Module 2 – (L6) Sustainable Watershed Approach Watershed Management Practices

  M odu le 2 – ( L6 ) Su st a in a ble W a t e r sh e d Appr oa ch M odu le 2 – ( L6 ) Su st a in a ble W a t e r sh e d Appr oa ch & W a t e r sh e d M a n a ge m e n t Pr a ct ice s

  6 Soil Erosion & Conservation

  6 Soil Erosion & Conservation

L6 L6 L6 – Soil Er osion & Con se r va t ion L6 Soil Er osion & Con se r va t ion

   

Topics Cove r e d Topics Cove r e d

    Soil erosion: causes, processes, Soil erosion: causes, processes, erosion factors, water erosion, types, erosion factors, water erosion, types, estimation of soil loss wind erosion estimation of soil loss wind erosion estimation of soil loss, wind erosion, estimation of soil loss, wind erosion, soil conservation practices soil conservation practices

    Keywords: Keywords: Soil erosion, Water erosion, Soil erosion, Water erosion, Wind erosion, Soil conservation. Wind erosion, Soil conservation. Wind erosion Soil conservation Wind erosion Soil conservation

I n t r odu ct ion t o Soil Er osion I n t r odu ct ion t o Soil Er osion

    Definition : Definition :

• – soil erosion is the detachment, transport & deposition soil erosion is the detachment, transport & deposition – of soil particle on land surface -- termed as loss of soil. of soil particle on land surface of soil particle on land surface termed as loss of soil of soil particle on land surface termed as loss of soil. termed as loss of soil
• – – measured as mass /unit area measured as mass /unit area -- tonne/ha or Kg/sq.m tonne/ha or Kg/sq.m

      Soil loss is of interest primarily on site effect of Soil loss is of interest primarily on Soil loss is of interest primarily on--site effect of Soil loss is of interest primarily on site effect of site effect of

erosion such as loss of crop productivity erosion such as loss of crop productivity

      Off site effect of erosion are siltation in ditches, Off site effect of erosion are siltation in ditches, Off site effect of erosion are siltation in ditches, Off site effect of erosion are siltation in ditches, streams , reservoirs streams , reservoirs

    Sediment generated by erosion processes are Sediment generated by erosion processes are g g y y p p prime carrier of agricultural chemicals that prime carrier of agricultural chemicals that pollutes stream or lakes. pollutes stream or lakes.

Soil Er osion Pr oble m

  

  Soil is the most precious gift of nature -Prime resource for food, fodder etc. Soil mismanaged less resource-for food, fodder etc. -Soil mismanaged-less productivity.

  

  In India, more than 100 million hectares soil degraded eroded unproductive degraded, eroded, unproductive

  

  About 17 tones/ha soil detached annually->20% of this is transported by river to sea 10% deposited in reservoir results 1 to 2% loss off storage capacity.

  Soil erosion in a watershed

Soil Er osion Pr oble m … I n dia ’s La n d D e gr a da t ion :

  Source: state of environment report 2009 MoEF report 2009 MoEF

   

  Soil erosion deteriorates soil quality & reduces Soil erosion deteriorates soil quality & reduces p productivity of natural , agricultural & forest ecosystem productivity of natural , agricultural & forest ecosystem p y y , g , g y y

   

  Soil erosion deteriorates quality of water Soil erosion deteriorates quality of water

   

  Increased sedimentation causes reduction of carrying Increased sedimentation causes reduction of carrying capacity of water bodies. capacity of water bodies. capacity of water bodies capacity of water bodies

Ca u se s of Soil Er osion Ca u se s of Soil Er osion

    H u m a n I n du ce d & N a t u r a l Ca u se s H u m a n I n du ce d & N a t u r a l Ca u se s

     

  Land use -- Over grazing by cattle Deforestation Land use Land use Land use -- Over grazing by cattle, Deforestation, Over grazing by cattle Deforestation Over grazing by cattle, Deforestation, arable land use, faulty farming, construction, mining arable land use, faulty farming, construction, mining etc. etc.

   

  Climatic conditions: precipitation & wind velocity Climatic conditions: precipitation & wind velocity l l d d d d l l

   

  Soil: soil characteristics -- texture, structure, water Soil: soil characteristics texture, structure, water retention and transmission properties. retention and transmission properties. retention and transmission properties. retention and transmission properties.

   

  Hydrology: Infiltration, surface detention, overland Hydrology: Infiltration, surface detention, overland flow velocity, and subsurface water flow. flow velocity, and subsurface water flow.

   

  Land forms: Land forms: Slope gradient, slope length and shape of L L d f d f Sl Sl Slope gradient, slope length and shape of di di l l l l h d h d h h f f slope slope

  Soil erosion in a watershed Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

Type s of Soil Er osion Type s of Soil Er osion

    Geological erosion, Natural erosion & Geological erosion, Natural erosion & Erosion from activities of human & animals Erosion from activities of human & animals Erosion from activities of human & animals Erosion from activities of human & animals

• – Geological erosion: Geological erosion: Soil forming and distribution Geological erosion: Geological erosion:--Soil forming and distribution Soil forming and distribution –

  Soil forming and distribution Long time process  Long time process

• – Human and animal: Human and animal:--Tillage, removal of plants and Tillage, removal of plants and – other vegetation other vegetation other vegetation other vegetation accelerated erosion accelerated erosion

  accelerated erosion  accelerated erosion 

• – Stream bank erosion Stream bank erosion –
• – Landslide, Volcanic eruption, flooding Landslide, Volcanic eruption, flooding Landslide, Volcanic eruption, flooding Landslide, Volcanic eruption, flooding –

  Water and wind: Water and wind: major factors of soil erosion – major factors of soil erosion – Soil erosion in a watershed

Agents of Soil Erosion Soil Er osion Pr oce sse s Soil Er osion Pr oce sse s

  _{Wind Water (mass movement)} Gravity Eg. Landslide Ba se d on Re f: G. D a s ( 2 0 0 0 ) : H ydr ology & Soil Con se r va t ion En gg. _{Water forms Glaciers} Pr e n t ice H a ll of I n dia , N e w D e lh i _{Rainfall Runoff And Oceans} Reservoirs Surface _{runoff Subsurface runoff runoff erosion Pipe Sheet/Interrill erosion erosion i erosion i} Rill Gully _{Stream bank erosion}

Soil Er osion Pa r a m e t e r s

   Soil erosion – function of:

• – Erosivity – depends on rainfall
• – Erodibility – property of soil
• – Topography – property of land
• – Management – contributed by man

  

Erodibility: Detachability & transportability

Topography: Slope, length, relation to other land

  Management: Land use & crop management

W a t e r Er osion W a t e r Er osion

   

Detachment & transport of soil particles from Detachment & transport of soil particles from

land mass by water including rain, runoff, land mass by water including rain runoff land mass by water including rain runoff land mass by water including rain, runoff, melted snow melted snow

     

Depends on: soil nature & capacity of water Depends on: soil nature & capacity of water Depends on: soil nature & capacity of water Depends on: soil nature & capacity of water

to transport to transport

      More on sloppy land More on sloppy land More on sloppy land More on sloppy land

    More velocity More velocity more transport  more transport 

     

Water erosion Water erosion Water erosion Water erosion accelerated by agriculture, accelerated by agriculture,

   accelerated by agriculture,  accelerated by agriculture, grazing and construction activities grazing and construction activities

  Soil erosion in a watershed

Fa ct or s a ffe ct in g Er osion by Fa ct or s a ffe ct in g Er osion by w a t e r w a t e r w a t e r w a t e r

   

Climate  Climate Precipitation, temperature, wind, humidity Precipitation, temperature, wind, humidity

and solar radiation and solar radiation and solar radiation and solar radiation

    Soil  Soil size, type of soil, soil texture, structure, organic size, type of soil, soil texture, structure, organic matter matter matter matter

   

Vegetation  Vegetation interception of rainfall interception of rainfall--reduce surface reduce surface

sealing & runoff, decrease surface velocity, sealing & runoff, decrease surface velocity, sealing & runoff decrease surface velocity sealing & runoff decrease surface velocity improvement of aggregation, increased biological improvement of aggregation, increased biological activity and aeration, transpiration, physical holding activity and aeration, transpiration, physical holding

   

Topography Topography  degree of slope, shape and length of degree of slope, shape and length of

slope and size and shape of watershed slope and size and shape of watershed

Type s of W a t e r Er osion Type s of W a t e r Er osion

    W a t e r Er osion Type s: W a t e r Er osion Type s: Interrill (raindrop and sheet), rill, Interrill (raindrop and sheet), rill,

  gully & stream channel erosion gully & stream channel erosion gully & stream channel erosion gully & stream channel erosion

   

  (splash erosion) (splash erosion) Soil detachment &  Soil detachment &

  Ra in dr op e r osion Ra in dr op e r osion

  transport -- from impact of raindrops directly on soil transport from impact of raindrops directly on soil particles or on thin water surfaces particles or on thin water surfaces particles or on thin water surfaces particles or on thin water surfaces

    On bare soil On bare soil  about 200 t/ha soil is splashed into the air  about 200 t/ha soil is splashed into the air

  by heavy rains by heavy rains

   

  Relationship Relationship -- erosion, rainfall momentum & energy erosion, rainfall momentum & energy -- by by raindrop mass, size, shape, velocity & direction raindrop mass, size, shape, velocity & direction

   

  Relationship: Rainfall intensity & energy Relationship: Rainfall intensity & energy Relationship: Rainfall intensity & energy Relationship: Rainfall intensity & energy (F (Foster et al., 1981) (Foster et al., 1981) (F t t t l t l 1981) 1981)

    E = 0.119 + 0.0873 log E = 0.119 + 0.0873 log ii ; ;

  E-- kinetic energy in MJ/ha-mm; i = E

  10 intensity of rainfall in mm/h

  10

Sh e e t Er osion / I n t e r r ill Sh e e t Er osion / I n t e r r ill Er osion Er osion

    Sh e e t e r osion : Sh e e t e r osion : Uniform removal of soil in thin layers Uniform removal of soil in thin layers

  from sloping land resulting from overland flow from sloping land resulting from overland flow -- Idealized Idealized form of sheet erosion rarely occurs form of sheet erosion rarely occurs

    Splash & sheet erosion Splash & sheet erosion sometimes sometimes combined combined & known as & known as Interrill erosion Interrill erosion Interrill erosion Interrill erosion

   

  Function of soil properties, rainfall and land slope Function of soil properties, rainfall and land slope Watson and Laften(1986) formula Watson and Laften(1986) formula ( ( ) )

  2

  2

  where, D where, D -- interrill erosion rate in kg/m interrill erosion rate in kg/m --s s

  ii

  4

  4

  4

  4 K K --interrill erodibility of soil in kg interrill erodibility of soil in kg--s/m s/m and ii--rainfall and rainfall ii

  intensity in m/s intensity in m/s

  S S S S --slope factor=1.05 slope factor 1.05 slope factor 1.05 0.85exp( slope factor=1.05 -- 0.85exp( 0.85exp( 4sin 0.85exp(--4sin 4sin 4sin slope in degrees slope in degrees θ); θ); θ); θ); θθ--slope in degrees θθ slope in degrees ff ff

Rill e r osion Rill e r osion

    Detachment and transport of soil particles by Detachment and transport of soil particles by

  concentrated flow of water; Predominant form of concentrated flow of water; Predominant form of e os o ; e os o ; erosion; Depends on hydraulic shear of water flowing erosion; Depends on hydraulic shear of water flowing epe ds o epe ds o yd au c s ea o yd au c s ea o a e a e o o g g in the rill, rill erodibility and critical shear in the rill, rill erodibility and critical shear

   Critical shear: shear below which soil detachment is negligible Critical shear: shear below which soil detachment is negligible

  Rill detachment rate (Dr)--erosion rate occurring Rill detachment rate (Dr) erosion rate occurring erosion rate occurring erosion rate occurring  Rill detachment rate (Dr)  Rill detachment rate (Dr) beneath submerged area of the rill beneath submerged area of the rill

  Dr-Rill detachment rate in kg/m2-s K K τ Rill erodibility resulting from shear in s/m τ-Rill erodibility resulting from shear in s/m

      Q Q _s D  K 

  1   

    _{r c} 

• critical shear below which no erosion occurs in Pa

  τ _c  

  T _c  

  Qs-rate of sediment flow in kg/m-s Tc-sediment transport capacity of rill in kg/m-s p p y g/ τ-hydraulic shear of flowing water in Pa=ρ g r s where,

  ρ-Density of water in kg/m3; g-acceleration due to gravity in m/s2 r-hydraulic radius of rill in m; s-hydraulic gradient of rill flow Soil erosion in a watershed

Gu lly e r osion Gu lly e r osion

  Advanced form of rill erosion – Advanced form of rill erosion –forms larger channels than rills forms larger channels than rills

• – Fou r st a ge s ou s a ge s ou s a ge s
• – Fou r st a ge s
• – Formation stage Formation stage –
• – Development stage Development stage –
• – Healing stage Healing stage –
• – Stabilization stage Stabilization stage –

  Gully & rill erosion in a watershed    

  Gullies may be small--1m or less Gullies may be small Gullies may be small 1m or less Gullies may be small 1m or less 1m or less

   

  Medium--1m to 5m Medium 1m to 5m

   

  Large--more than 5m Large g g more than 5m

• – banks or soil movement in channel banks or soil movement in channel

  St r e a m ch a n n e l Er osion : Removal of soil for stream Removal of soil for stream

• – St r e a m ch a n n e l Er osion :

  Soil erosion in a watershed

  

Measurement of Soil Loss Measurement of Soil Loss – – Water Erosion Water Erosion

 

  Measurement from runoff plots Measurement from runoff plots

  Size varies from 1/250 to 1/125 Hectare Size varies from 1/250 to 1/125 Hectare – – Size varies from 1/250 to 1/125 Hectare Size varies from 1/250 to 1/125 Hectare

• – – Runoff measured by Flume Runoff measured by Flume

    Measurement from streams Measurement from streams

    Measurement from streams Measurement from streams

• – – Silt observation Posts (SOP) Silt observation Posts (SOP)
• – – Suspension, saltation and surface creep (bed load) Suspension, saltation and surface creep (bed load)
• – – Both separately measured and added Both separately measured and added
• – – Soil Sampler: Soil Sampler: S = p* q*86400/1000 S = p* q*86400/1000

   S-amount of material transported in tones/day

   S amount of material transported in tones/day

   p-amount of material (1m ³ of water in kg),

   q-rate of stream flow in m ³ /sec

Est im a t ion of Soil Loss Est im a t ion of Soil Loss-- W a t e r W a t e r E osion E osion Er osion Er osion

    Universal soil loss equation (USLE) Universal soil loss equation (USLE) (th h i t ) (R j Vi Si h 2000) (th h i t ) (R j Vi Si h 2000) (through experiments) (Raj Vir Singh, 2000) (through experiments) (Raj Vir Singh, 2000)

P C S L RK A

  P C S L RK A 

• – – A A--Average annual loss: in ton/ha/year Average annual loss: in ton/ha/year
• – – R R--Rainfall & runoff erosivity index for location Rainfall & runoff erosivity index for location

  R R Rainfall & runoff erosivity index for location Rainfall & runoff erosivity index for location

• – – K K--Soil erodibility factor Soil erodibility factor
• – – L L--slope length factor slope length factor
• – – S S – – slope steepness factor slope steepness factor
• – – C C--cover management factor cover management factor
• – – P P--conservation practice factor conservation practice factor

  P P ti ti f t ti ti f t Rainfall and Runoff Rainfall and Runoff Erosivity Erosivity Index (EI) Index (EI)  

  100 /

  

30

    EI EI--by multiplying kinetic energy of storm to by multiplying kinetic energy of storm to maximum 30 min. intensity for that storm maximum 30 min. intensity for that storm y y

    KE KE--kinetic energy of storm kinetic energy of storm

   

  II

  30

  30 =Maximum 30 minutes rainfall intensity =Maximum 30 minutes rainfall intensity

  30

  30 y y of storm of storm

    KE=210.3 + 89 log I KE=210.3 + 89 log I -- in ton/ha in ton/ha--cm cm

   

  II--rainfall intensity in cm/hr rainfall intensity in cm/hr

Er odibilit y Er odibilit y fa ct or ( K) fa ct or ( K)

  Where, M Where, M--particle size parameter (% silt+% very fine particle size parameter (% silt+% very fine

  2;moderate 3;slow to moderate 4;slow 5;very slow 6) 2;moderate 3;slow to moderate 4;slow 5;very slow 6) 2;moderate 3;slow to moderate 4;slow 5;very slow 6) 2;moderate 3;slow to moderate 4;slow 5;very slow 6)

  c c--profile permeability class profile permeability class (rapid 1;moderate to rapid (rapid 1;moderate to rapid

  (very fine granular 1 fine granular 2 Medium or course granular 3 (very fine granular 1 fine granular 2 Medium or course granular 3 (very fine granular 1, fine granular 2, Medium or course granular 3, (very fine granular 1, fine granular 2, Medium or course granular 3, blocks, platy or massive 4) blocks, platy or massive 4)

  ,, p p ( y p p ( y sand)*(100 sand)*(100--%clay) %clay) a a--percent organic matter; b percent organic matter; b--soil structure code soil structure code

  3 ³  c

  3 10 * 3 .

   

    Soil erodibility factor K can be found by Soil erodibility factor K can be found by regression equation by Foster et al(1981) regression equation by Foster et al(1981) regression equation by Foster et.al(1981) regression equation by Foster et.al(1981)

  

   

  3 10 *

    

  2 ₃ ^{3 14 . 1 7}     

  12 10 * 8 .

  4

  3 .

  3 2 10 *

  3

  M b a K

Slope Le n gt h Fa ct or ( L) Slope Le n gt h Fa ct or ( L)

  m

  I  

  L        22  

  

Where, L Where, L--slope length factor; I slope length factor; I--slope length in m slope length in m

m-- dimensionless exponent m dimensionless exponent Sin

   m

   .

  05

  8 Sin Sin   . 269 (  )  .

• 1

  1 Where Where field slope steepness=tan (s/100) (s/100) θ--field slope steepness=tan θ

      s--field slope in % s s--field slope in % s field slope in % field slope in %

Slope St e e pn e ss Fa ct or ( S) Slope St e e pn e ss Fa ct or ( S)

    Slope Length shorter than 4m Slope Length shorter than 4m .

   3 . sin   .

  56  

    F For slope length longer than 4m and s<9% For slope length longer than 4m and s<9% F l l l l th l th l th th

  4 4 d d 9% 9% S S   10 .

  10 8 sin sin   .

  8

  03  

  03

    Slope length more than 4m and s >= 9% Slope length more than 4m and s >= 9% p p g g

  S S  16 . .

  16

  8 8 sin sin  . .

  5  

  5

Cr op m a n a ge m e n t fa ct or ( C) Cr op m a n a ge m e n t fa ct or ( C)

    Combined effect of crop sequences, Combined effect of crop sequences, productivity level, length of growing season, productivity level, length of growing season, p p y y , , g g g g g g , , tillage practices, residue management & tillage practices, residue management &

expected time distribution of erosive rain expected time distribution of erosive rain

storm with respect to planting & harvest date storm with respect to planting & harvest date t t ith ith t t t t l l ti ti & h & h t d t t d t

Crop Soil loss Value of C Eg. (tn/ha)

  Cultivated

  5

  1 Grass

  0.59

  0.12 Bajra Bajra

  2 0.38 0 38

  2

Con se r va t ion pr a ct ice fa ct or ( P) Con se r va t ion pr a ct ice fa ct or ( P)

    Ratio of soil loss with a specific supporting Ratio of soil loss with a specific supporting practice to the corresponding loss with up & practice to the corresponding loss with up & practice to the corresponding loss with up & practice to the corresponding loss with up & down cultivation down cultivation

e.g. e g Practice Practice P factor P factor

  a) Up and down

  1.0

  cultivation cultivation of of Jowar

  Kanpur

  b) Contour ) cultivation of

  0.39 Jowar

W in d Er osion W in d Er osion

    Process of detachment transportation and Process of detachment transportation and deposition of soil by action of wind deposition of soil by action of wind deposition of soil by action of wind deposition of soil by action of wind

    Depends on wind speed, soil, topographic Depends on wind speed, soil, topographic features and vegetative cover features and vegetative cover features and vegetative cover features and vegetative cover

    More problems in arid or semi More problems in arid or semi--arid region arid region     Change in texture of soil Change in texture of soil Change in texture of soil Change in texture of soil

    In India: Mainly occur in Rajasthan, Gujarat In India: Mainly occur in Rajasthan, Gujarat and parts of Punjab and parts of Punjab and parts of Punjab and parts of Punjab

  Wind erosion in a watershed

M e ch a n ism of W in d Er osion M e ch a n ism of W in d Er osion

   

  Initiation of movement – Initiation of movement –due to turbulence and wind due to turbulence and wind velocity velocity

     

  Transportation Transportation – Transportation – Transportation –depends on particle size gradation wind –depends on particle size, gradation, wind depends on particle size gradation wind depends on particle size, gradation, wind velocity and distance velocity and distance

   

  Deposition— Deposition —occurs when gravitational force is greater occurs when gravitational force is greater than forces holding soil particles in air than forces holding soil particles in air h h f f h ld h ld l l l l

   

  Types of soil movement by wind Types of soil movement by wind

• – Saltation Saltation Fine particles lifted from surface and Saltation Saltation-- Fine particles lifted from surface and Fine particles lifted from surface and Fine particles lifted from surface and – following specific path w.r.t wind and gravity following specific path w.r.t wind and gravity
• – Suspension Suspension--floating of small particles floating of small particles –
• – Surface creep Surface creep --rolling or sliding of large soil particles rolling or sliding of large soil particles – along soil surface. along soil surface.

Est im a t ion of W in d Er osion Est im a t ion of W in d Er osion

  F

  

525 2 (



  I ) 718 .

  F F--% of dry soil fraction greater than 0.84 mm % of dry soil fraction greater than 0.84 mm

  

  ) 718

525 2 (



  I 05 .

    Average annual loss Average annual loss

  ) (

  Where, E Where, E estimated average annual loss (tn/ha/year) estimated average annual loss (tn/ha/year)

   

  V L C K I f E 

  ) , , , , (

  Where, E Where, E--estimated average annual loss (tn/ha/year) estimated average annual loss (tn/ha/year)

  V L C K I f E  

  II-- soil erodibility index (ton/ha soil erodibility index (ton/ha--yr), K yr), K--ridge roughness ridge roughness factor, C factor, C--climate factor, L climate factor, L--unsheltered length of unsheltered length of eroding field (m) V eroding field (m) V--vegetative cover factor vegetative cover factor eroding field (m), V eroding field (m), V vegetative cover factor vegetative cover factor

Rou gh n e ss Fa ct or Rou gh n e ss Fa ct or

    A measure of effect of ridges made by tillage A measure of effect of ridges made by tillage implements on wind erosion implements on wind erosion implements on wind erosion implements on wind erosion

    Ridge roughness in mm Ridge roughness in mm

  2 .

  16 16 h h K

   r d h--ridge height in mm; d h h ridge height in mm; d h ridge height in mm; d--ridge spacing in mm ridge height in mm; d ridge spacing in mm ridge spacing in mm ridge spacing in mm from K from K , roughness factor K , roughness factor K rr

  12 

  6

  2 K .

  35 6 .

2 *

  10 Kr    K 

  18   r

Clim a t ic Fa ct or Clim a t ic Fa ct or

    Index of climatic erosivity Index of climatic erosivity--> depends on wind > depends on wind velocity and soil surface moisture velocity and soil surface moisture velocity and soil surface moisture velocity and soil surface moisture

  Mean wind velocity profile expression Mean wind velocity profile expression Where, u -wind velocity at z height (L/T) z

  0.5 τ0/ρ)

• u
• friction velocity (L/T)= (
• 2

  2

• shear stress at boundary (F/L ) )

     τ τ shear stress at boundary (F/L u u z z d d

   

  3 ln u 

  ) z

  ρ-air density (m/L   z

   k- Karman’s constant=0.4 o

    z-Height above a reference surface g d-an effective surface roughness height z -a roughness parameter (h) d=0.7h; z =0.13h h-height of vegetation h height of vegetation

Un sh e lt e r e d Be lt & V e ge t a t ive Cove r Fa ct or Un sh e lt e r e d Be lt & V e ge t a t ive Cove r Fa ct or

    Unsheltered distance (L)-- Unsheltered distance (L) Distance from a Distance from a sheltered edge of a field to end of unsheltered field sheltered edge of a field to end of unsheltered field sheltered edge of a field to end of unsheltered field sheltered edge of a field to end of unsheltered field

    Vegetative Cover-- Vegetative Cover Factor represented Factor represented by relating by relating the land quantity and orientation of vegetative the land, quantity and orientation of vegetative the land, quantity and orientation of vegetative the land quantity and orientation of vegetative

material to its equivalent of small grain residue material to its equivalent of small grain residue

  V w

  V   aR aR b b

    V--vegetative cover factor expressed as small grass equivalent V vegetative cover factor expressed as small grass equivalent in kg/ha; a, b--crop constants in kg/ha; a, b crop constants

  

R R – quantity of residual to be converted to small grain quantity of residual to be converted to small grain

w w equivalent in kg/ha equivalent in kg/ha g g

• –  

Photo, A.K. Singh, 2002 Pr e ve n t in g Soil Er osion

   Pr e ve n t in g soil e r osion r e qu ir e s polit ica l, e con om ic & t e ch n ica l ch a n ge s.

   Aspects of technical changes include:  use of contour ploughing and wind breaks;

   leaving unploughed grass strips between ploughed land; g p g g p p g ;

   making sure that there are always plants growing on the soil, and that the soil is rich in humus (decaying plant and animal remains). a a e a s)

   avoiding overgrazing and the over-use of crop lands;

   allowing indigenous plants to grow along the river banks

   encouraging biological diversity by planting several different en o ging biologi l di e it b pl nting e e l diffe ent types of plants together;

   conservation of wetlands.

Soil Con se r va t ion Pr a ct ice s

   Con se r va t ion m e a su r e s - reduce soil erosion by both water & wind. both water & wind.

  

  , as well a land

  Tilla ge a n d cr oppin g pr a ct ice s

  management practices, directly affect the overall soil erosion problem. erosion problem

  

  (Eg. contour plowing,

  Com bin a t ion of a ppr oa ch e s

  strip cropping, or terracing)

  

Ot h e r m e a su r e s : Silt Fencing, Erosion Control

  Blankets, Sediment Traps, Plastic Covering/Bank Stabilization, Pipeline Sand Bagging, Check Dams, Stabilization Pipeline Sand Bagging Check Dams Drain Inlets, Filter Berms & Silt Dikes Soil Conservation Practices - Types yp 

  Vegetative practices

• – Contouring Contouring – Strip cropping
• – Tillage operations Tillage operations
• – Mulching

   Mechanical practices p

• – Terraces – Bunds (graded & contour)
• – Check dams
• – Vegetated outlets & watercourses

Ca se St u dy: I n dia n Sce n a r io

  

  Soil erosion prevalent – almost 55% of total land almost 55% of total land

  

  Himalayan & lower Himalayan regions highly affected h

  

  More than 25% reservoir capacity lost

  

  Erosion rates in India-

  

  Iso-erosion lines- annual

  Erosion rates in ton km ^-2 year ^-1 _{(Garde & Kothyari, 1987; Kothyari, 1996)}

An n u a l Soil Loss Est im a t e An n u a l Soil Loss Est im a t e – – I n dia n Sce n a r io I n dia n Sce n a r io Re gion La n d- Use Soil loss( t / k m

  ² ) North Himalayan forest region

  Forest ~280 Punjab-Haryana alluvial plains Agriculture ~330 Upper-Gangetic-alluvial plains Agriculture/waste land ~1400-3300

Lower Gangetic alluvial plains Agriculture ~280-950

North-eastern forest region

  Agriculture/shifting cultivation ~2750-4100 Gujarat alluvial plain Agriculture ~300-3300

  

Red soil region Agriculture ~250-350

Black soil region Agriculture 2370 11000 Black soil region Agriculture ~2370-11000 Lateritic soil Agriculture ~4000 Ref: Ref: Raj Vir Singh (2000), Watershed Planning and Management, Yash Publishing House Raj Vir Singh (2000), Watershed Planning and Management, Yash Publishing House

Re fe r e n ce s Re fe r e n ce s

    State of Environment of India 2009: report of Ministry of Environment State of Environment of India 2009: report of Ministry of Environment and Forest ( source: and Forest ( source: http://moef.nic.in/downloads/home/home--SoE http://moef.nic.in/downloads/home/home SoE-- Report--2009.pdf R R Report 2009 2009 2009.pdf df df )) ))

   

Raj Vir Singh (2000), Watershed Planning and Management, Yash Raj Vir Singh (2000), Watershed Planning and Management, Yash

Publishing House P bli hi P bli hi Publishing House H H

    http://www.geo.fu--berlin.de/fb/e http://www.geo.fu berlin.de/fb/e-- learning/geolearning/en/soil_erosion/types/index.html learning/geolearning/en/soil_erosion/types/index.html

      http://iahs info/redbooks/a236/iahs 236 0531 pdf http://iahs info/redbooks/a236/iahs 236 0531 pdf http://iahs.info/redbooks/a236/iahs_236_0531.pdf http://iahs.info/redbooks/a236/iahs_236_0531.pdf

    _{ } http://www.ias.ac.in/currsci/25jan2010/213.pdf http://www.ias.ac.in/currsci/25jan2010/213.pdf

  

G. D a s ( 2 0 0 0 ) : , H ydr ology & Soil Con se r va t ion En gg., Pr e n t ice H a ll of G D a s ( 2 0 0 0 ) : H ydr ology & Soil Con se r va t ion En gg Pr e n t ice H a ll of

I n dia , N e w D e lh i

Tu t or ia ls - Qu e st ion !.?

   I llu st r a t e t h e possible soil con se r va t ion m e a su r e s w it h in t h e pe r spe ct ive of m e a su r e s w it h in t h e pe r spe ct ive of su st a in a ble w a t e r sh e d m a n a ge m e n t pr a ct ice s.

   

  Identify the components soil erosion Identify the components soil erosion

   

  Scientific interventions Scientific interventions

   

  Identify the problems Identify the problems Identif the p oblems Identif the p oblems

    Identify vegetative & mechanical measures. Identify vegetative & mechanical measures.     Importance of soil conservation. Importance of soil conservation. Importance of soil conservation. Importance of soil conservation.

  Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

Se lf Eva lu a t ion - Qu e st ion s!. Q

  

What are the causes and consequences of

soil erosion?. soil erosion?

   What is wind erosion & under what conditions does it occur?. conditions does it occur?

   Enumerate measures adopted for control of soil erosion caused by wind. soil erosion caused by wind.

  Prof. T I Eldho, Department of Civil Engineering, IIT Bombay P f T I Eldh D t t f Ci il E i i

  IIT B b

Assign m e n t - Qu e st ion s?. g Q

   Differentiate between geologic & accelerated erosion of soil. erosion of soil

   Illustrate soil erosion processes. 

  

What are the important factors affecting soil at a e t e po ta t acto s a ect g so

erosion by water?.

  

What are different types of water erosion?.

  Discuss each type. Di h t

Un solve d Pr oble m !. Un solve d Pr oble m !

    For your Watershed area, study the soil For your Watershed area, study the soil erosion problems?. erosion problems?.

    Identify the problems. Identify the problems.   Find out the ways to control soil erosion Find out the ways to control soil erosion problems. problems. bl bl

• – Carry out survey Carry out survey –
• – Consider traditional practices to control erosion Consider traditional practices to control erosion Consider traditional practices to control erosion Consider traditional practices to control erosion –
• – Suggest scientific methods for soil conservation Suggest scientific methods for soil conservation –

  Dr. T. I. Eldho Dr. T. I. Eldho Professor, Professor, Department of Civil Engineering, Department of Civil Engineering, p p g g g g Indian Institute of Technology Bombay, Indian Institute of Technology Bombay, Mumbai, India, 400 076. Mumbai, India, 400 076. Email: Email: Email: Email: eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in