Too dry?

In arid regions of the world green space in the urban environment is even more important because of its cooling and shading effect. Green space generates a high real estate value and offers citizens a great relaxing and healing escape from the heat and urban hustle and bustle. However, green space requires water in order to grow, which in these regions is a scarce and extra valuable commodity. The good news is that even in arid regions there are wastewater sources available, without using valuable groundwater or desalinated drinking water sources. Treated Sewage Effluent (TSE) and HVAC condensate are sources of available water, in large quantities, capable of supporting plant life.

Permavoid podium deck, Bank of Oman
Permavoid podium deck, Bank of Oman

Would it not be great to be able to double the amount green space, with the exact same amount of water as we use nowadays with conventional surface irrigation? Would it not be great if we could irrigate plants, trees and turf without the use of electricity, sprinklers, pipes hoses and failure prone valves? With the Permavoid capillary sub- surface irrigation system such savings over normal surface irrigation have been proven to be feasible (STRI research), without the use of all the aforementioned infrastructure or electricity. So let’s double the number of trees and green space area in these arid regions without using more water!

No drop of water leaves the city unless through evapotranspiration of a leaf!

Too hot?

No matter where you are, major cities report a measurable Urban Heat Island (UHI) effect. Sunlight absorbing paved and built areas collect a lot of heat from the sun during the day, and radiate the warmth back into the city at night, when people try to sleep. Humans sleep best if the temperature drops at night; nobody likes to lay awake twisting in their beds, because the temperature is uncomfortably high and refuses to drop. This impact on sleep quality and quantity has a negative affect on productivity and liveability in cities, a serious heath and economic concern.

UHI: a serious health impact
Increased water/energy consumption

Increasing the amount of green space in the urban environment helps to reduce the UHI effect. Plants reflect as much as 48% of all incoming sunlight back in to the atmosphere, instead of absorbing all of the sun’s energy. Plants, and especially trees, create shade, preventing heat build up in urban surfaces. Green roofs as such help to cool the building underneath by reducing the heat influx through the roof (by as much as 75%) and help extend the lifespan of the waterproof membrane (from 20 to 40 years). All plants and trees evaporate water, which helps to cool the city. But without this available at the roots, urban cooling by vegetation stops. Hence the importance of water for plants in the urban environment, and of course, we do not mean drinking water!

 Cities are ‘hot’! Too hot...

Too wet?

In temperate regions of the world, cities experience shorter and heavier rain events. Sewer systems are overloaded and city streets flood. Urban green space, such as parks and blue-green roofs, can absorb a lot of this water, but plants get as stressed from too much water as from too little. Hence the importance of proper drainage of plant growth supporting soils.

Flooding of cities during heavy rainfall
Permavoid Blue-Green Park in Amsterdam

The solution is not to store too much water in the rootzone of the plants, but in void space underneath the root zone. Being stored underneath the root zone in a shallow Permavoid tank, it can be made available for growth upon demand, via the capillary irrigation fibres, without the need for external (space-consuming) storage tanks, or the need for pumps, pipes, hoses and valves. And this sub-surface drainage, storage, conveyance and capillary irrigation system will operate in landscaped areas, under professional stadium quality sports pitches, equestrian fields or blue-green rooftops.

Too much of a good thing… requires innovative and nature based solutions!

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