Do Not Water Your Lawn
By: Paul Collar
Paul is a civil engineer and geologist and the publisher of this newspaper.
You may reach him at firstname.lastname@example.org
Costa Rica gets an average of 2.5 meters of rainfall per year. Parts of the Osa get over 5 m per year. The Southern Zone of Costa Rica gets up to three annual rice harvests a year from native rainfall alone.
It might be surprising to learn, therefore, that there are no small number in Costa Rica that consider irrigation of lawns during the dry summer months some sort of inalienable right, perhaps even factored right into the rentista or inversionista clauses of residency law. The preening lawn is of course one of America’s curious cultural heritages. The smell that fresh mown grass evokes in even me is like apple pie or that of a new car. Yet I am fooled by my nostalgic whimsy. Many of my fellow ex-pats that build in residential developments or private fincas here must be as well, for they often bring irrigation with them to perk up their beautiful lawns during the summer months when they mostly visit.
In developed-world societies, water is often perceived as bountiful—no more than a hose bib away—and little thought is given to watering the lawn. If it is July in Arkansas, it is time to turn on the sprinklers, end of story. Yet this activity is fraught with environmental recklessness, not just in paradises like Costa Rica, but everywhere, even in Arkansas. There are many instances in which irrigation serves a purpose in which a cost/benefits analysis can be used to debate its merits, particularly amid the geopolitical minefields of climate change. But watering lawns in Costa Rica is different. In societies in which supply and demand is factored into utilities costs, a person that can afford to pay for the water required should have every right to water his or her lawn. Nevertheless, this activity has only a single tiny upside, the subjective aesthetic of a single person, the owner of the lawn, and a galaxy of downsides, irrespective of whether or not you can afford it.
Let’s look at a few of those downsides.
First of all, lawn irrigation requires more water than human consumption and use. For instance, irrigation recommendations for golf courses in Costa Rica call for 5 mm of water per day. Across a single hectare this adds up to 9.2 gallons per minute of continuous water every day. Costa Rican potable water design criteria call for 375 liters per person per day, equal to 0.07 gallons per minute. In other words, the water required to irrigate one hectare of lawn to golf course standards is equal to the residential water demand of 131 people. A day’s worth of water for a human being is equal in water equivalence, therefore, to 76 square meters of lawn, about 0.02% of the average green, for instance, at Los Sueños’s La Iguana 18-hole course. The water criteria backed out for the entire facility acreage is about equal, therefore, to the daily potable water needs of 75,000 people.
Secondly, irrigation consists of the diversion of liquid water from whatever its source—well, stream, river, spring, municipal—to atmospheric water vapor, since up to 70% of irrigation water in the tropics is lost to the atmosphere as evapotranspiration. A fraction is incorporated in the biomass of grass, the rest percolated in soils or lost as runoff to streams. During the dry summer months, the transfer of valuable surface water to the atmosphere is the opposite of what the thirsty forest and rural populations and small towns need. Since the false-equivalent upside is a single individual’s aesthetic contentment over the look of his or her lawn, yard irrigation arguably blossoms into an argument centered not merely in environmental protection, but indeed in social justice.
Thirdly, rural sources of water include not just deep wells but also springs, streams and rivers. These water sources are typically prolific in the rainy season, when irrigation is “unnecessary.” But surface flow dims with the deepening of summer. Though ground water levels have been lowered from over-development in arid and tourism-popular parts of the country, ground water remains a prolific source of water. If you must water your lawn, then you should use this option and solace yourself with your sacrifice in high power costs to pump this water and introduce it to the atmosphere by way of your lawn. But to take this vital commodity of water away from a surface stream or spring and from nature and our forest’s animals that depend on it to give it to the sky, all for the vanity of a single homeowner’s affection for his lawn, is moral turpitude: a misdemeanor perhaps for those that have not yet thought it through, a high crime for those that do so despite knowing better.
Finally, lawn watering is a purely foreign import. Ticos don’t have the same suburban affection for a lawn that many ex-pats, Americans in particular, do. In fact, water law proscribes the use of public water from A y A and local asadas for irrigation use. Metropolitan suburbs of San Jose are reduced yearly to rationing water in April, when water shortfalls pop up all over the nation. Watering lawns in Escaleras as people carry water in five-gallon buckets in Desamparados is a jarring image that ex-pat homeowners will want to consider during landscape design of a dream home in paradise.
Forests and established tropical ecosystems get by in even the driest years without much dying. But saplings and plantings from reforestation efforts require irrigation. Sustaining and nurturing seedlings and young plants with water, particularly young fruit trees and hardwood reforestation saplings, is essential and an appropriate and key use of irrigation. Low-tech, inexpensive drip irrigation concentrates the water where it is most needed for conscientious and ethical irrigation practices and is the least wasteful and most effective form of irrigation.
California has long enjoyed a reputation as the vegetable and fruit bin of America. Yet the agricultural ascendancy of the Imperial Valley was founded on the unsustainable exploitation of a resource that was not renewable at the prevailing rates of extraction. Today’s Midwest of the United States, America’s bread-basket, is founded on “limitless” water from the Ogallala Aquifer that stretches across the midcontinent and contains 10,000 year-old glacial melt water that has little recharge today and supplies 30% of all the irrigation water used in the United States. It’s a non-renewable resource. In fact it’s a mine: a water mine that will be depleted as early as 2028. America’s wheat and almonds, therefore, have been agricultural industries not too unlike the mining of a finite mineral resource, in this case water. Once that water is gone, those almonds and bushels of wheat can no longer be produced, end of story. This is not hypothetical but a simple fact, and we are sliding down the falling tail of agro-industry curves. The boundless frontier turns out in the midterm to not be so boundless after all.
In Costa Rica, ground water levels have fallen from over-pumping as well, mostly in Guanacaste and largely the result, government and media sources remind us, of poorly controlled over-exploitation of tourism resources in the arid northwest. But despite that, Costa Rica is a bit of a different story from California and the American Midwest.
Costa Rica is still the motherlode of water, practically all of it renewable. In fact, the water that falls as rain on Costa Rica is enough to supply 49 liters every day to every man, woman, and child on the planet. As one of the most verdant spectacles on earth, the Republic of Costa Rica is optimal for appropriate landscaping for upscale homes and should not have to depend on irrigation at all. Consider drip irrigation for vegetable and herb gardens, young trees, and other sensitive plants, hand-watering of house plants, but if you opt for a Saint Agustin lawn you should let it get brown in the summer and keep our scant dry season hydric resource in the forest where it is needed most. Think feng shui. Look to local ornamentals, manicillo ground cover, veriver for slope stabilization, and like plants already steeped in equilibrium with our natural environment.
Lawn watering is a zero-sum frittering of a vital resource. Husbandry of this resource through responsible drip irrigation can be a win-win alternative, so long as it does not remove environmentally key water from sensitive watersheds.
If you must water at all, please don’t spray. Drip instead