Bahan kajian pada MK Pertanian Berlanjut
Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012
HIDROLOGI LANSEKAP DAN
RAINWATER HARVESTING
Diunduh dari Sumber: http://www.tiimes.ucar.edu/highlights/fy06/images/hydrological%20cycle.jpg….. 17/10/2012
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.coexploration.org/howsthewater/html/body_earth.html….. 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://ldas.gsfc.nasa.gov/resources/theory.php….. 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://www.eoearth.org/article/Hydrologic_cycle….. 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.pedrocreek.org/watershed.html….. 17/10/2012
DAERAH ALIRAN SUNGAI (DAS) …. WATERSHEDDAS 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.tucson.ars.ag.gov/dap/field_sites.htm….. 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: smno fpun… 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: ….. 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: www.gardenforglobalwarming.co.uk/2008.html….. 17/10/2012
CONTOH RAIN GARDEN….
Diunduh dari Sumber: ….. 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, sungai-sungai 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: bebasbanjir2025.wordpress.com/.../embung/ ….. 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: http://techalive.mtu.edu/meec/module01/Infiltration.htm….. 17/10/2012
INFILTRASISome 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://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
INFILTRASIInfiltration 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.
In this idealized profile for soil-water distribution for a homogeneous soil, five zones are illustrated
for the infiltration process.
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.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
INFILTRASISoil-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.
Source: Hillel, 1982
whenever water is ponded over the soil surface, the rate of infiltration exceeds the
soil infiltration capacity.
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.
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/Lwhere: 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 content2. Moisture content3. Soil structure and texture4. Porosity and permeability5. Soil bulk density and compaction6. Slope, landscape position, and
topography
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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 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 excessively-
drained sands and gravels. 4. High rate of water transmission (hydraulic
conductivity).
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.
Soils and infiltration….Group C.
1. Sandy clay loam.2. Low infiltration rates when thoroughly
wetted. 3. Consists primarily of soils with a layer
that impedes downward movement of water.
4. Moderately fine to fine structure. 5. Perched water table at 40-60 inches;
root-limiting at 20-40 inches.
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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).
Hydrologic soil properties classified by soil texture
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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
Screening criteria for infiltration practices ….
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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.
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.
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.
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.
Bedrock or impervious soils should be a minimum of 4 feet from the infiltrating surface
(i.e. bottom of trench).
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.
Point system for the evaluation of potential infiltration sites
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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 pointsØ Silty sand or loam 5 pointsØ Fine silt or clay 0 points
Point system for the evaluation of potential infiltration sites
Diunduh dari Sumber: http://iowacedarbasin.org/runoff/showMan.php?c1=2E-1 ….. 17/10/2012
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
… Types of infiltration practices.Design methodologies are presented for three infiltration practices
and two integrated (complementary) practices below:
1. Infiltration trenches2. Infiltration basins3. Bioretention area (and rain gardens)4. Soil quality restoration5. 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
Diunduh dari Sumber: http://toxipedia.org/display/toxipedia/Natural+Landscaping….. 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://civil-online2010.blogspot.com/2012/09/estimation-of-infiltration.html ….. 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.
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.
LAJU INFILTRASI….
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
•Berbagai penggunaan lahan tradisional dalam suatu lansekap mencerminkan sifat dan kondisi sumberdaya lahan (geologi, tanah, lereng, hidrologi, dsb)
Lansekap
Tradisional
•Adanya intervensi teknologi (revolusi hijau) yang bisa memanipulasi potensi lahan, mengakibatkan vegetasi tidak selalu mencerminkan sifat alami sumberdaya lahan
Lansekap
Modern
Lansekap Pertanian
Tekanan sosial dan ekonomi mengakibatkan fragmentasi dan fraksionasi lahan; ukuran individu persil semakin kecil, keaneka-ragaman dalam lansekap semakin besarSumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Sumber: SMNO.hutanpinus.pujon.nop2012
Lansekap hutan tanaman industri dataran tinggi di DAS Konto
Peta Tutupan/Penggunaan Lahan DAS Sumber Brantas (2005)
Sumber : Sudarto(2009)
No data
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Land resources planning:
Communities Need Analysis
Consumer Analysis &Participation Analysis
Demand Analysis
Priority Demand
Land Suitability Analysis
Land Capability Analysis
Scenarios Feasibility Analysis
Public Review
Land Resources Allocation Decision
Implementation, Monitoring, Evaluation, & Revision
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 Kanopi dan manajemen kanopio Pengolahan tanah (guludan, parit,
dsb)o Penutupan tanah
(terbuka/tertutup)o Pemupukano Pemberantasan Hama, Penyakit,
Gulmao Irigasi dan/atau Drainasio 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
APA yang digarap ? (Lahan usaha)
SIAPA YG berusaha (Masyarakat)
Domestik
Ekspor / Luar daerah
Eksternal input
KEBERDAYAAN
PLOT
Siklus Air dalam PlotPRESIPITASI
EVAPO-TRANSPIRASI
INTERSEPSILOLOS TAJUK
LIMPASAN PERMUKAAN
INFILTRASI
PERKOLASI DRAINASI
LATERAL
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 PlotKomponen 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/AtasIntersepsi Penutupan Tajuk :
• Kerapatan Tajuk• Tebal dan susunan Lapisan Tajuk
(strata)Lolos Tajuk • Intensitas dan durasi Hujan
• Kerapatan TajukInfiltrasi Laju Infiltrasi :
• Porositas (makro)• Profil Tanah• Intensitas Hujan dan Simpanan
PermukaanPerkolasi Permeabilitas Tanah, Ketebalan SolumEvapotranspirasi2)
Ketersediaan air tanah, cuaca dan kondisi tanaman
Limpasan Permukaan
Resultante semua komponenSumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Komponen Siklus Air Hutan Alam Hutan Tnm
Pinus Kebun Apel Sayuran : Kentang
Presipitasi 100 100 100 100
Aliran Lateral
Intersepsi
Lolos Tajuk
Infiltrasi
Perkolasi
Evapotrasnpirasi
Limpasan Permukaan
Komponen Siklus Air Hutan Alam Hutan Tnm
Pinus Kebun Apel Sayuran : Kentang
Presipitasi 100 100 100 100
Aliran Lateral ? ? ? ?
Intersepsi ? ? ? ?
Lolos Tajuk ? ? ? ?
Infiltrasi ? ? ? ?
Perkolasi ? ? ? ?
Evapotrasnpirasi ? ? ? ?
Limpasan Permukaan ? ? ? ?
DISKUSIEstimasi 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 ?
1) Aliran lateral tergantung dari limpasan yang berasal dari petak dibagian hulu/atasnya 2) 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
100%
50%
40%
10%
Hujan (Presipitasi)
Limpasan PermukaanInfiltrasi
Evapo(transpi)rasi
Contoh Neraca Air dari Kawasan
Hutan/Pertanian
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 2Limpasan 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 strip filter atau buffer sepanjang
bantaran/sempadan sungai bisa
mengurangi jumlah sedimen yang bisa masuk ke sungai,
sehingga air sungai bisa tetap jernih
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)
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
Sumber: Department of Agriculture Extension and Rural Sociology Institute of Agriculture and Animal Science Rampur, Chitwan, Nepal
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 eco-
friendly production technology.
Prinsip Pengelolaan di Tingkat Plot :
PERBAIKAN
NERACA AIR
MENGURANGI LIMPASAN
PERMUKAAN
MENINGKATKAN INTERSEPSI
MENINGKATKAN KAPASITAS INFILTRASI
MENINGKATKAN KAPASITAS
TANAH MENAHAN AIR
MENINGKATKAN KAPASITAS PERKOLASI
1
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Prinsip Pengelolaan di Tingkat Plot :
MENEKAN EROSI DAN PENCEMAR
AN AGROKIMIA
MENGURANGI LIMPASAN
PERMUKAAN
MENEKAN LAJU
LIMPASAN PERMUKAAN
MELINDUNGI PERMUKAAN
TANAH
MENGURANGI PENGGUNAAN
BAHAN AGROKIMIA
2
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
BMPs : (Tanaman) Penutup Tanah diantara Barisan Tanaman Pokok
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Mulsa seresah tanaman di antara barisan tanaman jagung
Teknik Pengelolaan di tingkat lansekap :
PERBAIKAN NERACA AIR KAWASAN
Meningkatkan LUAS lahan dengan tutupan permanen dan berlapis
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 :
MENGURANGI EROSI DAN PENCEMARAN
Mengendalikan laju aliran permukaan dengan cara mekanik dan biologi
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 ?
Lembah Aliran Sungai
Hutan Lindung
Hutan Lindun
g
Hutan Tanaman
Hutan Tanaman
Pengendali Limpasan
Pengendali Limpasan
Kawasan
Budidaya
Kawasan
Budidaya
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
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
61
Soemarno, 2005
…. Proses yg secara berkelanjutan mengoptimalkan manfaat SDL melalui penyerasian aktivitas ekonomi sesuai dg kapabilitas dan daya dukungnya
Peningkatan Kesejahteraan MASYARAKAT
Penghematan
Konservasi Rehabilitasi
PRODUKSI-DISTRIBUSI-KONSUMSI
• 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
INDIKATOR LINGKUNGAN PERTANIAN SEHAT
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Kualitas hidup manusia di daerah miskin / kritis semakin menurun , indikatornya:
Keterbatasan income rumah-tangga
Gizi Anak BALITA
Penyakit akibat kesehatan lingkungan
Kualitas Kawasan Konservasi/ Lindung
Pudarnya Budaya- Kearifan Masyarakat
Contoh Indikator Fungsi Hidrologi DASKarakteristik
Lokal Fungsi DAS (kriteria)
Relevansi bagi pengguna Indikator
Curah hujanBentuk lahanJenis tanahKedalaman akar (dari vegetasi alami)
Karakteristik Lokal
Fungsi DAS (kriteria)
Relevansi bagi pengguna Indikator
Curah hujanBentuk lahanJenis tanahKedalaman akar (dari vegetasi alami)
Transmisi air Pengguna air di daerah hilir
Ketersediaan air sepanjang waktu
(Sumber : Farida & Van Noordwijk, 2006)
Karakteristik Lokal
Fungsi DAS (kriteria)
Relevansi bagi pengguna Indikator
Curah hujanBentuk lahanJenis tanahKedalaman akar (dari vegetasi alami)
Transmisi air Pengguna air di daerah hilir
Ketersediaan air sepanjang waktu
Menyangga pada kejadian puncak hujan
Masyarakat yang tinggal di bantaran sungai dan bantaran banjir
Tinggi muka air sampai batas terkendali
Infiltrasi & melepaskan air secara bertahap
Masyarakat yang tidak memiliki sistem penyimpanan air
Sumur dangkal yang tidak kering
Memelihara kualitas air
Masyarakat yang tidak memiliki sistem purifikasi, PLTA
Ketersediaan air bersih sepanjang waktu
Karakteristik Lokal
Fungsi DAS (kriteria)
Relevansi bagi pengguna Indikator
Curah hujanBentuk lahanJenis tanahKedalaman akar (dari vegetasi alami)
Transmisi air Pengguna air di daerah hilir
Ketersediaan air sepanjang waktu
Menyangga pada kejadian puncak hujan
Masyarakat yang tinggal di bantaran sungai dan bantaran banjir
Tinggi muka air sampai batas terkendali
Infiltrasi & melepaskan air secara bertahap
Masyarakat yang tidak memiliki sistem penyimpanan air
Sumur dangkal yang tidak kering
Memelihara kualitas air
Masyarakat yang tidak memiliki sistem purifikasi, PLTA
Ketersediaan air bersih sepanjang waktu
Mengurangi longsor Masyarakat yang tinggal di kaki bukit
Intensitas kejadian longsor
Mengurangi erosi Petani, Nelayan, PLTA Ketebalan seresah & top-soil, biodiversitas ikan bioindikator bentos
Mempertahankan iklim mikro
Petani & wisatawan Suhu dan kelembabanSumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
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)
Contoh Indikator Fungsi Hidrologi DAS Kali Konto
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
PENCEMARAN DARI LAHAN PERTANIANPotensi Pencemar Air dari Lahan Pertanian :
1.Nitrogen2.Pospor3.Logam Berat4.Kotoran Ternak (manure)5.Pestisida6.Patogen (penyebab penyakit pada Manusia)7.Sedimen
Pemberian Bahan Agrokimia (Pupuk dan Pestisida) dan Bahan Organik (Pupuk Kandang) yang berlebihan berpotensi menjadi
potensi sumber pencemar
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Keuntungan yang diperoleh Pemilik Lahan (PETANI)
Tambahan biaya yang ditanggung masyarakat (Kerugian MASYARAKAT)
Kehilangan Air Bersih
Kehilangan Biodiversitas
Kehilangan Cadangan Karbon
Penebangan Hutan dan Alih Fungsi
Hutan ke Pertanian
Pertanian dengan Upaya
Konservasi Mandiri
Pertanian dengan Upaya
Konservasi
Imbalan Jasa
Diolah & dikembangkan dari : Pagiola (2003)Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
WATER QUALITY?
Foto2 : Kurniatun Hairiah
Layanan Lingkungan : Mereka perlu air bersih
Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012
Diunduh dari Sumber: http://www.fao.org/docrep/R4082E/r4082e07.htm#TopOfPage ….. 17/10/2012
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).
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). Effective rainfall (8) = (1) - (4) - (5) - (7)
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.
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 .. Effective rainfall and initial soil moisture content
Diunduh dari Sumber: http://extension.umass.edu/turf/fact-sheets/maximizing-irrigation-efficiency-and-water-conservation….. 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://www.nrcan.gc.ca/earth-sciences/climate-change/community-adaptation/assessments/424….. 17/10/2012
Forest hydrological cycle (Hélie et al., 2005)….
Diunduh dari Sumber: http://www.forestry.gov.uk/fr/INFD-6MVJ8B….. 17/10/2012
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.