LARGE SCALE INSTALLATION OF SUBSURFACE DRAINAGE SYSTEM

LARGE SCALE INSTALLATION OF
SUBSURFACE DRAINAGE SYSTEM
in Chambal Command, Rajasthan

Er. C.M. Tejawat, F.I.E., P. Eng.,
B.E. (Ag.), M.Sc. (Land Drainage Engineering)
Deputy Director (Monitoring), CAD Chambal, Kota (Raj.)

Gandhi Sagar Dam (M.P.) Rana Pratap Sagar Dam (Raj.)

Jawahar Sagar Dam (Raj.) Kota Barrage (Raj.)

Left Main Canal
(Rajasthan)

Right Main Canal
(Rajasthan & M.P.)

G.C.A. 4,85,000 ha Command Area - Chambal
C.C.A. 2,29,000 ha
Districts wise CCA
Kota – 1,04,000 ha
Baran - 28,000 ha
Bundi – 97,000 ha

Chambal Command Area, Rajasthan

Irrigable Area 2,29,000 ha.
Irrigation 1960
Started
Soils Uniform Clay – Loam

Vertisols

Below 1.5 – 2.0 m

• Yellowish brown heavy clay
layer
Yellow silty clay (murrum
layer) 20-30 m with higher
permeability

PROBLEMS

Waterlogging in the fields of head reaches.

Increase in Salinity and Alkalinity of Soil.

Decrease in Crop Production.

Wastage of Irrigation Water .

Extent of Problem

Water logging : 1,61,000 ha.

Soil Salinity : 25,000 ha.

UNDP Project

To find means to protect the Land from Salinity and
Waterlogging.

To study problem of weed control in existing
Irrigation Canals and Drains.

To Design and Execute Irrigation Improvement,
Land Shaping and Drainage on Pilot Areas.

To develop proper Water Management Principals
and to make recommendations.

To develop proper Land Use Pattern and Farm
Practices for Intensification of Agriculture.

World Bank Project

Started in 1974
Planned to provide Surface Drainage in 1,67,000 ha
area.
74 Drainages Sub-basins identified having
Waterlogging problem.
Sub-basin 1000-10,000 ha
A Main Drain
Several Secondary Drains at about 500 m
spacing.

Seepage drains alongside the canals.

Command Area Development Project

Main Objectives
Improvement and increase in the Capacity of Canal.

Increase in Crop production with the help of improved
Agriculture Techniques.

On-Farm Development Works.

The Major thrust was given to On Farm Development Works.

On Farm Development Works

Objectives
Efficient water utilization to increase Irrigated Cropping
Intensity.

Maximum yields by scheduling Irrigation water application,
providing adequate drainage & better cultivation
techniques.

Easy access to individual field through improved road
network.

Shaping the Land to enable efficient Irrigation of field
Crops.

O.F.D. Works

Construction of Irrigation & Drainage ditches for each
field.

Providing road network to each field.

Land shaping for efficient Irrigation.

Re-alignment of the farm boundaries.

RAJAD
Rajasthan Agriculture Drainage Research Project
(1992-1999)
INSTALLATION OF
R SUBSURFACE
DRAINAGE SYSTEM

A in Chambal Command,
Rajasthan

J
A
D

Selection of Reclamation Technology

Subsurface Drainage + Surface Drainage +
On Farm Development Works
Provides an integrated soil and water management
program to optimize sustainable crop production in saline &
waterlogged lands.

Chambal Command Area-Rajasthan

Area Selection

•RAJAD Project - 25,000 ha

Salinity
Ec > 4 dS/m in top 1.5 m soil profile in at least
50% of the selected area.

Waterlogging
Water table depth < 40 cm in 70% of the area
for duration of at least 3 days.
Water table depth < 1.2 m in 70% of the area
for a continuous duration of at least 30 days
during an average rabi/kharif season.

Drainage Investigation

ECe (dS/m) Area Area
(ha) (%)
0-2 24569 48.90

2-4 7743 15.41

Sub Total for 32312 64.31
non saline area
4-8 12869 25.61

8-16 4510 8.98

>16 555 1.10

Sub Total for 17934 35.69
saline area
Grand total 50246 100.0

Area Selection

•280 Observation wells installed

•256 ha (1600 m grid)

•2.5 m deep & 1.5 m deep

•Measurements were taken on weekly basis

•Farmers Participation was involved

•Data of 275 wells were analysed

•Monitoring period Dec. 94 to Jan. 97


Use of Total Station Survey Equipment


Auger Hole Method

Data Storage and Retrieval

Computerized Central Data Base
System

Development of Design Criteria

• 12 Research Sites
International
• 4 years of data monitoring Panel of Experts
& analysis

DESIGN OF SUBSURFACE DRAINAGE SYSTEMS

Design Criteria for SSD in Chambal Command Area

Saturated Hydraulic Conductivity
• Measured at 1.0, 1.5, 2.0 & 2.5 m depth
• Grid 8.58 ha
• Test plot results indicated:
•Top 1 m 0.25 – 0.55 m/day
•1 – 1.5 m 0.02 – 0.20 m/day
•Below 1.5 m 0.75 m/day


Geometry of a Transient State Drainage System


Modified Glower Dumn Equation

0.5 −0.5
⎡K *d *t ⎤ ⎡ ⎛ H 0 ⎞⎤
L=π⎢ ⎥ * ⎢ln⎜1.16 * ⎟⎥
⎣ μ ⎦ ⎣ ⎝ Ht ⎠⎦
H0
d = de +
2
L
de =
8*f h
2
[L- D* 2.0 ] 1 D
fh = + * ln
8 * D* L π r 0 * 2.0



Drainable Porosity

μ = {0.0376 * (Ksat) 0.25} Chambal Varient (68%)

μ = {0.0386 * (Ksat) 0.25} Kota Varient (28%)



Water Table Draw Down

20 cm in 3 days to control irrigation induced
salinity

Used for spacing calculation in transient
equation



Average Drain Depth

Depending on soil properties, crop,
extent of soils salinity, gravity outlet

1-1.5 m below ground surface with
average of 1.2 m



Simple Equations for Drain Spacing

For Chambal Soil Series

• Drain Spacing = 8.71 + 73.36 * Ksat0.5

For Kota Soil Series
• Drain Spacing = 13.61 + 67.92 * Ksat0.5



Computer Program for Drain Spacing

For calculating drain spacing grid wise

• Auger hole Ksat dat

• Drainable porosity v/s Ksat

• Design Criteria



Drain Spacing

Calculated for each grid (8.58 ha)

Geometric mean of calculated spacing (100-
150 ha area block)

Rounded to next multiple of 5 m

Range of spacing 35-85 m



Drainage Coefficient

• Laterals 1.5 mm/day
• Collectors 3.0 mm/day

For pipe capacity calculation only



Pipe Size

⎡ q *S *L*n ⎤
d =⎢
8 d
3

⎥
⎣ 0.31168 * i ⎦
1
2

Minimum pipe diameter
--- 72/80 mm


Manning’s Roughness Coefficient & Grade

I.D. (mm) O.D. (mm) n Minimum Grade
(%)
72 80 0.015 0.10
88 100 0.015 0.10
144 160 0.016 0.09
178 200 0.017 0.08
258 294 0.018 0.07
315 355 0.019 0.06
401 455 0.019 0.05



Length of Lateral

8/3 1/2
0.31168 * d * i
Lmax =
qd * S * n
Depends on physical limitation, farm size,
layout pattern etc.



Minimum Soil Cover

Depends on soil conditions & depth of outlet
drain

Minimum soil cover of 0.90 m

Exceptional cases:
Up to 100 mm dia 0.60 m
160-455 mm dia 0.80 m



Envelope Requirement
Clay % Envelope
Requirement

>40 Not required
30-40 & SAR >8 Required

<30 Required

Pipe grade >0.4% --- not required

Design of SUBSURFACE DRAINAGE SYSTEMS

Computer Aided Design Procedure

Computer
Aided
Design
Procedure

SSD Layout System

Parallel
Perpendicular

Position of Outlet

Field Drain
Carrier Drain
Main Drain

Minimum Permissible Clearance for
SSD Outlet
Depth of Base Flow Allowance for Free Depth to SSD Outlet
(db) Sedimentation Board Invert
(ds) (df)
Less than 65 cm 20 cm 15 cm SDBE+db+df
Min 45 cm & Max. 85 cm
More than 65 cm 20 cm Nil SDBE+db

Drainage Material

Up to 100 mm corrugated PVC pipes were available
Smooth Wall Rigid Pipes were used

Drainage Material

Plant set up at Kota for
Corrugated PVC pipes of 80, 100,
160, 200, 294, 355 and 455 mm
dia.
At Sangli 80-160 mm PVC & HDPE
as well as double wall corrugated
pipes up to 315 mm are produced

Envelope Material

SSD Installation

Excavation of trench
Laying of Pipe on the grade
Backfilling of the trench
Restoration of ROW

Manual

SSD Installation

Manual Excavator

Grade Control ???????

SSD Installation

Laser Excavator

SSD Installation

Bulldozer-Plow

SSD Installation

Drain Laying Plow

SSD Installation

Chain Trencher

SSD Installation

V Plow

SSD Installation

Import of Drain
Laying Equipments

Right of Way

Crop Compensation

Irrigation Shut Off

SSD Installation

Physical progress achieved
S.No. SSD installation method
at RAJAD

1 Manual installation 50 m/day with 20 labours

100 - 150 m/day per
2 Installation using excavator
excavator

Installed using a trenchless 4000 - 6000 m/day per
3
drain laying plow plow

1000 - 2000 m/day per
4 Installation using a trencher
trencher

About 2500 km of pipe installed in CCA

Supervision, Inspection and Quality Control

Preparation of Contract Document

Specification of Drainage Material &
Installation

Development of Contractors – national,
international

Human Resources Development
•Post Graduation in Drainage Engineering
•National & international Drainage Courses
•Use of Computers, Total Station, EM 38, GIS etc.
•Several workshops, seminars, awareness camps etc.

Assistance of International/National
Experts and Local/GOR Staff

People Participation

Subsidy

Coordination with State Government

Maintenance

Subsurface Drainage Installation in Chambal Command,
Rajasthan

Project Area installed Year
(ha)
Small Test Sites 410 1991-1993
Large Test Sites 1,010 1993-1994
Pre-CON/1 700 1995-1996
(Training Phase)
CON/1 10,671 1996-1999

Areas with Patchy 2,134 1997-1999
Salinity
Total 14,925 1991-1999

Yield 9.45 q/ha ECe 11.3 dS/m

Yield 0 q/ha ECe 19.2 dS/m Yield 9.45 q/ha ECe 11.3 dS/m Yield 12.8 q/ha ECe 10.4 dS/m

Yield 25.2 q/ha ECe 5.1 dS/m Yield 34.1 q/ha ECe 2.7 dS/m Yield 43.0 q/ha ECe 2.36 dS/m

IMPACT OF SUBSURFACE DRAINAGE

Soil Salinity Reclamation
• Continuous reduction in the salinity in the upper
15 cm depth.
• For the lower depths salinity levels increased
during first 3 years then salinity levels declined.
• Over a period of 5 years, the salinity level reduced
to below 4 dS/m
• After SSD salinity reclamation could be achieved
in 2 to 3 years for about 60% areas & within 3 to
4 years for 90-95% of the affected areas.
• About 5-10% of the affected area could take more
than 4 years for satisfactory reclamation

Crop Yield in Saline & Waterlogged areas and
non-saline & non-waterlogged areas
in the Chambal Command Area of Rajasthan.

Crop Crop Yield (Quintals/ha)

Saline Non-saline /
/waterlogged Non waterlogged
Wheat 17.0 34.0

Mustard 6.1 14.7

Paddy 17.0 29.0

Soybean 10.2 21.8

Berseem 360.0 520.0

Sugarcane na 567.5

Relationship between
Soybean Yield and Water table Depth

Average Water Soybean Relative Yield
Table Depth (cm) Yield (t/ha) (%)
80.0 2.18 100
70.0 1.93 88
59.6 1.69 77
50.0 1.44 66
40.0 1.20 55

Water Table Control

A drainage rate of 1.5 mm/day (an equivalent
water table draw down of 20 cm from soil
surface in three days) was considered
adequate to maintain a favorable salt balance.
Field observations since SSD installation in
various test sites have indicated that a water
table draw down of 20-40 cm in three days is
achievable.

Water Table Control

The water table control has an added positive
impact in advancing soil trafficability
conditions (tilth) by 6-10 days after a rainfall
or irrigation event, thereby allowing farmers
more time for farming operations

Good tilth conditions also provide a further
benefit, namely an opportunity to save fuel in
machinery operations.

Crop Performance

Increase in Crop Yield
The average increase in the crop yield in
SSD test sites compared with non-SSD
sites was about
• 56 percent for soybean and
• 55 percent for wheat.

Farmers have also reported
improvements in the quality and quantity
of produce, particularly vegetables.

Relationship with Soybean Yield,
Water Table depth and Soil Salinity

The analysis showed that soybean yield
was independent of the water table when
its depth was greater than 80 cm below
ground surface. The yield decreased as
the water table depth approached soil
surface.

The average optimum desirable water
table depth during growth season of
soybean is 80 cm for the CCA conditions.

Relationship with Soybean Yield,
Water Table depth and Soil Salinity

Monitoring at RAJAD indicated that an
average water table draw down of 20 – 40
cm within three days was achieved.
The majority of the drain flow rates from
these sites ranged from 1-4 mm per day.

The relationship between soybean yield
and soil salinity showed that crop yield is
independent of soil salinity, upto a
threshold ECe value of 4.1 dS/m. Beyond
that, the yield decreases.

Increase in Cropping Intensity

Water table control and salinity reclamation
in the test sites significantly alleviated
these constraints, which resulted in a 20-25
percent reduction in the amount of fallow
land in the Kharif season, and 5-6 percent
reduction in fallow during the Rabi season.

The pre-SSD cropping intensity was 150-
160 percent and the post – SSD cropping
intensity was 170-185 percent. The
cropping intensity is projected to further
increase.

POSITIVE IMPACTS OF
SUBSURFACE DRAINAGE

S.No. Impact Improvement
1. Salinity reclamation
I. Soils with EC 4-8 dS/m 2-3 years to achieve
II. Soils with EC 8-16dS/m 3-4 years to achieve
III. Soils with EC>16 dS/m > 4 years to achieve
2. Water table control 20-40 cm draw down
in 3-4 days
3. Soil trafficability Advanced by 6-10
days

POSITIVE IMPACTS OF
SUBSURFACE DRAINAGE

S.No. Impact Improvement
4. Crop Yield 56 % increase in
soybean;
55 % increase in
wheat yields
5. Cropping intensity Increased from 150-
160 percent to 170-
185 percent

Economics of Subsurface Drainage
As per economic and financial analysis of SSD
Assuming
• capital cost of SSD of RS. 34,250 per ha,
• using a discount rate of 12 percent and
• assuming that benefits would accrue from the
entire SSD installed area,
• the economic benefits of SSD for a 30 year life
expectancy were calculated as follows.
Benefit/cost ratio : 2.6
Net present value (NPV) per ha : Rs.54,900

The internal rate of return (IRR) = 28 %.

This relates to a 2.4 times return over the
market rate of interest that a farmer would
have to pay, if it was to be fully financed by
the farmer.

The above analysis indicated that SSD is a
cost effective method to reclaim
waterlogged and saline lands in the CCA.
This system can be replicated in other areas
of Rajasthan and India.

Selection of Reclamation Technology

Relationship between
Soybean yield and Soil Salinity
Average ECe (dS/m) Soybean Relative Yield
for the 0-30 cm Yield (t/ha) (%)
Soil Depth
4.1 1.81 100
6.0 1.60 88
8.0 1.39 77
10.0 1.17 65

LARGE SCALE INSTALLATION OF SUBSURFACE DRAINAGE SYSTEM

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