MENANAM POHON UNTUK

MEMANEN AIR HUJAN

AIR HUJAN

Soemarno - psdl ppsub 2013

Profil pohon dalam menangkap air hujan dan energi matahari.

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www.icsu-scope.org/.../scope51/chapter06.htmlA model illustrating fluxes of sulphur in a forest

ecosystem

4Schematic illustration of the biogeochemical processes of importance in long-term research of a watershed (Swank, 1986).

Sumber: www.aracruz.com.br/show.do?menu=true&id=943...

Vegetasi pohon mengamankan tebing curam dari bahaya longsor

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Sumber: sofia.usgs.gov/publications/posters/challenge/

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 on-the-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

SOIL WATER

Infiltration & percolation; permeability; PorosityZone of aeration: soil water storage; plant uptake & transpiration

evaporation; Throughflow; Water tableZone of saturation: groundwater flow; aquifer.

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

Sumber: www.uwsp.edu/geo/faculty/lemke/geog101/lectur.....

WATER BALANCEGains: 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.

Vegetasi Pohon memperbaiki neraca-air bentang lahan

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).

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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.

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 full-grown 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

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www.fastest-growing-trees.com/articles/10058-

...

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.cfmTrees 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 .

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 untuk pengisian air-tanah (groundwater)

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 sumber-sumber

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.

Vegetasi pohon membantu meresapkan air hujan ke dalam tanah

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.

Tekstur tanah menentukan kemampuannya meresapkan air hujan

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.

Deskripsi SingkatInfiltrasi 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.

Laju in filtrasi air hujan ke dalam tanah menurun dengan waktu

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.

Sumber: suwitogeografi.blogspot.com/2008_11_08_archiv...

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 TANAHAir 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.

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.

Sumber: kangheru.multiply.com/journal/item/5

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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

www.aboutcivil.com/hydrology.html

Water Balance ComponentsInflow:

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

http://www.physicalgeography.net/fundamentals/8k.html

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.

Interception, Stemflow, Canopy Drip,and Throughfall

http://www.physicalgeography.net/fundamentals/8k.html

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.

Interception, Stemflow, Canopy Drip,and Throughfall

http://www.physicalgeography.net/fundamentals/8k.html

Precipitation that is not intercepted can be influenced by the following processes

Interception, Stemflow, Canopy Drip,and Throughfall

http://www.physicalgeography.net/fundamentals/8k.html

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.

Interception (water)

en.wikipedia.org/wiki/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)

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

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

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 CharacteristicsIn 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 vertically-stratified 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