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PENANAMAN POHON MELESTARIKAN

SUMBER MATA AIRSoemarno - pslp ppsub 2010

BAHAN KAJIAN MANAJEMEN EKOSISTEM

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www.thecottagekey.com/watershed.htm

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Peran pohon dalam siklus

air

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• Provide social, ecological, and economic benefits

• Their leaves and roots clean the air we breathe and the water we drink

Trees: The Original Multi-taskers

Their beauty inspires writers and other artists.

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• Save Energy

• Improve air quality

• Extend life of paved surfaces

• Increase traffic safety

• Increase real estate values

• Increase sociological benefits

• Protect our water resources

Benefits of Trees in Urban Areas

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All water is part of this cycle

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Storm Water and the Hydrologic Cycle

• Urbanization dramatically alters the hydrologic cycle– Increases runoff– Increases flooding

frequency– Decreases infiltration and

groundwater recharge

• Nationwide impervious surfaces have increased by 20% in the past 20 years

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More Trees Means Less Runoff

Some Statistics

• Fayetteville, Arkansas: increasing tree canopy from 27-40% reduced their storm water runoff by 31%

• South Miami residential study found that a 21% existing tree canopy reduces the storm water runoff by 15% For every 5% of tree cover added

to a community, storm water is reduced by approximately 2%

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How Do Trees Effect Stormwater?

• Above ground effects:– Interception,

evaporation and absorption of precipitation

• Ground surface effects:– Temporary storage

• Below ground effects:– Infiltration, permeation

and filtration

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Above Ground Effects

• Intercept rainwater on leaves, branches and trunks – slowing its movement

• Evaporation of some of this intercepted precipitation of the tree surfaces

Absorption of a small portion into leaves or stems

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Leaf litter and other organic

matter can hold precipitation and

stemflow on a site, reducing the amount and peak

rates of runoff

Ground Surface Effects

Roots and trunk bases of mature trees tend to create hollows and

hummocks on the ground

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Below Ground Effects

• Organic material from leaf litter and other tree detritus tends to increase infiltration rates by increasing pore spaces in soil

• Organic material also increases the moisture-holding capacity of these sites

• Root mats of trees also tend to break up most soils further improving infiltration and moisture-holding capacity

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Below Ground Effects cont

• Deep roots tend to improve the rates of percolation of water from upper soil horizons into lower substrates

• Trees take up water through their roots that is eventually transpired onto leaf surfaces and evaporated

• Tree roots act as natural pollution filters (biofilters) using nitrogen, phosphorus and potassium

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EPA’s Tree Canopy Target Goals

• Set to protect a community’s green infrastructure and maximize the environmental benefits

• For metropolitan areas east of the Mississippi– Average tree cover for all land use

40%– Suburban residential

50%– Urban residential

25%– Central business districts

15%

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Complications?

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Complicating Factors• Presence of soil

compaction• Presence of soil textural

discontinuity– Has the site been

disturbed in the past?• Management of the ground

surface– Is litter layer removed?– Is soil surface exposed

in winter?– How much of the

surface is like a natural forest? (number and size of trees)

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Water Movement in Soils• Forces affecting the energy of

soil water– Matric force (absorption

and capillary)– Gravity– Osmotic forces

• Field Capacity is the amount of water held in the soil after gravitational water had drained away

• Movement of water is the soil is controlled :– Gravitational forces if

saturated– Matric forces if unsaturated

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Soil Factors Influencing Infiltration

• Infiltration is the mode of entry of all water into the soil

• Rate of infiltration determined:– Initial water content– Surface permeability– Internal characteristics

of the soil• Intensity and duration of

rainfall• Temperature of soil and

water

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Soil Factors Influencing Infiltration cont.

• Microrelief under trees provides catchment basins during heavy rains

• Removal of litter layer reduces the infiltration rate

• Forest soils have a high percentage of macropores

• The frost type found in forest soils promotes infiltration year-long

Soil compaction reduces the infiltration rate

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Importance of the Litter Layer

• Absorbs several times its own weight

• Breaks the impact of raindrops

• Prevents agitation of the mineral soil

• Discourages formation of surface crusts

• Increases soil biotic activity

• Increases incorporation of organics

• Slows down lateral movement of water

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Affect of Micropores in the Soil

• Develop in old root channels or from burrows and tunnels made by insects, worms or other animals

• Lead to better soil structure

• Increases organic matter incorporation

• Increases percolation rates and root penetration

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Soil Frost Types• Granular

– Small frost crystals intermingled with soil particles

– Found in woodland soils with litter

– May be more permeable than unfrozen soil

• Honeycomb– Has loose porous

structure– Found in highly

aggregated soils and also formed in organic layers and litter layers

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Source and fate of water added to a soil system.

The proportion of the soil occupied by water and air is

referred to as the pore volume. The pore volume is generally constant for a given soil layer but may be altered by tillage and compaction. The ratio of

air to water stored in the pores changes as water is added to or lost from the soil. Water is added by rainfall or irrigation. Water is lost through surface

runoff, evaporation (direct loss from the soil to the

atmosphere), transpiration (losses from plant tissue), and

either percolation (seepage into lower layers) or drainage.

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Components of Ground Water Use and Sources

of Recharge

There is a substantial amount of ground water recharge from surface

water and ground water used to irrigate

agricultural crops. Some of the irrigation

water flowing in unlined ditches and some of the water that is applied to irrigate crops infiltrates into the soil, percolates through the root zone

and recharges the ground water basins

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Ground waterGround water occupies the zone of saturation. Ground

water moves downward through the soil by percolation

and then toward a stream channel or large body of water

as seepage. The water table separates the zone of

saturation from the zone of aeration.

The water table fluctuates with moisture conditions, during wet times the water table will rise as more pore spaces are occupied

with water. Ground water is found in aquifers, bodies of earth material that have the ability to hold and transmit

water. Aquifers can be either unconfined or confined.

Unconfined (open) aquifers are "connected" to the surface

above.

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Aquifers replenish their supply of water very slowly.

The rate of ground water flow depends on the permeability of the aquifer and the hydraulic gradient. Permeability is affected by the size and

connectivity of pore spaces. Larger, better connected pore spaces creates highly permeable earth material. The hydraulic gradient is the difference in elevation between two points on the water table divided by the horizontal

distance between them.

The rate of ground water flow is expressed by the equation:

Ground water flow rate = permeability X hydraulic gradient

Groundwater flow rates are usually quite slow. Average ground water flow rate of 15 m per day is common. Highly

permeable materials like gravels can have flow velocities of 125 m per day.

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Ground water in an aquifer is under pressure called

hydrostatic pressure. Hydrostatic pressure in

a confined aquifer pushes water upward when a well is drilled

into the aquifer.

The height to which the water rises is called the peizometeric surface. If

the hydrostatic pressure is great

enough to push the peizometeric surface

above the elevation of the surface, water

readily flows out as an artesian well.

www.uwsp.edu/geo/faculty/ritter/geog101/textb...

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Following an infiltration event, in which the entire soil profile becomes saturated with water (indicated by a solid vertical line corresponding to a

water saturation of 1.0), water will drain from the soil profile primarily

under the influence of gravity (i.e., the pressure gradient is negligible).

Assuming that no additional water enters the system, the soil water

saturation profile at static equilibrium (dashed line) will decrease from a value of 1.0 in the saturated zone

(groundwater and capillary fringe) to a value corresponding to field capacity below the root zone. In effect, the soil

water profile is analogous to a soil water retention (pressure-saturation) curve. Hence, the solid and dashed lines represent the limits in water

content (saturation) between which soil water percolation occurs in soils

overlying an unconfined aquifer.

www.informaworld.com/smpp/95829679-70617050/c...

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Water is recharged to the ground-

water system by percolation of water from precipitation

and then flows to the stream through the

ground-water system.

ga.water.usgs.gov/edu/earthgwdecline.html

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Water pumped from the ground-

water system causes the water

table to lower and alters the direction of

ground-water movement.

Some water that flowed to the

stream no longer does so and

some water may be drawn in from the stream into

the ground-water system, thereby

reducing the amount of

streamflow.

.

                                                                                                                                               

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Contaminants introduced at the land surface may

infiltrate to the water table and flow towards a

point of discharge, either

the well or the stream. (Not

shown, but also important, is the

potential movement of contaminants

from the stream into the ground-water system.)

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Water-level declines may affect the

environment for plants and animals.

For example, plants in the riparian zone that grew because of the

close proximity of the water table to the land

surface may not survive as the depth to

water increases.

The environment for fish and other aquatic species also may be altered as the stream

level drops.

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The fate of applied water can be better understood if the total

hydrologic cycle is understood first.  The hydrologic cycle,

illustrated in Figure 1, describes the movement of water through its

different forms and locations.   Important processes in the

hydrologic cycle are: 1. Evaporation -the transformation

of liquid water into water vapor from free water surfaces.

2. Precipitation (rain or snow). 3. Runoff -water moving overland

or in a river or stream. 4. Infiltration -the movement of

water into the soil. 5. Percolation -the movement of

water through the soil. 6. Freezing - liquid water turning

into ice 7. Thawing - melting of ice

8. Transpiration - the movement of water vapor out through

plant/animal tissue surfaces into the atmosphere.

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www.forestry.ubc.ca/.../forwady/forwady.htm

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Forests and the Hydrologic Cycle

The surface water in a stream, lake, or wetland is most commonly precipitation that has run off the land or flowed through topsoils to subsequently enter the

waterbody. If a surficial aquifer is present and hydraulically connected to a surface-water body, the aquifer can sustain surface flow by releasing water to it.

In general, a heavy rainfall causes a temporary and relatively rapid increase in streamflow due to surface runoff. This increased flow is followed by a relatively

slow decline back to baseflow, which is the amount of streamflow derived largely or entirely from groundwater. During long dry spells, streams with a baseflow

component will keep flowing, whereas streams relying totally on precipitation will cease flowing.

Generally speaking, a natural, expansive forest environment can enhance and sustain relationships in the water cycle because there are less human

modifications to interfere with its components. A forested watershed helps moderate storm flows by increasing infiltration and reducing overland runoff.

Further, a forest helps sustain streamflow by reducing evaporation (e.g., owing to slightly lower temperatures in shaded areas). Forests can help increase recharge

to aquifers by allowing more precipitation to infiltrate the soil, as opposed to rapidly running off the land to a downslope area.

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• Forests and prairies rarely yield runoff regardless of steepness, even when frozen

Forested areas provide storm water protection and protect the

quantity and quality of groundwater

Implications of Frost Types

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Groundwater –Surface Water Flows

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Black Earth Creek Study

• Black Earth Creek receives 80% of its water from groundwater

• Main recharge occurs in spring and fall

• Recharge from the agricultural uplands is highly variable

• Forested slopes are significant recharge areas Wooded hill slopes generate

no significant runoff

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Effects are greatest during

the growing season

Effects are greatest on sites whose soils are

relatively impermeable

Trees and Storm Water: Conclusions

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The impact of urban trees on hydrology is extremely variable and complex, in general increases in tree cover and tree size

over a site will result in reduced total runoff amounts and peak runoff rates.

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Trees and Storm Water:

• Trees have a relatively greater effect on smaller storm runoff amounts than on large storm events

• Surface and below-ground effects on runoff are much more significant than the above-ground effects

• All of the effects on runoff are greatest when urban trees are large and well-established on undisturbed sites

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Contact Information:Mindy Habecker

Dane County UW-Extension 224-3718Habecker@co.dane.wi.us

46www.cropscience.org.au/.../1399_shahbazkhan.htm

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www.ene.gov.on.ca/envision/gp/4329e_1.htm

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www.aucklandcity.govt.nz/.../hgiapp15.asp

Typical root systems are made up of a combination of four types of roots: major lateral roots sinker roots woody feeder roots non-woody feeder roots.

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www.dof.virginia.gov/urban/landscape-

manual.shtml

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Tree and Root System on Bank of

Darling River, Kinchega National

Park, Outback, New South Wales,

Australia 

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en.allexperts.com/q/Trees-739/Douglas-Fir-Roo...

54www.forestry.ubc.ca/.../forwady/forwady.htm

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www.icsu-scope.org/.../scope51/chapter06.html

A model illustrating fluxes of sulphur in a forest ecosystem

57Schematic illustration of the biogeochemical processes of importance in long-term research of a watershed (Swank, 1986).

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

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

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61www.waterbucket.ca/rm/?sid=33&id=271&type=single

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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.

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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. 

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wwa.colorado.edu/treeflow/lees/treering.html

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SOIL WATER

infiltration & percolationpermeability

porosity

Zone of aeration:soil water storage

plant uptake & transpirationevaporationthroughflow

Water table

Zone of saturation:groundwater flow

aquifer

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

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HYDROLOGIC CYCLE & WATER BUDGETS

What happens to precipitation?

Water budget: local scale examination of the gains, uses, and losses of water

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

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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

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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.

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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

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Water cycle

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

72www.bgky.org/tree/care.php

73

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

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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.

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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.

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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

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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

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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 bisa meresap ke dalam tanah.

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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.

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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.

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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.

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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.

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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.

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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.

suwitogeografi.blogspot.com/2008_11_08_archiv...

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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

86

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.

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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

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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.

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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.

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

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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

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Hydrological SystemsA hydrologic system is as a structure or volume in space, surrounded by a

boundary, that accepts water and other inputs, operates on them internally, and produces them as outputs.

93

supit.net/main.php?q=aXRlbV9pZD02Mg==

Water supply to the roots,

infiltration, runoff,

percolation and redistribution of water in a one-

dimensional profile are

derived from hydraulic

characteristics and moisture

storage capacity of the soil.

94

www.treemail.nl/.../treebook7/soil/chapt6.htm

The processes directly affecting the root zone soil

moisture content can be defined as:

Infiltration: i.e. transport from the soil surface into the root

zone; Evaporation: i.e. the loss of

soil moisture to the atmosphere;

Plant transpiration: i.e. loss of water from the interior root

zone; Percolation: i.e. downward transport of water from the root zone to the layer below

the root zone; Capillary rise: i.e. upward

transport into the rooted zone.

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Preliminary infiltration

The infiltration rate depends on the available water and the infiltration capacity of the soil. If the actual surface storage is less then or equal to 0.1 cm, the preliminary

infiltration capacity is simply described as:

WhereINp : Preliminary infiltration rate[cm d-1]FI : Maximum fraction of rain not infiltrating during time step t[-]CI : Reduction factor applied to FI as a function of the precipitation intensity[-]P : Precipitation intensity[cm d-1]Ie : Effective irrigation[cm d-1]SSt : Surface storage at time step t [cm]Dt : Time step[d]

The maximum fraction of rain not infiltrating during time step t, FI can be either set to a fixed value or assumed to be variable by multiplying FI with a precipitation dependent reduction factor CI which is maximum for high rainfall and will be

reduced for low rainfall. The user should provide FI. The CI table is included in the model and is assumed to be fixed.

                                 

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The calculated infiltration rate is preliminary, as the storage capacity of the soil is not yet taken into account.

If the actual surface storage is more than 0.1 cm, the available water which can potentially infiltrate, is equal to the water amount on the surface (i.e. supplied via

rainfall/irrigation and depleted via evaporation):

WhereINp : Preliminary infiltration rate[cm d-1]P : Precipitation intensity[cm d-1Ie : Effective irrigation[cm d-1]Ew : Evaporation rate from a shaded water surface[cm d-1]SS : Surface storage at time step t [cm]Dt :Time step[d]

However, the infiltration rate is hampered by the soil conductivity and cannot exceed it. Soil conductivity is soil specific and should be given by the user.  

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Adjusted infiltration Total water loss from the root zone can now be calculated as the sum of

transpiration, evaporation and percolation. The sum of total water loss and available pore space in the root zone define the maximum infiltration rate. The

preliminary infiltration rate cannot exceed this value. The maximum possible infiltration rate is given by:

Where:INmax :Maximum infiltration rate[cm d-1]qmax :Soil porosity (maximum soil moisture)[cm3 cm-3]Qt :Actual soil moisture content[cm3 cm-3]RD :Actual rooting depth[cm]Dt :Time step[d]Ta:Actual transpiration rate[cm d-1Es :Evaporation rate from a shaded soil surface [cm d-1]Perc :Percolation rate from root zone to lower zone[cm d-1]

                                              

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PERKOLASI If the root zone soil moisture content is above field capacity, water percolates to the lower part of the potentially rootable zone and the subsoil. A clear distinction is made between percolation from the actual rootzone to the so-called lower zone, and percolation from the lower zone to the subsoil. The former is called Perc and

the latter is called Loss. The percolation rate from the rooted zone can be calculated as:

WherePerc : Percolation rate from the root zone to the lower zone[cm d-1]Wrz : Soil moisture amount in the root zone [cm]Wrz,fc Equilibrium soil moisture amount in the root zone [cm]Dt : Time step[d]Ta : Actual transpiration rate [cm d-1]Es : Evaporation rate from a shaded soil surface [cm d-1]

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The equilibrium soil moisture amount in the root zone can be calculated as the soil moisture content at field capacity times the depth of the

rooting zone:

WhereWrz,fc : Equilibrium soil moisture amount in the root zone[cm]Qfc : Soil moisture content at field capacity[cm3 cm-3]RD : Actual rooting depth[cm]

                 

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The percolation rate and infiltration rate are limited by the conductivity of the wet soil, which is soil specific and should be given by the user. Note that the

percolation from the root zone to the lower zone can be limited by the uptake capacity of the lower zone.

The value calculated is preliminary and the uptake capacity should first be checked.

The percolation from the lower zone to the subsoil, the so-called Loss, should take the water amount in the lower zone into account. If the water amount in the

lower zone is less than the equilibrium soil moisture amount, a part of the percolating water will be retained and the percolation rate will be reduced.

Water loss from the lower end of the maximum root zone can be calculated as:

WhereLoss :Percolation rate from the lower zone to the subsoil[cm d-1]Perc :Percolation rate from root zone to lower zone (see eq. 6.21)[cm d-1]Wlz :Soil moisture amount in the lower zone [cm]Wlz,fc :Equilibrium soil moisture amount in the lower zone [cm]Dt :Time step

                            

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Water loss from the potentially rootable zone, is also limited by the maximum percolation rate of the subsoil, which is soil specific and should be provided by the

user. The equilibrium soil moisture amount in the lower zone can be calculated as the soil

moisture content at field capacity times the root zone depth:

WhereWrz,fc : Equilibrium soil moisture amount in the lower zone[cm]Qfc :Soil moisture content at field capacity[cm3 cm-3]RDmax :Maximum rooting depth[cm]RD :Actual rooting depth[cm]

For rice an additional limit of five percent of the saturated soil conductivity is set to account for puddling (a rather arbitrary value, which may be easily changed in the

program). The saturated soil conductivity and is calculated with pF= -1.0 (i.e. a hydraulic head of 0.1 cm). The percolation rate from the lower zone to the sub soil is not to exceed this

value (van Diepen et al., 1988). The value calculated should be regarded as preliminary; the storage capacity of the

receiving layer may become limiting.

                                                       

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The storage capacity of the lower zone, also called the uptake capacity, is the amount of air plus the loss.

It can de defined as:

WhereUP :Uptake capacity of lower zone[cm d-1]RDmax :Maximum rooting depth[cm]RD :Actual rooting depth[cm]Wlz :Soil moisture amount in lower zone[cm]Qmax :Soil porosity (maximum soil moisture)[cm3 cm-3]Dt :Time step[d]Loss :Percolation rate from the lower zone to the subsoil[cm d-1]

Percolation to the lower part of the potentially rootable zone can not exceed the uptake capacity of the lower zone. Therefore the percolation rate is set equal to the minimum of the calculated percolation rate and the uptake.

                                         

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LIMPASAN PERMUKAAN : Surface runoff Surface runoff is also taken into account by defining a maximum value for surface storage. If the surface storage exceeds this value the exceeding water amount will

run off. Surface storage at time step t can be calculated as:

WhereSSt : Surface storage at time step t[cm d-1]P : Precipitation intensity[cm d-1]Ie : Effective irrigation rate[cm d-1]Ew : Evaporation rate from a shaded water surface[cm d-1]IN : Infiltration rate (adjusted)[cm d-1]

Surface runoff can be calculated as:

WhereSRt:Surface runoff at time step t[cm]SSt:Surface storage at time step t[cm]SSmax:Maximum surface storage[cm]SSmax is an environmental specific variable and should be provided by the user.

                                                                       

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Rates of change and root extension The rates of change in the water amount in the root and lower zone are calculated straightforward from the flows found above:

WhereDWrz :Change of the soil moisture amount in the root zone[cm]DWlz :Change of the soil moisture amount in the lower zone[cm]Ta :Actual transpiration rate[cm d-1]Es :Evaporation rate from a shaded soil surface[cm d-1]; IN :Infiltration rate[cm d-1]Perc :Percolation rate from root zone to lower zone[cm d-1]Loss :Percolation rate from lower zone to sub soil[cm d-1]; Dt :Time step[d]

Due to extension of the roots into the lower zone, extra soil moisture becomes available, which can be calculated as:

WhereRDt :Rooting depth at time step t[cm]RDt-1:Rooting depth at time step t-1[cm]RDmax:Maximum rooting depth[cm]Wlz:Soil moisture amount in the lower zone [cm]DWrz:Change of the soil moisture amount in the root zone[cm]DWlz:Change of the soil moisture amount in the lower zone[cm]

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The actual water amount in the root zone and in the lower zone can be calculated according to:

Where:

Wrz,t : Soil moisture amount in the root zone at time step t[cm]Wlz,t : Soil moisture amount in the lower zone at time step t[cm]Wrz,t-1: Soil moisture amount in the root zone at time step t-1[cm]Wlz,t-1: Soil moisture amount in the lower zone at time step t-1[cm]DWrz : Rate of change of the soil moisture amount in the root zone[cm]DWlz : Rate of change of the soil moisture amount in the lower zone[cm]

                        

                        

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Actual soil moisture content

The actual soil moisture content can now be calculated according to :

Whereqt : Actual soil moisture content at time step t [cm3 cm-3]Wrz,t : Soil moisture amount in the root zone at time step t [cm]RD : Actual rooting depth [cm]

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www.tutorvista.com/search/effects-of-soil-erosion

Effects of Deforestation1) Percolation and ground water

recharge has decreased.2) Floods and drought have become more frequent. 3) Soil erosion has

increased.

4) Pattern of rainfall has changed. 5) Land slides and avalanches are on

the increase.

6) Climate has become warmer in the deforested region due to lack of

humidity added by the plants. 7) Consumption of CO2 and

production of O2 is adversely affected.

8) Man has been deprived of the benefits of trees and animals. 9)

Extinction of many species of plants and animals, still not discovered by

scientists.

10) Shortage of fuel

108

www.cluin.org/studio/2003phyto/abstracts.htm

109

www.worldagroforestry.org/af2/?q=node/122

GenRiver: Generic River model on river flow

Overview of the GenRiver model; the multiple

subcatchments that make up the catchment as a whole

can differ in basic soil properties, land cover

fractions that affect interception, soil structure

(infiltration rate) and seasonal pattern of water

use by the vegetation.

The subcatchment will also typically differ in ‘routing time' or in the time it takes

the streams and river to reach the observation point

of main interest

110

Genriver Components GenRiver model consists of several sectors, which are related to one

another. Those sectors are:Water Balance is a main sector that

calculating the input, output, and storage changes of water in the

systems. Some components which are in this sector, rainfall, interception, infiltration,

percolation, soil water, surface flow, soil discharge, deep

infiltration, ground water area and base flow

Stream Network is a sector that estimating the flow of water from the river to the final outlet. Some

components which are in this sector, total ttream in flow, routing

time, direct surface flow, delay surface flow, river flow to final

outlet. Land Cover  ,

Subcatachment Parameter is a sector stired constant parameters that control to the changes of water balance, landcover and stream

network.

111

www.ecy.wa.gov/programs/sea/pubs/93-31/chap1.html

112

www.ecolotree.com/applications.html