Water is life. That’s why we need to take care of it. Even plentiful water supplies are moot if they are undrinkable. Climate change, pollution and growing populations only add to the urgency of maintaining adequate water supplies and water quality for humanity.
After doing archaeology for 35 years in Belize, focusing on the ancestral Maya, I have learned a great deal about living sustainably with water. I've learned that they lived in better harmony with the environment and kept water clean naturally. We can learn from them. We must.
Before the arrival of the Spanish invaders in the early 1500s in Central America, the Maya engaged with the environment differently for millennia, in accordance with their inclusive worldview. They did not overuse resources because to them, everyone and everything—soils, clouds, animals, reptiles, birds, insects and so on—played a role in maintaining the world. Maya and everything else had souls, and had respectful relations where everything and everyone were animated and connected through them. Unlike in modern thinking, they lacked Cartesian dichotomies like nature/culture or sacred/secular in their outlook. Humans and nonhumans co-existed and did not overtax each other. The Maya celebrated these connections through renewal ceremonies, where they aimed for forest collaboration, not forest management.
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They engaged with water the same way, asking permission from Earth gods and Chahk the rain god to use their materials (soils, limestone and rain) to build self-cleaning reservoirs. This particular relationship offers perhaps the most important lesson they have to teach us today.
Self-cleaning reservoirs, or constructed wetlands (CWs) as they are now known, supplied tens of millions of Maya in the Classic period (c. 200–900 C.E.) in their southern lowlands region, which spanned parts of modern-day Guatemala, Mexico and Belize, during the annual five-month dry season, when temperatures rose and humidity increased. Much of the rain that fell during the seven-month wet season there percolated through porous limestone bedrock, leaving little surface water.
That’s why reservoirs and kings in hundreds of Maya cities endured for more than 1,000 years, sustaining millions of people. By at least 400 B.C.E., the Maya began constructing increasingly sophisticated water systems. These lasted until 900 C.E., when the Maya left the cities amid the repercussions of several long droughts that struck between 800 and 900 C.E. Water levels dropped, crops failed and kings lost power after more than a millennia of sustainable living undone by changing climate. Maya farmers, however, persevered, and still do.
But how did the Maya maintain water quality for more than 1,000 years? By applying their knowledge of the tropical environment to design self-cleaning reservoirs. Their waters did not turn stagnant, or into breeding grounds for disease-carrying mosquitoes and waterborne diseases. Nutrients like nitrogen and phosphorus did not amass enough to feed algal blooms, like the ones we see today blanketing our coasts. The Maya created constructed wetlands, which, as defined by the EPA “use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.” No chemicals were needed like water treatment plants use today.
In a constructed wetland, aquatic biota work together to maintain water quality. Aquatic plants like cattails, water hyacinths, reeds and others take up nutrients, while biofilms created by decomposing plants break down nutrients. That’s not all. Certain aquatic bacteria absorb nitrogen and feed on harmful microorganisms like parasites, as do zooplankton or small aquatic microorganisms. Today's wetlands in the Maya area still have plentiful aquatic plants and other species that people used for food, medicine and tools, including bamboo to make fish spears, reeds for basketry, not to mention turtles, crustaceans, eels, mollusks, snails and fish.
The ancestral Maya knew water was clean when they saw water lilies (Nymphaea ampla). Why? Because they are sensitive aquatic plants. They can only grow in still waters not too deep, say three to 10 feet. The water cannot have too much calcium or other minerals or too many algae and cannot be too acidic. In other words, these flowers are only found in clean water (and in the iconography symbolizing Maya kingship, which is anotherstory).
These constructed water ecosystems are amazing—and are relevant and vital for future water needs. Currently, civil engineers are exploring broader uses of CWs, such as the Sedlak Research Group at the University of California, Berkeley. Although they are initially labor-intensive, they become self-sufficient with only some maintenance. And they do not need chemicals or fossil fuels to run.
One possible issue using CWs is their greenhouse gas emissions. However, this can be mitigated by harvesting aquatic plants that can then be used as fertilizer—as could the dredged bottom debris. We know that every few years the Maya would have had to dredge reservoir bottoms that were saturated with decomposing fish feces and other organics. And they would have had to replenish and replace aquatic plants. Extracted aquatic plants and bottom debris are rich with nutrients and excellent as fertilizer, which the Maya used for urban fields and gardens. They also used gray water for fishponds and construction projects and released it downslope for orchards, urban fields and gardens. Finally, reservoirs attracted game like deer, tapirs and peccaries, as well as waterfowl including herons, cormorants and ducks. The Maya did not waste water.
Where can we start following their lead? One idea is to voluntarily transform some of the over 10 million swimming pools in the U.S. alone into CWs, complete with fish, snails, turtles, mollusks, alongside edible and medicinal plants (and fertilizer). People could still swim in them. Companies are already making nonchemical self-cleaning pools. Let's take it to the next level—families, communities, towns, cities, governments, nations and transnational corporations need to get involved.
On the global stage, increasing the use of these kinds of CWs—a technology humanity perfected more than a thousand years ago—would also fulfill United Nations Sustainable Development Goal 6 to ensure access to clean water for everyone and encourage the participation of local communities.
The ancestral Maya and today's civil engineers can show us the way.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.