METHODOLOGICAL APPROACH FOR ADOPTION OF MICROIRRIGATION METHODS IN CANAL COMMAND AREA - A CASE STUDY

CONCERNED SCIENTISTS: DR. S. B. GADGEDR. S.D. GORANTIWARDR. VIRENDRA KUMAR DR. MAHESH KOTHARI

TECHNICAL SESSION: MICROIRRIGATION

INTRODUCTIONMicroirrigation adoption in the command area :Advantages

Need for study:Before actual adoption, it is necessary to check the technical and economical feasibility of the adoption of these systems to canal command area of irrigation project (under rotational water supply).

Methodology

BLOCK-1 BLOCK-4

BLOCK-5

BLOCK-6

BLOCK-2 BLOCK-3

BLOCK-7

MIN

OR

F 1

F 2

F 3

F 4

F 5 F 6

Reservoir

Block hydrant

Legend

Hydrant

Lateral line

Submain line

Field main line

Network mainline

Rising main line

Submain control valve

F 3 Field no.3

Outlet valve

study is divided into blocks with block hydrants. . minimal spanning technique to select the optimal

pipe line layout connecting all individual fields of the block

optimization technique to design individual link of this network. (selection of an optimal diameter)

Program modules : Optimal Crop Allocation Model (OCAM), Storage Reservoir Design Model (SRDM), Microirrigation Layout & Design Model (MILDM) and Pipe Network Design Model (PNDM)

CASE STUDY DESCRIPTION : Mula command- Direct Minor no.3•Total command area =431.73 hectares •Land holders = 346 •52.6% farmers are marginal land holders (<1 ha area)Crop area restriction : Sugarcane - 10% of the total minor command area (TMCA). fruit crops together (Papaya, Banana, Pomegranate and Lime) -10% of TMCA Kharif crops (Kharif Soybean, Kharif Groundnut, Cotton and Kharif Brinjal) -20% of TMCA . Rabi crops (Rabi Tomato, Rabi Onion, Gram, Potato and Cabbage) -40% of TMCA. summer crops (Summer Brinjal, Summer Cucumber, Summer onion, Summer Okra,

Summer Groundnut and Summer Chilli) -20% of TMCA.

Water availability

171279.4 m3 during the “ON” period of the water supply (7 days in 14 days interval) .

Development of a model Optimal Crop Allocation Model (OCAM) Objective function:

N

nnn XBZMax

1

In case the net benefits need to be estimated with costs of the common pumping units the objective function is represented as under:

Where,C = the cost of the pumping unit at common point.Bn = net benefit estimated from irrigation of nth crop without considering the cost of pumping unit for individual field, Rs/ha

CXBZMaxN

nnn

1

where,Z = total net benefits, RsXn = area to be irrigated under nth crop, haBn = net benefit estimated from irrigation of nth crop, Rs/haN = total number of cropsn = subscript for crop

ConstraintsArea

iAXN

nn

1

for i =1, I

where,A = total available cultivable area, hai = index for irrigation periodI = total number of irrigation periods.

Water availability

ii

N

nnni InfWXw

1

1

n

N

niniii XwInfWW

1

1121

IStWi 1

where,win = the irrigation requirement of nth crop during ith irrigation period, ha-mInfi = the inflow of water into reservoir from the outlet during ith irrigation period, ha-mISt = initial storage in the reservoir, ha-mWi = water storage in the reservoir at the beginning of ith irrigation period, ha-m.For surface irrigation method

i

N

nnni InfXw

1

for i = 1,I

C

cc AX max

C

cc AeqX

C

cc AX min

where,c = the index for those crops for which the total area need to be restrictedC = the total number of crops for which the area needs to be restrictedAmax = the maximum area which need to be restricted for ‘c’ crops (ha)Aeq = the area which need to be irrigated for ‘c’ crops (ha)Amin = the minimum area which need to be restricted for ‘c’ crops (ha)

Crop area restriction

No overlap constraintsj1 = index for those crops, the crop season of which does not match with crop season of crops having index ‘j2’and have similar system requirement .j2 = index for those crops, the crop season of which does not match with crop season of crops having index ‘j1’ but have similar system requirement. The net benefits are estimated without considering the cost of the set of microirrigation system.J1 = total number of crops with index ‘j1’J2 = total number of crops with index ‘j2’

Storage Reservoir Design Model (SRDM)Objective function

Minimize K

where,K= design storage capacity of the reservoir,

m3.Constraints

Continuity equation

Si (1-ai) + Qi –Li -Di ≥ Si+1(1+ai) for all i

i = index for the periodSi = the storage volume in the reservoir at the beginning of period i, ha-mQi = the inflow in the reservoir due from canal during period i, ha-mDi = demand of water for irrigation during period i, ha-mLi = losses in the reservoir during period i, ha-mSi+1 = the final storage volume in the reservoir at the end of the period i, ha-m.a= surface area per unit active storage or slope of the straight line segment with water surface area (y- axis) plotted against reservoir storage (x-axis)ei = evaporation rate during the period i, mm.

the inflow is assumed to be repetitive

T is the last period in the sequence.j = index for the year.

Storage capacity

Si ≤ K for all i

Non negative constraint

Si ≥ 0 for all i

Spilli = Si (1-ai) + Qi– Li -Di - Si+1(ai) – K, if positive = 0, otherwise

Different layouts of microirrigation system

the optimal layout among all the feasible options is the one with minimum cost of lateral, submain and main (fixed + operating cost).

L2S2 layout L2S4 layout L4S2layout L6S2layout

(Other options upto L10 S 8 )

•lateral size : 12 mm and 16 mm•submain and main: 32 mm to 110 mm diameter• emitters: 4 Lph average rated discharge

Design Criteria: Pressure variation in sub unit - 20 per cent

Optimization Technique for Solution to Pipe Network Design Objective function

opDC

opDE

opDP

where,annual fixed cost on pipe and accessories and operating

cost including maintenance, repairs, taxes and insurance costs, Rs

.

.

Dop = pipe diameter of a link.

annual energy costs, Rs.contribution towards annual fixed cost on pumping unit, Rs.

Annual fixed costsPWc(Dop)= present worth of pipe and

accessories, Rs.crf = capital recovery factorw = interest rate andy = the number of years the cost will

be incurred in future

cef= cost escalation factorQop= discharge through the link, lpsHop= total pressure requirement, mr= annual rate of escalationTaop= annual hours of operationRp= cost of power, Rs/KWhp= pump efficiency

Annual energy costs

Contribution towards annual fixed cost on pumping unitB=minimum cost of the pumping unit, RsRpu=cost of the pumping units, Rs/HP

Constraints:

Conservation of mass Qop=discharge requirement of the link opK=subscript for all the links joining to the junction oK=total number of links joining to the junction o

where,Hop =requirement of head at the end of link op

Hlop=head loss due to friction and other losses for the link op.

Hfo=head requirement at sink/field o

 

Conservation of energy

for communicating links

for primary links

RESULTS AND DISCUSSION

Optimal Crop Plan : Microirrigation Methods: 6% to Papaya crop, 6% to Sugarcane, 11 % to Kharif Brinjal, 33% to Cabbage, 11% to summer Onion and 33% of the total command area to the summer Brinjal (Net Benefits: 186 Million Rupees) .Surface method: Papaya, Sugarcane, Rabi Tomato rabi Onion, Kharif Brinjal and Cabbage .(50.0 Million Rupees)

Fig. cost and area lost under the reservoir Vs numbers of reservoirs

Fig. Net benefit under different irrigation methods

 Adoption of microirrigation methods over surface irrigation methods in the command area of a minor of the irrigation project is beneficial.

The adoption of microirrigation system using the field reservoir and pump for an individual field for the minor under case study ( CCA 431.75 ha) increases the total net benefits by 25% when compared to adoption of microirrigation system with common reservoir and pumping unit.

The strategies such as size and number of reservoirs and the crop plan influence the magnitude of total costs and total net benefits

Reutilization of the microirrigation system for the seasonal crops having similar system requirements saves the investment cost and increases the net benefit by 6 %.

Conclusions

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