Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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Bahan kajian pada MK Pertanian Berlanjut Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012 HIDROLOGI LANSEKAP DAN RAINWATER HARVESTING

Transcript of Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Page 1: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Bahan kajian pada MK Pertanian Berlanjut

Diabstraksikan oleh: smno.jursntnh.fpub. okt 2012

HIDROLOGI LANSEKAP DAN

RAINWATER HARVESTING

Page 2: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

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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.

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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.

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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.

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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.

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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. 

Page 8: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

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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%.

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Diunduh dari Sumber: www.gardenforglobalwarming.co.uk/2008.html….. 17/10/2012

CONTOH RAIN GARDEN….

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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.

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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.

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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).

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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.

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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.

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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.

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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.

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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

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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.

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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).

Page 21: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

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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.

Page 23: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 24: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 25: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

… 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

Page 26: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 27: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 28: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 29: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

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Keaneka-ragaman Penggunaan Lahan dan Tutupan Lahan dalam Lansekap Pertanian

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 31: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

•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

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Sumber: SMNO.hutanpinus.pujon.nop2012

Lansekap hutan tanaman industri dataran tinggi di DAS Konto

Page 33: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Peta Tutupan/Penggunaan Lahan DAS Sumber Brantas (2005)

Sumber : Sudarto(2009)

No data

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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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

Page 35: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 36: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

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KEBERLANJUTAN USAHA PENANGANAN LAHAN KRITIS

HASIL Usaha

APA yang digarap ? (Lahan usaha)

SIAPA YG berusaha (Masyarakat)

Domestik

Ekspor / Luar daerah

Eksternal input

KEBERDAYAAN

Page 38: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

PLOT

Siklus Air dalam PlotPRESIPITASI

EVAPO-TRANSPIRASI

INTERSEPSILOLOS TAJUK

LIMPASAN PERMUKAAN

INFILTRASI

PERKOLASI DRAINASI

LATERAL

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 39: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Siklus Air dalam Plot

?Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 40: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 41: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 42: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 43: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 44: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 45: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 46: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 47: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 48: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 49: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 50: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 51: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 52: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 53: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 54: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 55: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 56: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 57: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 58: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 59: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 60: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 61: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 62: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

• 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

Page 63: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 64: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 65: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 66: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 67: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 68: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

WATER QUALITY?

Foto2 : Kurniatun Hairiah

Layanan Lingkungan : Mereka perlu air bersih

Sumber: Pertanian Berlanjut: Lansekap Pertanian dan Hidrologi. Widianto 2012

Page 69: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 70: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 71: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 72: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 73: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 74: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 75: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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)

Page 76: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 77: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 78: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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

Page 79: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.

Page 80: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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)….

Page 81: Biodiversitas Lansekap dan Hidrologi : Kualitas dan Kuantitas Air

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.