Bahan kajian pada MK Pertanian Berlanjut
HIDROLOGI LANSEKAP
DAN
RAINWATER HARVESTING
Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012
HIDROLOGI….
“HIDROLOGI”
…. Kajian ilmiah tentang
sifat-sifat, distribusi dan
efek-efek air di
permukaan bumi, di
dalam tubuh tanah, di
dalam batuan bawah
tanah, serta air di
atmosfir.
….. Siklus Hidrologi
Diunduh dari Sumber: http://www.tiimes.ucar.edu/highlights/fy06/images/hydrological%20cycle.jpg….. 17/10/2012
PENTINGNYA VEGETASI POHON DALAM SIKLUS
HIDROLOGI….
Aliran air dalam siklus
hidrologi:
(1)Evaporasi air dari
permukaan;
(2)Transpirasi oleh
tumbuhan;
(3)Transport air di
atmosfir;
(4) Presipitasi (Hujan);
(5) Limpasan
permukaan (runoff)
dan aliran bawah
permukaan.
Diunduh dari Sumber: http://www.coexploration.org/howsthewater/html/body_earth.html….. 17/10/2012
NERACA AIR DAN NERACA ENERGI …. POHON….
Precipitation (P) is
any and all forms of
water that fall from
clouds and reach
the ground. Runoff
(R) is the water
from precipitation
that is not absorbed
into the soil, but
flows and reaches a
stream or another
body of water.
Evapotranspiration
(E) is water
evaporating from
wet surfaces and
the soil plus the
water release of
plants.
Diunduh dari Sumber: http://ldas.gsfc.nasa.gov/resources/theory.php….. 17/10/2012
PENTINGNYA HUTAN DALAM SIKLUS HIDROLOGI….
Air hujan yang jatuh dari
langit :
Menguap kembali ke
atmosfir, mengalir di
permukaan lahan
(runoff), meresap ke
dalam tanah (infiltration).
Proses-proses di atas
dikendalikan oleh
intensitas hujan,
karakteristik tanah dan
lahan, kemiringan lahan
dan vegetasi.
Diunduh dari Sumber: http://www.eoearth.org/article/Hydrologic_cycle….. 17/10/2012
DAERAH ALIRAN SUNGAI (DAS) …. WATERSHED
DAS meliputi semua lahan
yang menyalurkan air hujan
memasuki suatu sistem
sungai tertentu.
DAS menangkap dan
menyimpan air hujan,
melepaskan air tersebut
secara bertahap memasuki
alur sungai.
Perubahan dalam suatu DAS,
secara alamiah atau buatan
manusia, akan
mempengaruhi kualitas air,
kecepatan runoff, nilai habitat
dan erosi , yang pada
akhirnya akan berdampak
pada keseluruhan DAS.
Diunduh dari Sumber: http://www.pedrocreek.org/watershed.html….. 17/10/2012
…NERACA AIR DI BENTANG LAHAN.
Annual water balance for
the Walnut Gulch
Experimental Watershed.
The Walnut Gulch
Experimental Watershed is
located primarily in a high
foothill alluvial fan portion
of the San Pedro River
watershed.
Cenozoic alluvium is very
deep and is composed of
coarse-grained fragmentary
material, the origin of which
is readily traceable to
present-day mountain
flanks on the watershed.
Diunduh dari Sumber: http://www.tucson.ars.ag.gov/dap/field_sites.htm….. 17/10/2012
RAIN-WATER HARVESTING
Panen air hujan merupakan suatu metode memanfaatkan air hujan
untuk keperluan domestik dan pertanian, cara ini telah banyak
diaplikasikan di berbagai penjuru dunia.
DELAPAN PRINSIP KEBERHASILAN PANEN AIR HUJAN:
1. Mulai dari observasi lapangan dengan hati-hati dan kontinyu.
2. Mulai dari titik tertinggi drai bentang-lahan atau petakan lahan dan
bekerja menuruni kemiringan lahan.
3. Mulai dari kerja kecil dan sederhana.
4. Memperlambat, menyalurkan dan menginfiltrasikan air hujan.
5. Merencanakan saluran pelimpas dan memanfaatkan air limpasan
sebagai sumberdaya.
6. Memaksimumkan komponen organik /vegetatif dari tutupan lahan.
7. Memaksimumkan fungsi dan relasi-relasi yang baik dnegan jalan
“stacking functions.”
8. Memonitor hasil kerja dan memperbaikinya terus menerus.
Diunduh dari Sumber: smno fpun… 17/10/2012
RAIN GARDEN.
“A rain garden” adalah sekungan di permukaan lahan yang
ditanami (tumbuhan) yang memungkinkan air hujan yang mengalir
dari lahan di sekitarnya ditampung dan diresapkan ke dalam
tanah.
Hal ini dapat mengurangi runoff air hujan dan memungkinkan air
hujan meresap ke dalam tanah , sehingga dapat mengurangi
ancaman erosi, pencemaran air, banjir dan kurangnya pasokan air
ke dalam groundwater.
“Rain garden’ ini dapat mengurangi pencemaran perairan dan
sungai hingga sebesar 30%.
Diunduh dari Sumber: ….. 17/10/2012
CONTOH RAIN GARDEN….
Diunduh dari Sumber: www.gardenforglobalwarming.co.uk/2008.html
….. 17/10/2012
…EMBUNG PERTANIAN.
Embung atau tandon air merupakan
waduk berukuran mikro di lahan
pertanian ( small farm reservoir) yang
dibangun untuk menampung kelebihan
air hujan di musim hujan.
Air yang ditampung tersebut selanjutnya
digunakan sebagai sumber irigasi
suplementer untuk budidaya komoditas
pertanian bernilai ekonomi tinggi di
musim kemarau atau di saat curah hujan
makin jarang.
Embung merupakan salah satu teknik
pemanenan air HUJAN yang sangat
sesuai di segala jenis agroekosistem.
Pembuatan embung untuk
pertanian bertujuan antara lain
untuk :
1. Menampung air hujan dan aliran
permukaan ( run off) pada
wilayah sekitarnya serta sumber
air lainnya yang memungkinkan
seperti mata air, parit, sungaisungai kecil dan sebagainya.
2. Menyediakan sumber air
sebagai suplesi irigasi di musim
kemarau untuk tanaman
palawija, hortikultura semusim,
tanaman perkebunan semusim
dan peternakan.
Diunduh dari Sumber: ….. 17/10/2012
. PERSYARATAN LOKASI EMBUNG….
1. Daerah pertanian lahan
kering/perkebunan/ peternakan
yang memerlukan pasokan air
dari embung sebagai suplesi air
irigasi.
2. Air tanahnya sangat dalam.
3. Bukan lahan berpasir.
4. Terdapat sumber air yang dapat
ditampung baik berupa air
hujan, aliran permukaan dan
mata air atau parit atau sungai
kecil.
5. Wilayah sebelah atasnya
mempunyai daerah tangkapan
air atau wilayah yang
mempunyai sumber air untuk
dimasukkan ke embung, seperti
mata air, sungai kecil atau parit
dan lain sebagainya.
Konstruksi pembangunan embung dapat
dilakukan oleh kelompok tani secara padat karya
dan bertahap.
Diunduh dari Sumber: bebasbanjir2025.wordpress.com/.../embung/ ….. 17/10/2012
INFILTRASI
Some of the precipitation that
falls on land seeps into the
ground where it is stored in
aquifers and is transported to
streams and lakes by
subsurface flow.
The amount of infiltration is
influenced by the
permeability and moisture
content of the soil, the
presence of vegetation and
the volume and intensity of
precipitation.
The amount of water in an
aquifer is indicated by the
height of the water table (the
upper boundary of aquifer).
Diunduh dari Sumber: http://techalive.mtu.edu/meec/module01/Infiltration.htm….. 17/10/2012
INFILTRASI
Infiltration is the downward
movement of water from the land
surface into the soil profile.
1. Infiltration. The downward entry of
water into the immediate surface of
soil or other materials.
2. Infiltration capacity. The maximum
rate at which water can infiltrate into
a soil under a given set of conditions.
3. Infiltration rate. The rate at which
water penetrates the surface of the
soil, expressed in cm/hr, mm/hr, or
inches/hr. The rate of infiltration is
limited by the capacity of the soil and
the rate at which water is applied to
the surface. This is a volume flux of
water flowing into the profile per unit
of soil surface area (expressed as
velocity).
4. Percolation. Vertical and lateral
movement of water through the soil
by gravity.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
INFILTRASI
Figure : Zones of the
infiltration process for
the water content profile
under ponded conditions
The distribution of water
during the infiltration
process under ponded
conditions is illustrated
in Figure.
Transmission zone. This zone is characterized by a small change
in water content with depth. In general, the transmission zone is a
lengthening unsaturated zone with uniform water content. Gravity
forces primarily drive hydraulic gradient in this zone.
In this idealized profile
for soil-water distribution
for a homogeneous soil,
five zones are illustrated
for the infiltration
process.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
INFILTRASI
Source: Hillel, 1982
whenever water is ponded over the soil
surface, the rate of infiltration exceeds the
soil infiltration capacity.
Soil-water infiltration is
controlled by the rate and
duration of water application,
soil physical properties,
slope, vegetation, and surface
roughness.
Generally, soil-water
infiltration has a high rate in
the beginning, decreases
rapidly, and then slowly
decreases until it approaches
a constant rate.
As shown in Figure , the
infiltration rate will eventually
become steady and approach
the value of the saturated
hydraulic conductivity.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
SISTEM INFILTRASI
Surface infiltration can be achieved through the use of grass
buffer strips, vegetated swales, and porous pavement
systems. Infiltration systems such as infiltration trenches,
infiltration basins, and bioretention areas (including rain
gardens) are designed specifically to capture a defined
volume of storm runoff and transfer it directly to the soil
profile.
Several integrated practices, such as soil quality restoration
and native landscaping, can be used in conjunction with
these practices to improve the infiltration capacity of
compacted urban soils.
An infiltration BMP is designed to capture a volume of
stormwater runoff, retain it, and infiltrate all or part of that
volume into the ground.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Infiltration hydraulics and process….
. A fundamental principle for describing the flow of water in a homogeneous, porous
media is given by Darcy’s Law (Chow, Maidment, and Mays, 1988; McCuen, 1989):
Q = KA h/L
where: Q = flow (cfsec); K = saturated hydraulic conductivity; characteristic of a specific
porous medium when effectively saturated with water (fps); A = cross-sectional area
through the porous medium perpendicular to the flow (ft2); h/L = hydraulic gradient, the
difference in hydraulic head,h, per unit distance in the direction of flow, L ft/ft
The velocity of flow through the porous medium can be determined from Equation 1 by
substituting the continuity equation Q = qA to obtain:
q = K (h/L)
where: q = velocity of water through a unit cross section of the porous medium (fps)
The velocity of water through the pores of the medium is described by:
V = q/s
where: V = fluid velocity (in/hr); s = water content of the medium (in3/in3) equal to the
medium’s porosity less the volume of trapped air in the pore spaces.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Soils and infiltration….
Factors that control infiltration rate
and capacity:
1. Vegetative cover, root
development, and organic content
2. Moisture content
3. Soil structure and texture
4. Porosity and permeability
5. Soil bulk density and compaction
6. Slope, landscape position, and
topography
Group A.
1. Sand, loamy sand, or sandy loam soil
types.
2. Low runoff potential and high infiltration
rates, even when thoroughly wetted.
3. Includes deep and well- to excessivelydrained sands and gravels.
4. High rate of water transmission (hydraulic
conductivity).
Hydrologic soil group (HSG).
The HSG refers to the soil characteristics
that tend to decrease or increase the
amount of runoff produced from a
precipitation event.
The HSG is used in the determination of
the runoff curve number (CN) developed
by the Natural Resource Conservation
Service (NRCS).
Group B.
1. Silt loam or loam.
2. Moderate infiltration rate when thoroughly
wetted.
3. Includes moderately deep to deep,
moderately well- to well-drained soils.
4. Moderately fine to moderately coarse
textures.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Soils and infiltration….
Group C.
1.
2.
3.
4.
5.
Sandy clay loam.
Low infiltration rates when thoroughly
wetted.
Consists primarily of soils with a layer
that impedes downward movement of
water.
Moderately fine to fine structure.
Perched water table at 40-60 inches;
root-limiting at 20-40 inches.
Group D.
1. Clay loam, silty clay loam, sandy clay, silty
clay, and clay.
2. Very low infiltration rates when thoroughly
wetted.
3. Consists chiefly of clay soils with high
swelling potential, soils with a permanent
high water table, soils with a claypan or
clay layer at or near the surface, and
shouldow soils over nearly impervious
material.
Soil texture.
The hydrologic design methods presented
are based on the use of two hydrologic
soil properties; the effective water
capacity (Cw) and the minimum infiltration
rate (f) of the specific soil textural groups.
Effective water capacity.
The fraction of the void spaces available
for water storage (in/in).
Minimum infiltration rate.
The final rate that water passes through
the soil profile during saturated conditions
(in/hr).
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Hydrologic soil properties classified by soil texture
Soil texture class
Hydrologic
soil group
Effective water
capacity (Cw)
(in/in)
Minimum
infiltration rate (f)
(in/hr)
Effective porosity, θe
(in3/in3)
Sand
A
0.35
8.27
0.025 (0.022-0.029)
Loamy sand
A
0.31
2.41
0.024 (0.020-0.029)
loam
B
0.25
1.02
0.025 (0.017-0.033)
Loam
B
0.19
0.52 **
0.026 (0.020-0.033)
Silt loam
C
0.17
0.27
0.300 (0.024-0.035)
Sandy clay loam
C
0.14
0.17
0.020 (0.014-0.026)
Clay loam
D
0.14
0.09
0.019 (0.017-0.031)
Silty clay loam
D
0.11
0.06
0.026 (0.021-0.032)
clay
D
0.09
0.05
0.200 (0.013-0.027)
Silty clay
D
0.09
0.04
0.026 (0.020-0.031)
Clay
D
0.08
0.02
0.023 (0.016-0.031)
Note: Minimum rate: soils with lower rates should not be considered for infiltration BMPs
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Screening criteria for infiltration practices ….
Evaluation of the viability of a particular site includes:
Determine soil type from mapping and soil
survey to review other parameters such as
the amount of silt and clay, presence of a
restrictive layer or seasonal high water table,
and estimated permeability.
Groundwater separation should be at least 4
feet from the basin invert to the measured
groundwater elevation. Seasonal high
groundwater should be a minimum of 4 feet
below the infiltration surface.
The soil should not have more than 30
percent clay or more than 40 percent clay and
silt combined.
Eliminate sites that are clearly unsuitable for
infiltration.
Bedrock or impervious soils should be a
minimum of 4 feet from the infiltrating surface
(i.e. bottom of trench).
If the surface and underlying soils are Group
D or the saturated infiltration rate is less than
0.52 in/hr, the site should not be used for
infiltration.
Location should be the following distances
away from structures:
1). Buildings, slopes, and highway pavement:
greater than 25 feet
2). Wells and bridge structures: greater than
100 feet.
Infiltration practices should not be placed in locations that cause water problems to
downgrade properties.
Infiltration facilities should be set back 25 feet (10 feet for dry wells) down-gradient
from structures.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Point system for the evaluation of potential infiltration sites
1 Ratio between tributary-connected impervious area (AIMP) and the infiltration area (AINF):
•
AINF > 2 AIMP
20 points
•
AIMP ≤ AINF ≤ 2 AIMP
10 points
•
0.5 AIMP ≤ AINF ≤ AIMP
5 points
Urban catchments with pervious surfaces smaller than 0.5 AIMP should not be used for
infiltration.
2 Nature of surface soil layer:
•
Coarse soils with low ratio of organic material
7 points
•
Normal humus soil
5 points
•
Fine grained soils with high ratio of organic material
0 points
3 Underlying soils:
•
If the underlying soils are coarser than surface soils, assign the same
number of points as for the surface layer under criterion #2.
•
If the underlying soils are finer-grained than the surface soils, use the
following points:
Ø
Gravel, sand, or glacial till with gravel or sand
7 points
Ø
Silty sand or loam
5 points
Ø
Fine silt or clay
0 points
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Point system for the evaluation of potential infiltration sites
4 Slope (S) of the infiltration surface:
·
S < 7%
5 points
·
7% ≤ S ≤ 20%
3 points
·
S > 20%
0 points
5 Vegetation cover:
·
Healthy, natural vegetation cover
5 points
·
Lawn – well established
3 points
·
Lawn – new
0 points
·
No vegetation – bare ground
-5 points
6 Degree of traffic on infiltration surface:
·
Little foot traffic
5 points
·
Average foot traffic
3 points
·
High foot traffic (i.e. playing/sports fields)
0 points
Source: Adapted from Urbonas and Stahre, 1993
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
… Types of infiltration practices.
Design methodologies are presented for three infiltration practices
and two integrated (complementary) practices below:
1.
2.
3.
4.
5.
Infiltration trenches
Infiltration basins
Bioretention area (and rain gardens)
Soil quality restoration
Native landscaping.
Infiltration trench and infiltration basin systems rely directly on the
site soil conditions to infiltrate the design capture volume of
stormwater. Infiltration trenches and basins can be used on
single/multi-family residential sites of up to 10 acres and up to 5
acres for commercial sites.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
Slow the Flow: Manage and Reuse Storm Water On-Site….
Store and reuse stormwater
beneficially:
Soil amendment and infiltration
is the most cost-effective way to
store rainfall for landscape use
Stormwater detention
vaults/cisterns, if required, may
be designed to feed filtration and
reuse for toilet flushing or
vehicle washing, or to store late
spring storms for summer
landscape irrigation.
Diunduh dari Sumber: http://toxipedia.org/display/toxipedia/Natural+Landscaping….. 17/10/2012
LAJU INFILTRASI….
Infiltration is the process
by which water on the
ground surface enters the
soil.
Infiltration rate in soil
science is a measure of
the rate at which soil is
able to absorb rainfall or
irrigation.
It is measured in inches
per hour or millimeters per
hour.
The rate at which water
infiltrates into a ground is
called the infiltration
capacity.
Diunduh dari Sumber: http://civil-online2010.blogspot.com/2012/09/estimation-of-infiltration.html ….. 17/10/2012
LAJU INFILTRASI….
When a soil is dry, the
infiltration rate is usually high
compared to when the soil is
moist.
For an initially dry soil
subjected to rain, the
infiltration capacity curve
shows an exponentially
decaying trend .
The observed trend is due to
the fact that when the soil is
initially dry, the rate of
infiltration is high but soon
decreases, as most of the soil
gets moist.
The rate of infiltration reaches
a uniform rate after some time.
Diunduh dari Sumber: http://civil-online2010.blogspot.com/2012/09/estimation-of-infiltration.html ….. 17/10/2012
INDEKS INFILTRASI….
The average infiltration rate is called the Infiltration Index and the two types of indices
commonly used are explained in the next section.
Infiltration indices
The two commonly used infiltration indices are : φ – index and W – index
The φ - index :
the rate of infiltration above which the rainfall volume equals runoff
volume.
The W – index
This is the average infiltration rate during the time when the rainfall intensity exceeds the
infiltration rate. Thus, W may be mathematically calculated by dividing the total
infiltration (expressed as a depth of water) divided by the time during which the rainfall
intensity exceeds the infiltration rate.
Total infiltration may be fund out as under:
Total infiltration = Total precipitation – Surface runoff – Effective storm retention
The W – index can be derived from the observed rainfall and runoff data. It differs from
the - index in that it excludes surface storage and retention. The index does not have any
real physical significance when computed for a multiple complex watershed. Like the
phi-index the - index, too is usually used for large watersheds.
Diunduh dari Sumber: http://civil-online2010.blogspot.com/2012/09/estimation-of-infiltration.html ….. 17/10/2012
Keaneka-ragaman Penggunaan Lahan dan Tutupan Lahan
dalam Lansekap Pertanian
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Lansekap Pertanian
Lansekap
Tradisional
•Berbagai penggunaan lahan
tradisional dalam suatu lansekap
mencerminkan sifat dan kondisi
sumberdaya lahan (geologi, tanah,
lereng, hidrologi, dsb)
Lansekap
Modern
•Intervensi teknologi (revolusi hijau)
bisa memodifikasi sifat2 lahan,
sehingga vegetasi tidak selalu
mencerminkan sifat dan kondisi
alami sumberdaya lahan
Tekanan sosial dan ekonomi mengakibatkan fragmentasi dan fraksionasi
lahan; ukuran individu persil semakin kecil, keaneka-ragaman dalam lansekap
Sumber: semakin
Pertanianbesar
Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Lansekap hutan tanaman industri dataran tinggi
di DAS Konto
Sumber: SMNO.hutanpinus.pujon.nop2012
Peta Tutupan/Penggunaan Lahan DAS
Sumber Brantas (2005)
No data
: Sudarto(2009)
Sumber: Pertanian Berlanjut: Lansekap Pertanian danSumber
Hidrologi.
Widianto 2012
Land resources planning:
Communities Need
Analysis
Consumer Analysis &
Participation Analysis
Land Suitability
Analysis
Scenarios
Feasibility
Analysis
Public Review
Demand Analysis
Priority Demand
Land Capability
Analysis
Land Resources
Allocation
Decision
Implementation,
Monitoring, Evaluation,
& Revision
34
Tutupan Lahan & Penggunaan Lahan di DAS Sumber
Brantas
Perhatikan hal-hal berikut dalam setiap macam tutupan
lahan dan penggunaan lahan yang anda lihat di DAS
Brantas Hulu :
o
o
o
o
o
o
o
Kanopi dan manajemen kanopi
Pengolahan tanah (guludan, parit, dsb)
Penutupan tanah (terbuka/tertutup)
Pemupukan
Pemberantasan Hama, Penyakit, Gulma
Irigasi dan/atau Drainasi
Pembuangan limbah/sampah
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
KEBERLANJUTAN USAHA PENANGANAN
LAHAN KRITIS
HASIL Usaha
Domestik
Eksternal
input
APA yang
digarap ?
(Lahan usaha)
SIAPA YG
berusaha
(Masyarakat)
KEBERDAYAAN
Siklus Air dalam Plot
PRESIPITASI
EVAPOTRANSPIRASI
INTERSEPSI
LATERAL
LOLOS TAJUK
INFILTRASI
LIMPASAN
PERMUKAAN
PERKOLASI
DRAINASI
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Siklus Air dalam Plot
?
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Siklus Air dalam Plot
Komponen Siklus Air (yang relevan) :
• Presipitasi (Hujan)
• Intersepsi (oleh tajuk tanaman)
• Lolos Tajuk
• Infiltrasi
• Perkolasi
• Limpasan Permukaan
• Aliran Lateral (masuk dan keluar)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Faktor yang berpengaruh terhadap besaran komponen siklus air di tingkat
plot
Komponen
Siklus Air
Faktor yang mempengaruhi besaran komponen
Presipitasi
(variabel bebas)
Aliran Lateral1)
Kondisi Petak di bagian Hulu/Atas
Intersepsi
Penutupan Tajuk :
• Kerapatan Tajuk
• Tebal dan susunan Lapisan Tajuk
(strata)
Lolos Tajuk
• Intensitas dan durasi Hujan
• Kerapatan Tajuk
Infiltrasi
Laju Infiltrasi :
• Porositas (makro)
• Profil Tanah
• Intensitas Hujan dan Simpanan Permukaan
Perkolasi
Permeabilitas Tanah, Ketebalan Solum
Evapotranspirasi2)
Ketersediaan air tanah, cuaca dan kondisi tanaman
Limpasan
Permukaan
semua komponen
Sumber:
PertanianResultante
Berlanjut: Lansekap
Pertanian dan Hidrologi. Widianto 2012
DISKUSI
Estimasi Neraca Air dalam Petak Tanaman saat terjadi hujan
Diskusikan :
• Berapa proporsi masing-masing komponen ketika terjadi hujan 100 %
• Berapa besarnya limpasan permukaan dari berbagai macam penggunaan lahan ini
• Komponen apa saja yang berbeda? Mengapa demikian ?
Komponen
Siklus Air
Hutan Alam
Hutan Tnm
Pinus
Kebun Apel
Sayuran :
Kentang
100
100
100
100
Aliran Lateral
?
?
?
?
Intersepsi
?
?
?
?
Lolos Tajuk
?
?
?
?
Infiltrasi
?
?
?
?
Perkolasi
?
?
?
?
Evapotrasnpirasi
?
?
?
?
Limpasan Permukaan
?
?
?
?
Presipitasi
1)
2)
Aliran lateral tergantung dari limpasan yang berasal dari petak dibagian hulu/atasnya
Evapotranspirasi sangat kecil (nol) karena durasi kejadian yang singkat dan cuaca hujan (kelembaban udara maksimum/jenuh)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Contoh Neraca Air dari
Kawasan Hutan/Pertanian
Hujan (Presipitasi)
100%
Evapo(transpi)rasi
40%
Infiltrasi
50%
Limpasan Permukaan
10%
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Apa saja yang bisa terbawa keluar dari Plot
bersama dengan aliran permukaan ?
• Material Tanah (sedimen)
• Bahan Organik :
• Pupuk Kandang (manure)
• Kompos
• Sampah, seresah
• Unsur-unsur kimia :
• Unsur Hara
• Pupuk
• Pestisida, Herbisida, dsb
• Lainnya ........ ?
 Kondisi seperti apa yang bisa mendorong terangkutnya bahan2 tsb
bersama limpasan permukaan ?
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
PETAK dan LANSEKAP
Apakah hal-hal yang terjadi dalam petak akan sama
dengan yang terjadi di lansekap ?
1. Debit sungai merupakan akumulasi limpasan permukaan dari
semua petak pertanian dan non pertanian dalam lansekap
2. Jumlah sedimen yang terangkut sungai merupakan akumulasi
dari erosi dari seluruh petak dalam lansekap
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Apakah hal-hal yang terjadi di tingkat petak akan
sama dengan di tingkat Lansekap ?
Indikator
Kemungkinan 1
Kemungkinan 2
Limpasan
Permukaan dan
Debit
Debit Banjir di sungai lebih besar
dari jumlah semua limpasan yang
keluar dari setiap petak dalam DAS
Debit Banjir di sungai lebih kecil
dari jumlah semua limpasan yang
keluar dari setiap plot (petak)
dalam DAS
Erosi dan
Sedimen
Jumlah Sedimen yang terangkut di
sungai lebih besar dari jumlah erosi
(kehilangan tanah) dari setiap
petak dalam DAS
Jumlah sedimen yang terangkut di
sungai lebih kecil dari jumlah erosi
(kehilangan tanah) dari setiap
petak dalam DAS
Fungsi Lansekap
(DAS)
DAS atau lansekap tidak memiliki
fungsi menahan (buffer) dan
menyaring (filter).
DAS atau lansekap mempunyai
fungsi menahan (buffer) dan
menyaring (filter).
Pertimbangkan
Longsor tebing sungai dan jalan
Limpasan dari jalan dan pemukiman
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Adanya cekungan alami
(embung) dan relief mikro
menjadi tempat singgah air
permukaan sehingga tidak
langsung mengalir ke sungai,
meningkatkan kapasitas
infiltrasi kawasan dan
mengendapkan bahan terangkut
air (sedimen dsb)
Adanya strip filter atau
buffer sepanjang
bantaran/sempadan sungai
bisa mengurangi jumlah
sedimen yang bisa masuk
ke sungai, sehingga air
sungai bisa tetap jernih
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Debit Banjir (tahunan)
Jumlah Sedimen Terangkut
Debit dasar (tahunan)
Dimodifikasi dari sumber : Susswein, van Noordwijk and Verbist (2002)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
A Review on Organic Farming for Sustainable Agriculture
Ananata Ghimire . June, 2002
Organic farming seems to be more appropriate as it considered the important aspects like sustainable. Agriculture is
the most important sector for ensuring food security, alleviating poverty and conserving the vital natural resources
that the world’s present and future generation will be entirely dependent upon for their survival and well being, in the
name of development, the environmental resources have been beyond comprehension.
Acid rain, deforestation, depletion, smog due to automobiles and discharge of industrial pollution, soil degradation,
depletion of ozone layer and discharge of toxic wastage by industrial units into rivers and oceans are some
environmental problematic issues. Intensive use of inorganic fertilizers and pesticides has been an important tool in
the drive for increased crop production. In fact more fertilizers consumption is a good indication of agricultural
productivity but depletion of soil fertility is commonly observed in soils. Due to heavy use of chemical herbicides,
pesticides and intensification of agricultural production during the past few decades has led to other harmful effects
like nitrate in the ground water, contamination of fooding materials, eutrophication, stratospheric changes etc. High
agricultural inputs are unlikely to be sustainable for very long unless the inputs are correctly judged in terms of both
their quality and quantity. To escape from these harmful effects, the concept of organic farming was emerged from
the conference of Atlanta in 1981.
Organic Farming seems to be more appropriate as it considered the important aspects like sustainable natural
resources and environment. It is a production system, which favors maximum use of organic materials like crop
residues, FYM, compost, green manure, oil cakes, bio-fertilizers, bio-gas slurry etc. to improve soil health from the
different experiment, microbial fertilizers like Rhizomic, Azotobacter, Blue green algae, Azolla etc. have increased the
yield and also played important role for minimizing the harmful effect of pesticides and herbicides.
Organic farming is a practical proposition for sustainable agriculture if adequate attention is paid to this issue. There
is urgent need to involve more and more scientist to identify the thrust area of research for the development of ecofriendly production technology.
Sumber: Department of Agriculture Extension and Rural Sociology Institute of Agriculture and Animal
Science Rampur, Chitwan, Nepal
Prinsip Pengelolaan di Tingkat Plot :
1
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Prinsip Pengelolaan di Tingkat Plot :
2
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
BMPs : (Tanaman) Penutup Tanah diantara Barisan Tanaman Pokok
Mulsa seresah tanaman di antara
barisan tanaman jagung
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Teknik Pengelolaan di tingkat lansekap :
Meningkatkan LUAS lahan dengan
tutupan permanen dan berlapis
PERBAIKAN NERACA
AIR KAWASAN
Meningkatkan kapasitas simpanan
permukaan (surface storage) melalui
kekasaran permukaan
Meningkatkan kapasitas tanah untuk
menahan air
Meningkatkan kapasitas infiltrasi dan
drainasi untuk pengisian groundwater
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Teknik Pengelolaan di tingkat lansekap :
Mengendalikan laju aliran permukaan dengan
cara mekanik dan biologi
MENGURANGI EROSI
DAN PENCEMARAN
Meningkatkan luas kawasan dengan tutupan
permanen
Mengurangi dan mengendalikan penggunaan bahan
agrokimia
Membangun zona penyaring (filter)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber : Bruno Verbist (2009)
Penanaman yang rapat di sepanjang KAKISU (Sempadan Sungai)
BAGAIMANA MERANCANG FILTER ATAU BUFFER ?
Kawasan
Budidaya
Pengendali
Limpasan
Hutan
Tanaman
Hutan
Lindung
Sumber: Pertanian Berlanjut:
Lembah
Aliran Sungai
Lansekap
Pertanian
Hutan
Lindung
Hutan
Tanaman
Pengendali
Limpasan
dan Hidrologi. Widianto 2012
Kawasan
Budidaya
Manajemen pertanian terkait
dengan kualitas air :
 Praktek pertanian yang meningkatkan
bahan organik dan biologi tanah
 Praktek konservasi tanah dan air untuk
mengendalikan limpasan dan erosi
 Kombinasikan tanaman tahunan, semak,
rumput dan tanaman semusim
 Tanaman yang bisa menangkap unsur
hara seperti penutup tanah
 Kawasan penyangga antara lahan
dengan tubuh air (sungai, danau, dsb)
 Pengelolaan irigasi untuk menghindari
pencucian hara
 Mengintegrasikan ternak dalam sistem
pertanian
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
…. Proses yg secara berkelanjutan mengoptimalkan manfaat SDL melalui
penyerasian aktivitas ekonomi sesuai dg kapabilitas dan daya dukungnya
Soemarno, 2005
Peningkatan
Kesejahteraan
MASYARAKAT
Konservasi
PRODUKSIDISTRIBUSIKONSUMSI
Rehabilitasi
61
Penghematan
INDIKATOR LINGKUNGAN PERTANIAN
SEHAT
• Tidak ada tanah yang terbuka (bero)
• Dalam selokan dan parit mengalir air yang jernih
• Terdapat hewan/binatang liar sangat banyak
• Dijumpai ikan pada selokan dan sungai yang mengalir melalui
lahan pertanian
• Pada Lansekap Pertanian dijumpai aneka vegetasi (sangat
beragam)
Preston Sullivan, 2003
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Kualitas hidup manusia di daerah miskin / kritis semakin
menurun , indikatornya:
Penyakit akibat
kesehatan
lingkungan
Keterbatasa
n income
rumahtangga
Gizi
Anak BALITA
Pudarnya
BudayaKearifan
Masyarakat
Kualitas
Kawasan
Konservasi/
Lindung
Contoh Indikator Fungsi Hidrologi DAS
Karakteristik
Lokal
Curah
Curah hujan
hujan
Bentuk
Bentuk lahan
lahan
Jenis tanah
tanah
Jenis
Kedalaman
Kedalaman akar
akar (dari
(dari
vegetasi
vegetasi alami)
alami)
Fungsi DAS (kriteria)
Relevansi bagi
pengguna
Indikator
Transmisi
Transmisi air
air
Pengguna
Pengguna air
air di
di daerah
daerah hilir
hilir
Ketersediaan
Ketersediaan air
air sepanjang
sepanjang
waktu
waktu
Menyangga
Menyangga pada
pada kejadian
kejadian
puncak
puncak hujan
hujan
Masyarakat
Masyarakat yang
yang tinggal
tinggal di
di
bantaran
bantaran sungai
sungai dan
dan
bantaran
bantaran banjir
banjir
Masyarakat
Masyarakat yang
yang tidak
tidak
memiliki
memiliki sistem
sistem
penyimpanan
penyimpanan air
air
Masyarakat
yang tidak
tidak
Masyarakat yang
memiliki
memiliki sistem
sistem purifikasi,
purifikasi,
PLTA
PLTA
Tinggi
Tinggi muka
muka air
air sampai
sampai
batas
batas terkendali
terkendali
Mengurangi longsor
Masyarakat yang tinggal di
kaki bukit
Intensitas kejadian longsor
Mengurangi erosi
Petani, Nelayan, PLTA
Ketebalan seresah & topsoil, biodiversitas ikan
bioindikator bentos
Infiltrasi &
& melepaskan
melepaskan air
Infiltrasi
air
secara
secara bertahap
bertahap
Memelihara
Memelihara kualitas
kualitas air
air
Sumur
Sumur dangkal
dangkal yang
yang tidak
tidak
kering
kering
Ketersediaan air
bersih
Ketersediaan
air bersih
sepanjang
sepanjang waktu
waktu
Mempertahankan iklim
Petani & wisatawan
Suhu dan kelembaban
mikro Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: Pertanian
Contoh Indikator Fungsi Hidrologi DAS Kali Konto
Perubahan distribusi musiman aliran
sungai di (A) DAS Kalikonto (Indonesia),
dimana pada periode ke II (1951-1972)
terjadi alih guna hutan menjadi lahan
pertanian dalam skala besar (sumber:
Bruijnzeel, 1990)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
PENCEMARAN DARI LAHAN PERTANIAN
Potensi Pencemar Air dari Lahan Pertanian :
1. Nitrogen
2. Pospor
3. Logam Berat
4. Kotoran Ternak (manure)
5.Pemberian
Pestisida
Bahan Agrokimia (Pupuk dan Pestisida) dan Bahan Organik (Pupuk Kandang)
yang berlebihan berpotensi menjadi potensi sumber pencemar
6. Patogen (penyebab penyakit pada Manusia)
7. Sedimen
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Penebangan
Hutan dan Alih
Fungsi Hutan
ke Pertanian
Pertanian
dengan Upaya
Konservasi
Mandiri
Pertanian
dengan Upaya
Konservasi
Imbalan Jasa
Keuntungan yang diperoleh
Pemilik Lahan (PETANI)
Kehilangan Air Bersih
Tambahan biaya yang
ditanggung masyarakat
(Kerugian MASYARAKAT)
Kehilangan Biodiversitas
Kehilangan Cadangan Karbon
Diolah & dikembangkan dari : Pagiola (2003)
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Layanan Lingkungan : Mereka perlu air bersih
WATER
QUALITY?
Foto2 : Kurniatun Hairiah
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Need for drainage
During heavy rainfall the upper
soil layers become saturated and
pools may form.
Water percolates to deeper layers
and infiltrates from the pools.
Part of the water present in the
saturated upper soil layers flows
downward into deeper layers and
is replaced by water infiltrating
from the surface pools.
When there is no more water left
on the soil surface, the downward
flow continues for a while and air
re-enters in the pores of the soil.
This soil is not saturated anymore.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
GROUNDWATER TABLE ….
After heavy rainfall the groundwater
table may rise and reach the rootzone
The water flowing from the saturated soil
downward to deeper layers, feeds the
groundwater reservoir. As a result, the
groundwater level (often called
groundwater table or simply water table)
rises. Following heavy rainfall or
continuous over-irrigation, the groundwater
table may even reach and saturate part of
the rootzone.
Again, if this situation lasts too long, the
plants may suffer. Measures to control the
rise of the water table are thus necessary.
The removal of excess water either from
the ground surface or from the rootzone, is
called drainage.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
SOIL PROFILE….
A very general and simplified soil
profile can be described as follows:
a. 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.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
THE GROUNDWATER TABLE ….
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.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Perched groundwater table….
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
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Depth of the groundwater table….
The depth of the groundwater
table varies greatly from place
to place, mainly due to
changes in topography of the
area.
In one particular place or field,
the depth of the groundwater
table may vary in time.
Following heavy rainfall or
irrigation, the groundwater
table rises. It may even reach
and saturate the rootzone. If
prolonged, this situation can
be disastrous for crops which
cannot resist "wet feet" for a
long period.
The groundwater table can
also be very deep and distant
from the rootzone, for
example following a prolonged
dry period.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
HUJAN EFEKTIF….
Effective Rainfall
When rain water ((1) in Fig. 63) falls
on the soil surface, some of it
infiltrates into the soil (2), some
stagnates on the surface (3), while
some flows over the surface as
runoff (4).
When the rainfall stops, some of
the water stagnating on the
surface (3) evaporates to the
atmosphere (5), while the rest
slowly infiltrates into the soil (6).
Effective rainfall (8) = (1) - (4) - (5) - (7)
From all the water that infiltrates
into the soil ((2) and (6)), some
percolates below the rootzone (7),
while the rest remains stored in the
rootzone (8).
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Effective rainfall and depth of the rootzone….
DEPTH OF THE
ROOTZONE
Soil water stored in deep
layers can be used by the
plants only when roots
penetrate to that depth.
The depth of root
penetration is primarily
dependent on the type of
crop, but also on the type
of soil.
The thicker the rootzone,
the more water available to
the plant.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Effective rainfall and topography….
Topography
On steep sloping
areas, because of
high runoff, the
water has less time
to infiltrate than in
rather flat areas.
The effective
rainfall is thus
lower in sloping
areas.
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Effective rainfall and initial soil moisture content….
Initial soil moisture
content
For a given soil, the
infiltration rate is
higher when the soil is
dry than when it is
moist.
. Effective rainfall and initial soil moisture content
This means that for a
rain shower occurring
shortly after a
previous shower or
irrigation, the
infiltration rate is
lower and the surface
runoff higher .
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
Maximizing Irrigation Efficiency and Water Conservation
MAXIMIZE THE AMOUNT OF
WATER ENTERING THE
TURFGRASS ROOTZONE
(STORAGE) BY:
1. controlling water
movement below the root
zone (leaching),
2. minimizing evaporative
losses,
3. controlling surface water
runoff and ponding of
irrigation water.
Diunduh dari Sumber: http://extension.umass.edu/turf/fact-sheets/maximizing-irrigation-efficiency-and-waterconservation….. 17/10/2012
Forest hydrological cycle (Hélie et al., 2005)….
Diunduh dari Sumber: http://www.nrcan.gc.ca/earth-sciences/climate-change/community-
How much water do forests use?….
Trees and forests have the
ability to use more water
than shorter types of
vegetation.
In general, conifers lose
between 25 to 45% of
annual rainfall by
interception, compared to
10 to 25% for broadleaves
and almost 0% for grass.
Conifers tend to lose an
additional 300 mm to 350
mm per year due to
transpiration, compared to
300 mm to 390 mm for
broadleaves and 400 mm
to 600 mm for grass.
Diunduh dari Sumber: http://www.forestry.gov.uk/fr/INFD-6MVJ8B….. 17/10/2012