MENANAM POHON
UNTUK
MEMANEN AIR HUJAN
AIR HUJAN
Soemarno - psdl ppsub 2013
Profil pohon dalam menangkap air hujan dan
energi matahari.
www.icsu-scope.org/.../scope51/chapter06.html
A model illustrating fluxes of sulphur in a forest
ecosystem
3
Schematic illustration of the biogeochemical
processes of importance in long-term research
of a watershed (Swank, 1986).
4
Sumber:
www.aracruz.com.br/show.do?menu=true&id=943...
Vegetasi pohon mengamankan tebing curam dari
bahaya longsor
Sumber:
sofia.usgs.gov/publications/posters/challenge/
6
Sumber:
www.waterbucket.ca/rm/?sid=33&id=271&type=single
Tajuk pohon menangkap sejumlah air hujan dan
emenguapkannya kembali ke udara
Four-Way Collaboration
The Water Balance Model includes a tree canopy module
so that the rainfall interception benefits of trees in the
urban environment can be quantified. To populate the
module with local data, a four-way collaboration has been
established under the umbrella of the Inter-Governmental
Partnership (IGP) that developed the Water Balance Model.
The Greater Vancouver Regional District and Ministry of
Community Services are providing funding, and the
University of British Columbia and District of North
Vancouver are making in-kind contributions in carrying out
the applied research project. The District of North
Vancouver is acting on behalf of the IGP in leading this onthe-ground initiative.
Tree canopy interception is the process of storing
precipitation temporally in the canopy and releasing it
slowly to the ground and back to the atmosphere. It is an
important component of the water balance, easily
accounting for up to 35% of gross annual precipitation.
Removing trees will in general decrease interception and
thus increase annual runoff and rainwater runoff.
Vegetation also reduces rainfall intensity due to the
temporal storage effect.
Sumber:
wwa.colorado.edu/treeflow/lees/treering.html
www.uwsp.edu/geo/faculty/lemke/geog101/lectur...
SOIL WATER
Infiltration & percolation; permeability; Porosity
Zone of aeration: soil water storage; plant uptake & transpiration
evaporation; Throughflow; Water table
Zone of saturation: groundwater flow; aquifer.
Sumber: www.uwsp.edu/geo/faculty/lemke/geog101/lectur.....
HYDROLOGIC CYCLE & WATER BUDGETS
What happens to precipitation?
Water budget: local scale examination of the gains, uses, and
losses of water
Vegetasi Pohon memperbaiki neraca-air bentang lahan
WATER BALANCE
Gains: precipitation
Soil moisture storage Losses: utilization and evapotranspiration;
Actual evapotranspiration (AE) ; Potential evapotranspiration
(PE).
Simple water balance:
Moisture abundant environments : P > PE and therefore AE = PE
Moisture limited environments: P < PE and therefore AE < PE
Seasonal moisture environments.
www.ecologyandsociety.org/vol3/iss2/art5/
The hydrological cycle, showing the repartitioning of rainfall into
vapor and liquid freshwater flow (modified from Jansson et al.
1999).
INVISIBLE GREEN WATER VAPOR AND
VISIBLE BLUE LIQUID WATER
It is distinguished between water vapor flows and liquid
water flows. In the literature on water and food
production, water vapor and liquid water are sometimes
called green water and blue water, respectively .
Both concepts provide useful tools for the analysis of
local, regional, and global flows in the hydrologic cycle.
Liquid (blue) water flow is the total runoff originating
from the partitioning of precipitation at the land surface
(forming surface runoff ) and the partitioning of soil
water (forming groundwater recharge) .
Water vapor (green) is the return flow of water to the
atmosphere as evapotranspiration (ET), which includes
transpiration by vegetation and evaporation from soil,
lakes, and water intercepted by canopy surfaces .
We regard ET as the result of the work of the whole
ecosystem, including the resilience it needs for securing
the generation of ecosystem services in the long run.
15
https://www.uwsp.edu/natres/nres743/T1Eco2.htm
Nutrient cycle
We already know trees rely on nutrients like phosphorous and
nitrogen for healthy growth and reproduction.
Throughout a trees life stages, they constantly use and return
nutrients to the soil.
Nutrient cycles regularly transform nutrients from the non-living
environment (air, soil, water, rocks) to the living environment and
then back again
SIKLUS AIR
Water is constantly cycling. The water cycle collects, purifies,
and distributes the world�s water. Without the water cycle, life
on earth would be impossible. Trees and plants are part of this
water cycle.
Transpiration is the controlled evaporation process by which
plants lose H2O through the pores in their leaf structures. A fullgrown tree can transpire hundreds of gallons of water a day
during growing season.
https://www.uwsp.edu/natres/nres743/T1Eco2.htm
www.bgky.org/tree/care.php
www.fastest-growingtrees.com/articles/10058-...
19
Sumber: phytosphere.com/vtf/treewater.htm
Water deeply rather than frequently.
Because most tree roots are found in the upper 18 - 24 inches of
the soil, this is the zone that should be wetted up in each
irrigation cycle.
Each deep irrigation will meet a tree's water needs for between 10
days to 4 weeks during the hottest part of the summer,
depending on the tree species and soil type.
www.cmhc-schl.gc.ca/en/co/maho/la/la_003.cfm
Trees require water for many biological functions, but the
function requiring the greatest quantity of water is transpiration .
Transpiration is the movement of water vapour from the leaves of
plants to the atmosphere.
The soil in which trees grow is the reservoir from which tree
roots draw water.
Sumber: www.cmhc-schl.gc.ca/en/co/maho/la/la_003.cfm
As a general rule of thumb, management of trees near
buildings in sensitive clay soils should begin no later than
when the height of the tree is equal to the horizontal
distance of the tree to the building .
www.flemings.com.au/treefacts_environmental.asp
Tree Facts - Environmental Benefits
Trees intercept and slow storm water, decreasing the likelihood of flooding and
erosion, and improving water quality
Large trees have a greater benefit in terms of reducing pollution than small trees
Trees, shrubs, hedges and grasses have a positive effect on the environment by the
transpiration of water and the emission of oxygen by photosynthesis. Plantings
around buildings are a proven method of reducing the demand for artificial heating
and cooling with a resultant, and important, lower use of fossil fuels. Greenery
provides ‘white noise’ reducing the effects of man-made sounds .
Vegetasi pohon untuk pengisian air-tanah
(groundwater)
Air hujan yang jatuh ke tanah tidak seluruhnya langsung mengalir
sebagai air permukaan, tetapi ada yang terserap oleh tanah.
Peresapan air ke dalam tanah pada umumnya terjadi melalui dua
tahapan, yaitu infiltrasi dan perkolasi.
Infiltrasi adalah gerakan air menembus permukaan tanah masuk ke dalam
tanah. Perkolasi adalah proses penyaringan air melalui pori-pori halus
tanah sehingga air dapat meresap ke dalam tanah.
Vegetasi pohon membantu meresapkan air hujan ke dalam
tanah
Kuantitas air yang mampu diserap tanah sangat tergantung
beberapa faktor, yaitu: jumlah air hujan, kondisi fisik tanah seperti bobot
isi, infiltrasi, porositas dan struktur tanah, jumlah tumbuh-tumbuhan
serta lapisan yang tidak dapat ditembus oleh air. Terbentuknya sumbersumber air di alam mengalami serangkaian proses.
Air hujan jatuh ke tanah kemudian meresap ke dalam tanah. Sebelum
mencapai jenuh, air masih dapat diserap oleh tanah. Sampai di
kedalaman tertentu, air tersebut tertahan oleh lapisan batu-batuan
(lapisan kedap air), yang membendung air sehingga tidak terus meresap
ke bawah sehingga membentuk air tanah.
Jika telah mengalami jenuh, air yang jatuh ke permukaan tanah akan
dialirkan sebagai air permukaan.
Tekstur tanah menentukan kemampuannya meresapkan
air hujan
Secara mudah ilfiltrasi digambarkan seperti disebalah ini. Kalau
tanahnya berbutir kasar dan berpori-pori bagus, maka air akan
terserap. Ketika air hujan menjatuhi tanah lanau yg lebih halus,
maka kapasitas ilfiltrasinya berkurang banyak. Demikian juga
ketika air hujan turun tepat diatas lempung, ya lebih sulit lagi
terserap.
www.tanindo.com/abdi18/hal1101.htm
Saat terjadinya hujan, air dapat masuk ke dalam tanah
(infiltrasi) atau mengalir di permukaan tanah (limpasan
permukaan / surface run-off).
Air dalam tanah yang terikat oleh pori-pori dan mineral
tanah, ada yang dapat dimanfaatkan oleh tanaman sebagai
air tersedia, menguap dari permukaan tanah atau mengalir
di permukaan atau ke dalam tanah (perkolasi), dan
tersimpan dalam tanah sebagai air tanah.
Telah diketahui bahwa Konsep daur hidrologi DAS
menjelaskan bahwa air hujan langsung sampai ke
permukaan tanah untuk kemudian terbagi menjadi air
larian, evaporasi dan air infiltrasi, yang kemudian akan
mengalir ke sungai sebagai debit aliran.
Laju in filtrasi air hujan ke dalam tanah menurun dengan
waktu
Deskripsi Singkat
Infiltrasi dari segi hidrologi penting, karena hal ini menandai peralihan
dari air permukaan yang bergerak cepat ke air tanah yang bergerak
lambat dan air tanah.
Kapasitas infiltrasi suatu tanah dipengaruhi oleh sifat-sifat fisiknya dan
derajat kemampatannya, kandungan air dan permebilitas lapisan bawah
permukaan, nisbi air, dan iklim mikro tanah.
Air yang berinfiltrasi pada sutu tanah hutan karena pengaruh gravitasi
dan daya tarik kapiler atau disebabkan juga oleh tekanan dari pukulan air
hujan pada permukaan tanah.
Sumber:
suwitogeografi.blogspot.com/2008_11_08_archiv...
Sirkulasi air yang berpola siklus itu tidak pernah berhenti dari
atmosfir ke bumi dan kembali ke atmosfir melalui kondensasi,
presipitasi, evaporasi, dan transpirasi.Pemanasan air samudera
oleh sinar matahari merupakan kunci proses siklus hidrologi
tersebut dapat berjalan secara kontinu. Air berevaporasi,
kemudian jatuh sebagai presipitasi dalam bentuk hujan, salju,
hujan batu, hujan es dan salju (sleet), hujan gerimis atau kabut.
Pada perjalanan menuju bumi beberapa presipitasi dapat
berevaporasi kembali ke atas atau langsung jatuh yang
kemudian diintersepsi oleh tanaman sebelum mencapai tanah.
Setelah mencapai tanah, siklus hidrologi terus bergerak secara
kontinu dalam tiga cara diantaranya melaui kondensasi,
presipitasi, evaporasi dan transpirasi.
A number of management options have been tried to
conserve water in the soil, improve structural stability and
increase productivity. The available management options
can be grouped into three categories:
a. Tillage based systems
b. Organic systems
c. Biological systems
Sumber: alonashwjis.blogspot.com/2009/11/water-cycle.html
Precipitation rains water onto the ground, after
that it starts to sink in the ground that is called
infiltration.
INFILTRASI - PERKOLASI
Infiltrasi/Perkolasi ke dalam tanah Adalah Air bergerak ke
dalam tanah melalui celah-celah dan pori-pori tanah dan
batuan menuju muka air tanah.
Air dapat bergerak akibat aksi kapiler atau air dapat
bergerak secara vertikal atau horizontal dibawah
permukaan tanah hingga air tersebut memasuki kembali
sistem air permukaan
LENGAS TANAH
Air tanah merupakan air yang mengisi rongga-rongga
batuan di bawah permukaan tanah pada zone jenuh air.
Kondisi air tanah sangat beragam dan pada musim
tertentu akan mengalami perubahan dan faktor tersebut
juga merupakan faktor cuaca dan iklim serta faktor radiasi
terestrial.
Radiasi yang masuk pada tanah pada musim hujan dan
musim kering akan sangat berbeda dan suhu yang terjadi
juga akan mengalami perubahana dengan daya serap
tanah akan berbeda.
Sumber: kangheru.multiply.com/journal/item/5
Sebagian dari air tanah dihisap oleh tumbuh-tumbuhan melalui
daun-daunan lalu menguapkan airnya ke udara (transpiration).
Air yang mengalir di atas permukaan menuju sungai
kemungkinan tertahan di kolam, selokan dan sebagainya
(surface detention), ada juga yang sementara tersimpan di
danau, tetapi kemudian menguap atau sebaliknya sebagian air
mengalir di atas permukaan tanah melalui parit, sungai, hingga
menuju ke laut ( surface run off ), sebagian lagi infiltrasi ke dasar
danau-danau dan bergabung di dalam tanah sebagi air tanah
yang pada akhirnya ke luar sebagi mata air.
AIR TANAH
Air tanah adalah air yang terdapat dalam pori-pori tanah
atau pada celah-celah batuan. Air tanah terbentuk dari
air hujan.
Pada saat turun hujan, sebagian titik-titik air meresap ke
dalam tanah (infiltrasi). Air hujan yang masuk itu yang
menjadi adangan air tanah. Volume air yang meresap ke
dalam tanah tergantung pada jenis lapisan batuannya.
Berdasarkan kenyataan tersebut terdapat pula dua jenis
batuan utama, yaitu lapisan kedap (impermiable) dan
lapisan tanah tidak kedap air (permeable)
Kadar pori lapisan kedap atau tak tembus air sangat
kecil, sehingga kemampuan untuk meneruskan air juga
kecil.
Contoh lapisan kedap, yaitu geluh, napal, dan lempung.
Sedangkan kadar pori lapisan tak kedap air atau tembus
air cukup besar. Oleh karena itu, kemampuan untuk
meneruskan air juga besar.
Contoh lapisan tembus air, yaitu pasir, padas, krikil dan
kapur. Kita akan lihat bersama gambar lapisan kedap
dan lapisan tak kedap pada air tanah di halaman
berikutnya
36
www.aboutcivil.com/hydrology.html
Water Balance Components
Inflow:
Precipitation
Import defined as water channeled into a given area.
Groundwater inflow from adjoining areas.
Outflow:
Surface runoff outflow
Export defined as water channeled out of the same area.
Evaporation
Transpiration
Change in Storage:
This occurs as change in:
Groundwater
Soil moisture
Surface reservoir water and depression storage
Detention Storage
Interception, Stemflow, Canopy Drip,
and Throughfall
Vegetation often modifies the intensity and
distribution of precipitation falling on and
through its leaves and woody structures. The
most obvious effect plants have on falling
precipitation is interception.
Interception can be technically defined as the
capture of precipitation by the plant canopy and
its subsequent return to the atmosphere through
evaporation or sublimation.
The amount of precipitation intercepted by
plants varies with leaf type, canopy architecture,
wind speed, available radiation, temperature, and
the humidity of the atmosphere.
http://www.physicalgeography.net/fundamentals/8k.html
Interception, Stemflow, Canopy Drip,
and Throughfall
Vegetation can intercept up to 50% of the rain
that falls on its leaves. The leaves of deciduous
trees commonly intercept anywhere from 20 to
30% of the falling rain.
Water dripping off leaves to the ground surface
is technically called leaf drip.
http://www.physicalgeography.net/fundamentals/8k.html
Interception, Stemflow, Canopy Drip,
and Throughfall
Precipitation that is not intercepted can be influenced by
the following processes
http://www.physicalgeography.net/fundamentals/8k.html
Interception, Stemflow, Canopy Drip,
and Throughfall
1. Stemflow - is the process that directs precipitation
down plant branches and stems. The redirection of
water by this process causes the ground area
around the plant's stem to receive additional
moisture. The amount of stemflow is determined
by leaf shape and stem and branch architecture. In
general, deciduous trees have more stemflow than
coniferous vegetation.
2. Canopy drip - some plants have an architecture
that directs rainfall or snowfall along the edge of
the plant canopy. This is especially true of
coniferous vegetation. On the ground, canopy drip
creates areas with higher moisture content that
are located in a narrow band at the edge of the
plant canopy.
3. Throughfall - describes the process of
precipitation passing through the plant canopy .
This process is controlled by factors like: plant
leaf and stem density, type of the precipitation,
intensity of the precipitation, and duration of the
precipitation event. The amount of precipitation
passing through varies greatly with vegetation
type.
http://www.physicalgeography.net/fundamentals/8k.html
Interception (water)
Interception refers to precipitation that does not
reach the soil, but is instead intercepted by the
leaves and branches of plants and the forest
floor.
It occurs in the canopy (i.e. canopy interception),
and in the forest floor or litter layer (i.e. forest
floor interception).
Because of evaporation, interception of liquid
water generally leads to loss of that precipitation
for the drainage basin, except for cases such as
fog interception.
en.wikipedia.org/wiki/Interception_(water)
Interception (water)
en.wikipedia.org/wiki/Interception_(water)
Canopy interception.
Canopy interception is the rainfall that is intercepted by
the canopy of a tree and successively evaporates from the
leaves. Precipitation that is not intercepted will fall as
throughfall or stemflow on the forest floor.
Many methods exist to measure canopy interception. The
most often used method is by measuring rainfall above the
canopy and subtract throughfall and stem flow (e.g.,
Helvey and Patric [1965]. However, the problem with this
method is that the canopy is not homogeneous, which
causes difficulty in obtaining representative throughfall
data.
Another method that tried to avoid this problem is applied
by e.g., Shuttleworth et al. [1984], Calder et al. [1986],[ and
Calder [1990]. They covered the forest floor with plastic
sheets and collected the throughfall. The disadvantage of
this method is that it is not suitable for long periods,
because in the end the trees will dry due to water shortage,
and the method is also not applicable for snow events.
The method by Hancock and Crowther [1979] avoided
these problems, by making use of the cantilever effect of
branches. If leaves on a branch hold water, it becomes
more heavy and will bend. By measuring the displacement,
it is possible to determine the amount intercepted water.
en.wikipedia.org/wiki/Interception_(water)
Throughfall
In Hydrology, throughfall is the process which
describes how wet leaves shed excess water
onto the ground surface.
These drops have an erosive power because
they are larger than rain drops, however, if they
travel a shorter distance their erosive power is
reduced. In the case of a high canopy, higher
than what is required for the drops to reach
terminal velocity, about 8 metres, the erosive
power is increased.
Rates of throughfall are higher in areas of forest
where the leaves are broad-leaved. This is
because the flat leaves allow water to collect.
Drip-tips also facilitate throughfall. Rates of
throughfall are lower in coniferous forests as
conifers can only hold individual droplets of
water on their needles.
http://en.wikipedia.org/wiki/Throughfall
Stemflow
In hydrology, stemflow is the flow of intercepted
water down the trunk or stem of a plant.
Stemflow, along with throughfall, are responsible
for the transferral of precipitation and nutrients
from the canopy to the soil.
In tropical rainforests, where this kind of flow
can be substantial, erosion gullies can form at
the base of the trunk.
However, in more temperate climates stemflow
levels are low and have little erosional power
http://en.wikipedia.org/wiki/Stemflow
Stemflow
The primary meteorological characteristics of a
rainfall event that influence stemflow are:
1. Rainfall continuity – the more frequent and
extended are the gaps during the event where
no rainfall occurs, the higher the likelihood
that potential stemflow volume is lost to
evapotranspiration; this is also governed by
air temperature, relative humidity and most
significantly, wind speed
2. Rainfall intensity – the amount of total
stemflow is diminished when the amount of
rain in a given period surpasses the capacity
of the flow paths
3. Rain angle – stemflow generally starts earlier
when rainfall is more horizontal; this is more
of a determinant in an open forest with a
lesser degree of crown closure
.
Stemflow
The species of the tree affects the amount of
timing and stemflow. The particular
morphological characteristics that are key
factors are:
1. Crown size – stemflow potential is greater as
crown size relative to the diameter at breast
height increases
2. Leaf shape/orientation – leaves which are
concave and elevated horizontally above the
petiole are able to contribute to stemflow
3. Branch angle – stemflow potential heightens
as the angle of the branches and twigs
increases
4. Flow path obstructions – abnormalities on the
flow path, such as detached pieces of bark or
scars, on the underside of the branch can
divert water from stemflow and become a
component in throughfall
5. Bark – stemflow is affected by the degree of
absorptive ability and smoothness of the bark
alongside the branch and stem
http://en.wikipedia.org/wiki/Stemflow
Stemflow
Stand Characteristics
In addition to the effects of individual tree
species, the overall structure of the forest stand
also influences the amount of stemflow that will
ultimately occur, these factors are:
1. Species composition – the total stemflow for
the stand is determined by the contributions
of individuals and their species-specific traits
2. Stand density – morphological characteristics
such as branch angle and thickness are
largely determined by the amount of density
of competing trees in the stand
3. Canopy structure – individuals located in the
understory in a stand with multiple verticallystratified stories will have a lessened amount
of total stemflow due to the interception of
dominant and codominant individuals
http://en.wikipedia.org/wiki/Stemflow
Stemflow
Other
1. Seasonality – in the case of deciduous or
mixed forests, stemflow rates are slightly
higher in the dormant season when no leaves
are present and evapotranspiration is
reduced; this effect becomes more
pronounced as the stem diameter increases
2. Diurnality – variations in branch weight
influence the amount of stemflow; branches
are heavier in the morning (with dew) and
lighter in the afternoon
http://en.wikipedia.org/wiki/Stemflow