water distribution schedule under warabandi system considering seepage...

Water Distribution Schedule under Warabandi System considering Seepage Losses for an

Irrigation Project-A case Study

Sunil AjmeraAssociate Professor, SGSITS, Indore

Civil Enginering and Applied Mechanics Department,SGSITS, 23, Park Road, Indore- 452003, M.P., India

Dr. R.K.ShrivastavaProfessor, SGSITS, Indore

Civil Enginering and Applied Mechanics Department, SGSITS, 23, Park Road, Indore- 452003, M.P., India

Abstract: Warabandi system of water distribution is followed for canal irrigation system at many parts in India including Madhya Pradesh. It is observed that tail end fields receive less amount of water compared to fields situated at or near the head of water courses. This is because of seepage losses in unlined water courses. For improving the water supply for the tail end fields considering seepage losses, an attempt has been made in the present study for modification in Roster of conventional Warabandi System for achieving equitable water distribution under existing land holdings in the command area of a minor canal of Choral projects in Madhya Pradesh.

Key words: Water Distribution Schedule, Warabandi, Modified Warabandi, Seepage Losses, Chak, Evapotranspiration.

I. INTRODUCTION:Important aspect of irrigation management requires Efficient and fair distribution of water. Water distribution methods affect the performance of Irrigation system and ultimately affect the water use efficiency of the project. Main aim of irrigation system operation is to supply the water as and when it is required. The art and the science of the distribution of water over the time and space are termed as Irrigation Scheduling. For deciding the amount of irrigation and its scheduling it is necessary to calculate crop water requirement considering climatic and soil water relationship. This requires calculation of consumptive use of water by crop over the growth period.

II. STUDY AREAThe Choral River Project situated near Mhow Tehsil of Indore under Water Resources Deptt. of M.P. has

been considered as a case study for obtaining Water distribution Schedule for 1LMinor in the Command Area in the present study. Choral River a tributary of River Narmada, originates from Vindhyan ranges and flows through Indore and Khargone districts. The Choral Reservoir is located in Rampuriya village under Mhow Tehsil of Indore district. The latitudes and longitudes of the project site are 75°46’N and 22°25’E respectively. The index map of the Choral Project is shown in Figure1. The site of Choral Reservoir is situated at a distance of 15 kms from Mhow by road. It is a trans-basin diversion project having command area under Chambal basin and catchment area under Narmada basin. Earthen dam of height 27.82m is constructed across the river having gross storage of 21.91 million cubic meters (MCM) with live storage capacity of 17.21 MCM and Dead storage capacity of 4.7 MCM. The cropping pattern under the project is given in table 1. The command area under 1-L minor is 271 hectare. The entire command area under this minor consists of small holdings of individual farmers; the smallest area of holding is 1.468 hect. and the largest holding area is 6.152 hect. The command area under this minor is divided into seven Chaks and the details of holdings under these Chaks are given in table 2. The position of outlets for different Chaks is shown in Figure 2.

International Journal of Innovations in Engineering and Technology (IJIET)

Vol. 2 Issue 4 August 2013 178 SSN: 2319-1058

Figure 1. Choral River Project

Figure 2. Plan of 1L Minor Showing the Position of Outlets



Table 1. Details of Crop Pattern in Command Area under study

Particulars Area in Hectares

Kharif Crop:

a. Maize 20

b. Jower 15

c. Ground Nut 5

d. Vegetable 7

Rabi Crop:

a. Wheat 2145

b. Gram 234

c. Potato 585

d. Onion 78

e. Vegetable 78

Table 2. Details of area of Holdings in Hectares under 1-L Minor

S. No A B C D E F G

1 2.654 2.46 2.30 3.009 1.920 2.418 2.312

2 1.650 2.663 4.80 2.271 2.413 3.238 5.090

3 2.442 2.295 1.98 1.849 2.970 3.471 3.390

4 3.821 2.016 3.39 2.189 2.100 2.249 2.816

5 3.110 2.321 3.89 2.457 2.164 2.29 1.521

6 2.970 2.553 1.98 1.829 2.228 2.189 2.720

7 2.704 2.216 1.72 1.957 3.210 2.690 2.612

8 3.092 2.706 4.06 1.942 2.780 1.784 3.772

9 2.282 2.914 2.39 1.854 2.125 3.020 2.660

10 2.111 3.469 2.15 1.864 2.280 1.572 2.835

11 1.793 1.654 2.28 2.474 1.830 2.640 3.623

12 2.463 2.767 1.47 3.253 2.120 2.850

13 2.6 2.01 3.035 3.460 2.810

14 2.182 3.56 3.773 2.224

15 1.854 2.12 1.733 3.102

16 1.584 2.34 2.184

17 6.15 2.710

18 1.84



19 2.78

20 1.65

21 3.13

Total 31.092 38.254 57.96 35.489 26.020 33.14 49.23

III. WARABANDI SYSTEM

The term Warabandi is originated from two vernacular words ‘Wara’ and ‘bandi’. The meaning of wara is ‘turn’ and bandi means ‘fixation’. Taken together, the term Warabandi means rotation of water supply according to a fixed schedule. “Warabandi is a system of equitable water distribution by turns according to a predetermined schedule specifying the day, time and duration of supply to each irrigation in proportion to holdings in the outlet command”For implementation of Warabandi the following basic requirements are fulfilled:(1) To provide network of field channel, so as to ensure water to every holding within the Chak.(2) To ensure design discharge in distributory or minor at each outlet.(3) Farmer’s participation.

A. Terms used in the study:

a. Water Allocations

Each unit of culturable command area is allocated a certain rate of flow of water termed as water allowance, its value is decided after a compromise between demand and supply. The carrying capacity of field channels andwater courses is on the basis of this allowance.

b. Capacity Factor

No distributory operates for all the days during a crop, nor is this advisable, if the means of salinity and waterlogging is to be guarded against. The ratio which the operating period of distributory bears to the total period of the crop is called ‘capacity factor’. This is again a compromise between demand and supply and is separately designed for each of the sub periods of crop. This factor helps in the operation of the distributaries while drawing water from the reservoir.

c. The Chak Units

The command area of an outlet is called Chak. The Chak is a function of the application rate at the field, the peak design irrigation requirement at the outlet and the operating characteristics of the system. The Chak is further divided into sub Chak units for better planning and management.

B. Fixing of Chak

This is an important work if properly done will ensure fair distribution of water in the Chak. The field officers of irrigation department, should survey the Chak at site and fix its boundaries keeping the following points in view:

(1) While fixing the boundaries of the Chak for village, the nallas, C.T. crossing, village boundaries, road, railway line etc. are kept in mind. The area of the Chak is limited upto 60 hectares.

(2) While demarcating the boundaries of the Chak, few extra outlets existing within the Chak shall have to be removed and irrigation ensured from the authorized outlet.

(3) The network of field channels within the Chak should be such that every holding within a Chak is connected by field channel.

C. The Irrigation Channel

The size of irrigation channels in the distribution system should be such that flow could be easily handled by the farmers. Further, it should be sufficient to achieve high water application efficiency. The capacity of the channels should be adequate to carry the peak demand of water requirement. The alignment of water courses is fixed keeping in view covering the Chak of area upto 60 hect. and that the water surface just high enough to serve the field with 3 cm to 10 cm. head. Depth of water in water courses may vary from 0.15 m. to 0.40 m. The velocity of water in water courses should be less than 0.50 m/sec. The length of water courses may be kept to a minimum, to



minimize the seepage loss. The alignment of a water course is made in such a way that it touches each holding and provides one point for delivery to each holding. This delivery point is called Nakka and the Warabandi roster is framed with respect to their Nakka. Water from a water course through field channel is allocated to farmer in the ratio of their holding on 7 days week basis, for the sake of equity and proper monitoring all water courses must be run full for such 7 days period.

D. Management of Warabandi System

The distribution of water in Warabandi system is of two tier operation and each is managed by a separate agency. In the upper tier which is managed by the state, all distributaries and consequently water courses are always operated at full and not partial discharges. This results in minimizing the running time and conveyance losses in distributaries.The distribution of water coming out of an outlet and flowing into a water course is the second tier of distribution and this is managed by the cultivator and the state employees. The distribution of water is done on seven days rotation basis with the help of an approved roster.Whenever a distributory is in operation a water course receives an authorised share of water at a constant rate round the clock and water distribution proceeds from head to tail. The time rotation once started, continues even when the distributory is closed and there is no water in a water course. Thus each cultivator is entitled to receive the entire water in a water course only on a specific week day and at a specific time including night time. A schedule of water supply indicating the time of starting and closing to a particular land holding is known as Roster of turns. There is no provision in this system to compensate any individual farmer who may fail to receive his turn or share of water for any reason, because there is no unalloted time.

E. Flow Time with Conventional Warabandi System

Before a farmer can receive his share of water, he must have spent some time filling up his water course between the point of his taking over to the point of delivery. This time is called Bharai, in the present case, it’s value is taken as 16.76 meter per minute. The cycle of turns on a water course or its branch starts from its head, proceeds downward and ends at its tail. The supply has to be cutoff from the head when the last farmer having his turn, the length of upper position which has been filled with common pool time (Bharai) can be discharged only into his field and normally the total time spent on its filling should be recovered from him in lieu of this, but he does receive all this water at a constant rate. When the supply is cuts off from head, it starts depleting at tail and gradually approaches zero. Such a supply, beyond a limit is not efficient from the point of view of field application. The farmer needs to be compensated for it and this is done be allowing a certain discount on the recovery Bharai time, the discounted value of ‘Bharai’ is known as ‘Jharai’. After allowing amendment for Bharai and Jharai, the flow time (F.T.)for unit area and for an individual farmer are given by the following equations:

And

F. Flow Time with Modified Warabandi System

Flow rate available at the head points of different fields do not correspond to the outlet’s discharge rate, owing to the seepage losses in water courses. Hence, it is essential to account for the seepage losses in respect of different fields to determine the actual flow rate reaching at their fields. The seepage losses vary greatly with time and from soil to soil and, therefore, need to be determined in situ. Seepage losses also depend on the antecedent moisture condition of the soil of the channel. The losses will be more if the interval between consecutive uses of channel is more. The flow rates reaching the head points of different fields is given by –

Where, Qi = Flow rate reaching to ith field (m3/hr). Qo = Flow rate of the outlet (m3/hr). S = Seepage rate (cumecs per million sq.m. of wetted area). P = Average wetted perimeter of the water course (m). Wli = Length of water course connecting ith field with the outlet (m).The seepage factor is the ratio of flow rate of the outlet and the flow rate reaching a field.



Thus, Net allotted time for different fields determined as per conventional Warabandi rostering procedure(NTi)were multiplied by the corresponding seepage factor and the values of revised net allotted time (RTi) were determined as follows:

After determining the revised net allotted time for different field in the command area of an outlet, a correction factor (CF) is determined as follows:

Corrected net irrigation time (CT) for different fields are determined by multiplying their revised net allotted time by the correction factor as follows:

Total time allotted for each field (TTi) is finally determined as follows:

Where, Fi = Bharai Time, and

Di = Jharai Time. From this value of time, the Roster is prepared.

G. Roster of Turn

The turns are fixed on the basis of first come, first served basis from head to tail. The operation of the schedule present no difficulty. A farmer understands that there will be no compensation for a missed turn and, hence, missing even a part of the turnis avoided. The water will be kept open for such a duration so that about 50% of the water requirement of crops of the sub Chak will be fulfilled. At the same time the remaining turnout of the same Chak will be kept closed. In this way in one turn of 7 days all the sub- Chaks of the same Chak will get about 50% of the fortnightly water requirement. In second rotation, or round of seven days fortnightly crop water requirement of the chak will be fulfilled.

IV. CROP WATER REQUIREMENT

. “Crop Water Requirements” have been worked out for the various crops considered for the project area. Estimation of the irrigation water requirement involves the determination of Special needs (SPL), Crop evapotranspiration (ETc), Crop factor (kc), Reference crop evapotranspiration (ETo) and Effective rainfall (ER) of the project area. The SPL value for individual crops has been determined using prevailing practice in the Water Resources Department, Govt. of M.P. The FAO Penman-Monteith method (Allen et al., 1998) is used for the computation of Reference crop evapotranspiration (ETo) from meteorological data in the vicinity of the Project Area. The estimated values of ETo have been further multiplied by crop factor Kc to get the crop evapotranspiration (ETc) for individual crops. The value of crop factor “kc” has also been taken from the FAO-56/Agriculture department.

The estimation of crop evapotranspiration ETc consists of:

1. Identifying the crop growth stages determining their length and selecting the corresponding Kc factor.2. Constructing the crop curve to determine Kc value for any period during the growth period.3. Calculating stage wise ETc as the product of ETo and Kc.

Based on above fortnightly crop water requirement for Rabi crop was worked out assuming effective rainfall and groundwater consideration as zero. Results are shown in table no.3.



Table no 3. Gross Water requirement of Crop in Ha. m. for a plot of 1000 Ha. Area

V. PLANNING ANALYSIS AND COMPUTATION

A. Channel Network

The peak water requirement has been calculated at the outlet utilizing the maximum value of fortnightly water requirement for Rabi season which is 58.60 ha m. for I fortnight of February. The value of field channel efficiency and field application efficiency each are taken as 90%, in addition 2% allowance for losses is also added .Considering the same, the value of peak discharge required in water course at the head of minor would be 0..610 lit/sec/Ha..

B. Fixing of chaks

The Chaks and sub Chaks have been fixed on the guidelines as detailed in Para III. B. In all seven Chaks have been considered for the design of modified Warabandi system under 1-L minor of Choral Project. The Layout of Chak ‘A’ is shown in Fig. 3

C. Design Computations

a. Parameters for water course and field channel design

The total area considered for planning is divided into Chaks and sub Chaks. After finalizing these, the alignment of the water course and field channel network have been determined . The water course and the field channel has been designed with a capacity of 0.61 lit/sec/Ha. The bed width is kept 0.30 m., depth of water is takenas 0.20 m, side slope is kept 1.5:1and wetted parimeter as 1.021m. There is no provision of lining of water course as well as field channel. The value of rugosity constant is adopted as 0.018. The field drains and collecting drains have been aligned according to topography of land. The Layout of water course and the field channel for a Chak ‘A’ is shown in Figure 3

S No.Particulars of Crop

Area in

Hect.Oct Nov Dec Jan Feb Mar

I II I II I II I II I II I1 Wheat 687.5 0.00 0.00 41.25 11.88 21.07 23.69 32.49 37.24 44.13 44.51 29.432 Gram 75 4.50 1.73 1.41 2.36 2.17 2.72 3.25 3.66 3.71 3.61 0.003 Potato 187.5 0.00 11.25 4.41 4.94 6.19 6.76 8.89 9.97 9.34 0.00 0.004 Onion 25 1.50 1.01 1.02 1.00 1.04 1.01 1.08 1.23 1.42 1.58 1.555 Vegetable 25 0.00 1.50 0.82 0.95 0.93 1.01 1.06 0.36 0.00 0.00 0.00

Total 1000 6.00 15.50 48.91 21.13 31.40 35.19 46.77 52.47 58.60 49.69 30.99



Figure 3. Layout of Subchaks,Water Course and Field Drains for Chak-A

D. Roster Computations for Conventional Warabandi

The allocation of turn is done so as to allot to each farmer a volume of water proportionate to area of land holdings in an outlet command. The proposed water management envisages the running of the entire conveyancesystem with respect to full supply discharge in all channels during the peak demand periods. The main canal, minors and water courses will be running full for 14 days in a fortnight. The complete roster has been prepared for Chak‘A’ is shown in Table 4, similar computations are made for the other Chaks also.

E. Roster Computation for Modified Warabandi Method

The equitable distribution of water to each farmer especially for farmers at tail end is not possible due to seepage losses in the serving length of the channel. Thus, the designed system of Conventional Warabandi is required to be modified for achieving the objective of equitable distribution to each farmer as per his land holding irrespective of the location of his holding in the area under Irrigation. Considering seepage rate of 1.6 cumecc/million wetted perimeter for B.C. Soil, A modified roster has been prepared for Chak ‘A’ is shown in Table 4, similar computations are made for the other Chaks also. Comparison of water supplied by conventional and modified warabandi system is shown in Table 5.



Table 4. Water Distribution Schedule under Conventional and Modified Warabandi System for Chak – A

Table 5. Comparison of Water Distribution Schedule under Conventional and Modified Warabandi System for Chak – A

FIELD NO. AreaFlow Rate in m3/

Hr

Conventional Warabandi Modified WarabandiTime Hr.

Water supplied in m3

Time Hr.

Water Supplied in m3

a7 2.47 49.17 17.50 860.27 16.47 809.78a8 2.16 47.94 14.70 704.82 14.15 678.57a9 1.83 47.41 12.32 584.16 11.99 568.49a10 1.69 46.67 11.44 534.14 11.31 528.02a12 1.97 45.86 13.34 611.85 13.42 615.43a11 1.43 45.65 9.35 426.85 9.45 431.49a5 2.49 47.14 17.02 802.30 16.66 785.45a6 2.38 45.61 16.05 732.00 16.23 740.25a4 3.06 45.14 20.82 939.90 21.27 960.15a1 2.12 44.48 14.33 637.58 14.86 661.10a3 1.95 44.10 13.15 579.99 13.75 606.56a2 1.32 43.86 7.96 349.30 8.42 369.38

Total 24.87 168.00 7763.17 168.00 7754.67

Field No Area 'Ha'

Serving length

of water course

M

Water course filling time 'Hr'

Water course drain time Hr

Net allotted

time Hr

Total Time Hr.

Expected flow Rate

m3/ Hr

Revised net

allocated time Hr

Corrected net

allocated time Hr

Total allocated time Hr

Filling Drain (NTi) (Qi) (RTi) ( CTi) (TT i)a7 2.474 926 0 0.92 0 16.58 17.50 49.17 18.41 15.55 16.47a8 2.163 210 0 0.21 0 14.49 14.70 47.94 16.51 13.94 14.15a9 1.826 90 0 0.09 0 12.23 12.32 47.41 14.09 11.90 11.99a10 1.689 126 0 0.13 0 11.31 11.44 46.67 13.24 11.18 11.31a12 1.970 138 0 0.14 0 13.20 13.34 45.86 15.72 13.28 13.42a11 1.434 36 600 0.04 0.3 9.61 9.35 45.65 11.50 9.71 9.45a5 2.488 346 0 0.35 0 16.67 17.02 47.14 19.31 16.31 16.66a6 2.376 260 260 0.26 0.13 15.92 16.05 45.61 19.06 16.10 16.23a4 3.057 340 0 0.34 0 20.48 20.82 45.14 24.78 20.93 21.27a1 2.123 113 0 0.11 0 14.22 14.33 44.48 17.47 14.75 14.86a3 1.954 64 0 0.06 0 13.09 13.15 44.10 16.22 13.69 13.75a2 1.320 41 1830 0.04 0.92 8.84 7.96 43.86 11.01 9.30 8.42

TOTAL 24.874 2690 2690 2.69 1.35 166.66 168.00 197.34 166.66 168.00



V. CONCLUSION

The results of Roster for Conventional Warabandi and Modified Wrabandi system are shown in Table 5 for a Chak under 1L minor of canal project i.e. the study area. It reveals from the results that the rescheduling of timing as obtained using Modified Warabandi system considering seepage losses in serving length of the channel will provide adequate water as per requirement even to the farmers at the tail end, which was not possible with Conventional Warabandi System

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water distribution schedule under warabandi system considering seepage...

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