Sustainable Urban Water Systems?

Water availability has always been the key factor for the development of human society. While in many countries this is plainly evident, those of us who – like me – live in a water-rich country, tend to forget about it. But even in my home country Switzerland – also known as Europe’s water tower – 2018 was a drought year.

Its famous glaciers, which currently still provide a constant water flow in the rivers throughout the summer months, keep melting away [1]. They are suspected to be completely gone by the end of the 21st century.

There are currently five main strategies for dealing with water-scarcity:

  1. Slowing down runoff and storing water, e.g., during the rainy season for later use in the dry season. The ancient “Wevas” (= reservoirs) in Sri Lanka [2] demonstrate how long this strategy has been used in human history.
  2. Diverting water from water-rich areas to water-scarce areas, such as the Roman Empire did it with its aqueducts [3].
  3. Tapping new sources, e.g., by milking clouds [4], desalinating seawater [5] or by using fossil groundwater sources [6].
  4. Efficient use, e.g., through using water-saving shower heads, low-flush toilets, efficient washing machines or drip-irrigation.
  5. Recycling and reusing water, e.g., by reusing treated wastewater for irrigation [7].

Strategies 1-3 completely focus on satisfying a given demand and pay little attention to the ecology of the areas affected by their measures. Due to humanity’s eternal thirst, too many rivers don’t reach the ocean anymore [8][9], and too many mountain areas are running dry. This aggravates the ecological situation there and effects the living quality of people in these areas. You can’t swim or fish in a dry river and hiking in a dry forest without birds is not a funny recreation. Strategies 4 “efficient use” and 5 “recycling/reuse” usually don’t consider ecological issues, but aim for supplying more people with a given amount of water.

In my view, we need a sixth strategy, based on an ecologically engineering way of design. Maybe it’s time to let the old ways (in their pure form) die…

What can ecological engineering contribute to a more sustainable practice regarding water use? It promotes the importance of system’s thinking in the design process. The adoption of a holistic system’s view is crucial in my view, and may lead to painful (but necessary) changes in the way we design our water systems!

For example, the current water-based sanitation- and urban drainage systems require a constant flow of water, lest the sewers start clogging. Water-saving devices are a commonly suggested method to save water. However, less water in the sewers leads to more sediments, which may eventually clog them and need to be removed. Usually this is done by pumping a lot of water from a truck into the sewers by the maintenance crews. Thus, without rethinking the sewer system as a whole, water-saving devices may even turn out to be technically counter-productive.

A holistic system’s planning aims to integrate the whole urban watershed – including water supply and urban drainage – with the needs of surrounding ecosystems into the planning process. It aims to be multi-focused: Hygiene, sanitation, cooling issues, drainage, food production and the recycling of nutrients in urine and fecal matter should all be considered.

An ecologically engineered urban water system should aim to treat (or even better: reuse) any remaining wastewater on-site. Its main feature is the avoidance of wastewater as much as possible. The remaining volume of wastewater should be so small that it can be easily treated on-site, e.g., on a roof, in a facade or in the garden with natural means.

Within the houses, the water system should be inspired by the vision of a closed cycle. This is possible if a) human feces and urine are completely kept out of the water cycle and treated separately, and b) if household chemicals are made “fit for circular systems” (which currently isn’t the case).

In my view this is the necessary next step! But how can it be done? Well, regarding ecological sanitation, a lot of basic work has been done in the past 20-30 years (e.g., [10]). However, there’s still space for a lot of ground-breaking, disruptive innovations here.

If you like to continue to think with me, stay tuned with this blog.



Sustain ability!!!

We should look with awe at the immense ability of Earth’s biosphere to sustain itself. In the millions of years of life on Earth, this ability always persisted. This is why life (and therefore humanity) is still around today. The biosphere has been resilient enough to weather several mass extinctions of global scale in its geological past, e.g., caused by asteroid impacts [1].

Can humans have an impact on Earth’s biosphere to the extent of an asteroid? I think so. If we’d really wage a war with nuclear weapons, the effect might be comparable. But even without such a disaster, we are now testing the limits of the current state of the biosphere.

Ecological science has documented numerous cases, where ecosystems irreversibly passed tipping points due to human activities [2]. A small example is Lake Sempach in Switzerland, which happens to be in my neighbourhood. Ever since a massive fish kill in 1984, caused by eutrophication, is has been artificially aerated. Even today (2018) there are still no prospects for completely switching off aeration.

When a certain threshold is passed, it is difficult or even impossible to revert an ecosystem to its previous state. Does the biosphere as a whole also have such tipping points? Ecology suggests that it does.

Sustainable development is an expression whose meaning is somewhat difficult to grasp. It is often defined as development that “meets the needs of the present without compromising the ability of future generations to meet their own needs” [3]. But what does “ability of future generations” mean? Let’s illustrate this with an image.

If humanity were a weightlifter, sustainable weightlifting would mean that we’d not ever be allowed to put down the dumbbells*. A threshold effect, such as a climate tipping point, would continuously put more weight on the dumbbells. Unexpected disturbances would weaken the weightlifter. Even a trained weightlifter would eventually break down.

Ability of future generations implies the “capacity, fitness, or tendency to act in a (specified) way” ([4]) to meet their needs. We should lighten the burden of our kids and our grandchildren instead of adding the weight of an irreversible ecological change to it. I also think we need to teach and train them how to engineer their direct environment holistically and based on findings from ecology. Sustain ability with Ecological Engineering!


* this type of weightlifting is fortunately not an olympic discipline…


[2] Resilience Alliance and Santa Fe Institute. 2004. Thresholds and alternate states in ecological and social-ecological systems. Resilience Alliance. (Online.) URL:

Ecology and Engineering – a perfect match?

If ecology and engineering would meet at an evening speed-dating event, they might not immediately fall in love with each other. On a quick glance, they seem to be too different. However, later at night, when lying in bed back at home and trying to catch some sleep, chances are that both would start pondering about the other.

Engineering offers a long experience in problem solving and the rigor and power of the methods used for it. Ecology offers deep insights into natural processes and the methods to analyze and quantify them. The application of engineering methods often affects the subjects of study of ecology, while changes in ecology may in turn affect engineered systems. If these two would marry, both fields could benefit from each other.

This becomes obvious in cases where both of the fields meet directly. Decommissioned mining sites – a left-behind of engineering activities – illustrate how difficult it can be to restore ecosystems. Often the hydrological cycle was fundamentally altered by the mining acivities. The migration routes of large animals were interrupted. The original fauna and flora were removed, together with the humus. In addition, abandoned mine tailings release acidic water into the environment – an almost unstoppable microbiological process. Engineers tend to be overstrained with this problem, because they may lack ecological understanding. On the other hand, even if ecologists knew what could be done, they often wouldn’t know how to do it. Both of them need each other.

The same phenomenon, just a little less obvious, can be observed in cities. Cities keep growing rapidly in almost all parts of the globe. Their urban water management practice is usually heavily built on an old invention, the sewer. Sewers allow to quickly drain away water from human infrastructures, carrying with them human fecal matter, industrial and hospital effluents, road runoff and a lot of other unwanted things. This is beneficial for the cities but causes a lot of problems dowstream. In many places on the world, the wastewater is just discharged directly to natural waters. This practice produces a lot of harm in these environments. Even if treatment exists, nutrients are usually not recovered.

Ecology offers some fundamental opportunities to engineering: A profound understanding of ecosystems, natural cycles, their functions and their properties; the capability to think in different scales; and system’s thinking, together with the tools to support it. In turn, engineering offers, e.g., the tools and practices to conceptualize, design and build infrastructures, the skills to develop new practices and devices needed for low- or zero energy cities and a closed-loop circular society.

I think, ecology and engineering are a perfect match! However, it’s a long way from nightly considerations to a wedding. Let’s have a closer look at this sprouting relationship in the next weeks. Stay tuned 😉

Why should engineers care about ecology?

Engineering as a field of practice has deep roots in human history. It dates back at least to the ancient Greeks, and might be much older. In ancient civilizations, the predecessors of engineers were probably craftsmen and artists. I believe that this eternal urge to do things better has always been their main driver. Since new solutions usually come through a long chain of trial and error, this is critical for success,

Current engineering practices in the Western world evolved since renaissance times. Mathematics, physics, chemistry and a diversity of other practical and scientific disciplines were increasingly included. Engineering is widely ramified today. All fields of engineering encompass a large formalized body of knowledge and practices, which is carefully guarded by engineering boards.

Engineering has become the single most important human practice on Earth. Compared to earlier ages, the potential impact of engineering has drastically increased in scale. Successful engineering design may now lead to its global distribution in a very short time. Think, e.g., of new types of plastics, pharmaceuticals, anticorrosive coatings, or sunscreens based on nanoparticles. If such inventions are introduced into the global market, they often also enter the global ecological cycles. This may (and often does) lead to unforeseen and unintended consequences in ecosystems.

Almost all ecological processes on Earth are connected through material cycles. The tremendous amount of human activities and our high mobility accelerate the velocity of material distribution through these cycles. The global biosphere is now changing in an unprecedented way. Nature has sustained life on Earth for more than a billion years, in spite of disasters of all kinds. Do we really want to find out by trial and error, if it can continue sustain us?

Forming a sustainable human civilization is the greatest challenge we face today. As a civilization, we need to understand how we – a biological being and part of nature – can co-exist with all the other biological beings in nature in a healthy and sustainable way. The science of ecology has been unraveling and trying to understand the incredibly flexible, yet resilient web of life on Earth. The principles and processes found by ecologists can inform engineers and inspire a new kind of truly sustainable design. This is why engineers should care about ecology.

After all, we are dealing with our own life-support system! In the following weeks, I want to explore how an ecologically inspired practice of engineering might look like.

Why should ecologists care for engineering?

Simply spoken: because engineering is the most influential human practice on Earth. “It is no longer possible to understand, predict, or successfully manage ecological pattern, process, or change without understanding why and how humans reshape these over the long term“, Erle C. Ellis, a well-known anthropoecologist, stated in 2015 [1].

We humans have learned to engineer machines, devices, tools and processes across several orders of magnitude, ranging from lakes or mile-deep open-pit-mining holes to molecules, nanoparticles or microorganisms. The outcomes of engineering – and the waste it produces – heavily influence our climate and all ecosystems. The effects can be measured at the highest mountain summit and in the deepest ocean abyss.

IEES aims to become an umbrella organization for ecologists, engineers and a wide range of other professionals who share a holistic view on Earth’s ecology and the human influence on it. IEES promotes the idea that a sustainable co-existence of humans and nature can be achieved. Interested in ideas how this works in practice? Stay tuned to this weekly blog.


[1] Erle C. Ellis, Ecology in an anthropogenic biosphere, Ecological Monographs 85(3), 2015, pp. 287-331