmers of Arizona, even today, use branches of desert brush, to reduce the velocity of the sheet wash, in their nearly level fields.  For the same purpose, the Hopi and the Southern Sinagua, of Arizona (Reid & Whittlesey, 1997), as well as the Maya, of the upper Grijalva basin in Mexico (Matheny, 1982), all of them, contoured with fieldstones, their gently sloping terrain.  Controlling runoff, in more inclined slopes, require stronger blockades, like the Metapantli terraces (piles of earth, backed by a row of Maguey plants - Denevan, 1980) in Mexico, or like those ‘walls,’ made of large, non-bonded, blocks of cangagua (hardened earth), in Ecuadorian Andes.  On steeper grades, they built masonry terraces, like those that scale almost every mountain slope in the southern Andes, which, not only facilitate cultivable surfaces, but also, improve the ground infiltration of rainwater.  Marca Huamachuco people, in the department of La Libertad, Peru, had given a perfect demonstration of such: they erected an artificial terraced mound, at the top of their sacred hill, Cerro Amaru, to trap a greater part of the scarce rain.  Three, fully stone-lined, bottlenecked wells, called Chiles, built into the mound, collect the infiltration, and supply the inhabitants of the Cerro today, just as they helped the thirsty pilgrims yesterday.

The techniques mentioned above, collect water without directly blocking the streams; damming stream flow in the American continent, known for its intense rainstorms, triggered by El Niño events, demand heavy precautions.  That did not deter, however, the ancient Ecuadorians, of the peninsula of Santa Elena, who dotted its gentle hill slopes with hundreds of albarradas, small ponds formed by earth dikes, laid across the streams.  Many of those, even today, feed numerous springs and wells in the plains below, because their designers acted with prudence: the streams were blocked right where they are born, where they barely crawl.  An ongoing study corroborates another aspect of ancestral wisdom: that, they located the albarradas, only on permeable or semi-permeable ground (Álvarez et al, 2001), where infiltration is optimal. 

The engineers of the past also accepted the challenge, of blocking larger streams: they built great pools of water at valley necks, but only where the circumstances guaranteed, a structure that would last.  A large such earthen dike, the 18-meter-high Purrón dam (Yapa, 2000), in Puebla, Mexico, has a base width that would amaze a modern engineer, almost 100 meters, which resisted successfully, the erosive forces of the stream, for more than a millennium.  The 1400-meter-long dam-aqueduct, of Ascope, in La Libertad, Peru, created a lake of 22 million cubic meters (Deza, 1999), and even El Niño rains could not overtop its earthen dike.  Many enormous dam-aqueducts, lay across north coast streams of Peru, and none is equipped with a bottom outlet: may be they all were designed to trap the inflow to nourish the groundwater.  The huge lake, La Tapada, located at the brim of Chongon-Colonche hills, above the semi-arid, Las Balsas valley, in Ecuador, has a natural bottom outlet; a voluminous spring, bubbling under the dam, whose outflow filters-in at the valley neck and feeds the wells.  Apparently, the ancient inhabitants augmented the lake volume, by raising the height of the naturally formed blockade, to assure a year-round flow of water, and to prevent a calamitous spillover during storm seasons.

Irrigation in permeable or semi-permeable lands also recharges the underground aquifers.  The great Chimú Empire, in the north coast of Peru, saturated the Moche valley right bank, with many irrigation canals (Moseley, 1992), because their gargantuan capital city, Chan Chan, which depended heavily on groundwater, lay down slope.

Given these ingenious, multi-faceted, and economical, American solutions to the groundwater shortage, what technique, do you think, the State of Arizona would adopt to solve their problem?  The most expensive of them all!  They would pump the Colorado River water over a ridge, transfer it over hundreds of kilometers, through the multi-million-dollar, Central Arizona Project canal, and then, let the desert seep it in. 

Fortunately, some modern engineers look for cheaper alternatives, to trap humidity in the ground.  A series of ‘polders,’ U-shaped low earth dikes, each pooling several hectares of rainwater, built recently at the head of gently sloping, coastal rice-belt of Guyana and Suriname, feeds the paddies year-round.  An attempt by the Venezuelan Government, to adopt them to the floodplains of Río Apure, caused havoc, because its technicians did not have the patience, to observe the nature’s response, and modify the designs to suit.  They wanted to trap runoff, in small ponds (termed módulos), to grow pasture when the water recedes, but they had built so many, so close and so fast, that water spilling over the upper módulos, caused a ‘domino effect’ and completely destroyed the lower dikes (Yapa, 1997).

As planned for the módulos of Apure, cultivating within the drying reservoir constitutes the simplest, and the most direct means of exploiting the soil humidity.  Many desert farmers, like the Papago of Arizona, the albarrada users of Ecuador, or the bancada growers of coastal Peru, as well as the qocha owners of Peruvian altiplano, all plant their seeds at the edge of the water line, to get the most out of their sweat.  The terrace farmers too make full use of freshly wet soil, if they do not have irrigation facilities.

Nevertheless, in the extremely dry Peruvian littoral belt, where the evaporation, in a matter of hours, erases without even a hint whatever precipitation occurred, the farmers require a permanent supply of humidity to sustain their plants.  Hence, the constant pressure to build irrigation canals, to cover every possible corner of the desert floor.  However, many rivers, upon entering the desert valley, seek refuge in their thick beds of gravel, and run dry on the surface, a situation quite common in the southern Peruvian coast.  Undeterred, the Nasca farmers there have tunneled into the conglomerate deposits, crisscrossing the riverbed, to capture the filtration.  These 'subterranean rivers' daylight into surface reservoirs, and convert themselves into irrigation canals.  Some filtration galleries in Tehuacán Valley, of Puebla, Mexico, penetrate the soft limestone deposits there as deep as 10 kilometers, to collect groundwater (Woodbury and Neely, 1972).

Many of these traditional technologies, that exploit groundwater, truly follow the basic engineering principles: the efficient use of resources and the effectiveness of the system.  Yes, they require significant initial investments, mainly, organized manual labor.  The traditional societies could muster such resources, without negatively affecting the daily routines, through the obligatory community service work.  Once in place, these engineering schemes needed no operating expenses, only routine maintenance, which, again, the community service could handle very easily.  And their effectiveness? The continuing existence of many schemes readily demonstrates that. 

Why don’t we apply the same measures to evaluate the modern projects? 

Let’s see.  What do you think, how would the State of Arizona exploit, the Colorado River water, it pumped over and stored in the desert? 

You guessed right: by pumping it out!

I rest my case.

-September 2001.  Guayaquil, Ecuador.

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