APPROACH
TO PLANNING, CONSTRUCTION AND MAINTENANCE OF ON FARM DEVELOPMENT WORKS
Introduction:
The
purpose of irrigation is to enable the farmers to improve the agricultural
production. The modern irrigation management aims at high efficiency of water
conveyance and appropriate methods of water application, through participatory
irrigation management at each stage of irrigation development. The Govt. of
Maharashatra in Irrigation Department has taken appropriate decision to promote
and implement the theme of participatory irrigation management in all the
Irrigation projects through formation of
Waterciations(WUA)Users’.TheapproachAssotoplanning, design, construction and
maintenance of OFD works needs to be, therefore, reoriented from this new
angle.
On
Form Development Works:
The
efficient management of irrigation water for maximizing productivity requires
both, firstly the efficient on farm water management and secondly the
optimization of the use of water and land, through appropriate methods of water
application. The efficient onfarm water management is related to water delivery
system
and allied works in the command area of chak, which distributes the water to
each farm. The items of works pertaining to on farm water management are termed
as “ On farm development works”.
The on farm development
works comprise of following,
a)
Field channels for conveyance of water
b)
Control structures
c)
Crossings
d)
Surface drainage system
e)
Farm roads
f)
Field channel protection works and
g)
Land forming (Smoothening / grading /
levelling).
In Maharashtra, the OFD
works are divided into two parts:
PartI (a) to (f) as
above
PartII Land forming
The General approach to
design and execution of OFD works:
The general approach to
design and execution of OFD works shall be in accordance with the Govt. technical
circulars, the Govt. Resolution and other directives issued by the Govt. from
time to time for this purpose. The participatory irrigation management and
efficient water delivery system to provide timely as well as adequate water
supply to each farm, shall be the main focus points in the design and
implementation of OFD works.
The basic issues of
general approach are,
a)
Systems approach
b)
Sequence of design and execution
c)
Functional utility
d)
Farmers’
Participation
e)
Organizational coordination
Systems
approach:
The
conveyance system from the dam to the farm gate is one live system and it is
necessary that the designs of the different components are matched properly.
The water management proposed to be adopted on the canal system should always
be kept in view as a reference frame. Presently, canals and branches are
designed for a 14 day rotation (irrigation interval) including a 12 day running
period and a 2 day closure (except in unusual peaks when there is a 14 days
running period); minors and distributories are designed to complete the
irrigation in half period. The chaks will be so laid out and designed that the
entire irrigation thereon is completed in 6 days. The outlets are operated in
sequence from tail to head of the minor. Outlets with a less than 6 day running
period are alternated or rotated. Thus, basically a chak water delivery system
will be designed to provide at the farm gates, (turnout or property head)
within a 6 'day running period, water requirements of 14
days irrigation
interval.
Sequence
of design and execution:
(a) The
ideal sequence of finalization of design would be obviously from the tail to
the head. First, according to the topography and soil conditions, the land
forming of each farm would be decided, so as to ensure efficient irrigation.
Next, the chak water delivery system and
surface
drains would be designed so as to ensure adequate water deliveries to the
different farms and proper drainage. According to the number of outlets and
period for which they would operate, the design capacity of the of minor is
decided and in turn, that of the
distriburtory
and of the main canal.Conditions do not always permit this ideal sequence of
design and therefore the design may have to proceed from head to tail.
Sometimes this may lead to designs with inadequate conveyance capacities in the
distributories and minors. One should keep these limitations in mind.
(b) The
execution of OFD works shall be done only in places where canal water has
actually reached. The OFD works get disturbed and deteriorated if these are not
put to use immediately. As far as possible, the construction of OFD works may
not be taken up till the
formation of
Water Users’ Association.
(c) After
construction of OFD works, preparation of workdone drawings of OFD works
(record drawings) form the basic record for planning irrigation management.
Hence, these should be canvas mounted and hard bound. The completion report
shall include design report and work done cost estimates. The design report
should explain the chak size, field channel alignments and gradients, network
of surface drains and their design, details of OFD structures etc. The
completion report shall explain for any deviations from the design and
limitations, if any, arising out of these deviations for irrigation management.
Functional utility:
The
purpose of the OFD works is to provide timely and adequate supplies of water to
each holding and preserve environmental balance as well, by avoiding seepages,
leakages and stagnations of water which trigger problems like water logging,
causing adverse impact on environment. To achieve this functional utility, the
planning and design of OFD works has to be hydraulically better and socially acceptable.
The OFD works also need to be such that these are economical for the
construction and maintenance. The functional utility of OFD works depends on
levels of accuracies and quality of construction. In a water delivery system,
accuracies are very important. Separate tolerances are, therefore, prescribed
for
different
works of onfarm development. The quality of construction governs the cost of
maintenance and overall life of OFD works.
Thus the functional
utility of OFD works is governed by following aspects
i)
Hydraulic design
ii)Economy
for construction and maintenance
iii)
Social acceptance i.e. User friendliness
to community of farmers who will be actually using OFD works and
iv)
Levels of accuracies and quality of
construction.
These issues need to
have a proper bearing in approach to design and execution of OFD works.
Farmers
Participation:
Success
of canal irrigation depends on the response of the farmer, both as an
individual and as a member of the group benefited by the outlet. The irrigation
facilities should be designed with a view to meet his requirements,
particularly in respect of land forming. Active participation of the farmer at
the stage of design should therefore be encouraged. This will also help in
building up of an atmosphere of common purpose and thereby in the unification
of the beneficiaries into a homogeneous group. The Govt. of Maharashtra in
Irrigation Dept. has taken a decision to promote and expedite the formation of
WUA’s,
so that all the created potential under va Associations. The Govt. is also
promulgatingtion sepa system. Hence, it would be necessary to revamp the
approach, if necessary, in accordance with the provisions and procedures laid
down by the Govt. from time to time
Organizational
Coordination:
The
works from the canal head down to the distributory and from the distributory
head to the outlet are carried out by the Construction Organization (C.O.) of
the Irrigation Department. The outlet of a capacity of about 30 liters/second,
is the last Government structure on the canal system. Below outlet, OFD works
are the community works.Presently the work below the outlet is entrusted to the
Land Development Divisions (L.D Divisions). Design and construction proceed on
the basis of the location of the outlet and its sill level. Experience has
shown that when the work is done in isolation by construction Organization and
Command Area Development wing, many a time errors creep in. The L..D. Divisions
may not be aware of the problems faced on the design and construction of distributories/minors
on the other hand the Construction Organization may not be aware of the
problems that often come up, if the locations/elevations of outlets are not
appropriate in relation to the chak topography. Providing irrigation
facilities, is a joint effort by the Construction Organization and the L.D.
Division. To ensure a coordinated effort, it is necessary at the stage of
design, that the design of a minor is treated as an overlapping function. Thus
the L.D. Division should not consider the design and layout of a minor as a
work unrelated to the work below the outlet. Instead, at least conceptually,
the process of design of the works below the outlet, should continue upto the
head of the minor. For this purpose the Land Development Divisions should approach
the Construction Organization for the details of the designs and layouts of the
distributories/minors. There should be a continuous dialogue between the two
wings on this aspect. In near fut of design and construction.
Procedure for taking up
OFD works:
The
OFD works are part of CAD works. The cost estimates for OFD works are generally
formulated in two parts.
a) Part
I works.: Cost estimates for chak water delilvery system, field channel
protection works and surface drainage works in a chak.
b)
Part II: Cost estimate for land forming
works for each holding.
The design and cost estimates for Part I works s chaks under the command area of minor. This is essential because the design of a chak delivery system should not be done in isolation without consideration of the adjoining chaks. This helps to decide the efficient way of designing surface drains for the overall topography and so also the disposal of excess irrigation water. The overall average cost per ha for Part compared with the prescribed cost norm.
The
cost estimate for land forming works is prepared on individual holding basis
after getting consent of concerned farmer and completing the financial
formalities. The preparation of cost estimate for land forming is explained in
chapter No. 8 on Land Forming for Irrigation. The design and cost estimate for
field channel protection works may be done for each chak separately.
The construction of OFD works may be taken up as per Govt.’s circulars and instructions in accordance with various provisions in Govt. Resolutions and Acts in vogue. As far as possible the OFD works may not be taken up till the formation of WUA.
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