"Examining water, agriculture, and wet waste"
Sean Maciel - Miguel Sanchez Enkerlin - Nathan Wang - Beatris Bogomilova - Felix Cheong - Myles McCaulay - Ashley Pacheco - Sabrina Leung

November 4, 2009

Container Agriculture in Mexico City

By Miguel Sanchez Enkerlin

As a result of the droughts on the Mexican countryside, food prices have gone up, something which is logically inconvenient for those in the city living under the poverty line (the majority). In 2001 a group of around 20 Non-Governmental Organizations, by the name of ANADEGES, launched a project to develop a system for the people to grow their own food and hence become autonomous. The aims of the project were to create the most affordable and healthy supply of food possible, for this to be achieved the new technology had to require little to no infrastructure investment, require no chemicals, require little to no land, and be light enough to be cultivated on rooftops. By amateur experimentation of trial and error, which took over 3 years. The technology developed does not only meet these aims, but also creates a system to recycle certain garbage’s. Drainless containers, between 18 and 20 liters in capacity, 4/5 of the containers are filled with recycled leaves or grass clippings, the other 5th is good soil, where the seeds will be embedded. Holes are drilled just above the bottom to allow drainage while keeping a water reservoir for the plant. This composition makes the container much lighter. The issue of fertilization was perhaps the most clever solution; urine. Chemical fertilizers had an additional cost and relatively ineffective, particularly in the container farming, whereas urine was organic, domestically made, and much more effective. The immensely useful fertilizer was given a fancier name, liquid organic fertilizer (LOF). The high nitrogen content in urine was immensely beneficial, however phosphorus and potassium could not be found organically, and are being temporarily supplied chemically.

Data was collected in the years after the technology was released, found how effective the container farming was. Overall, plants grew faster, bigger and healthier, yielding superior crops to those yielded by conventional agricultural techniques. Addressing the poverty and the cities massive water needs, the container farming not only provided cheap food for the poor, but actually used much less water as well. However, most fruit bearing plants were not successively grown. Another notable find was that the plants were far more resistant to insects pests and diseases.

Of course this container technology is very simple if you have hundreds of dollars to buy containers and fertilizers, which are not as effective as your own urine, but the purpose of the project was to provide this technology for the poor people living in the slums of Mexico City. The Project has gained support from private benefactors and some companies; a Mexican supermarket chain has pledged to donate containers it no longer uses to the project. Although the technology is still under development, there are hundreds of families already benefiting from its genius and cost effective nature; the development shows that a lot can come of what would seem like waste, additionally it conserves water for the enormous city, something which could possibly, or rather hopefully, restore the water supplies in the areas surrounding the city, saving cattle and crops.


Mexico City

By Miguel Sanchez Enkerlin

As the 20th century progressed, the capital of the United States of Mexico, Mexico City, grew rapidly. Possibly due to government corruption, and neglect for the people, the city becameuncontrollably large and famous for its air pollution problems. Naturally, other problems arose; skyrocketing crime, rampant poverty, and a constant struggle to provide the enormous and mostly impoverished population with appropriate infrastructure.

By the 1990’s, about half the population (40 million) of Mexico fell below the poverty line, and about 15 million citizens in extreme poverty. The extreme poverty was concentrated around the urban centers, logically, the majority, around Mexico City, by far the countries largest city. By then, the population had reached over 18 million, and by the 2000s, the dire situation for the poor (a majority) had only worsened. The City itself is continuously causing problems for itself. Aside from its shocking pollution levels and traffic, the city takes in too much water; subsequently it has raped its own (previously rich) supply of subterranean water, and began to take water from neighboring states. Part of the problem is that the city consumes about 1.5 times the water per person per day that other cities in Mexico take in (300L to 200L), a problem which is due to how cheap the local government makes the water, yet it’s not drinkable, making Mexico the second largest consumer of bottled water, producing even more pollution. The water that is being taken has had far-reaching side effects on the nation as a whole. The city’s thirst has triggered droughts in Mexico’s countryside, causing cattle deaths (over 100,000), and crop losses, which are only expected to worsen with an estimated 20 million tones of crops at risk. Some believe the now scarce subterranean water supply of the city can be replenished slowly, by revitalizing the forests at the foot of the great mountain, or rather volcano, the Popocatepetl. Federally paid biologists now take care of the nation park between the volcano and the city that is rich in pine trees. They are hoping to restore the “water factory”, a naturally occurring retention of water by the ecosystem, which replenishes its water supply. The pine trees collect/retain rainwater, which then goes to the underground wells. Currently there are not enough trees and cattle in the park are consuming part of the water. The program works at maintaining and replanting trees, and taking are of the excess cattle in that area. If successful, this government program could gradually restore the city’s natural supply.


November 3, 2009

Wastewater Reuse: Analysis and Practice

Although saving our water supply is plausible with water conservation and management, there will inevitably be wastewater. In today’s world, we need to find a new way to efficiently reuse this water in order to save the dwindling water supply and provide safe drinking water for everyone.

What is Wastewater?

Wastewater: water that has been adversely affected through human behavior, and contains waste and other contaminants that lower its quality

Wastewater includes but is not limited to sewage, municipal wastewater, industrial waste, agricultural return, storm water. These waters are dangerous to consume and are unsafe for human use. Though some may be reclaimed for other uses (more on that later). Wastewater needs to be collected and treated, because they contain toxins, organic and inorganic waste, minerals, solid waste, and pathogens that are dangerous for humans.

Industrial Wastewater Treatment

In developed countries, most urban wastewater goes down a sanitary sewer or a storm sewer or a combined sanitary and storm sewer to a wastewater treatment plant (WWTP).

Chart of industrial wastewater treatment process

There the water gets processed to remove impurities. The wastewater first gets filtered. Then through sedimentation, more solid wastes are removed. The water is transferred to a sludge pond where organisms consume the organic waste in the water. Finally, the water can be further filtered, disinfected, and other fine impurities can be removed if desired.

Although these WWTP’s are capable of transforming wastewater into any quality of drinking, or potable, water, they do not always aim for the highest quality of water. Often they do not purify the water to its highest quality, partly because of economic and time feasibility and partly because many uses do not require a super high quality of water (ex. Human consumption). Many traditional WWTP’s aim only to limit wastes enough for the water to be dumped back in

to the body of water and for the water to be indirectly used again down river. When a WWTP’s tanks cannot hold all the water, especially in heavy rains, it simply opens a release valve and dumps all the untreated water into a nearby body of water. Even more alarming, in the developing world, 90% of wastewater is simply dumped back into the rivers, untreated. One in five does not have access to safe drinking water.


In order to conserve the water supply and provide safe water for everyone, we must find methods of reusing wastewater.

One method is to harvest rainwater, either from a roof runoff drain or other rainwater collection source. The rainwater is collected in a tank and purified for use. (This system is described in more detail in “Roof Catchment Rainwater Harvesting System”)

Another similar method is the use of passive rainwater harvesting systems. These systems are often at grade and are designed to direct the rainwater to irrigate surrounding foliage or to benefit the surrounding landscape. One example is where the City of Portland, Oregon, retrofitted street curbs to direct street runoff from storm sewers that fed into the Willamette River, to water surrounding greenery.

Fog collection is another method of catching natural water that would otherwise be waste. In this low-tech but efficient method, large find nets are stretched between to poles. When the fog moves by the nets, it condenses and falls into a reservoir. In Canada, FogQuest, a nonprofit organization, is looking to implement this technology all over the world.

There are also many technologies that help make homes self-sufficient, in reusing current water supplies.

Potter for Peace, a South American organization, is making a cheap, low-tech water purifier called Filtron. This purifier consists of a pot containing sawdust and colloidal silver. This technology purifies the water by filtering with sawdust and clay, and killing bacteria with the silver. The purifier only costs 9 dollars and is being used by the Red Cross and Doctors With-out Borders in rural communities.

There are also solar based purifiers that clean wastewater into drinking water. Most work through evaporating the water with the sun’s heat. Then condensing the water vapour into clean drinking water.

Another invention that helps us reuse wastewater is an alternative sewage treatment marsh. These mini-treatment plants can provide recycled water for consumption for a small community. The treatment system mimics that of a marsh. Hardy plants like cotton tails consume and filter toxins form the wastewater and bacteria clean out organic waste. In the end, what you get is a supply of clean drinking water.

The recycling shower is another option to help you reuse wastewater. Water from the shower drain of the recycling show is immediately brought into a treatment system where the water is clean, then reheated and comes back out of the showerhead.

Case study: EcoHous

A prime example of reusing waste water to preserve the water supply is the EcoHous located in the Urca neighborhood in Rio de Janeiro, Brazil. In this house, a raincatchment system is deployed. Rainwater is caught from the roof and patio into a drain and through a gravity driven filter. The water is then brought to a water recycling tank. And from there is gravity fed to areas throughout the house for reclaimed non-potable water use. The system comprised of 28% of water use in the house.

There is also a sewage recycling system where gray water, water from sinks, showers, washing machines, are purified and reused in much the same manner as the rain catchment system.

A green roof is also watered by natural rainwater. The garden feeds the residents of the house while using rainwater that would have gone to waste. This house proves that wastewater reuse is a practical idea for today’s homes.

Through the development of new ideas and techniques, it will be possible to reuse most wastewater and consequently save our water supply and provide safe drinking water for many.

November 2, 2009

Wastes Helping the Future

By Beatris Bogomilova

China is a highly populated country where people are not very wealthy and many live in substandard housing. Rural areas in China are very common and unfortunately a large part of China’s population consists of farmers. In order to assist farmers with a more financially pleasing lifestyle and to prevent some of the world’s greenhouse gases, the ancient ways of biogas digesters are brought back. Biogas is a combustible composition of gases created by organic wastes that can ferment in the absence of oxygen. The use of simple biogas digesters began in 1920 and slowly progressed to the 1980s and solved minor problems such as manure disposal and hygiene improvement. In China, biogas is now used as anaerobic digestion (also called biogas digestion) that manages wastes and results in beneficial results.


Farmers create human and animal wastes on a daily basis and those wastes often end up in water bodies, which then pollutes the water for used for agriculture and human necessities such as drinking or hygiene use. In order to prevent the waste disposal discarded into the rivers and lakes and keep the reusable substances from the waste, biogas digesters are created. Biogas digesters take the different wastes and break them down into components that can be used for types of energy and agriculture. Biogas digesters provide methane that can be used for fuel for cars, cooking and heating water, as well as providing a great organic fertilizer with major nutrients such as nitrogen or phosphorus for crops to grow faster. “Using the biogas digesters to deal with the pig and poultry wastes, biogas energy becomes available for processing tea and heating the chicken coop, and there’s a fodder for fish and pigs and fertilizers for tea trees and the paddy fields, and no pollution is exported to surrounding areas.” This reuse of wastes really makes wet waste a great thing for future of our world since it will save the world’s most useful natural resource - water.


The biogas digester helps the living conditions of farmers in many ways. Farmers do not have a lot of fresh vegetables in the winter and the pigs in the farms do not fatten in the winter either. The digester gives energy through biogas, slurry and residue as fertilizers while the pigs enrich the greenhouse by producing quality to the vegetation through carbon dioxide. This then results in a longer spam for storage of fruit and grin and destroys unwanted insects, mould and bacteria that cause diseases.

Since biogas technology is very efficient, the Chinese have tried to make it more popular by holding classes that result in professionals who would introduce and encourage the technology to the rest of the world. In 2005, six thousand farmers were trained in Shanx Province and four thousand of them got National Biogas Professional Technician Certificates that then provides international training.

In conclusion, biogas digesters help farmers with disposing the waste from human sewage and animal wastes in a way that will not pollute the waters or affect the agriculture. Waste can be seen as a positive aspect to the world if reused for its beneficial substances and biogas digesters are invented just for that reason. Farmers profit from selling fuel and valuable crops thanks to the fertlizer produced and they also take part in saving the future of the earth’s waters, agriculture and wastes. Today, a lot of the Chinese population is moving from rural areas to the urbanizing cities, which helps to decrease the slums in China due to the high population rate and wastes. ...On the way to a better world!



Video of Biogas Digester in China


"Agricultural Biogas Production in China from Anaerobic Digestion." Anaerobic Digestion (AD) Technical Pages. Anaerobic treatment and disposal.. http://www.anaerobic-digestion.com/html/agricultural_biogas_production.php (accessed November 4, 2009).

"Biogas China." The Institute of Science In Society. http://www.i-sis.org.uk/BiogasChina.php?printing=yes (accessed November 4, 2009).

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DuByne, David. "Biogas? China size it (Science Alert)." Science Alert: Australia & NZ Science News, Scholarships, Jobs, Events. http://www.sciencealert.com.au/opinions/20080905-17301.html (accessed November 4, 2009).

"GE powers China's largest chicken waste biogas plant|GE Reports." GE Reports. http://www.gereports.com/ge-poers-chinas-largest-chicken-waste-biogas-plant/ (accessed November 4, 2009).

Water Shortage and Solutions in Lima Peru

By Felix Cheong (20342006)

When speaking of survival in an urban setting Lima, Peru is definitely a location worth looking. Lima has the 4th and 5th largest mega slums in the world today due to the dramatic population growth and urbanization going on in that region. The climate in Lima adds to its problems because it has a mild desert climate. The temperature is never too hot or too cold, ranging from around 19°C to 29 °C during the summer, and the climate is greatly affected by global warming and weather fronts from other regions. Rainfall is almost nonexistent in this city producing an average annual precipitation of only 26mm, and even less in the mountainous regions. These low annual rainfalls and sudden changes in climate causes a lot of problems including droughts, water shortage and crop failure, making it very difficult for the citizens of Lima to earn an honest living or even acquire the basic necessities for life.


The root cause to the poor living conditions in parts of Lima is the unavailability of potable water, leading to disease and famine. A technology that can help attack this issue is the portable water filtration system. These small devices use UV radiation from the sun and from the device itself to inhibit and sterilize microbes in contaminated water. This allows for any fresh water from wells or even puddles to be disinfected for drinking. This decontamination is applicable for eliminating dangerous bacteria and viruses to prevent Dysentery, Cholera, Typhoid Fever and many other diseases. The device is lightweight, easy to carry as well as effective. It is already being used by many third world countries in need of clean drinking water, making it a necessity for survival in Lima since a majority of the water supply comes from contaminated ground water.


There are other solutions that tie into water filtration, which in theory can have a positive impact in the water conservation, agricultural growth, and wet waste disposal in Lima. One factor that can help with the issue of conservation is the implementation of grey-water recycling systems like the ones described by Myles in an earlier post. These systems reuse the water from certain aspects of the home such as the sink, laundry and bath. It recycles the “grey-water” for the use of waste disposal and irrigation. This can greatly reduce the water used in residential areas. This grey-water recycling system is different from rain water collection because it is using already existing water for different purposes. Lima can only benefit from this system due to the complete lack of rain, making rain collection impossible and impractical. The benefits of this type of water recycling is two fold, since the grey water for irrigation can help deplete the water normally required for agricultural uses. It also helps fertilize the soil, and the excess can be filtered through the portable UV filtration system for drinking.


The grey-water system in combination with the introduction of a plant called Sorghum can help both the water shortage and crop failure in Lima. Sorghum is a type of drought-resistant crop that can survive and grow off very little water. It also thrives best at a temperature close to 25°C, making it perfect for Lima’s desert climate. The supplementary irrigation style that can be given by the grey-water system is perfect for this crop, meaning that it can go for weeks with a minimal amount of water. Sorghum also has many different applications from making bread to pasteurizing cattle, making it one of the top five most important cereal grains in the world. By using grey-water to irrigate Sorghum, Lima can save a great deal of water and thus conserve for future droughts but still produce enough agriculture for sustenance. All these factors can allow for survival in the hash conditions of Lima.



"Aqua Sun International manufactures self contained, portable, water purification systems providing clean, safe drinking water to remote areas where water purification is unattainable or impractical.." Aqua Sun International manufactures self contained, portable, water purification systems providing clean, safe drinking water to remote areas where water purification is unattainable or impractical.. http://www.aqua-sun-intl.com/ (accessed November 4, 2009).

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Grey Water and Gravel Bed Hydroponic Reed systems

This blog post will investigate alternative methods of treating and disposing of wet waste, including grey water and gravel bed hydroponic reed beds. It will investigate how these techniques can provide wet waste disposal without infrastructure, how they can conserve water, and contribute to agriculture.

To begin, what is grey water? Grey water can also be called wash water, It typically makes up 50 - 80% of household waste water and accounts for everything except for toilet water. This includes waste water from sinks, showers, washing machines and dishwashers. It contains relatively few disease organisms in comparison to toilet water (termed black water), however it decomposes quickly and can rapidly degenerate to a state of septic sludge comparable to black water; meaning that this water can not be stored. Grey water makes up a significant portion of sewage and diverting it will greatly reduce stress on the sewage and septic systems that are going to face increased traffic in the future as a result of the booming population. Furthermore, the centralized collection of sewage for treatment creates toxic sludge; diverting grey water will not only reduce the amount of sludge created, but it will also provide an opportunity to capitalize on the many benefits that the effective use of grey water can provide. The best way for grey water to be handled is for it to be introduced to a layer of topsoil. This biologically active top soil will help break down the grey water, and its nutrients can be absorbed by plants and vegetation.

For these reasons agricultural irrigation is an obvious application for grey water because it takes full advantage of its benefits and is also compatible in terms of size, soil and climate that are suitable for grey water irrigation. Grey water irrigation is not recommended in colder climates, or when there is not enough soil, or the soil is of a quality to poor, to adequately absorb and treat the grey water. Agricultural irrigation easily satisfies all of these requirements and can use grey water to conserve valuable fresh water resources, maintain soil fertility, and foster plant growth through the absorption of nutrients such as phosphorous, nitrogen and potassium. This process will not only benefit the crops but will effectively treat the grey water by removing organic pollutants (phosphorous, nitrogen and potassium) and replenishing ground water. Using grey water for agricultural irrigation is incredibly efficient, simultaneously treating waste water and replenishing natural water sources while conserving valuable fresh water that would otherwise have been used.

Although the use of grey water irrigation in the US has not been linked to any illnesses certain precautions should be taken. These include preventing contact and consumption; grey water is still sewage and should be handled as such. It can not be stored and the irrigation system can not be overloaded, excess grey water must be diverted through normal sewage lines. This will generally not be an issue for agricultural irrigation which in most cases will have the capacity to absorb any surplus grey water. Diversion through normal sewage channels is also necessary in the case of chemical contamination, care should be taken not to pour chemicals down sinks that are part of the irrigation system. Also, grey water can not be distributed through a sprinkler system, this will result in the presence of harmful microorganisms in the air that can be inhaled. Finally, these same microorganisms can be transferred to plants through irrigation and therefore grey water must be treated before being used in this manner, treatment can be mitigated by using cleaner sources of grey water (no food residue).

Clivus Greywater Filter System Constructed Wetland Drain to Mulch Basin

There are many different types and configurations of grey water irrigation systems, diagrams have been provided in this blog, however, more details are provided in their respective web pages; links can be found underneath the pictures and in the bottom link section. This blog will focus on the “anaerobic to aerobic” system as it is the most appropriate for agricultural irrigation, however, I encourage the reader to use the links provided to investigate alternate systems. The anaerobic to aerobic system is not the cheapest, but it is simple to maintain and is one of the most effective methods of onsite water treatment. It consists of a three stage septic tank that traps grease and sludge, followed by a sand filter and finished off with a planters bed. The final result of this treatment method is water that is near potable and ready to be used for irrigation. I will direct you to Sabrina’s post, where the irrigation process and methods are discussed in greater detail. It is also important to note that grey water alone will likely not be sufficient to support agricultural irrigation on its own and it would be most effective combined with rain water capture systems.

Anaerobic Aerobic Treatment System

The major problem with the grey water irrigation system previously discussed is that it requires access to basic plumbing infrastructure, which sadly excludes 2.5 billion people around the globe. Alternative methods are necessary to provide those without any plumbing infrastructure with the same services. Gravel Bed Hydroponic reed beds (GBH) are one example of a system that could be used to treat human waste water for use in agricultural irrigation. This idea was initially pioneered at the University of Portsmouth in the 1980’s and consists of a two meter wide forty centimeter deep drainage channel that extends for one hundred meters and is sealed by an impermeable material. This channel is filled with gravel and hydroponically grown reeds which waste water passes through. The presence of the reeds fosters the microbial activity that treats the sewage purifying the water to a level that is acceptable for restricted irrigation (can only be used to irrigate crops not eaten raw by humans). This method has been tested in Egypt and has proven to be an effective. While there may be some logistical difficulties (most notably the reliance on gravity and water flow in the absence of a pump) it is an affordable and relatively effective sewage treatment system that warrants further investigation and implementation.

In conclusion, the use of grey water and GBH treated waste water for irrigation is an extremely effective way to deal with wet waste without infrastructure. These two systems are able to provide water for agricultural irrigation thereby conserving fresh water supplies, in addition to treating waste water satisfactorily and in a way that replenishes ground water. Developing these already incredibly useful technologies is crucial in a crowded future where large scale infrastructure can not be relied on.


"DFID ENGINEERING THEME W4 SUMMARY - R4573: Gravel bed hydroponic wetlands for wastewater." Loughborough University. http://www.lboro.ac.uk/well/resources/consultancy-reports/task0065/htm/D4573.htm (accessed November 4, 2009).

"Greywater irrigation - grey waste treatment." Greywater irrigation - grey waste treatment.
http://www.greywater.com/ (accessed November 4, 2009).

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http://www.letsgogreen.com/greywater-recycling.html (accessed November 4, 2009).

"Planter Box." Tredyffrin.
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"Simple sewage solution could save millions living in third world." University of Technology, Sydney.
http://www.uts.edu.au/new/releases/2002/November/11.html (accessed November 4, 2009).

Roof Catchment Rainwater Harvesting Systems

The Region of Waterloo has taken to organizing Rain Barrel Distribution Events every April. Over the course of eight years, they've sold 34,000 rain barrels to interested citizens at a cost of $30 each. Overall, it appears to be a fairly productive project for the municipality to undertake.

Source: Region of Waterloo (link above)

Most rainwater harvesting in Canada appears to make similar use of the roof catchment systems used by the rain barrels being sold here in the region. The barrels are used for the collection and storage of rainwater from the roof, mainly for gardening. However, there is so much potential within the realm of this basic technology that should be explored beyond simple suburban lawn maintenance. The good news is it is being explored on a larger scale, with many different end purposes in mind.

In case you were unaware, the vast majority of our buildings are designed with roofs. In climates where it can be a problem, polling of precipitation is avoided by sloping roofs; furthermore, most buildings feature gutters that exist for the purpose of moving water from the rooftop to a preferable location away from the building.

Incidentally, the roof catchment rain harvesting system is nearly identical to these systems as they already exist: the addition of a tank for storage of the rainwater makes the most basic household water harvesting system possible. Additions to this design are predicated on the intended purpose of the system- for example, outdoor rain barrels can feature a filter to prevent leaves and debris from entering the barrel, which could lead to increased maintenance requirements. It also prevents mosquitoes from using the standing water as a breeding ground, which eliminates the possibility of disease being spread.

In terms of larger scale rainwater harvesting systems, we have several options for exploration. Based in British Columbia, The Rainwater Connection is a company that specializes in the development of personalized rainwater collection systems for homes that only have access to wells with high contaminant levels.

An example of the systems they create is the house on Galiano Island, which is fitted with leaf traps, ultraviolet filters, and a 15,000 gallon storage cistern.
Source: Rainwater Connection (Link Above)

This allows the household to use solely rainwater for all tasks, including toilet flushing, which accounts for 30% of the water used in Canadian households. Having a wet waste disposal system is extremely beneficial, for obvious reasons.

This system is expensive, as you would expect. However, cheaper alternatives exist- the Global Water Challenge has installed several roof collection systems on schools in Tanzania for hand washing at far cheaper cost. While the filtration systems used are not as intricate as those of The Rainwater Connection, the fact is that with little investment, these systems work.

Rainwater and Subsistence

Source: www.re-nest.com (link below)
This second story rooftop garden is watered by sub-irrigation with a rain barrel watering system. The rainwater falling on the roof is diverted into a series of several rain barrels in the basement of the building where it is stored until the water is required, at which point a pump is activated to bring the water onto the roof. This is a relatively small-scale system costing around $700, which is admittedly not incredibly cheap, but the value of the system is the opportunities it holds for urban agriculture- being able to grow the food you eat within the city, defying any reliance upon external farms and shipping fees, is vital to the concept of subsistence.

Furthermore, consider lavatories running entirely on rainwater collected on roof and fed downwards. The Rainwater Connection has altered at least one set of public washrooms to completely make use of rain harvesters. A larger system isn't inconceivable, as long as the waste has a destination.

There would be technical issues- preventing debris and leaves from entering the is a main issue that must be avoided, and filtration and purification systems may also be a requirement, but these issues are not particularly difficult to address.

Feasibility should also be touched upon: Peru wouldn't benefit, but there are areas that could: Kowloon Walled City, as an old example, in a region that receives 2500-2800 mm of rain per year.
Source: HKO
The city was approximately 6.5 acres in size, so assuming a reasonable amount of rain- 2600 mm- approximately 68 million liters of water falls on this patch of land every year (The average Chinese individual uses 86 liters of water daily, though subsistence conditions would anticipate less.) Not all locations receive as much rain as Hong Kong, obviously, but even in locations that receive 200 to 300 mm of rain a year could make use of rainwater harvesting to supplement further water sources.

The simple fact is that the systems are simple, easy enough to construct, and extremely beneficial for obtaining water for many purposes without having to rely on traditional infrastructure for access. In a subsistence urbanity, this is, quite simply, a extremely vital building block.

-Sean Maciel


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Irrigation and water conservation

By Sabrina Leung

Irrigation, or artificial application of water to soil, is a major consumer of the world's water supply. Close to 60% of our world's freshwater withdrawals are used in irrigation. Unfortunately, large portions of water are wasted as a result. Only half the water that we use for irrigation is actually reusable, because of the loss to evaporation, transpiration and runoffs.

Among the many irrigation techniques that are employed today, one can determine which is most efficient depending on the agriculture and soil that is applied to the particular area.
Below are some common irrigation methods.

Flood or Furrow Irrigation
This one is rather self-explanatory. The soil is flooded with water and it simply runs on gravity around the crops. Flood irrigation is the most wasteful technique, yet the most practical for underdeveloped areas because it does not require much of any equipment. In turn, it is the most common form of irrigation world wide.

Much of the water is wasted through evaporation or runoff. However farmers can prevent that by releasing the water at intervals to reduce runoff. Storing and re-using runoff, via tailwater return systems is also a possibility. Return systems essentially collect the water from runoffs in a pond for reuse in irrigation later. Leveling the farmland will also save on yield, in case there are raised areas of land that are not reached by the flood.
Source: http://www.desertusa.com/mag08/jun08/water-southwest-problems.html

Sprinkler Irrigation
Water travels to certain points around the field and is then distributed overhead via sprinklers or guns. Common types of sprinklers include rotors (rotating sprinklers) and center pivot systems (equipment rotates around a pivot). Center pivot systems yield a distinct circular pattern of irrigated farmland, which can be viewed in the image below.

Although less wasteful than flood irrigation, water is still lost from evaporation and runoff.

Sprinkler spacing should be considered when designing the irrigation system. Having uniform water distribution can prevent over-watering and the development of diseases within the area. Below is a diagram on overhead sprinkler spacing.

Drip Irrigation
Pipes are placed directly near the plants' roots and water is trickled slowly through them. This is probably the most efficient irrigation method today because only the required amount of water for each plant is used. Drip irrigation uses up to 30% less water than a common sprinkler system. It can be adapted to uneven terrains and soil textures and wastes minimal water to evaporation, runoff or percolation, therefore making it a viable solution for areas where water is scarce or expensive. It also eliminates the need to "re-water" certain areas of a field because of inadequate distribution.

The droughts that many farmers experience are a crucial issue, because irrigation will always be a necessity. Otherwise, much of the world's farmlands would not be capable of growing crops at all. In order to conserve as much water as possible, reusing from runoffs or from rooftops are feasible solutions.
Irrigation scheduling, which refers to the use of water management techniques in order to optimize water use, yield and quality, should also be considered. Soil is an important factor in irrigation scheduling. Once soil is completely saturated with water, it will start to runoff the surface or drain beyond the root zone of the plant. In turn, dry soil may not necessarily mean that the crops need to be re-watered. Monitoring the moisture content of soil at the root zone is more accurate for determining irrigation scheduling.
The species of plant should also be considered when deciding when to irrigate. In general though, they should be watered as much as possible per irrigation session. As a result, irrigation does not have to be nearly as frequent and plants are encouraged to root deeper into the soil.
New irrigation technology is also in development. Many systems run on simple timers that switch irrigation on or off at specified time intervals. With the invention of "smart controllers", irrigation can be run based on soil moisture content, temperature and rainfall levels. Approximately 15%-30% of outdoor water use has been saved by using smart controllers.


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"Flood Irrigation Introduction." Alliance for Water Efficiency. http://www.allianceforwaterefficiency.org/Flood_Irrigation_Introduction.aspx (accessed November 4, 2009).


"IRRIGATION SCHEDULING TO IMPROVE WATER- AND ENERGY-USE EFFICIENCIES." Department of Biological and Agricultural Engineering @ NC State University, Raleigh, North Carolina. http://www.bae.ncsu.edu/programs/extension/evans/ag452-4.html (accessed November 4, 2009).


"Irrigation Water Conservation." Benefits of Recycling . http://www.benefits-of-recycling.com/irrigationwaterconservation.html (accessed November 4, 2009).


"Irrigation technology: Smart water solutions for state's farmers." California Farm Bureau Federation CFBF.com. http://cfbf.com/agalert/AgAlertStory.cfm?ID=1087&ck=A26398DCA6F47B49876CBAFFBC9954F9 (accessed November 4, 2009).


"Irrigation water use, from USGS Water Science.." USGS Georgia Water Science Center. http://ga.water.usgs.gov/edu/wuir.html (accessed November 4, 2009).


traditional, use of. "Irrigation: Irrigation techniques." USGS Georgia Water Science Center. http://ga.water.usgs.gov/edu/irmethods.html (accessed November 4, 2009).

Sabrina Leung