SWRM: SUSTAINABLE WATER RESOURCES MANAGEMENT

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SWRMSUSTAINABLE WATER RESOURCES MANAGEMENT
ASSESSMENT of COMPETENCY AREAS
Bahan kajian MK. Perecanaan Lingkungan dan
Pengembangan Wilayah PSDAL-PDIP-PPS FPUB.
Penyaji Soemarno 2011
2
Water resources are sources of water that are
useful or potentially useful to humans. Uses of
water include agricultural, industrial,
household, recreational and environmental
activities. Virtually all of these human uses
require fresh water. Fresh water is a renewable
resource, yet the world's supply of clean, fresh
water is steadily decreasing. Water demand
already exceeds supply in many parts of the world
and as the world population continues to rise, so
too does the water demand. Awareness of the
global importance of preserving water for
ecosystem services has only recently emerged as,
during the 20th century, more than half the
worlds wetlands have been lost along with their
valuable environmental services.
Biodiversity-rich freshwater ecosystems are
currently declining faster than marine or land
ecosystems. The framework for allocating water
resources to water users (where such a framework
exists) is known as water rights.
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Water management is the activity of planning,
developing, distributing and optimum use of water
resources under defined water polices and
regulations. It may mean Management of water
treatment of drinking water, industrial water,
sewage or wastewater Management of water
resources Management of flood protection
Management of irrigation Management of the
water table.
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Shift in Thinking is Needed from Blue Water to
Green Water Under the pressures of population
growth, development aspirations and a growing
knowledge of the importance of ecosystem support
and services, water is increasingly understood as
a key factor in socio-economic development.
This will require a broadening of the global
water debate from its current concentration on
managing blue water resources in rivers, lakes
and aquifers, and its current focus on the
provision of potable water, the financing of such
provision, and whether more water for irrigation
can solve the worlds food challenge.
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Green water is a significant water resource, much
larger volume-wise than the water replenishing
streams, lakes and aquifers (blue water).
http//chaire-landoltetcie.epfl.ch/en/conferences
/water-food
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A conceptual breakthrough that allowed an
integrated land-water approach came at a UN Food
and Agriculture Organization seminar in January
1993, when the concept of green water was
proposed for soil moisture . According to this
concept, rainfall constitutes the basic water
resource and is partitioned between green
water, which is consumed by vegetation, and
blue water, which constitutes water in rivers
and aquifers, accessible for societal use. Green
water is important to terrestrial ecosystems. It
is involved in (rainfed) plant production and,
therefore, in the production of food, fuelwood,
biofuels, timber, and forests. Because changes in
plant cover alter the partitioning between green
and blue water resources, this plant cover change
is a key phenomenon in deforestation and
reforestation. Blue water, on the other hand, is
the base for the household, municipality,
industry, and irrigated agriculture water supply
a carrier of solutes and silt through the water
systems and the habitat for aquatic ecosystems.
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GREEN BLUE BALANCE
Sumber http//ga.water.usgs.gov/edu/watercyclesum
mary.html
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The reality of the big picture is that in a
drainage basin perspective, the rainfall over an
area is the water resource. Part of the water is
consumed in terrestrial ecosystems by vegetation
and evaporation from moist surfaces (green water
fl ow), while the surplus recharges aquifers and
rivers (blue water) becoming available for
societal use and aquatic ecosystems. Naturally,
indicated, the green-blue balance is determined
by the local hydroclimate.
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GREEN WATER MANAGEMENT The water necessary to
produce the food required for an expanding human
population is usually discussed only as an issue
of blue water for irrigation (the water we use
from rivers and quifers). Most food production
is from rain fed farming. This is critical not
least in hunger and poverty stricken areas with
rapid population growth, areas that depend not on
blue water but on green water from infi ltrated
rain (the soil moistures used by plants and
returned as vapour flow). A shift in water
thinking which considers soil moisture is
essential in order to find realistic and
sustainable options to feed the world of tomorrow.
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Rain is the global water resource. How well we
capture and manage it will determine if we can
feed the planets 9 billion inhabitants by 2050.
Blue water is the liquid water in rivers and
aquifers. The narrow focus on blue water as the
only water resource leads us to believe that
agriculture uses 70 of the worlds freshwater,
industry 20 and domestic use 10. In reality,
this is not the case.
Green water is the soil moisture, exhaled during
plant growth as vapour flow from land to the
atmosphere.
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A sustainable water future needs to incorporate
the green water-consuming systems, which are
generally much larger and which provide life
support to humans and nature.
The bulk of future freshwater needs for food
production will have to come from green water
management. This will affect downstream water
availability.
Of the worlds poor, 70 live in rural areas and
often depend on rainfall-based sources of income.
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The planet will need an additional 5,600 km3/yr
of water to feed itself by 2050. The most
optimistic irrigation projections show that no
more than 800 km3/yr could be contributed by blue
water by expansion and effi ciency improvement of
irrigation.
Climate change is a strong driving force for
lessening societys large-scale dependence on
fossil fuels through increased use of renewable
energy, though such a move will increase
consumptive water use for biomass-based fuel
alternatives.
The future conflicts of interest will be over
land use-water use, water quantity-quality,
upstream-downstream availability, and
humans-ecosystems.
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A sustainable water future needs to incorporate
the water from infiltrated rain and the
water-consuming vegetation systems which provide
life support to humans and nature
Water is of central importance in other sectors
industry production, forestry and fibre
production, fisheries, etc.
Huge amounts of water are needed to feed
humanity, and today nearly three time more water
is used in rain fed agriculture than in irrigated
agriculture, with a total global consumption of
7,000 km3/year. In short, 50 to 100 times more
water is needed to produce food for one person
than the amount needed on a household domestic
consumption level.
Upstream land use and water management
determines the volumes, patterns of fl ow and
quality of water for downstream use, making
upstream land use for forestry, rainfed farming
and grazing (all of which consumes freshwater) a
determinant of blue water availability downstream.
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A sustainable water future needs to incorporate
the water from infiltrated rain and the
water-consuming vegetation systems which provide
life support to humans and nature
Huge volumes of blue water fl ows are required
to sustain aquatic ecological functions in
rivers, lakes, riparian zones and estuaries.
Water supply for various sectors of society is
getting increasingly complicated as water
contamination escalates, and awareness grows
among water users of the links between upstream
polluters of water with downstream water users.
The largest freshwater consumption is required to
sustain biomass growth in terrestrial
ecosystems, supporting key ecological functions
such as biodiversity, carbon sequestration and
anti-desertifi cation.
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Key
Recommendations 1. Raise awareness of the
distinction between blue water in rivers and
aquifers and green water in the soil. 2. Accept
in scientifi c, management, political and other
circles the fundamental fact that there is not
enoughblue water left to meet competing food,
water and environment needs for the future in
large regions. 3. At the same time realise that
proper management of the green water in the soil
represents a large potential for global food
production. 4. Analyse the linkages between
global trade regimes and different strategies to
attain national food security. 5. Introduce a
green water dimension and incorporate land-use
into IWRM and adequate governance
activities. 6. Further clarify the linkages
between global poverty, hunger and shortage of
green and/or blue water. 7. Raise awareness of
the improvements possible in the livelihoods of
communities particularly those in water-scarce
regions through a broadened approach to
water. 8. Further clarify the linkages between
rain fed agriculture and both green and blue
water.
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Integrated Water Resources Management Integrated
Water Resources Management (IWRM) has been
defined by the Technical Committee of the Global
Water Partnership (GWP) as "a process which
promotes the coordinated development and
management of water, land and related resources,
in order to maximize the resultant economic and
social welfare in an equitable manner without
compromising the sustainability of vital
ecosystems."
IWRM approaches involve applying knowledge from
various disciplines as well as the insights from
diverse stakeholders to devise and implement
efficient, equitable and sustainable solutions to
water and development problems.
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Integrated Water Resources Management IWRM is a
comprehensive, participatory planning and
implementation tool for managing and developing
water resources in a way that balances social and
economic needs, and that ensures the protection
of ecosystems for future generations. Waters
many different usesfor agriculture, for healthy
ecosystems, for people and livelihoodsdemands
coordinated action. An IWRM approach is an
open, flexible process, bringing together
decision-makers across the various sectors that
impact water resources, and bringing all
stakeholders to the table to set policy and make
sound, balanced decisions in response to specific
water challenges faced.
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• It has been agreed to consider water as an
  'finite and economic commodity , in order to
  emphasize on its scarcity in the
• Fresh water is a finite and vulnerable resource,
  essential to sustain life, development and the
  environment.
• Water development and management should be based
  on a participatory approach, involving users,
  planners and policy makers at all levels.
• Women play a central part in the provision,
  management and safeguarding of water.
• Water has an economic value in all its competing
  uses and should be recognized as an economic
  good, taking into account of affordability and
  equity criteria.

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Green and blue water flow domains for human life
support, distinguished in direct functions
(direct social and economic support) and indirect
functions (water for ecosystem support).
20
Sumber Daya Air (SDA)  mempunyai sifat mengalir
dan dinamis serta berinteraksi dengan sistem
sumber daya lain dari berbagai sektor dengan
berbagai kepentingan dari para pemilik
kepentingan sehingga membentuk suatu sistem yang
disebut sistem wilayah sungai yang tak jarang
sangat kompleks, contohnya saja sistem wilayah
sungai Brantas.
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DAS adalah kesatuan terkecil dari pengelolaan
air, aspek pengelolaannya meliputi Daerah
tangkapan hujan Kuantitas air Kualitas
air Pengendalian banjir Jasa Lingkungan DAS
Prasarana pengairan
Sumber http//prairierivers.org/tag/watershed-pla
nning/
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CALCULATING A MONTHLY WATER BUDGET
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NERACA AIR Keseimbangan air masuk dan air ke
luar di suatu daerah hidrologi yg ditetapkan,
misalnya cekungan, danau, dan lainnya, dengan
diperhitungkan bahwa tempat menyimpan tidak
berubah (water balance)
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IRRIGATION

• A. Definition Supplying water to plants in an
  artificial manner. (39 of all freshwater in the
  US is used to irrigate crops)
• 1. Ancient practice first irrigation used
  ditches to divert rivers and streams.
• 2. Modern agriculture relies on irrigation.
• a. Tropical climate
• b. Crop diversification
• c. Economics

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Surface Irrigation
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Surface Irrigation

• Water flows across the soil surface to the point
  of infiltration
• Oldest irrigation method and most widely used
  world-wide (90) and in U.S. (60)
• Used primarily on agricultural or orchard crops

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Types of irrigation Systems

• Water Spreading or Wild Flooding
• Relatively flat fields -- allow water to find its
  own way across the surface
• Minimal preparation and investment
• Rather inefficient
• Basin
• Dikes used to surround an area and allow for
  water ponding (no runoff)
• Basins are usually level

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Flood Irrigation

• Advantages
• inexpensive
• less labor
• large amounts of water leach salts
• rodent control

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Flood Irrigation

• Disadvantages
• land must be leveled or contoured
• uses large amounts of water
• water loss through evaporation
• may cause disease in some crops if applied
  incorrectly
• run off water can cause problems (silt buildup in
  rivers, may contain pesticides)

http//article.wn.com/view/2009/12/10/Irrigation_i
mprovement_must_for_agriculture_growth_PM/
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Furrow Irrigation

• Used in row crops such as beans, tomatoes, corn,
  sugar beets other vegetable crops.
• Similar advantages and disadvantages to flood
  irrigation.

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Furrow Irrigation
http//luirig.altervista.org/cpm/thumbnails.php?al
bum60page9
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Sprinkler Irrigation

• Many types micro-sprinklers, solid set, aluminum
  pipe
• a. Advantages use less water, more precise
  amounts of water can be applied, less run off
  (tail water), may be used on slightly hilly land
• b. Disadvantages expensive (installation,
  labor, filters, maintenance), salt buildup

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KANDUNGAN AIR DAN TEGANGAN
KURVA ENERGI - LENGAS TANAH Tegangan air menurun
secara gradual dengan meningkatnya kadar air
tanah. Tanah liat menahan air lebih banyak
dibanding tanah pasir pada nilai tegangan air
yang sama Tanah yang Strukturnya baik mempunyai
total pori lebih banyak, shg mampu menahan air
lebih banyak Pori medium dan mikro lebih kuat
menahan air dp pori makro
Tegangan air tanah, Bar 10.000 Liat Lem
pung Pasir 0.01 10 Kadar air tanah,
70
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Soil moisture content The soil moisture content
indicates the amount of water present in the
soil. It is commonly expressed as the amount of
water (in mm of water depth) present in a depth
of one metre of soil. For example when an amount
of water (in mm of water depth) of 150 mm is
present in a depth of one metre of soil, the soil
moisture content is 150 mm/m
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• A very general and simplified soil profile can be
  described as follows
• The plough layer (20 to 30 cm thick) is rich in
  organic matter and contains many live roots. This
  layer is subject to land preparation (e.g.
  ploughing, harrowing etc.) and often has a dark
  colour (brown to black).
• b. The deep plough layer contains much less
  organic matter and live roots. This layer is
  hardly affected by normal land preparation
  activities. The colour is lighter, often grey,
  and sometimes mottled with yellowish or reddish
  spots.
• c. The subsoil layer hardly any organic matter
  or live roots are to be found. This layer is not
  very important for plant growth as only a few
  roots will reach it.
• d. The parent rock layer consists of rock, from
  the degradation of which the soil was formed.
  This rock is sometimes called parent material.

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Gerakan Air Tanah Tidak Jenuh
Gerakan tidak jenuh gejala kapilaritas air
bergerak dari muka air tanah ke atas melalui pori
mikro. Gaya adhesi dan kohesi bekerja aktif pada
kolom air (dalam pri mikro), ujung kolom air
berbentuk cekung. Perbedaan tegangan air tanah
akan menentukan arah gerakan air tanah secara
tidak jenuh.
Air bergerak dari daerah dengan tegangan rendah
(kadar air tinggi) ke daerah yang tegangannya
tinggi (kadar air rendah, kering). Gerakan air
ini dapat terjadi ke segala arah dan berlangsung
secara terus-menerus.
Pelapisan tanah berpengaruh terhadap gerakan air
tanah. Lapisan keras atau lapisan kedap air
memperlambat gerakan air Lapisan berpasir
menjadi penghalang bagi gerakan air dari lapisan
yg bertekstur halus. Gerakan air dlm lapisan
berpasir sgt lambat pd tegangan
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Gerakan Jenuh (Perkolasi)
Air hujan dan irigasi memasuki tanah,
menggantikan udara dalam pori makro - medium -
mikro. Selanjutnya air bergerak ke bawah melalui
proses gerakan jenuh dibawah pengaruh gaya
gravitasi dan kapiler. Gerakan air jenuh ke arah
bawah ini berlangsung terus selama cukup air dan
tidak ada lapisan penghalang
Lempung berpasir
Lempung berliat cm 0 15 mnt 4
jam 30
60 90 1 jam 24 jam
120 24 jam 48 jam 150
30 cm 60 cm

Jarak dari tengah-tengah saluran, cm
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Part of the water applied to the soil surface
drains below the rootzone and feeds deeper soil
layers which are permanently saturated the top
of the saturated layer is called groundwater
table or sometimes just water table
42
A perched groundwater layer can be found on top
of an impermeable layer rather close to the
surface (20 to 100 cm). It covers usually a
limited area. The top of the perched water
layer is called the perched groundwater table.
The impermeable layer separates the perched
groundwater layer from the more deeply located
groundwater table
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PERKOLASI
Jumlah air perkolasi Faktor yg berpengaruh 1.
Jumlah air yang ditambahkan 2. Kemampuan
infiltrasi permukaan tanah 3. Daya hantar air
horison tanah 4. Jumlah air yg ditahan profil
tanah pd kondisi kapasitas lapang
Keempat faktor di atas ditentukan oleh struktur
dan tekstur tanah Tanah berpasir punya kapasitas
ilfiltrasi dan daya hantar air sangat tinggi,
kemampuan menahan air rendah, shg perkolasinya
mudah dan cepat
Tanah tekstur halus, umumnya perkolasinya rendah
dan sangat beragam faktor lain yg
berpengaruh 1. Bahan liat koloidal dpt
menyumbat pori mikro medium 2. Liat tipe 21
yang mengembang-mengkerut sangat berperan
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LAJU GERAKAN AIR TANAH
Kecepatan gerakan air dlm tanah dipengaruhi oleh
dua faktor 1. Daya dari air yang bergerak 2.
Hantaran hidraulik Hantaran kapiler daya
hantar i k.f dimana i volume air yang
bergerak f daya air yg bergerak dan k
konstante.
Daya air yg bergerak daya penggerak, ditentukan
oleh dua faktor 1. Gaya gravitasi, berpengaruh
thd gerak ke bawah 2. Selisih tegangan air
tanah, ke semua arah Gerakan air semakin cepat
kalau perbedaan tegangan semakin tinggi.
Hantaran hidraulik ditentukan oleh bbrp
faktor 1. Ukuran pori tanah 2. Besarnya
tegangan untuk menahan air Pada gerakan jenuh,
tegangan airnya rendah, shg hantaran hidraulik
berbanding lurus dengan ukuran pori Pd tanah
pasir, penurunan daya hantar lebih jelas kalau
terjadi penurunan kandungan air tanah Lapisan
pasir dlm profil tanah akan menjadi penghalang
gerakan air tidak jenuh
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RETENSI AIR TANAH
KAPASITAS RETENSI MAKSIMUM adalah Kondisi tanah
pada saat semua pori terisi penuh air, tanah
jenuh air, dan tegangan matrik adalah
nol. KAPASITAS LAPANG air telah meninggalkan
pori makro, mori makro berisi udara, pori mikro
masih berisi air tegangan matrik 0.1 - 0.2 bar
pergerakan air terjadi pd pori mikro/ kapiler
KOEFISIEN LAYU siang hari tanaman layu dan malam
hari segar kembali, lama-lama tanaman layu siang
dan malam tegangan matrik 15 bar. Air tanah
hanya mengisi pori mikro yang terkecil saja,
sebagian besar air tidak tersedia bagi
tanaman. Titik layu permanen, bila tanaman tidak
dapat segar kembali
KOEFISIEN HIGROSKOPIS Molekul air terikat pada
permukaan partikel koloid tanah, terikat kuat
sehingga tidak berupa cairan, dan hanya dapat
bergerak dlm bentuk uap air, tegangan matrik-nya
sekitar 31 bar. Tanah yg kaya bahan koloid akan
mampu menahan air higroskopis lebih banyak dp
tanah yg miskin bahan koloidal.
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Status Air Tanah
Perubahan status air dalam tanah, mulai dari
kondisi jenuh hingga titik layu



Jenuh Kap. Lapang
Titik layu
Padatan Pori
100g air 40g
tanah jenuh air
100g 20g
udara
kapasitas lapang
100g 10 g udara
koefisien layu
100g 8g udara
koefisien higroskopis
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Agihan air dalam tanah
Berdasarkan tegangan air tanah dapat dibedakan
menjadi tiga bagian Air bebas, kapiler dan
higroskopis
Koef. Higroskopis Kap. Lapang
Jml ruang pori kurang
lebih 31 atm kurang lebih 1/3 atm
Lapisan olah Air higros- Air
Kapiler Ruang diisi udara
kopik Peka thd gerakan
Biasanya jenuh uap air Hampir tdk
kapiler, laju pe- Setelah hujan
lebat menunjukkan nyesuaian me-
sebagian diisi air, sifat cairan
ningkat dg me- tetapi air
cepat hi-
ningkatnya ke- lang krn gravitasi
lembaban tanah
bumi Lapisan bawah
tanah Karena pemadatan ruang
pori
berkurang Strata bawah
(jenuh air) Kolom tanah Jumlah ruang pori
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• 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

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SUPLAI AIR ke TANAMAN
Dua proses yg memungkinkan akar tanaman mampu
menyerap air dlm jumlah banyak, yaitu 1. Gerakan
kapiler air tanah mendekati permukaan akar
penyerap 2. Pertumbuhan akar ke arah zone tanah
yang mengandung air
LAJU GERAKAN KAPILER
Bulu akar menyerap air
Tegangan air tanah meningkat
Jumlah air tanah berkurang
Terjadi perbedaan Tegangan dg air tanah di
sekitarnya
Terjadi gerakan kapiler air menuju bulu akar
Laju gerakan tgt perbedaan tegangan dan daya
hantar pori tanah
Gerakan kapiler 2.5 cm sagt penting
LAJU PERPANJANGAN AKAR Selama masa pertumbuhan
tanaman, akar tanaman tumbuh memanjang dengan
cepat, sehingga luas permukaan akar juga tumbuh
terus. Jumlah luas permukaan akar penyerap yang
bersentuhan langsung dengan sebagian kecil air
tanah (yaitu sekitar 1-2)
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KEHILANGAN UAP AIR DARI TANAH
HADANGAN HUJAN OLEH TUMBUHAN Tajuk tumbuhan mampu
menangkap sejumlah air hujan, sebagian air ini
diuapkan kembali ke atmosfer. Vegetasi hutan di
daerah iklim basah mampu menguapkan kembali air
hujan yg ditangkapnya hingga 25, dan hanya 5 yg
mencapai tanah melalui cabang dan batangnya.
Awan hujan
Pembentukan Awan
presipitasi
transpirasi
evaporasi
Run off
infiltrasi
Tanah permukaan
perkolasi
Sungai - laut
Groundwater
Batuan
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Hadangan hujan oleh tanaman semusim
Sekitar 5 - 25 dari curah hujan dihadang tanaman
dan dikembalikan ke atmosfer. Besarnya tergantung
pada kesuburan tanaman dan stadia pertumbuhan
tanaman . Dari curah hujan 375 mm, hanya sekitar
300-350 mm yang mencapai tanah.
Hadangan curah hujan oleh jagung dan
kedelai Keadaan hujan
Persen dari curah hujan total untuk

Jagung Kedelai Langsung ke tanah 70.3 65.0 Me
lalui batang 22.8 20.4 Jumlah di
tanah 93.1 85.4 Yang tinggal di atmosfer
6.9 14.6 Sumber J.L.Haynes, 1940.
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Lingkaran Tanah-Air-Tanaman
LTAT mrpk sistem dinamik dan terpadu dimana air
mengalir dari tempat dengan tegangan rendah
menuju tempat dengan tegangan air tinggi.
Air kembali ke atmosfer (evapo-transpirasi)
Hilang melalui stomata daun (transpirasi)
Air dikembalikan ke tanah melalui hujan dan
irigasi
Penguapan
Serapan bulu akar
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EVAPO-TRANSPIRASI
Kehilangan uap air dari tanah 1. EVAPORASI
penguapan air dari permukaan tanah 2.
TRANSPIRASI Penguapan air dari permukaan
tanaman 3. EVAPOTRANSPIRASI Evaporasi
Transpirasi Laju penguapan air tgt pd perbedaan
potensial air selisih tekanan uap air
perbedaan antara tekanan uap air pd permukaan
daun (atau permukaan tanah) dengan atmosfer
Faktor Iklim dan Tanah 1. Energi Penyinaran 2.
Tekanan uap air di atmosfer 3. Suhu 4. Angin 5.
Persediaan air tanah
Air tanah Evapotranspirasi (cm Jagung Medic
ago sativa Tinggi 17.7 24.4 Sedang 12.7 2
0.5 Sumber Kelly, 1957.
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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 gt PE and therefore AE PE moisture limited environments P lt PE and therefore AE lt PE seasonal moisture environments
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Ketersediaan Air Tanah vs Evapo-transpirasi
Ketersediaan air di daerah perakaran sangat
menentukan besarnya evapotranspirasi. Kedalaman
daerah perakaran tanaman 50 - 60 cm. Air tanah
pada lapisan olah mengalami pengurangan karena
evaporasi permukaan Air tanah pd lapisan bawah
mengalami pengurangan karena diserap akar tanaman
Kedalaman tanah (cm) Evapotranspirasi
(cm) Jagung Padang Rumput Hutan 0 -
17.5 24.25 23.45 23.27 17.5 -
180.0 20.75 21.17 22.25 Sumber Dreibelbis dan
Amerman, 1965.
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Soil moisture balance diagrams (Thornthwaite and
Mather - 1955) - soil depth 50 cm.
57
Soil moisture balance diagrams (Thornthwaite and
Mather - 1955) - soil depth 300 cm.
58
PEMAKAIAN KONSUMTIF (PK)
Pemakaian Konsumtif merupakan jumlah kehilangan
air melalui evaporasi dan transpirasi. Lazim
digunakan sebagai ukuran dari seluruh air yg
hilang dari tanaman melalui evapotranspirasi Ini
merupakan angka-praktis untuk keperluan pengairan
Dua faktor penting yg menentukan PK adalah 1.
KEDALAMAN PERAKARAN TANAMAN 2. FASE PERTUMBUHAN
TANAMAN PK dapat berkisar 30 - 215 cm atau
lebih 1. Daerah basah - semi arid dg irigasi
37.5 - 75 cm. 2. Daerah panas dan kering dg
irigasi 50 - 125 cm.
EVAPORASI vs TRANSPIRASI Faktor yg berpengaruh
adalah 1. Perbandingan luas tutupan tanaman thd
luas tanah 2. Efisiensi pemakaian air berbagai
tanaman 3. Perbandingan waktu tanaman berada di
lapangan 4. Keadaan iklim Di daerah basah
EVAPORASI ? TRANSPIRASI Di daerah kering 1.
EVAPORASI ? 70 - 75 dari seluruh hujan yg
jatuh 2. TRANSPIRASI ? 20 - 25 3. RUN OFF ? 5
59
WUE Water Use Efficiency
WUE ? Produksi tanaman yg dapat dicapai dari
pemakaian sejumlah air tersedia WUE dapat
dinyatakan sbg 1. Pemakaian konsumtif (dalam
kg) setiap kg jaringan tanaman yg
dihasilkan 2. Transpirasi (dalam kg) setiap kg
jaringan tanaman yg dihasilkan NISBAH
TRANSPIRASI Jumlah air yg diperlukan untuk
menghasilkan 1 kg bahan kering tanaman
NISBAH TRANSPIRASI Untuk tanaman di daerah humid
200 - 500, di daerah arid duakalinya Tanaman Nis
bah Transpirasi Beans 209 - 282 -
736 Jagung 233 - 271 - 368 Peas 259 - 416 -
788 Kentang 385 - 636 Sumber Lyon, Buckman dan
Brady, 1952.
60
Pengendalian Penguapan
MULSA PENGELOLAAN Mulsa adalah bahan yg
dipakai pd permukaan tanah untuk mengurangi
penguapan air atau untuk menekan pertumbuhan
gulma. Lazimnya mulsa spt itu digunakan untuk
tanaman yang tidak memerlukan pengolahan tanah
tambahan
MULSA KERTAS PLASTIK Bahan mulsa dihamparkan di
permukaan tanah, diikat spy tdk terbang, dan
tanaman tumbuh melalui lubang-lubang yg telah
disiapkan Selama tanah tertutup mulsa, air tanah
dapat diawetkan dan pertumbuhan gulma
dikendalikan
MULSA SISA TANAMAN Bahan mulsa berasal dari sisa
tanaman yg ditanam sebelumnya, misalnya jerami
padi, jagung, dan lainnya Bahan mulsa
dipotong-potong dan disebarkan di permukaan
tanah Cara WALIK DAMI sebelum penanaman kedelai
gadu setelah padi sawah
MULSA TANAH ? Pengolahan tanah Efektivitas
mulsa tanah dalam konservasi air-tanah
(mengendalikan evaporasi) masih diperdebatkan,
hasil-hasil penelitian masih snagat beragam
61
Mulching is an alternative to turf around trees,
and its use eliminates potential competition. A
2- to 4-inch layer of wood chips, bark, or other
organic material over the soil under the drip
line is recommended because it Helps retain
soil moisture Helps reduce weeds and controls
grass Increases soil fertility when mulch
decomposes Improves appearance Protects the
trunk from injuries caused by mowing equipment
and trimmers that often result in serious tree
damage or death Improves soil structure (better
aeration, temperature, and moisture conditions)
62
Olah Tanah vs Penguapan Air Tanah
Alasan pengolahan tanah 1. Mempertahankan
kondisi fisika tanah yg memuaskan 2. Membunuh
gulma 3. Mengawetkan air tanah.
Pengendalian Penguapan vs Pemberantasan
Gulma Perlakuan Hasil jagung (t/ha)
Kadar air tanah () hingga kedalaman 1
m Tanah dibajak dg persiapan yg baik 1.
Dibebaskan dari gulma 2.9 22.3 2.
Gulma dibiarkan tumbuh 0.4 21.8 3. Tiga
kali pengolahan dangkal 2.5 21.9 Persiapan
Buruk 4. Dibebaskan dari gulma
2.0 23.1 Sumber Mosier dan Gutafson, 1915.
Pengolahan tanah yg dapat mengendalikan gulma dan
memperbaiki kondisi fisik tanah akan berdampak
positif thd produksi tanaman Pengolahan tanah yg
berlebihan dapat merusak akar tanaman dan
merangsang evaporasi, shg merugikan tanaman
63

CURAH HUJAN Air cair yg turun dari atmosfer ke
permukaan dinyatakan sbg kedalaman air pd
permukaan mendatar (rainfall) Presipitasi Banyakn
ya curahan pd permukaan mendatar selama sehari,
sebulan atau setahun, yg digunakan unt menyatakan
curahan hatrian, bulanan atau tahunan

• (3) mendelegasikan kewenangan dan tanggung jawab
  kepada pemerintah daerah dalam pengelolaan
  sumberdaya alam dan lingkungan hidup secara
  bertahap
• Keterbukaan Persyaratan "pemberitahuan" perlu
  dimasukkan sehingga semua peraturan mengenai
  lingkungan yang dapat berdampak terhadap
  perdagangan tidak bermakna ganda secara
  internasional.
• Keabsahan Tindakan perlindungan lingkungan yang
  membatasi perdagangan harus sah jadi didukung
  oleh bukti ilmiah yang kuat.

64
HUJAN Curahan berupa air semua ukuran, baik yg
berbentuk tetes yg bergaris tengah lebih dari 0.5
mm maupun yg lebih kecil (rain) HUJAN
es Curahan berupa bola kecil atau butiran es yg
bergaris tengah antara 5 dan 50 mm, kadang-kadang
lebih, jatuhnya secara terpisah-pisah atau
bergabung menjadi gumpalan yg bentuknya tak
teratur (hail)
65
Soil Moisture and Groundwater
66
Stream Flow 
67

Banjir Luapan aliran akibat air atau bentuk air
lain yg melebihi normalnya, atau penumpukan air
akibat pengaliran di suatu daerah yg biasanya
terendam (flood) Banjir bandang Banjir yg
berlangsung dlm selang waktu pendek dg puncak
debit yg cukup tinggi Banjir tahunan Debit
puncak harian yg tertinggi dalam tahun air,
atau Banjir yg ketinggiannya sama atau melebihi
rata-rata tahunannya

• (3) mendelegasikan kewenangan dan tanggung jawab
  kepada pemerintah daerah dalam pengelolaan
  sumberdaya alam dan lingkungan hidup secara
  bertahap
• Keterbukaan Persyaratan "pemberitahuan" perlu
  dimasukkan sehingga semua peraturan mengenai
  lingkungan yang dapat berdampak terhadap
  perdagangan tidak bermakna ganda secara
  internasional.
• Keabsahan Tindakan perlindungan lingkungan yang
  membatasi perdagangan harus sah jadi didukung
  oleh bukti ilmiah yang kuat.

68
To conserve soil moisture for agronomic crop
production, we investigated feasibility of
producing narrow row corn with subsurface drip
irrigation combined with conservation tillage.
We found that plant biomass and yield decreased
significantly with distance from the laterals. 
http//www.ayushveda.com/tipson/tips-to-conserve-w
ater-by-drip-irrigation/