Recent Advances in Environmental and Earth Sciences and Economics
Water cycle and green roof and wall role in it
Zuzana Poórová, Mohammed Salem AlHosni, Zuzana Vranayová
0,687 % presents besides eccentrically placed glaciers the
greatest wealth on the land that exceeds several times the
volume of water in all rivers and lakes of the entire world.
Water in the soil in terms of the quantity of benefits is more
important than water in rivers. This undiscovered treasure is
misunderstood and overlooked, neglected and destroyed [1].
The water in the atmosphere. The volume of the water in
the atmosphere, in all three states is approximately 10 times
biger than the volume of water in all the rivers. Theoretically,
if all the water in the atmosphere felt in time in the form of
precipitation, it would create on the imaginary ground surface
25 mm layer of water. Just like the seas and oceans have key
global thermoregulation role on the planet, the water in the
atmosphere has crucial local thermoregulation function [1].
The water in the biota. The water surrounds us. It is not
just around us, but it is inside us. In living organisms, water
volume is about 0,00004% of all the water on the Earth, what
is the smallest amount of total volume of the water, but what is
lacking on the volume is the highly balanced in crucial
importance of this water for daily individual form of life. For
example, the human body contains more than 60% of water,
and all the physiological processes take place in a medium
whose main component is water. The water content in plants
varies depending on the species and often is much higher than
water content in animal perionyx. The volumes of water
accumulated in the vegetation cover are not negligible, just
like the volumes of water stored in the soil due to the existence
of vegetation. The vegetation on the land, among other
functions, has in particular the critical role in the regulation of
evaporation from the soil. Therefore, on the land greatly aids
thermal stability. Upon which depends its own prosperity and
even its existence. On the existence and prosperity of
vegetation depends consequently all higher life on the Earth
[1].
Abstract—How inappropriate to call this planet Earth when it is
clearly Ocean. ~Arthur C. Clarke. Natural ability of the land to
absorb excess rainfall is lost under new hard landscaping and existing
surface water drainage systems. Claim of this article is pointing at
natural water cycle that is being broken and examples of solutions
that might solve many problems. Retention features of green roofs
and walls using natural blue principles. The article points at positive
effects of green roofs and walls in terms of water management.
Keywords— catching water, green roofs and walls, hydrological
cycle, water loop, water retention.
I. INTRODUCTION
T
HERE is about 1400 million km3 of water on the Earth.
The water in the seas, the water on the land, the water in
the atmosphere and the water in living organisms. Of course
water meant in all its states. The gaseous state, liquid state and
solid state.
II. WATER
The water of the seas and oceans covers 70,8% of the
Earth's surface and forms the largest part, up to 97,25%, of all
water on the Earth. The seas and the oceans the planet would
be suffering from changing of extreme temperatures, what
would make life as we know it impossible. Even a slight
fluctuation of temperature compared to the current
temperatures could have fatal consequences for food security
on our planet. Among other functions of the seas and the
oceans is interesting water supply to precipitation on the land
[1].
The water on the land. The water is often being fixated on
the water in the rivers or natural or artificial lakes. Water in
solid form ice, snow ) forms 2,05 % of all water on the Earth
and shelters up to 70% of the world's freshwater supplies.
Visible surface water in rivers forms only 000001 % and in
lakes (including salt lakes and inland seas) 0,01 % of all water
on the Earth. Groundwater and water forming soil moisture
III. HEAT
Water is very unique. At temperatures common on Earth can
naturally exist in all three states. The solid state, the liquid
state and the gaseous state. During the change of state heat is
consumed, respectively released. During the change of state
from solid or liquid state to gaseous state, it gains high
mobility thanks to which it is capable of quick motion. Thanks
to the motion, is capable of quick moving in large volumes in
horizontal and vertical directions. Water also has the highest
specific heat capacity, thus the ability to receive thermal
energy from known materials. With its ability to bind and
release energy, and transfer skills, reflection and dissipation of
This work was supported by: VEGA 1/0202/15 Bezpečné a udržateľné
hospodárenie s vodou v budovách tretieho milénia/ Sustainable and Safe
Water Management in Buildings of the 3rd. Millennium.
Zuzana Poórová, Ing. arch., PhD student, Technical University of Košice,
vysokoškolská 4, Košice 042 00; e-mail: zuzana.poorova@ tuke.sk
Mohammed Salem AlHosni, Ing., PhD student, Technical University of
Košice, vysokoškolská 4, Košice 042 00; e-mail: mohammedsalem.alhosni@
tuke.sk
Zuzana Vranayová, prof. Ing., Phd. professor, Technical University of
Košice, vysokoškolská 4, Košice 042 00; e-mail: zuzana.vranayova@ tuke.sk
ISBN: 978-1-61804-324-5
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energy, water in all its states according to the needs cools or
heats the planet. It is keeping it at a temperature that supports
life on Earth.
radiation hits the drainage area, most of the solar energy turns
into sensible heat, in the year-long sufficiently humid areas,
most of the solar energy is consumed for evaporation.
Therefore, water areas, soil saturated with water and
vegetation have important role in the water cycle on the land.
Functional vegetation fulfills the function of the valve between
the soil and the atmosphere. It protects the soil from excessive
overheating and thus drying out and optimizes the amount of
the water evaporation through the transpiration of amount of
air channels on the leaves. Vegetation well stocked with water
thus has a significant cooling and air conditioning feature.
Vegetation, its quantity, type and quality significantly affect
the runoff in the watershed. Deforestation, agricultural and
urban activities are changing the amount of water in the
country. Man unwittingly changes flow of huge amount of
water and energy [2].
Water balances the temperature differences between day
and night, between seasons and between different areas. Thus
water also reduces weather extremes. Water vapor is the most
wide-spread greenhouse effect in the atmosphere. The content
of water vapor in the atmosphere is highly variable, but its
typical range is 1-4 % (for comparison , the CO2 content is
0,0383%). The more water in the atmosphere, the stronger
effect of temperature balance. Thus there are less weather
amplitudes. The less water in the atmosphere, the weaker
effect of temperature balance Thus there are more extreme
weather amplitudes. Where is the lack of the water in the soil
and lack of the water in the atmosphere, extreme temperature
conditions usually persist. Water and water vapor affect the
climate in the most significant way on the Earth. Nevertheless,
the role of water and water vapor in the atmosphere is poorly
understood and little discussed issue [2].
V. ROOFS
Extensive green roofs are lightweight veneer systems of
thin soil or substrate layers of drought tolerant self-seeding
vegetated roof covers. Extensive green roofs require special
types of plants. Plants are usually native from dry locations,
semi-dry locations, stony surfaces such as alpine environment.
These kinds of plants have typical mechanisms to survive
extreme conditions. Mechanisms like water storage organs,
thick leaves, thick leaves surfaces, narrow leaves etc.
Extensive green roofs are known by using colorful sedums,
grasses, mosses and meadow flowers requiring little or no
irrigation, fertilization or maintenance after establishment.
Extensive green roofs can be constructed on roofs with slopes
up to 33%. Also, they can be constructed on existing structures
with little, or no additional structural support. Construction of
this kind of roof is mostly single-wall, or double-wall [3].
IV. THE COOLING EFFECT
Incident solar radiation evaporates water from the seas,
lakes, rivers, wetlands, soil from plants into the atmosphere.
Evaporation of each molecule of water consumes heat, which
cools the Earth's surface. Evaporated water creates clouds in
the atmosphere (including fog, rain-fall or ice crystals). Rised
vapor higher in the atmosphere condense under the influence
of cold, releasing heat. Cooled higher in the atmosphere return
back in the form of rain. Repeating this process is an effective
mechanism for the elimination of spare heat and is similar to
the sophisticated refrigeration device. There is a rule that
about half of the earth's surface is all the time in a cloud´s
shadow. Clouds restrict the entry of solar radiation into the
atmosphere and on the Earth's surface. Limitation of solar
radiation that reaches the earth's surface, reduces evaporation
and the formation of clouds [2].
Function of clouds. Clouds play an essential role in
regulating of energy balance of the Earth concerning the sun
radiation. They reflect part of shortwave solar radiation, thus
limiting its entry into the atmosphere and on the Earth's
surface, thus protecting the Earth from overheating. Clouds
capture part of the longwave (thermal) radiation from the
Earth, which otherwise would escape to the space, waht has a
warming effect. The cooling or warming effect of clouds
depends on their type and height. Low situated cumulous
clouds (cumulus) cool the Earth, high situated thin clouds
(cirus) warm the Earth. The research of thermoregulatory
effects of clouds and their balance, with regard to the current
problems of mankind proves to be very promising and
interesting [2].
Function of vegetation. When the solar radiation hits water
well-stocked area, most of the solar energy is consumed for
evaporation and only the rest is consumed for sensible heat,
heating the soil, reflection, or photosynthesis. When the solar
ISBN: 978-1-61804-324-5
Fig. 2 Green roof sketch [4]
Intensive green roofs are designed to look like gardens,
landscapes. They need similar management as ground gardens.
Urban rooftops are really challenging places for design. We
could say they are useless places. But these typical useless
spaces in our towns are becoming a remedy of constructing
healthier environment through more sustainable practises.
People in the city on the roof usually look for the view.
Positive change happens, when habitant of the city is not
forced to be looking for the views, because it is in front of him
on the rooftop. Unexpected blue and green grasses, colourful
flowers in the middle of concrete, steel and glass.
Contemporary technological conditions allow many things.
Waterproof membranes help to capture water for irrigation,
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Recent Advances in Environmental and Earth Sciences and Economics
drainage support growing medium and resist invasion of roots
of plants. During the day, temperature of asphalt roof is
unbelievably high. On green roof, soil mixture and vegetation
act like an insulation. Reducing heating, cooling the building.
When it is raining, water floods down to city´s artificial
canyons. A living roof absorbs water, filters it and slows it
down [5].
VI. GREAT WATER CYCLE
The great water cycle is an exchange of water between the
ocean and the land. About 550 000 km3 of water evaporates
into the atmosphere each year. From the seas and the oceans
around 86% evaporates, from the mainland 14% of the total
evaporation from the surface of the Earth. Out of the total
atmospheric precipitation, which arise from the evaporation,
74% drops over the seas and the oceans, and 26 % drops over
the land. The seas and the oceans through the evaporation and
precipitation subsidize land with some volume of water. This
amount of water by the atmospheric and thermodynamic flows
is getting through long distances over continents where expires
(or falls in the form of snow).
VII. SMALL WATER CYCLE
The small water cycle is a closed water cycle in which
vaporized water falls in the form of precipitation over the same
terrestrial environments on the land. Just like small water cycle
exists over the land, it exists over the sea or ocean. Between
the small water cycles, over the large territories with different
morphology and surfaces with varying humidity, ongoing
interactions are going on. The small water cycle performs
horizontal water circulation, but unlike the large water cycle, it
is characteristic vertical movement for it. Evaporation from
neighboring areas with different temperatures can cooperate on
the design and conduct of cloud. We can say that small water
cycles circulate around the country at the same time. We can
say that above the landscape the water is circulating in many
small water cycles that are donated by the amount of the large
water cycle.
Fig. 3 Green roof sketch [4]
Green facades use climbing plants (lianas, vines and
scramblers) to cover building walls, offering a flexible and
adaptable tool for environmental design Like other forms of
green infrastructure, they cool building walls by intercepting
and absorbing solar radiation (shading), providing cooling,
increasing albedo (reflecting solar radiation), providing a
thermally insulating air cavity, depending on the distance of
the green facade from the wall and reducing surface wind
speed on the wall.
The collapse of water cycle. If there is a widespread
disruption of vegetation cover (deforestation, agricultural
activities, urbanisation), solar energy hits all the surfaces with
low vapor and a part is converted to heat. This is how extreme
gives rise to significant variations in temperature and the
temperature difference between day and night, or only between
sites with a different temperature regimes grow. Air circulation
will increases, hot air is drifted away and most of the
evaporated water from the country is being lost. Small and
frequent rainfall decrease and more powerful and less frequent
rainfall from the sea increase. The cycle opens, large water
cycle starts to dominate, which is in contrast to the small one
characteristic with erosion and washing away of soil and
nourish to the sea. Restoring the dominance of the small water
cycle, which is for man, vegetation and landscape suitable
depends on the functional recovery of plant cover area and
water areas in the country [7].
Fig. 3 Green wall sketch [6]
Green facades offer many benefits to their surrounding
environment including buffering building temperatures,
cooling the local air temperature, providing air filtration,
reducing storm water runoff, ameliorating noise pollution,
removing carbon from the air, providing shade, and creating
habitats for plants and animals. In many cases , green facades
are intended to be aesthetically pleasing. Research shows this
aesthetic makes people more relaxed, productive, studious and
mentally healthy.
Green facades can potentially reduce energy consumption.
Plants on the facade shade a structure’s surface, as well as cool
the surroundings through the process of evapotranspiration.
Green facades reduce wall surface temperatures by as much as
25°F (14°C) compared with exposed wall surfaces
ISBN: 978-1-61804-324-5
VIII. CONCLUSION
The green roof and green wall is a very well known
sustainable tool that can be used for solving many ecological
issues [8,9,10]. All named problems in the article are pointing
at failing water cycle. Lack of soil, vegetation, moisture, water,
wet lands, drainaging continents. One possible way how to
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Recent Advances in Environmental and Earth Sciences and Economics
help humans thus Earth is to start building green roofs on the
tops of the buildings that took place from nature and turned it
into piece ruining the water cycle. Creating natural surface on
the top of the building means creating natural surface that will
help the small thus great water cycle. The problematic of green
roofs and green walls is not the main point of this article, the
aim was to show the importance of water in urban area and the
idea of green roof and wall that might be solving this problem
in very easy way.
ACKNOWLEDGMENT
This work was supported by: VEGA 1/0202/15 Bezpečné a
udržateľné hospodárenie s vodou v budovách tretieho milénia/
Sustainable and Safe Water Management in Buildings of the
3rd. Millennium.
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konference s mezinárodní účastí : Velké Bílovice, Brno : Ardec, 2014
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[4] Extensive green roof. [online] [available] Retrieved from
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[5] J King, “In progress: Van Ness MOB green roof". [online] [available]
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[7] Phoenix botanical garden. [online] [available] Retrieved from
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x-botanical-garden
[8] Z. Poórová, et al., “Green roofs performance towards cooling heat island
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přednášek konference s mezinárodní účastí : Velké Bílovice, Brno:
Ardec, 2014 pp. 205-210.
[9] Z. Poórová, Z. Vranayová, “Green Roofs as a Means of Creating Micro
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