Greywater, Wild Gardens, and the Future of Water
- Jennie Vercouteren
- Jun 30
- 8 min read
Updated: Jul 7
Lessons from a Living System in the Pyrenees
Roots, Resilience, and the Hidden Power of Natural Filtration
After my last interview with Michel and Marie-Andrée, our conversation drifted from plants and design into something deeper. “It’s one thing to learn about ecological gardening,” Michel said, “but it’s another to embody it.”
That stayed with me.
I hadn’t planned on diving into ecological water systems. But as often happens in the Pyrenees, the right people and the right questions came at just the right time.
A Call That Changed Everything
A few days later, while I was researching a local permaculture retreat, my phone rang.
“I’m going to be rebuilding the water filtration system for the pond,” Michel told me.
“Do you need help?” I asked without hesitation. “I’d love to learn more.”
Within the hour, I was walking down a narrow path, winding past wildflowers and fig trees, the soft bowl of Mount Pibeste curving in the distance. I was excited. And I was nervous. What did I know about wetlands?
Learning by Doing (and Unlearning)
“You’ll be learning a mix of science, architecture, and craftsmanship,” Michel told me on my first day. I admitted, half embarrassed, that I had always struggled with math.
“That’s okay,” he said, smiling. “Anyone can learn if they apply themselves. A builder should understand the elements. Otherwise, they’re just following plans—not evolving.”
It wasn’t just about wetlands. It was about understanding the natural systems we live in—and working with them.
For the last month, I’ve been learning by doing. Together, we’ve been designing and rebuilding a small-scale but highly efficient greywater wetland that filters household water and channels it into a thriving pond. The system uses natural materials—slate, reeds, and gravel. What began as a practical water project became a quiet revolution in how I see water, soil, and our role in restoring ecosystems.
What We Actually Need
Early in the project, as we sat at his desk reviewing the design, Michel paused and looked up.
“What does a human really need to survive?” he asked.
“Air, water, food, and shelter," he continued after a moment, "and we can survive only a few minutes without air, a few days without water, and up to forty days without food.”
He let the thought settle.
Water is survival. Yet we treat it like waste.
We let rainwater run into sewers. We flush toilets with potable water. We wash dishes and watch water disappear into pipes. But what if we stopped seeing water as something to dispose of—and started seeing it as something to honor? Michel’s wetland got me thinking: What if every home in Lourdes—where rain falls abundantly—could turn roofs into reservoirs? The math, it turns out, is startlingly simple…
Reclaiming Rainwater
In Lourdes, we’re blessed with an average of 1,200 mm of rainfall per year. That might sound like just another climate stat—until you realize what it really means. With a simple 50 m² roof and thoughtful ecological design, one family can meet all of their water needs—without relying on municipal supply or stressing the land.
This isn’t a pipe dream. It’s just smart math.
Rethinking Water Demand: Less is So Much More
The average French person uses about 150 liters of water per day. Multiply that by four, and a typical family consumes roughly 219,000 liters per year. But with two simple shifts, we can dramatically reduce the demand:
Composting toilets: Eliminate the biggest water drain—flushing. That’s 30% of daily use gone.
Greywater reuse: Redirects shower, sink, and laundry water (about 50% of daily use) to irrigate gardens or recharge wetlands.
With composting toilets (no flushing) and greywater reuse (showers/laundry diverted to irrigation), the family’s clean water demand shrinks to drinking, cooking, and light cleaning—just ~30 liters/person/day of clean water—for drinking, cooking, and a bit of cleaning. That’s just ~44,000 liters per year.
The Rainwater Equation: Nature Provides
Let’s do the math:
Roof area: 50 m²
Annual rainfall: 1,200 mm
Collection efficiency: 95% (to account for minimal loss)
Result: 50 × 1,200 × 0.95× 0.001 = 57,000 liters/year harvested
Greywater: Turning Waste into Wealth
By redirecting Greywater = showers + sinks + laundry = ~50–80% of indoor water use. It can then be used for
Drip irrigation
Constructed wetlands to clean and reuse
Subsurface garden watering
Beautiful and vibrant ponds
This means every drop of rainfall and every reused liter serves a second purpose.
The Big Picture: A Closed-Loop, Regenerative System
Rainwater ( approximately - 57,000 L/year) → Covers all potable water needs
Greywater (approximately 35,000 L/year) → Supports the garden, trees, or wetland recharge
Composting toilets → Eliminate sewage entirely
The result? A water system that doesn’t just sustain life—it regenerates it. A family of four can
become fully water self-sufficient in a place like Lourdes—with margin to spare by reusing, cleaning, and circulating the water on-site—without depending on overdrawn aquifers or energy-hungry treatment plants.
France (and the U.S.) Have It Backwards
Once you start seeing how water moves, it’s hard to unsee.
In the current model, clean rainwater lands on our rooftops—only to be channeled directly into sewers. There, it’s mixed with toilet water, then pumped to centralized treatment plants that burn electricity to clean it. France spends €0.30 to €0.50 per cubic meter to treat water that was clean when it fell from the sky.
Meanwhile, we flush toilets with drinking water, ignore the rain, and pay for tap water drawn from rivers and aquifers that are increasingly stressed by drought and overuse.
It’s not just inefficient. It’s backwards.
Why Greywater Wetlands Are a Radical Act
Instead of treating water like waste, we can treat it like a cycle. In Michel's wetland project, greywater from showers, sinks, and laundry flows into a small septic tank where solids settle. The water then moves through a constructed wetland filled with gravel, soil, and native plants. As it travels slowly through this natural filter, plants and microorganisms break down pollutants, cleaning the water in a low-tech, eco-friendly way that supports biodiversity and reduces pollution. From there, it flows into a pond that supports fish, reeds, and local wildlife.
This is about more than just saving water. It’s about restoring balance.
Wetlands filter water, yes—but they also:
Support biodiversity, from frogs to dragonflies to birds
Prevent erosion, absorbing and slowly releasing rainwater
Reduce energy use, by treating water without electricity
Create beauty and habitat, right in your backyard
Rebuild local water cycles, mimicking how nature filters and reuses water
Why It’s Better Than a Hose
Watering your garden with a hose might keep your plants alive—but a constructed wetland keeps your whole system alive.
Hose watering is isolated, linear, and wasteful. Wetlands are circular, constant, and regenerative.
The difference?
A hose delivers water.
A wetland moves water.
The result is a garden that breathes, drinks, and grows—without waste.
Why Septic Tanks Aren’t Enough
Septic tanks are a common solution in rural areas, but they’re limited. In Michel's case the water flows out of the house into a small septic tank. In this tank, any remaining solids settle at the bottom, and the water flows out into a constructed wetland. While they do separate solids and begin decomposition, they don’t remove nutrients, neutralize soaps, or eliminate pathogens. Even eco-friendly products leave residues.
That’s where wetlands come in. They finish the job by filtering water through multiple biological stages—leaving it clean enough to reuse in the landscape.
Why Aren’t We All Doing This?
If constructed wetlands are this effective, why aren’t they everywhere?
The reasons are practical—and solvable.
Out of sight, out of mind: Most people don’t think about where their water goes once it leaves the house. If the municipality takes care of it, why bother?
Regulatory hurdles: In France and the U.S., greywater reuse is often buried in red tape. Permits are confusing. Authorities aren’t always informed.
Aesthetic bias: Wetlands are sometimes seen as wild or messy. But with good design, they can be sculpted, beautiful, and integrated into any landscape.
Lack of expertise: Most landscapers haven’t been trained in ecological water systems. And many DIY gardeners don’t know where to start.
Awareness gap: Simply put, most people have never seen one in action.
But that’s changing. More gardeners, designers, and communities are realizing that ecological design isn’t just possible—it’s powerful.
Global Context: France, the U.S., and the Future of Water
France currently gets about 60% of its tap water from groundwater, especially in rural areas. But in the south, aquifers are running low—some dangerously so. Climate change is shifting rainfall patterns and reducing snowmelt, especially in the Alps and Pyrenees.
The government’s goal is to recycle just 10% of water by 2030 (currently it’s around 1%). That’s a start, but individual systems like this one can do even more—and immediately.
In fact, new regulations passed in July 2024 now make it easier for households in France to reuse rainwater and greywater legally for non-potable uses like toilet flushing, laundry, garden irrigation, and more. This shift opens the door for more small-scale, decentralized systems like the one we built with Michel—systems that not only reduce pressure on municipal supplies but also restore local ecosystems in the process.
In the U.S., the situation is worse. Water comes mostly from surface sources, aging infrastructure threatens safety, and chemical pollution (PFAS, nitrates, etc.) impacts over 6,000 systems. And still, rainwater is rarely used.
Constructed wetlands offer a way forward in both countries. They reduce demand, clean water naturally, and localize responsibility in a way that’s empowering—not overwhelming.
A Living System That Heals
Michel’s garden reminded me that sustainability isn’t about guilt or restriction—it’s about regeneration. It's about creating systems that give back more than they take. That includes water.
Whether you’re planning to build your own—or just dreaming of what’s possible—I hope this story inspires you to look at water a little differently.
It’s not just something to use. It’s something to understand.
✍️With the right flow, even a small garden can become a biodiversity hotspot—buzzing with pollinators, birdsong, and the shimmer of water moving through stone. Each trickle, each pond, each shaded reed bed becomes an invitation for life to return.
This is what ecological design makes possible. Not just efficiency—but aliveness.
Whether you're planning a full-scale greywater system or simply dreaming of a rain-fed stream weaving through your garden, we invite you to join us and share your ideas and projects in the comments below.
In this series, we will be getting hands on with building a wetland, showcasing other real life examples of using rainwater from our roofs and grey water in our homes to create beauty and activate life in the garden. This is just the beginning of our exploration into ecological water systems. Join us in the coming weeks as we dive deeper into practical how-tos and inspiring examples right here in the Pyrenees and beyond.
And if this resonates with you, share it with a gardener, a designer, or someone who just loves the sound of water after rain. The future of water starts with stories like this—shared, imagined, and built, one beautiful system at a time.
Disclaimer: Always check local laws before building a greywater system. Permits and restrictions vary.
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