50 Liters http://50liters.com Love Water, Live Better Fri, 17 Apr 2020 12:54:23 +0000 en-US hourly 1 https://wordpress.org/?v=5.4.2 147879476 How Windhoek banks on water security underground http://50liters.com/how-windhoek-banks-on-water-security-underground/ http://50liters.com/how-windhoek-banks-on-water-security-underground/#respond Fri, 17 Apr 2020 12:54:18 +0000 http://50liters.com/?p=1956 If you’ve been to Namibia, the country’s strained relationship with water is obvious. The parched landscape makes for an impressive sight. Dunes that undulate from glaringly white to copper red attract visitors from afar. At places, a lone aloe might break the otherwise bare horizon. The bitterly cold Atlantic that runs along its coast jealously guards moisture, rarely letting enough ...

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If you’ve been to Namibia, the country’s strained relationship with water is obvious. The parched landscape makes for an impressive sight. Dunes that undulate from glaringly white to copper red attract visitors from afar. At places, a lone aloe might break the otherwise bare horizon. The bitterly cold Atlantic that runs along its coast jealously guards moisture, rarely letting enough go to form clouds heavy enough for rain. It is the most arid country south of the Sahara Desert.

A dry capital in a dry country

The capital, Windhoek, is placed at the centre of the country, and far from water. The closest perennial river to Windhoek, the Okavango River, lies along the northern border 700 km away. Windhoek itself receives only about 360 mm rain per year, with annual evaporation rates as much as 2 170 mm.

Water to the city is supplied by NamWater, the national supplier of bulk water in the country. Windhoek’s water supply is mostly from the so-called “three dam system” through which water is transferred to the Von Bach Water Treatment Plant near the town of Okahandja. This is supplemented by the Windhoek reclamation scheme (I’ve written about how Windhoek taps water from sewage before) and groundwater in the Windhoek and northern aquifers.

Large-scale abstraction from the complex Windhoek Aquifer started in the 1950s and is a vital part of the supply to keep the largest urban and industrial development in the country going. However, the aquifer was being tapped dry to feed growing numbers of people and industry.

The Windhoek aquifer is tapped dry

In 2018, the population of the city was 326 000, projected to grow to 790 000 by 2050. It’s of little surprise that water demand is set to almost double in the same time, from 27 million m³ per year to over 50 million m³.

Already by the late 1990s water levels in the Windhoek aquifer had dropped by about 40 m in the main wellfield areas, and were steadily declining in other areas too. The resources from the aquifer were being mined beyond what it could sustain.

Experts said the aquifer would need up to a decade of rest to recover fully, and authorities started investigating different options for water supply to the city. They settled on managed aquifer recharge (MAR), among other reasons because it was the most cost-effective alternative. The idea was to use the Windhoek Aquifer as a water bank. Treated surface water would be transferred to the aquifer for storage, to be used when water was scarce.

Banking water underground

Starting in 1997, the project became the first major MAR scheme in the world to be constructed in a complex, fractured, hard-rock aquifer. The aquifer is injected with treated, drinking-quality water. The water that is put in the aquifer has to adhere to strict quality guidelines in order to prevent it from affecting the quality if the groundwater quality, and for clogging of the boreholes to take place.

The water is a blend of three-parts dam water, and one-part treated, reclaimed water. After seven years of recharge, parts of the aquifer were filled to their highest levels since the 1950s when large scale abstraction began.

The overall aim of the ongoing project is to use as much of the aquifer’s storage as possible. After the initial success, the scheme was expanded in 2011 with ten more injection and abstraction boreholes each.

A safety net during drought

When Namibia experienced extreme drought in 2016, a major crisis loomed for the bigger towns in the central area of the country, including Windhoek. Part of the emergency response was the installation of 12 more large, deep-well boreholes in the Windhoek area. There were linked to the Windhoek water supply network.

This project allowed for three times the previously available capacity from the Windhoek aquifer to be abstracted. This would cater for about two-thirds of the 2016 suppressed water demand of the city. As a result, not a single tap in Windhoek was closed during the crisis, and the benefits remain available to the city’s residents for similar emergency situations in future.

Keeping taps open into the future

Water supply in arid Namibia and Windhoek remains a major challenge. Inland water sources are already tapped to capacity, and the city has repeatedly stated that they are very mindful of the challenges of the fragile environment that they make a living in.

The Windhoek aquifer is key to this process. When fully developed, it is expected that the city can bank enough water there to keep them for three years during drought. This will allow the city the opportunity to continue, and even flourish, long beyond what other cities in a similar situation would have been able to.

Sources:

  • Transformational Strategic Pan for the City of Windhoek 2017 – 2022
  • Water Management Plan for the City of Windhoek (version 2/2017)
  • Windhoek, Namibia: From conceptualising to operating and expanding a MAR scheme in a fractured quartzite aquifer for the city’s water security by Ricky (EC) Murray, Don Louw , Ben van der Merwe and Immo Peters

Notes

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How Windhoek taps water from sewage http://50liters.com/how-windhoek-taps-water-from-sewage/ http://50liters.com/how-windhoek-taps-water-from-sewage/#respond Fri, 28 Feb 2020 12:58:53 +0000 http://50liters.com/?p=1947 For obvious reasons, sewage is unappealing and drinking it, completely unfathomable. Yet, while most of the world is still debating if you should even try to treat household sewage to drinkable standards, Windhoek has been tapping water from it for decades. In 2018, Namibians marked the 50th anniversary of the first direct potable (drinking-quality standard) reuse plant in the world, ...

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For obvious reasons, sewage is unappealing and drinking it, completely unfathomable. Yet, while most of the world is still debating if you should even try to treat household sewage to drinkable standards, Windhoek has been tapping water from it for decades.

In 2018, Namibians marked the 50th anniversary of the first direct potable (drinking-quality standard) reuse plant in the world, the Goreangab Water Reclamation plant. In fact, it’s so successful, a second was kicked into action in 2002. The New Goreangab Reclamation Plant now puts improved water treatment technology into practice. In general though, there are three ways to tackle sewage treatment – all of which are becoming more common.

Different ways to tap from sewage

The first, is direct potable reuse. This is when sewage is treated to drinking-water standards and fed into the water distribution system. This is what is happening at Windhoek. The process has been taken up in other countries, including South Africa, where a water reclamation plant was constructed in Beaufort West.

The second is indirect potable reuse. Here, treated sewage is released back into natural systems like rivers to mix with water. Then, it is abstracted and treated to drinking standards. They do this in Singapore during droughts.

The last option is treated effluent reuse. For this, sewage is treated, but not all the way to a quality that makes it fit for drinking. The water is then used for stuff like irrigation or industrial use. This is also happening in South Africa, both in Cape Town and in Durban.

The Durban Water Recycling Project (commissioned in 2001) treats effluent and industrial wastewater to near drinking quality standards, and then sells it to industrial customers to use in manufacturing processes. The so-called sewage-to-clean-water plant can reportedly free up enough drinking water for about 300 000 people.

All three options can make a huge difference to the water security of a town, city, and country. Windhoek is a perfect example.

Why dry Windhoek looked to wastewater

Namibia, of which Windhoek is the capital, has the dubious distinction of the country with the lowest average rainfall in Southern Africa. Droughts are common, and in general, water is scarce. For decades already, all naturally available water sources in the centre of the country (where Windhoek is located) have been tapped to the max.

The city is committed to exploiting the maximum amount of water from all sources it has available. In Windhoek, every drop of water counts. Even the moisture in sewage cannot be allowed to go to waste.

A new water source is born

The reclamation plant was brought into operation in 1968, following severe water shortages before the extension of the state water supply scheme could be completed.

The plant is fed from two sources, the Gammams Sewage Treatment Plant and the Goreangab Dam. The plant can be split into two streams. One stream is to treat effluent from the sewage treatment plant and the other for the treatment of Goreangab Dam water. The raw waters can also be blended and treated as a single stream.

Another serious drought in 1997 led to the construction of the second plant, to cater for the ever increasing demand for water. The new plant applies all the best practices and lessons from the first plant. This old one now treats water to irrigate parks and sports fields but, since it began in 1968, nobody in Windhoek has ever gotten sick because of the water it produced.

Still turning your nose up at sewage?

The treatment of wastewater to the point where we can drink it poses extraordinary challenges. Yet, Windhoek is living proof that it is possible and even necessary.

As more international examples of sewage reuse for different purposes emerge, the case has already been made. With the correct technology and know how, our dirty water can be a new tap to help quench the thirst of cities of the future.

Notes

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San Francisco embraces wastewater for bright future http://50liters.com/san-francisco-embraces-wastewater-for-bright-future/ http://50liters.com/san-francisco-embraces-wastewater-for-bright-future/#respond Thu, 27 Feb 2020 10:12:26 +0000 http://50liters.com/?p=1952 In San Francisco, all water is seen to be of value; as little as possible should be wasted. So much so that, in 2012, San Francisco became the first municipality in the country to adopt groundbreaking legislation to allow onsite non-potable water systems. Tapping from alternative water sources The Non-potable Water Ordinance allows for the use of alternative water sources ...

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In San Francisco, all water is seen to be of value; as little as possible should be wasted. So much so that, in 2012, San Francisco became the first municipality in the country to adopt groundbreaking legislation to allow onsite non-potable water systems.

Tapping from alternative water sources

The Non-potable Water Ordinance allows for the use of alternative water sources like rainwater, greywater, stormwater, foundation drainage, and blackwater. Soon, they developed the Non-potable Water Programme. This provides the design and development community with a streamlined permitting process to develop such projects on building sites.

The San Francisco Public Utilities Commission (SFPUC) collaborates with city partners including the San Francisco Department of Public Health, Department of Building Inspection and Public Works Department to provide oversight and management of the use of treated non-potable water (water that is not clean enough to drink). In this way they ensure that the public health is not endangered.

“These onsite non-potable water systems are transforming the way we live and do business in San Francisco”, says Steven R. Ritchie, SFPUC Assistant General Manager, Water. He says they are pioneering new ways to collect and treat water for reuse within buildings and neighborhoods. “We recognise the opportunity to build upon our centralised water infrastructure by integrating smaller, onsite water treatment systems to produce water fit for toilet flushing and irrigation. This approach not only matches the right resource to the right use, but helps us stretch our drinking water supplies.”

Always upwards and onwards

Since 2012, the programme has expanded to allow for district-scale projects. Now, two or more parcels of land can share alternative, treated water sources. In 2015, the programme became a mandatory requirement for new commercial, mixed-use, and multi-family development projects over 23 225 m².

Today, recycling water is integral to a reliable, long-term water supply to the city. Wastewater is now an essential part of the resources mix that the city relies on. Others include water supply diversification, water transfers and water conservation.

Notes

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Wastewater management – the blessing in the curse http://50liters.com/wastewater-management-the-blessing-in-the-curse/ http://50liters.com/wastewater-management-the-blessing-in-the-curse/#respond Tue, 25 Feb 2020 12:57:49 +0000 http://50liters.com/?p=1945 Nowadays, cities seem to be the places to be for more and more people. For one, they can get access to better services, like water and sewage. In fact, the United Nations says that, between 1998 and 2008 alone, 1 052 million people accessed better drinking water in cities. A whopping 813 million accessed better sanitation, and the numbers are ...

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Nowadays, cities seem to be the places to be for more and more people. For one, they can get access to better services, like water and sewage. In fact, the United Nations says that, between 1998 and 2008 alone, 1 052 million people accessed better drinking water in cities. A whopping 813 million accessed better sanitation, and the numbers are set to grow. Of the 39% of the global population (2.9 billion people) that use safe sanitation, most live in cities; as much as three out of every five people. Two out of five people in rural areas across the planet have access to piped water, while four out of every five people in urban areas enjoy this privilege.

The trend is unlikely to turn. Under the umbrella of the Sustainable Development Goals, countries, cities and industries have committed themselves to a future with access to safe water and suitable sanitation to all.

Yet, all of this comes at a price. The more water we use, the more water we make dirty. Wastewater management today is a enormous part of managing a city. And, as much as water can give people better quality of life, as big is the price that we pay for it.

The flipside of safe water and sanitation

The water that we use must come from somewhere. The more people that access water, the more needs to be taken from nature to feed the system. At the same time, as the amount of water used by people increases, so does the amount of dirty water we produce in the process.

Over and above that, examples of places where safe water is getting harder to come by are common. And, as this is happening, it’s become clear that the dirty water we flush away, is a valuable opportunity washed down the drain.

It’s a broken circle. We take clean water, dirty it, and then send it back to pollute the system where we take our water from. At the same time, we already don’t have enough clean water.

To change this, some say that our perception of dirty water must change. In fact, an entire rethink of the traditional wastewater treatment model is necessary. In this picture, ‘dirtied’ water is not a problem to be managed, but rather an opportunity to solve many of problems inherent to wastewater management.

What is this dirty water?

Let’s take South Africa as example. Here, about 23% of the freshwater in the country is used by municipalities. This water is the oil that keeps the machinery of households running, though it mostly only passes through. The water enters the house clean enough to drink. Then, it swiftly exits the property again after it has been used for stuff like washing dishes, laundry and people, and flushing toilets. However, now the water is seen to be dirty and even dangerous to our health.

Lots of water is also used outside for gardens, although this water does not leave the property as waste. Rather, it goes back into natural system. Some water evaporates or infiltrates back into the groundwater table. A small amount of water could also run into the stormwater system; when water runs down paving after washing cars or from over-watering gardens.

For our purposes, we’re interested in that water that does not enter the natural or stormwater systems after it has been put to work. That’s the so-called wastewater, and that’s what’s being eyed as a new ‘tap’ of water to be developed.

Of course, what wastewater can be used for, depends on how dirty it is.

Not all dirty water is equal

In general, the wastewater produced in homes is divided into greywater and blackwater. Blackwater is from toilets and is commonly collected via sewer systems. This water has high concentrations of stuff that can possibly make you sick, like disease-causing microorganisms, organic loads (bits of animals and plants) and nutrients. This water is usually dark in colour and smells.

Still, although controversial, the reuse of treated blackwater is becoming more common. In Windhoek, for example, they’ve been depending in this water for decades.

Greywater is mostly untreated wastewater from all household uses except for toilets. Water from kitchen sinks and dishwashers is sometimes excluded too. Also called greywater, sullage and light wastewater, it contains some nutrients and microorganisms but usually at a much lower levels than blackwater.

What makes dirty water so attractive

Firstly, if we were to use wastewater, we would have more water available to us. Cities use vast amounts of water and as a result, generate ginormous amounts of wastewater. If wastewater instead of freshwater can be used for some stuff, the natural sources that the freshwater is taken from will also get a break. It has been reported that residents of developments that make use of wastewater can save up to 50% of drinking-standard water compared with those that don’t.

The lovely Padysha-Ata, a small transboundary river in Kyrgyzstan.

Not only will using wastewater help build security in our water reserves, but it can also result in better overall water quality. This is because the dirty water will be prevented from entering the environment again.

Plus, the stuff in the wastewater can be put to good use elsewhere. The energy, organics, phosphates, nitrogen and cellulose can be mined and, in turn, lead to financial gains. This could perhaps cover some of the operations and maintenance costs to run the process.

Using wastewater instead of getting rid of it, thus opens up many opportunities to create places that are more water secure, healthy and clean, while creating business opportunities.

But its not all smooth sailing ahead with wastewater. Dirty water comes with as many risks as opportunities.

What can we do with our dirty water?

Because of this potential risk to people’s health, recycled and treated wastewater, in South Africa at least, has mostly been used to water open grounds like sports fields, parks or plants not meant to be eaten. In rare cases this water is used irrigate fodder, but this is strictly regulated.

However, its a different ball game when drought hits. When few other options are available, greywater is often used for gardening, especially in middle to upper income suburbs. In lower income, informal and peri-urban areas, people tend to use it to also water vegetable and fruit gardens, though this is not done without health concerns.

The different uses of greywater, and its quality, also depends on the environment where it is created. Not only do people living in formal urban areas tend to use greywater for different functions than residents in informal areas, but the quality of the greywater produced from these areas differ greatly.

Where you live changes the wastewater you make

In a formally developed area, water enters the home, is used and is taken away again. During drought, some wastewater (greywater) might be collected with a bucket from the shower or bathtub and used to flush the toilet or water the garden.

In comparison, the journey of water in an informal settlement is very different. First, the basic infrastructure to remove used water from the household is often non-existent. Still, the household might have access to some means to bring water into the house, like a communal tap or a river.

In informal settlements water thus often needs to be collected away from the home and carried back. This is hard work and takes time, so water is used multiple times. When there is no infrastructure to remove the used water, the wastewater is generally thrown outside of the house. Here it can mix with other forms of waste.

Especially where settlements are densely populated, a lot of dirty water accumulates in streets and other areas used by people. This leads to a myriad of potential harmful impacts on people’s health, the direct environment that they live in, and the broader environment that the water flows towards.

Because this water is so seriously polluted, some refer to the greywater generated from unsewered, informal settlements as dark greywater. This water is often more like blackwater than greywater, and is hazardous.

Wastewater management in informal settlements

It’s not possible to reuse this water without extensive treatment. In general, the consensus is that this water should really only be diverted to a sewer, to be managed in the same way as blackwater. In informal settlements the challenge is not how to make better use of wastewater. Rather, the challenges is how to tackle wastewater management so it does not endanger the health of people and the environment.

The most ideal places for wastewater use

At least locally (in South Africa), the most promising source of greywater to add to the country’s water security is at low-density, high-income areas. Here more greywater is produced and there are fewer health concerns.

Especially promising is large buildings such as office blocks, public buildings and hostels. At these places, greywater can be collected and treated for reuse under proper supervision.

How to tackle better wastewater management

General consensus is that as a starting point, the aim of managing wastewater is to improve health, conserve water and protect the environment. Then, where possible, wastewater can be recycled and reused.

In South Africa, the recycling of water for any purposes, whether it is domestic, agricultural or industrial is strictly regulated. By and large, our laws are not aimed at regulating reuse of wastewater. Mostly, they aim to protect and conserve the country’s natural water resources.

At the moment the goal is thus largely to return treated wastewater to the natural water environment. Ideally, we want to recover as much of the volume of water originally extracted. Then, we want to ensure that the reclaimed water does not harm the natural ecological status of the environment to which it is returned.

There is a lot of work to be done before the benefits of wastewater can become reality. This depends as much on technology and management intervention, as it is on shifting perspectives and new thinking.

What needs to change for better wastewater management?

The linear model of traditional water treatment, in which water is extracted from the source, treated and used before the wastewater is treated and disposed of, needs to change. A new, circular model is called for. In this plan, less water is extracted by reducing the water used and consumed. Water is recycled and reused for different purposes depending on the quality of the water, allowing the water resources to recover.

In order to see this become a reality, a number of things need to change. For one, the purpose of wastewater treatment plants need to be re-imagined as a place where water and other resources are recovered.

Planning should also move from focusing on individual wastewater plants for individual municipalities to bigger scale thinking that considers the basin.

To do this, regulation, policies and incentives across sectors must be aligned. At the same time, the institutions that ensure that such laws and policies are applied, must have clear and enforceable sanctions.

While it’s a long haul ahead, there are examples of places that have chosen to go down this road. Singapore, for example, sees wastewater as one of the central pillars of its future water security. In San Francisco, again, the country’s first legislation to allow for alternative water sources to be used in buildings has been written. Even in South Africa, there are great examples. Wastewater has been part of the mix of water supply to Atlantis in the Western Cape for decades.

Some would say that wastewater is our greatest untapped water resource. From this point of view, one of the biggest curses of the development of cities, can be seen as a potential blessing, helping people that move to cities to live their best lives, along the way.

Notes

Sources

  • A Review of the Applicability of the South African Guide for the Permissible Utilisation and Disposal of Treated Sewage Effluent in Agriculture and Aquaculture, by P Jagals & M Steyn (WRC Report No. 1039/1/02)
  • Sustainable Use of Greywater in Small-Scale Agriculture and Gardens in South Africa, by Nicola Rodda, Kirsty Carden, Neil Armitage (WRC Report No. 1639/1/10)
  • The reuse opportunity – IWA Wastewater Report 2018
  • Understanding the use and disposal of greywater in the nonsewered areas in South Africa, by Kirsty Carden, Neil Armitage, Kevin Winter, Owen Sichone and Ulrike Rivett (WRC Project 112 WRC GLOBAL SERIES: WATER RESILIENT CITIES K5/1524 final report)
  • Wastewater? Shifting Paradigms: From Waste to Resource, Preliminary Insights for the Latin America and Caribbean Region for the World Water Forum 2018, accessed at www.worldbank. org
  • Wastewater treatment: A critical component of a circular economy by Diego Rodriguez for the World Bank
  • www.unwater.org
  • www.watersensitivecities.org.au

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The promise and peril of stormwater management in Johannesburg http://50liters.com/the-promise-and-peril-of-stormwater-management-in-johannesburg/ http://50liters.com/the-promise-and-peril-of-stormwater-management-in-johannesburg/#respond Tue, 24 Dec 2019 07:16:29 +0000 http://50liters.com/?p=1943 Founded in 1886, Johannesburg is one of the world’s youngest major cities. The metropole grew up fast, however, quickly taking on enormous proportions – both in size and impact. Expanding from a tented camp, to a town of tin shanties, it soon morphed into a city of modern skyscrapers. Today is the commercial, industrial and financial hub of South Africa. ...

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Founded in 1886, Johannesburg is one of the world’s youngest major cities. The metropole grew up fast, however, quickly taking on enormous proportions – both in size and impact. Expanding from a tented camp, to a town of tin shanties, it soon morphed into a city of modern skyscrapers. Today is the commercial, industrial and financial hub of South Africa.

Johannesburg
Joburg.

Stormwater in a city of Joburg’s proportion is no joke. I lived there once – it’s a beast! In the suburbs there are many trees, but is covers vast areas of grey and hard surfaces. Towards the centre, the belly of the beast is filled with cement, tarred roads and buildings. The way the city is built dictates the route that rainwater takes once it hits all these hard surfaces. In Cape Town, the 21 catchments that city sits on dictates how stormwater is managed there. Durban, again, is located right at the bottom of a catchment, between the mountains and the sea, which shapes the route of rainwater there.

To understand the promise and the peril of stormwater management in any city, you have to understand its location. Let’s look at Johannesburg.

Where Joburg gets its water from

Joburg straddles a major watershed, the Witwatersrand. From here rivers flow either into the Indian Ocean to the east, or to the Atlantic Ocean in the west. Drinking water for the city’s 4 million plus people is imported (purchased in bulk from Rand Water). It’s pumped about 50 km from the region of the Vaal River.

This source, again, is supplemented with water transferred all the way from Lesotho via the Lesotho Highlands Water Project – Africa’s largest ever water transfer project.

One of Johannesburg's conspicuous water towers.
One of Johannesburg’s conspicuous water towers

Rain on the city itself usually falls in short, sharp showers in the summer (between September and April). The area is renowned for impressive thunderstorms and sometimes, explosive hail makes Joburgers run for cover.

Stormwater management in Johannesburg

As with other cities, the approach to stormwater in Johannesburg has been to send the water away as quickly and efficiently as possible. Here, it happens via a combination of man-made infrastructure and natural features. The water is sent towards 12 river systems and 106 dams within the municipal boundaries. This is complimented with detention or retention ponds, as well as wetlands and other natural features that retain water.

The meteoric rate of development has not been without consequence. In particular, the stormwater system and the environment that it is sent to, are showing the strain.

The state of stormwater in Johannesburg

The entire system is described as being under severe stress. For some time already, many parts of it have been functioning close to or beyond peak capacity.

Poor maintenance and budget constraints contribute to the crisis. Estimated annual clean-up costs associated with rain and stormwater (as reported in 2007/8) has spiraled to R25 to 30 million. The bulk is for clearing of stormwater drains from major blockages. Mostly, its blocked by mountains of litter.

Most natural features like rivers have been severely degraded over the years. Wetlands have been progressively filled and drained to make space for the ever increasing demand for urban development.

In addition, portions of streams have been canalised to try and improve their degradation. All surface water quality within the city has been severely affected by the growing city, its blocked sewers, aging infrastructure and the sea of litter transported by the stormwater.

Johannesburg stormwater system.
The Jukskei River, now a polluted and canalised stream that flows through the back-alleys of Joburg.

For Joburg, times of drought, times of floods

As the hard surfaces in the city grew, the runoff patterns and peak flows of rivers in Joburg have were dramatically altered. Though the city suffers from water scarcity at times, it is thus also familiar with floods.

Already, the problems associated with the quantity and quality of stormwater in Johannesburg has a substantial, detrimental knock-on impact on the health and safety of the people that live there. The infrastructure will take more punches due to climate change. This is likely to aggravate existing issues, including increased volumes of stormwater and flooding overloading the already overburdened system.

The people that run the city are not unaware of the situation. The alarm has been raised long ago. Many reports have highlighted these, serious concerns regarding the city’s stormwater (and sanitation) systems.

The potential that lurks in the stormwater system

However, where there are big challenges, there is large room for improvement. For Johannesburg this is encapsulated in policies that are laying the groundwork for water resilience through stormwater management.

“Stormwater is an untapped resource that can help to offset drinking water supply or supplement and reduce the pressure on the stormwater system downstream”, says Jane Eagle, the City of Johannesburg’s Deputy Director for Open Space Planning, that falls under the Department of Environment and Infrastructure Services.

Jane Eagle talks Johannesburg stormwater management
Jane Eagle, the City of Johannesburg’s Deputy Director for Open Space Planning

“To me it is underrated, and offers many solutions,” she says. The flagship work that has been done in this regard in Johannesburg is encapsulated in the stormwater bylaw and draft design manual.

Laws and regulations for stormwater management in Johannesburg

The Stormwater Management By-laws were promulgated in 2010, and addresses some of the key issues regarding stormwater management in the city.

The recent Stormwater Design Manual takes these further and emphasises the retention and attenuation of stormwater at source. It stipulates that the developer must attenuate runoff if the development covers more than 500 m² with impermeable surfaces.

The draft Stormwater Design Manual Guidelines provides detailed requirements for stormwater attenuation and for discharge into the receiving environment. The city has also just embarked on a feasibility study for regional attenuation for supplementing water supply.

Light at the end of the stormwater tunnel

“We are making headway,” says Jane. The stormwater design manual contains “quite revolutionary stipulations”, including requirements for attenuation at all scales. Further, it ensures that runoff meets certain quality standards, reducing the negative impact on the receiving environment and improving the health of the city’s rivers.

In this way, sustainable stormwater management is also seen as key to creating a more resilient Johannesburg in the face of climate change. This includes the basic principles of increased infiltration to decrease runoff and reduce the impacts of floods.

Sustainable stormwater management system in Johannesburg
Walkways that let water through, allowing it to infiltrate into the soil

Critically, the guidelines also addresses the quality of stormwater generated by a property. “It gives you the option to look at complex filters contained in natural systems and green infrastructure,” says Jane. “We are making a call for more green solutions which mimic natural systems,” she says.

Hurdles in the way of change

However, though the groundwork has been laid by the Stormwater Management Bylaws, among others, the benefits have been hampered by slow implementation. Jane says there are a number of challenges to overcome to ensure that there is compliance.

For one, implementation of the policies is held back by a fragmented institutional model, as the provisions need to be applied by both the Johannesburg Roads Agency, as well as Environment and Infrastructure Services Department.

Not only are roles and responsibilities unclear, but the mandates are often conflicting. Traditionally, stormwater was regarded as only the domain of roads departments or entities. They have the responsibility to keep the city safe from flooding, and to ensure that stormwater is efficiently conveyed off sites and roads.

Increasingly, however, stormwater is a concern also for Environment and Infrastructure Services because of the substantial impact that stormwater has on the receiving environment and natural systems. “Building relationships are important, but this requires ongoing effort” notes Jane.

Another challenge is a lack of knowledge on the bigger- scale application and impacts. There is also a lack of skills and experience both in-house and within the profession to correctly apply this. Pilot sites to test and demonstrate effective application of concepts are necessary, but currently lacking.

Blocked stormwater management system in Johannesburg
A blocked stormwater drain in the streets of Johannesburg

A range of roleplayers also need to be brought on the bandwagon. “Engineers, architects and property developers need to be convinced of the validity and co-benefits of these concepts and then take the baton and run with it,” says Jane. There is thus also a need for champions.

The status quo is not an option

The transformation of mindsets is key to transforming stormwater management in Johannesburg.

“I’m not saying sustainable stormwater management is easy,” says Jane. “The question is rather, if we take the rate of development, the increased scarcity of water, and the lurking dangers hidden in our current urban infrastructure in mind, if we can afford not to try.”

Notes

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The promise and peril of stormwater management in Durban http://50liters.com/the-promise-and-peril-of-stormwater-management-in-durban/ http://50liters.com/the-promise-and-peril-of-stormwater-management-in-durban/#comments Wed, 18 Dec 2019 12:26:17 +0000 http://50liters.com/?p=1941 Durban’s location is at once a blessing and a curse. While the city hugs world renowned beaches, it is also placed squarely in the way of rainwater on the way there. As for any city, the route and impact of stormwater in Durban depends very much on where it is placed. Welcome to the eThekwini municipality The eThekwini Municipality, that ...

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Durban’s location is at once a blessing and a curse. While the city hugs world renowned beaches, it is also placed squarely in the way of rainwater on the way there.

As for any city, the route and impact of stormwater in Durban depends very much on where it is placed.

Durban city
Durban’s location is both a blessing and a curse

Welcome to the eThekwini municipality

The eThekwini Municipality, that Durban is part of, is located on the East coast of South Africa. It overlooks the balmy Indian Ocean. The municipality spans an area of about 2 555 km², rich in diverse biodiversity, spread over a steep and dissected landscape.

The municipality has 98 km of coastline, 18 major river catchments, 16 estuaries and 4 000 km of rivers. The city of Durban itself lies low in the catchment. It lies right at the bottom in fact, in the vicinity of the mouth of the Umgeni River.

Lying this low in a catchment full of steep slopes, Durban is familiar with floods. This creates a number of unique challenges, underlined by the rich mixture of people that call it home. It’s not for nothing that Durban is often called a ‘melting pot’ of cultures.

The people of Durban

Most (around 68%) of the municipal area is considered rural with pockets of dense settlement. Commercial farms and metropolitan open space make up about 10% of the rural areas. The rest is hilly, rugged terrain with scattered settlements.

The rest of the municipal area (about 32%) is urban. This is where you will find residential, commercial and industrial developments. There are also many informal settlements scattered across the city, especially towards the borders. These are also often located on steep terrain or flood plains.

The hilly landscape, expanding city and growing informal areas together, have created living spaces ripe to all the possible dangerous impacts of stormwater. Floods, erosion and pollution are rife.

How Durban manages its stormwater

In order to try and keep people and infrastructure safe from stormwater, the municipality maintains an intricate system. This includes just over 3 600 km of stormwater pipes, over 171 300 manholes, 620 km of culverts and canals and 19 detention ponds. Then, a number of attenuation ponds slow down the flow of water during floods.

The whole stormwater system mostly collects the rainwater and sends it directly to the rivers and the sea without treatment.

As with most cities, the system is designed to cater for the probability of floods. You can see this best in the size of the pipes that the water has to go through. The system is built according to the return period of floods (the estimated average time between floods). This statistical measure is typically based on historic data taken over a long period of time.

In Durban, this system is designed to deal with minor and major floods.

Balancing small floods and big floods

Inlets at the side of the road, for example, are designed for a one in three-year return period (a small storm). Major systems like canals are designed for one in 50-year return periods. These are much bigger storm events, says Randeer Kasserchun, Deputy Head of the municipality’s Coastal, Stormwater and Catchment Management Department. “When you get a storm that exceeds the design capacity, you expect flooding,” he explains.

Randeer Kasserchun talks about stormwater management in Durban
Randeer Kasserchun, Deputy Head of the eThekwini Municipality’s Coastal, Stormwater and Catchment Management Department

In this way, Durban has been maintaining a relatively acceptable balance with the stormwater that it generates. In general, the impact of rain is almost unnoticeable. Sometimes, however, more rain falls than what the system can handle. As Randeer says, this then, is when there is a flood.

Be that as it may, the balance is increasingly swinging out of hand. The system is feeling the pressure of a changing environment. More often, the balance is swaying in favour of those times that the system cannot achieve its primary purpose anymore. This is why…

Durban develops ahead of its stormwater system

For one, the eThekwini municipal population is growing rapidly. In 2001 it was 3.09 million. This number is growing at an average of 1.13% each year and reached 3.44 million in 2011. By 2016, the population was some 3.6 million people. Projections place numbers at 4.4 million by 2030. As people increase, so does houses. At the same time, the services that the municipality has to provide has to be cranked up.

As the developed area expands, more areas are covered with things like buildings and streets. Now, water that would have filtered into the soil, rushes down hard surfaces, downwards. The municipality has experienced a dramatic increase in the velocity of river flows.

“People expect all of that extra water to go into a pipe, but it was designed to only cater for a specific proportion of water,” says Randeer.

The great headache of stormwater pollution

Except for the quantity of stormwater, the quality is a big headache. In particular, trash has become a forceful foe to reckon with.

“Our biggest problem is pollution,” says Randeer. We have both soluble and non-soluble contaminants in the water, so while water quality is a challenge we also get huge blockages caused by litter, which impacts negatively on the stormwater system capacity, he says.

Durban’s rivers and estuaries are feeling the punch.

In 2010, an estimated 40% of rivers were considered to be in a poor condition and only six (or just over 3%) were classified as near natural. Only about 10% of the total municipal estuarine areas were classified to be in good condition. The results are due to impacts from multiple sources. Still, the quality of stormwater is said to be a big contributor.

The consequences ripple out far and wide. The rivers become highways that transport litter and pollution to Durban’s famous beaches, a huge drawcard for the tourism-dependent city. And, says Randeer, the poorest of the poor is often the most harshly affected. Often, they still directly depend on the services offered by the rivers and streams that they live next to.

Durban's polluted beaches
Durban’s famous beach front

The municipality has been driving various initiatives to try and improve the situation.

The responsibility of home owners

Fore one, building regulations ensure that stormwater runoff from individual properties is reduced, says Randeer. For Durbs, the stipulations are provided in the municipal Guidelines and Policy for the Design of Stormwater Drainage and Stormwater Management Systems. This policy places the responsibility of managing and reducing runoff in the hands of the property owner. This is because they are increasing the impermeable surface area of the city when they build. As a result, they are creating more stormwater runoff.

This is a problem because, back in the day, the municipality designed the piped stormwater systems on the basis that not more than 40% of the area of the residential properties would be hardened. This is no longer the case. Now, many properties have hardened their sites with extra patios, canopies, entertainment areas and pool surrounds.

Commonly, there are now more driveway and parking areas and larger garages. All of these improvements increase the stormwater generated from the sites. This now calls for onsite management, harvesting and retention of rainwater.

As a result, the owner of any development connected to the eThekwini municipal stormwater system, of which more than 40% of the surface is hardened, must manage the excess runoff generated from his site.

“We would not approve your development if you do not adhere to this stipulation,” says Randeer.

How you can manage your stormwater

The policy also stipulates preferred options to manage stormwater runoff. These include options to keep it on site (retain it) or catch it to make use of it (harvesting).

Soakpits (which allow rainwater to infiltrate into the groundwater table, or to tanks for reuse) are suggested as the better, responsible and preferred option. Guidance for a range of other controls is also supplied, such as attenuation ponds and stormwater harvesting tanks.

In this way the municipality is actively promoting rainwater harvesting. People can then use it in gardens, to flush toilets and wash cars, for example. The guidelines also stipulate that paving, surfaced driveways, pool surrounds and the likes should mostly drain to buried tanks unless the topography allows otherwise.

Green roofs are another option seen to hold great potential in Durban. The municipality’s Environmental Planning and Climate Protection Department initiated a Green Roof Pilot Project (GRPP) in 2008. The project investigated the effectiveness of green roofs in Durban, in particular to reduce temperatures and stormwater runoff. Results proved to be very promising in Durban. (In Toronto, green roofs have proven to be an extremely efficient, and budget friendly, stormwater management approach.)

As part of the initiative in Durban, guidelines for the design of green roof habitats were developed.

Green roof at Durban Municipality
Durban’s Green Roof Pilot Project

Why stormwater is not harvested in Durban

However, large-scale harvesting of rainwater across the city is hampered by its location. “We are right at the end of the catchment, so for us to catch and use large-scale stormwater runoff we’d probably have to pump it upwards again for storage somewhere,” says Randeer.

Not only would this result in more costs and infrastructure, but it’s also not practical to create a dam in Durban.

How they are managing the stormwater quality in Durban

Ongoing campaigns are run to improve the quality of stormwater runoff across the municipality. For one, nets have been constructed at some of the main catchments of the area to capture the vast amounts of litter before it washes downstream.

Here, Randeer sees one of their biggest challenges to change people’s mindsets about their contribution to the problems the municipality has to manage.

To try and change that, the municipality now runs regular clean-up and awareness campaigns. “Our catchment management education work is extremely important.” Randeer says they also focus heavily on schools. “We aim for the messages to be taken home by the children from school,” he says. “When a parent wants to throw their cigarette butt out of the window, the hope is that the child will tell them not to do that.”

Different city, different stormwater management issues

This then, is how Durban is trying to work more sustainably with its stormwater. In this city’s case, the bigger challenge is not how to use the water that is ‘going to waste’, but rather how to keep people and the environment safe from the impact of the water. The journey ahead is a long and arduous one.

Now, compare this to the journey that Cape Town is on. This city’s location is resulting a vastly different perils, and promises a completely new opportunity for development.

Notes

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The promise and peril of stormwater management in Cape Town http://50liters.com/the-promise-and-peril-of-stormwater-management-in-cape-town/ http://50liters.com/the-promise-and-peril-of-stormwater-management-in-cape-town/#respond Wed, 11 Dec 2019 08:16:50 +0000 http://50liters.com/?p=1939 Cape Town is a place like no other. That’s why millions of local and international visitors stream to the city’s famous shores each year. A large part of the attraction is the natural environment that it’s built on – not only the famous Table Mountain, the endless beaches and the icy sea, but also a vast array of rivers and ...

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Cape Town is a place like no other. That’s why millions of local and international visitors stream to the city’s famous shores each year. A large part of the attraction is the natural environment that it’s built on – not only the famous Table Mountain, the endless beaches and the icy sea, but also a vast array of rivers and wetlands.

In Cape Town, life happens in close collaboration with nature, and the city is intimately dependent on the services it supplies (also known as ecological services).

“Cape Town is very unique,” says Richard Nell, Head of Strategy Specialist Support for the City of Cape Town’s Catchment, Stormwater and River Management Division. He explains that Cape Town actually sits on 21 catchments, which are the mainstay of its stormwater system.

A city with a natural stormwater system

Though the city mostly depends on rainfall for its water supply, this is imported via a supply system of six dams outside the municipal boundaries. The rain that falls on the city itself mostly drain as stormwater into the mentioned rivers to the sea.

The Berg River Dam supplies water to Cape Town
The Berg River Dam now supplies water to Cape Town, located many kilometres away.

The system that keeps the city safe from flooding is actually a combination of built stormwater infrastructure and natural systems. The backbone of the stormwater system is about 1 920 km of rivers and 7 800 man-made and natural wetlands. Built infrastructure includes 5 100 km of pipes, 500 km of channels and canals, 10 stormwater dams, 892 detention ponds, 35 pump stations and 64 rainfall and flow monitoring stations.

The challenges of stormwater management

The challenges that the city faces regarding stormwater management, are similar to the problems experienced by cities across the globe. Richard lists some of these to include old infrastructure, failure of small pump stations and “development that gets ahead of itself”.

Stormwater management system in Bo-Kaap, Cape Town
There it goes! Stormwater drains in the Bo-Kaap, one of Cape Town’s oldest suburbs.

Urban growth is outpacing the capacity of the stormwater infrastructure, he says. In Cape Town, challenges like these are made worse during the winter rainfall season, when water from stormwater system can overflow into the sewage treatment works and overload the infrastructure.

Pollution is another problem. Litter, garden waste, dog poop and industrial pollution are but some of the endless list of things that contribute to contamination.

Richard says that they also often encounter some forms of sabotage. People put things like mattresses and lawnmowers down the system which causes blockages and overflows, he says. “Throughout the city there are huge pollution problems.”

Though the bulk of the city’s stormwater management to date has focused on managing runoff quantity and quality, the municipality was one of the earliest in South Africa to embrace the principles of Sustainable Drainage Systems, or SuDS, towards becoming a water sensitive city.

Cape Town embraces sustainable stormwater management systems

They started around 2005, says Richard, and this work resulted in the promulgation of two policies in 2009. Both took their lead from the water sensitive cities concept in Australia.

The Management of Urban Stormwater Impacts Policy aims to “minimise the undesirable impacts of stormwater runoff from developed areas by introducing Water Sensitive Urban Design principles and SuDS to urban planning and stormwater management in the Cape Town metropolitan area.”

The second, The Floodplain and River Corridor Management policy recognises the importance of watercourses and wetlands to the stormwater management system, the city’s biodiversity network, and recreational and economic opportunities.

The objectives of this policy are to reduce the impact of flooding on communities and the economy, keep us healthy, protect the natural aquatic environments, and improve and maintain water quality for recreational purposes.

Richard says that the concept of SuDS was initially a tough sell, and the uptake slow, especially from technical experts. “Roads engineers traditionally look at stormwater as the enemy, and that’s a difficult mindset to change.”

Still, since then the municipality has forged ahead. The concept has progressively been incorporated into development plans.

Big plans start with small steps

For one, the management of catchments and stormwater was moved from the previous Roads and Stormwater Department, to fall under the jurisdiction of Water and Sanitation.

“In the past we use to issue directives against the sewage department, but now we collaborate with them,” says Richard.

While the city’s stormwater bylaw and the two policies are under review, a green infrastructure plan is in process to help sustainable management of valuable natural infrastructure (this is stuff like wetlands and rivers). A comprehensive water resilience strategy is also being written. This will identify challenges and opportunities for the city.

Though the municipality has been working away at more sustainable stormwater management for years, the topic was thrust in the spotlight during the recent water crisis. At that time, stormwater was punted as an untapped water resource going to “waste” seeing as very small amounts of stormwater is currently put to use. In fact, Richard puts a rough estimate at less than 10%!

However, he points out that changing this is not as simple as it may seem.

Tapping into the potential of stormwater in Cape Town

The biggest problem of stormwater harvesting in a winter rainfall region is that you’re receiving the water when you don’t need it, he says. The water thus needs to be stored somewhere until necessary, usually in a dam or reservoir, large infrastructure for which very limited space is left in Cape Town.

Storing the water is not the only challenge. First, it has to be captured. Some of the municipal rivers are short, with small catchments, leading to quick runoff during rain.

The road of stormwater in Cape Town
It’s easy to see that Cape Town is a city still heavily dependent on nature. Still, steep slopes, such an iconic part of this city, make catching water more difficult. Once it falls, it goes!

Should you try to capture the water upstream, time to do so is even more limited, while attempts to capture the water close to the outfall leaves the upstream system vulnerable to floods.

Furthermore, the infrastructure underlying the city has been built to accommodate water pumped from outside, limiting its capacity to transport a sudden increase of water supply from sources within.

The challenges continue

While storage and transport are issues, so is water quality. Seeing as Cape Town’s main water supply is from outside the city, this is also where the potable water treatment plants are located.

Should water be harvested in the city, it would call for construction of suitable treatment facilities too.

Our cities will develop even more in future.
Cape Town – now where can we put that water treatment plant, or dam?

There are small stormwater harvesting schemes currently active in the city for purposes of irrigation as one example. But, says Richard, the challenges particular to Cape Town has led to the general idea that stormwater harvested here would not be stored, but rather be treated to a good enough quality to be returned to the rivers. In this way, less water needs to be abstracted from dams.

Taking this is mind, (at the time of the interview) the city is in the process of writing a stormwater harvesting strategy.

Bringing Capetonians back to the rivers

One of the biggest thing we have to get right is to attract people back to the rivers, says Richard. “The minute people see rivers as an asset they will care for them better.” Richard mentions places like the Kruger National Park and Singapore as examples. Though these are vastly different, they are both places where rivers are loved, and favourite destinations for visitors to relax and enjoy. As a result, there is strong public sentiment for their conservation.

“In Cape Town many of the rivers and wetlands have become places where people don’t want to be.” Instead, the rivers are used as dumping grounds, rather than public spaces to enjoy and conserve.

This will be addressed in the strategies under development. “We are working towards livable urban waterways,” says Richard. This includes creating places where people can grow gardens and spend their leisure time. “We want to open up canalised rivers to create blue green corridors throughout the city,” he says. These will create pleasing spaces for people to enjoy, while serving practical purposes like water quantity and quality management.

The difficult thing is to change people’s mindsets, he says. Should the municipality be able to do this, both within the public domain and governmental spheres, Cape Town too can become a place where the rain is embraced once again.

Notes

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Pushed aside, Atlantis once took the lead for water wise cities http://50liters.com/pushed-aside-atlantis-once-took-the-lead-for-water-wise-cities/ http://50liters.com/pushed-aside-atlantis-once-took-the-lead-for-water-wise-cities/#respond Mon, 09 Dec 2019 16:26:41 +0000 http://50liters.com/?p=1937 In fiction, Atlantis is a city that fell out of favour with the deities and sank to the bottom of the ocean. In South Africa, the town of Atlantis had similarly volatile dealings with the powers that be. But, it will go down in history books as a place that rose above one of its biggest challenges. Placed far away ...

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In fiction, Atlantis is a city that fell out of favour with the deities and sank to the bottom of the ocean. In South Africa, the town of Atlantis had similarly volatile dealings with the powers that be. But, it will go down in history books as a place that rose above one of its biggest challenges.

Placed far away from water, Atlantis has become an example of a water wise city long before its time.

Atlantis was established as a ‘growth point’ according to the apartheid-based development plans of the then-government. Located 50 km north of Cape Town along the west coast, it was to be a coloured-only town with incentives to attract industries.

Judging by sight alone, the area displays an almost complete lack of water. Yet, in part due to its unpractical location, it has become an award-winning example of a water resilient city long before many others caught onto the concept.

At Atlantis, stormwater and treated effluent, traditionally seen as waste-water, were used as major resources of water to create a water secure settlement. Only around 25 years after it was founded was more water piped into the town from further away.

Water out of sight, but not out of bounds

The development of Atlantis started in 1976, planned to grow to up to 500 000 residents. Government also provided incentives to industries to move there. Water was initially supplied from a local spring (the Silwerstroom) and boreholes, but it was always understood that these sources would not be enough over the long term.

The challenge was that Atlantis was located far away from most other possible sources. The closest was the Berg River 70 km away, where the Misverstand Dam was commissioned to accommodate water demand from Atlantis. This was, however, far too far in the future to ease the already-existing concerns of water supply.

Thinking out of the box, and under the ground

Town planners and engineers had to make another plan. For a solution, they turned their eyes underground. Atlantis is located in a semi-arid type climate. Most of the 450 mm rain that falls there, does so between April and September. Up to 30% of this water drains into the aquifers. This is where the town has drawn its water from since its establishment.

The town actually rests on the Atlantis aquifer, a groundwater system that covers an area of about 130 km² inland from the Atlantic Ocean to the town itself. The groundwater enters the aquifers through the sandy surface, in particular, at the bare sand dunes, and then flows towards the coast down a relatively steep gradient.

The aquifer originally drew the attention of town planners because of changing laws. In South Africa, it used to be common to get rid of waste water by pouring it in the sea, but by the 1970s the public really started complaining about this.

At the same time, government started seeing the practice as a waste of valuable water. This eventually led to a change in laws. Suddenly, municipalities needed to make alternative plans with their dirty water.

From finding new water, to re-using used water

At Atlantis, the recharging of stormwater and treated wastewater into the aquifers through the sandy soils started in 1979. Unusual at the time, it was also to here that town planners and engineers turned their attention when they had to make new plans to ensure a secure water supply for the town. They decided to shift their focus to recharging and recycling water in order to increase the yield of the aquifer enough to meet the long-term water needs of the town.

New choices, big changes

This decision resulted in major developments. First, stormwater was used to top up the aquifer and eventually, domestic and industrial waste water were separated to allow for only the best quality water in the areas of greatest importance.

The Atlantis Water Resource Management Scheme

As a result, the Atlantis Water Resource Management Scheme (AWRMS) could make use of treated domestic effluent (wastewater), all of the domestic stormwater, and most of the industrial stormwater for recharging the aquifer. Throughout, the undertaking was also that no water of a lesser quality should be put back into the aquifer. As a result, the town was supplied totally from groundwater for over two decades, while enhancing the local environment in the process.

The Atlantis Water Recharge Management Scheme (AWRMS)

In a nutshell, the AWRMS is a great example of managed aquifer recharge, or MAR, in practice. MAR is an indirect water recycling method through the transfer of surface water underground. The water is then stored in an aquifer either via infiltration from basins, dams or ponds or through injection boreholes.

In this way water can be stored during wet periods or when there is more than enough, to be abstracted during dry periods. In the process, water and the environment is conserved. As a result, dams aren’t necessary and because the water is stored underground, the minimum is lost to evaporation. In addition the water is relatively safe from pollution and the porous medium (in this instance, sand) through which it infiltrates acts as a filter to improve water quality.

Why Atlantis, and not everywhere else?

Part of the relative ease with which the practice has been applied at Atlantis is due to town planning. The layout of the town allows for the separation of stormwater from the industrial and residential areas as well as separate treatment of domestic and industrial wastewater. Stormwater and industrial wastewater are channeled into separated systems to each undergo sufficient treatment.

Domestic wastewater undergoes full treatment and is sent towards a series of maturation ponds. Stormwater from the residential areas is collected in a system of detention and retention basins and blended with the treated domestic wastewater. This is then sent into the main recharge basins for artificial recharge of the Witzand wellfield.

The stormwater from the industrial area is more saline, and is discharged into different recharge basins along the coast. From here it seeps into the ocean through the subsurface. This also helps prevent that seawater flows back into the aquifer.

Water for the town’s people and industries is then abstracted from the Witzand and Silwerstroom wellfields. The first contains a blend of natural and recharged water, and the second contains natural groundwater. It is estimated that the groundwater abstracted as part of the AWRMS represents a blend of 30% water derived from recycling and 70% natural groundwater.

The performance of the water recycling system at Atlantis has proven to be relatively good. Based on what we know, the recycling of the water does not threaten the drinking water supply.

A complex system that needs expert management

The AWRMS is a complex, large-scale system that depends on specialised management. Long-term sustainability of the system depends on proper maintenance of all components, requiring a multidisciplinary approach. The challenges are many.

The challenges to run the system

New pollutants and varying quality of groundwater throughout the system are some of these challenges. The erratic quality of urban run-off and wastewater add to this. As fine sediments and organic material settle on the bottom of recharge basins over time, it gets clogged.

If too much water is extracted from the aquifer the water levels drop, allowing air into the system. This disrupts the balance of the natural ecology at the borehole site and can lead to fouling of the water.

Uncontrolled abstraction by illegal users, and invasive alien plants affects predictions of how much water exactly can be taken out. The natural characteristics of the aquifer material, such as calcrete and calcareous sands affect the groundwater quality. As a result the water tastes a little hard.

Furthermore, the Atlantis aquifer is unconfined and thus vulnerable to pollution from several other sources.

Looking beyond Atlantis

The planned water supply to Atlantis from the Berg River system was never realised. Since 2000 the town’s water supply has been linked to the Cape Town distribution system. Some water also come from a reservoir at Melkbosstrand.

The town also never reached the potential that was originally envisioned. It was later joined with the metropolitan area of Cape Town. A 2011 census reported a population of just over 67 000 residents.

Still, the town stands as a good demonstration of stormwater harvesting and treated sewage effluent reuse at scale. Ultimately, the Atlantis Water Resource Management Scheme has proven to be an innovative scheme to supply bulk water for drinking and industry. It has proven that these types of recharge schemes can work.

It set an example that others now follow

A pioneering innovation at the time, it resulted in new thinking about stormwater and wastewater in the Cape and beyond. For one, the concept of ‘natural groundwater recharge’ was included in the City of Cape Town draft stormwater by-laws.

Furthermore, lessons from Atlantis contributed to the development of the then Departments of Water Affairs and Forestry’s National Artificial Recharge Strategy in 2007.

The city of Atlantis has a checkered past. Yet, it has shown that bulk reuse of stormwater and wastewater is possible, and sustainable.

As such, the legacy of Atlantis has not become one of the failures of the past. Rather it’s an example of how to meet the future.

Notes

  • This blog was included in the book, Water Resilient Cities, I wrote for the Water Research Commission. Atlantis really is a fascinating example. It shows us what we can do if we practice sustainable stormwater management. Its one of the key concepts of a water resilient city which, again, is a key concept for cities that will face dryer futures.
  • The lead photo is of one of the AWRMS’s coastal infiltration basins
  • The lead photo and graphic is from the publication, The Atlantis Water Resource Management Scheme: 30 years of Artificial Groundwater Recharge, published by the Department of Water Affairs in August 2010.

Sources

  • The Atlantis Water Resource Management Scheme: 30 years of Artificial Groundwater Recharge, published by the Department of Water Affairs in August 2010.
  • Water Management in Atlantis, by N Armitage, PB King and ATP Bishop

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Gough: The remote island that brings the weather close to home http://50liters.com/gough-the-remote-island-that-brings-the-weather-close-to-home/ http://50liters.com/gough-the-remote-island-that-brings-the-weather-close-to-home/#respond Thu, 05 Dec 2019 10:11:43 +0000 http://50liters.com/?p=1961 Every October, a small crowd gathers at the East Pier Quay at Cape Town to welcome the SA Agulhas II home. On-board is a small group of people that just spent a year at one of the most remote places on Earth with a constant human presence. It’s called Gough Island. The Subantarctic and Antarctic are extreme regions both in ...

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Every October, a small crowd gathers at the East Pier Quay at Cape Town to welcome the SA Agulhas II home. On-board is a small group of people that just spent a year at one of the most remote places on Earth with a constant human presence. It’s called Gough Island.

The Subantarctic and Antarctic are extreme regions both in look and feel. Conditions are harsh, and landscapes daunting. Yet, we keep on sending people there, for the weather.

Gough-Island-by-Tom-McSherry
Gough Island (photo by Tom McSherry)

Where is Gough Island?

Gough is described as a lonely place. The total human population numbers five to eight people: three meteorologists, a doctor, a diesel mechanic and field assistants. Though most South Africans are unaware of the small team’s presence on Gough, their persistent work benefits us all, and reverberates far beyond the borders of the country.

Gough Island lies about 2 600 km from Cape Town, and just over 3 200 km from the point closest to us in South America. The island is part of the Tristan da Cunha group of islands, which lies about 400 km North West from Gough. The islands are, with Saint Helena, British territory.

Since the 1950s, South Africa has been leasing a patch of land to run a weather station, which is now technically a district of Cape Town. The weather station is managed by the South African Weather Service (SAWS). The members of the teams stationed there are part of the South African National Antarctic Programme (SANAP). As with all of the country’s Antarctic stations, it is administered by the Department of Environmental, Forestry and Fisheries, Directorate: Southern Ocean and Antarctic Support.

Inspecting-the-Stevenson-screen on Gough Island
Inspecting the Stevenson screen on Gough Island (photo taken 1978)

Gough Island is 91 km² big. Peaks rise to 900 m above sea level. There are also small satellite islands and rocks; places like Saddle Island, Round Island, Cone Island, Lot’s Wife, Church Rock, Penguin Island and The Admirals. Conditions are harsh. The island clings onto the edge of the “roaring forties” in reference to its location between 40° and 50° south in the South Atlantic, and the frequent gale-force winds. Summers are cool, rain falls often and sunshine is scarce.

This then, is where the South African team observes various climatic parameters and keeps an eye on the automatic weather station. Port Meteorological Officer for the SAWS (Cape Town Weather office), Mardené de Villiers, explains that they do this in 24 hours shifts, 365 days a year.

Gough Island and weather forecasts

The automatic weather station includes temperature and humidity sensors, a wind sensor and a pressure sensor, says Mardené. The observer on duty, one of the three meteorologists based on Gough also temperature, humidity, pressure, wind speed and direction, horizontal visibility, cloud height and type, present and past weather, and rainfall.

Twice a day they also launch a weather balloon into the upper atmosphere. Mardené explains that the balloon’s flight into the upper air provides a crucial vertical profile of the atmosphere. Here, the instruments collect real-time temperature, humidity, pressure and wind speed and direction.

Gough Islands birds
A young Wandering Albatross (Photo by Tom McSherry)

Last, she says, they also monitor data from a mounted weather buoy on Tristan da Cunha, where valuable atmospheric pressure data is collected.

The weather station thus operates much in the same way as others across South Africa, which also commonly provides hourly climate observations and upper-air ascents (the weather balloons). Yet, the volcanic island’s location makes the data from here particularly important.

Data from the west

The majority of the weather systems affecting South Africa originate to the west of the country, says SAWS Senior Forecaster, Kate Turner: “This is because the predominant wind flow that governs these weather systems is from west to east, which results in the weather systems affecting South Africa moving in the same direction.” As a result, it is crucial to have data stream to the west of South Africa to understand and gather information of the approaching weather, she explains.

Looking to what lies to the west of country, the choices of locations for weather stations are severely limited. In fact, the whole region is described as “extremely data sparse for climate studies”. Gough is one of the few locations filling this gap.

Kate says that the data from Gough is not only beneficial for information on approaching weather systems, but also for a better, 3D picture of the atmosphere. This data gets fed into numerical models to show us the state of the atmosphere.

“The more data points we have from across the southern African domain, including land and ocean, to “colour in” and map the current state of the atmosphere, the better the model forecast will be.” If you do not have good and sufficient data to feed into the models, she says, you cannot expect good, high quality forecasts.

As such, the data from Gough is really important for weather forecasts and for warnings of looming severe weather. Kate says that the data gathered from Gough and other stations over the decades is “extremely important” not only for research purposes, but also to understand climate conditions and to map climate change.

The impact of the data ripples across and beyond South Africa.

Why we should care about this data

First, it is used for direct day-to-day forecasting for the island itself and particular operations that require an indication of the weather, says Mardené .

Then, the data from here is vital to forecast weather across southern Africa. “The data is also sent to the Global Telecommunication System (GTS) where various international users access it to be incorporated into global weather models.” Last, it is also used for various research projects.

Now reaching back over half a century, the data set from Gough has become indispensable to local and international climate studies. We access the fruits of their labour easily. We can see it every time we check the weather forecast online, open the newspaper or watch it over the news.

Gough Island weather readings
As was required by the Weather Service the weather balloon is released on Gough Island twice a day (photo taken in 1968)

Still, the effort that goes into the data is more obscure. Digging into the archives of the Antarctic Legacy of South Africa, our history in the region is marked by great achievement, as well as tales of “mutiny, attempted murder, shipwreck, drownings and much more.” That’s how it was described by Lieut. Frank McCall, who led the first missions to build South Africa’s weather stations in the region.

A tale of great adventure

South African activities in the Antarctic already began in the previous century, when sealers launched their ships there from Cape Town. The national flag of the Union of South Africa was formally raised on Marion Island for the first time on 29 December 1947. The feat was part of operation Snoektown, a naval operation during which the uninhabited, Subantarctic archipelago of the Prince Edward Islands was officially annexed by South Africa.

According to Lieut. McCall, “The story begins in 1954 when Jannie Smuts, the Prime Minster of South Africa, sent a confidential message to certain scientific authorities warning that South Africa had better occupy the Prince Edward Islands before Russia did. This would be by means of a weather-research station.”

Volunteering for the job, McCall wrote of “a lonely, wild, volcanic island halfway to the Antarctica mainland,” where they subsequently put a small group of weathermen in a tiny hut. “They were the only human inhabitants,” he wrote. “This was Marion Island.” At least one relief expedition per year to the weather station on Marion has been carried out ever since.

Motivation for the establishment of the next weather station, on Gough, was driven by the International Geophysical Year of 1957/58. The initiative entailed scientists from around the world taking part in a series of coordinated observations of various geophysical phenomena.

Activities spanned the globe from the North to the South Poles, but special attention was given to the Antarctic. Here, research on ice depths yielded radically new estimates of the Earth’s total ice content. The research also contributed to improved meteorological prediction, advances in the theoretical analysis of glaciers, and better understanding of seismological phenomena in the Southern Hemisphere.

Team members of Gough 8 preparing the catch of the day for a meal.

The weather stations that followed

In preparation, the weather station was established on Gough in 1956, to be operated by South Africa. McCall writes of a mission to “work out where to put a base on that uninhabited island which lies south of Tristan Da Cunha.” Pending the building of the base, he writes, some weathermen were left there in a small hut. McCall writes that on his return six months later, the leader was “raving”. “He had tried to exercise authoritarian rule over his group and they “sent him to Coventry” (refused to talk to him.)”

A weather station was consequently built at a place called ‘The Glen’, and later moved to the South Western lowlands of the islands (in 1963) for more accurate weather observations.

South Africa has paid expensively for its presence on Gough. According to a History of South African involvement in Antarctica and at the Prince Edward Islands by J Cooper and RK Headland, “Gough Island may be reckoned as a dangerous place: four team members have died there since 1956, three by exposure in the mountains and one by drowning while fishing.”

SANAP’s last scientific station was built on the Antarctica mainland in 1961. First called Norway station, it was later renamed South African National Antarctic Expedition (SANAE) and has been in continuous operation since. The current South African research base, SANAE IV is located at Vesleskarvet, Queen Maud Land.

Though it cannot be described as a hospitable environment to humans, Gough Island is special for various reasons beyond meteorology. It’s a UNESCO Natural World Heritage Site, a Ramsar Wetland of International Importance and part of the Tristan da Cunha Nature Reserve. It’s also been declared an Important Bird and Biodiversity Area, and is considered home to one of the most important seabird colonies in the world.

Gough’s other inhabitants

Gough Island is one of the only homes to the critically endangered Tristan Albatross. January dated newsletters written by those stationed there, tell of the interior of the island dotted with white birds nested on mounds that hold their enormous white eggs. While the Tristan Albatross is perhaps its most famous avian inhabitant, the island is also home to almost the entire global breeding populations of the endangered Atlantic Petrel and MacGillivray’s Prion.

Tristan albatross on Gough Island
A Tristan Albatross (Gough Island)

These are some of the 22 breeding seabird species found on Gough Island. It’s also home to 35% of the population of the endangered Sooty Albatross, and about 20% of the endangered Atlantic Yellow-nosed Albatross. The Gough Finch and Gough Moorhen are endemic to the island.

Unfortunately, the birds are paying a price for people arriving at the island. Docking at Gough in the 19th century, house mice reportedly arrived with those sealers. They are famously big, having grown substantial larger than house mice elsewhere due to the favourable conditions the island offers. There are no natural predators or competition for the food that’s available in ample supply.

Especially in winter, this takes the form of vulnerable Tristan Albatross and Atlantic Petrel chicks. Bird numbers have dropped dramatically as a result. In partnership with the Royal Society for the Protection of Birds, the Department of Environmental, Forestry and Fisheries is launching a mice eradication programme in 2020.

Do you want to go to Gough?

The island is not completely out of bounds to South Africans. As per agreement, the annual Gough Island relief voyage with the SA Agulhas II also takes paid passengers to Tristan die Cunha on its outward and return voyage, stopping at Gough along the way. For most of us however, the near imperceptible connection to Gough remains to be via our everyday weather forecasts.

Notes

  • Thanks to the Antarctic Legacy of South Africa (ALSA) for the photographs used in this article.
  • The featured image was taken by Tom McSherry
  • This article was first published by the Water Research Commission, in the Nov/Dec 2019 edition of the Water Wheel

Sources

  • History of South African involvement in Antarctica and at the Prince Edward Islands by J Cooper and RK Headland (S. Afr. Antarct. Res., Vol 21 No 2, 1991)
  • Where is Antarctica, by Lieut. Frank McCall, 1955 (general report on his visits to Antarctica and Sub-Antarctic islands.)
  • https://www.environment.gov.za/projectsprogrammes/ antarctica_southernoceans_islands
  • The Antarctic Legacy of South Africa archives (http://blogs. sun.ac.za/antarcticlegacy/)
  • The impacts of introduced House Mice on the breeding success of nesting seabirds on Gough Island by Anthony Caravaggi, Richard J. Cuthbert, Peter G. Ryan, John Cooper and Alexander L Bond, published in the Ibis International Journal of Avian Science: , 22 October 2018
  • http://www.nas.edu/history/igy/

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How green roofs save Toronto on the cheap http://50liters.com/how-green-roofs-save-toronto-on-the-cheap/ http://50liters.com/how-green-roofs-save-toronto-on-the-cheap/#respond Wed, 04 Dec 2019 11:27:18 +0000 http://50liters.com/?p=1923 Toronto, Canada’s most populous metropolitan area, sits anchored on the northwestern shore of Lake Ontario. The city is incredibly diverse. The roughly 2.7 million people here speak over 160 languages. The city rests on a broad sloping plateau crossed with rivers and ravines, though the skyline is marked by skyscrapers and high-rise buildings. The city is famous for being one ...

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Toronto, Canada’s most populous metropolitan area, sits anchored on the northwestern shore of Lake Ontario. The city is incredibly diverse. The roughly 2.7 million people here speak over 160 languages. The city rests on a broad sloping plateau crossed with rivers and ravines, though the skyline is marked by skyscrapers and high-rise buildings.

The city is famous for being one of the most multicultural and cosmopolitan cities in the world. However, it’s also making waves for its innovative developments; in particular for choosing to go with green roofs.

Green roof management in Toronto
The green roof atop the King West building in Toronto, Canada

What is a green roof?

A green roof is a roof of a building that is partially or completely covered with plants. At a minimum, a roof should include a root repellent and drainage system, filtering layer, growing medium and plants. It should be built on a waterproof layer.

Making green roofs law

Toronto is the first City in North America to have a bylaw that requires and governs green roofs on new developments. Since 2010, new developments bigger than 2 000 m² must include between 20% and 60% green roof space.

Published with the bylaw, green roof construction standards and guidelines provide people with best practices and instructions. It provides information, for example, on the depth of growth media and plants to choose from. These are usually native or adaptive from the Southern Ontario area, appropriate for the local climate and building exposure. Plants that do well in drought are usually recommended and the list results in a variety of species to be grown across the city.

The Toronto City Hall green roof

Why should you choose green roofs?

Green roofs have many benefits. They help to cool cities. In the process, energy bills that would have been racked up to do this with electricity are reduced. By soaking up rainwater, they help to reduce flooding. Plus, less pollutants and litter now enter the stormwater system. It’s a prime example of what we are working towards when we talk about sustainable stormwater systems. Plants improve air quality, the city is left looking more beautiful and with more biodiversity.

Yet, one of the biggest reasons for Toronto to push for the implementation of green roofs, is money.

Green roofs make financial sense

The city’s 2006 Green Roof Strategy follows on results of a study that showed that widespread green roofs would provide significant economic benefits.

According to Shayna Stott, environmental planner at the City of Toronto, the study estimated benefits based on 4 984 ha of potential green roof implementation. The financial benefits are staggering.

Stormwater benefits amounted to an estimated infrastructure saving between $2.8 and $79 million. A pollutant reduction benefit of $14 million could be achieved, and savings from erosion control measured $25 million. The total stormwater benefit was estimated to range from $41.8 to $118 million.

Since the bylaw was passed, permits for approximately 420 green roofs for a total of approximately 400 000 m² of green roof area have been passed, says Stott. At the time of the interview, a triple bottom line analysis on costs and benefits was in the pipeline.

Green roofs against climate change

Except for the financial benefits and other mentioned above, Stott says that “green roofs are part of the toolkit required to make Toronto more resilient to the impacts of climate change, which will include hotter, wetter and more intense climate”.

As such, green roofs are always factored into the required stormwater analysis for development applications to the city. “They are a key strategy in meeting our requirements for water to be retained onsite,” she says. While an analysis of the collective benefits of green roofs in the city was in the pipeline, the existing benefits were already so clear that the programme was being expanded.

“Because our requirements apply to new development only they are helping to mitigate impacts on those buildings,” says Stott. Yet, there are still stormwater issues related to the vast majority of buildings that existed prior to the requirement. “We are in the process of increasing stormwater requirements and as such green roofs will play an even more important role in meeting the higher standards.”

Notes

  • All photos were kindly provided by the City of Toronto
  • As mentioned, green roofs are an excellent example of sustainable stormwater management. This again, is where the whole movement of water resilient cities started. Don’t know exactly what this is? Read this – it’s an overview of everything you should know.
  • Wondering why all of this matters? This is why we must save water.
  • Thank you again to the Water Research Commission (WRC) in South Africa, who published the book Water Resilient Cities, where this blog was first published

Sources

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