TECHNICAL SESSION: MICROIRRIGATION
METHODOLOGICAL APPROACH FOR ADOPTION OF MICROIRRIGATION METHODS IN CANAL COMMAND AREA - A CASE STUDY CONCERNED SCIENTISTS: DR. S. B. GADGE DR. S.D. GORANTIWAR DR. VIRENDRA KUMAR DR. MAHESH KOTHARI
INTRODUCTION Microirrigation 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).
MINOR
Methodology BLOCK-2
BLOCK-3
BLOCK-1
BLOCK-4
Block hydrant
Reservoir F 1 F 6
BLOCK-7
F 5 F 4
F 2
BLOCK-5
F 3 BLOCK-6
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)
Legend Hydrant Lateral line Submain line Field main line Network mainline Rising main line Submain control valve F3
Field no.3 Outlet valve
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)
where, Z = total net benefits, Rs Xn = area to be irrigated under nth crop, ha N Bn = net benefit estimated from irrigation of nth n n crop, Rs/ha n =1 N = total number of crops n = subscript for crop In case the net benefits need to be estimated with costs of the common pumping units the objective function is represented as under:
Objective function:
Max Z = ∑ B X
N
Max Z = ∑ Bn X n n =1
− C
Where, C = the cost of the pumping unit at common point. Bn = net benefit estimated from irrigation of n th crop without considering the cost of pumping unit for individual field, Rs/ha
Constraints Area N ∑ Xn n =1
A i
≤
for i =1, I
Water availability N
∑w
in
n =1
Wi −1
Xn
≤ Wi −1 + Inf i
= Wi −2 + Inf i −1
N − ∑ win −1 X n n =1
Wi −1 = ISt For surface irrigation method N
∑w n =1
in
Xn
≤
Inf i
where, A = total available cultivable area, ha i = index for irrigation period I = total number of irrigation periods.
where, win = the irrigation requirement of nth crop during ith irrigation period, ha-m Infi = the inflow of water into reservoir from the outlet during ith irrigation period, ha-m ISt = initial storage in the reservoir, ha-m Wi = water storage in the reservoir at the beginning of ith irrigation period, ha-m.
for i = 1,I
Crop area restriction where, C
∑X
≤
c
A max
c
C
∑X
c
= Aeq
c
≥
c
C
∑X c
A min
c = the index for those crops for which the total area need to be restricted C = the total number of crops for which the area needs to be restricted Amax = 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)
j1 = index for those crops, the crop season of which does not match No overlap constraintswith crop season of crops having index ‘j ’and have similar system 2 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, 3 m i =. index for the period
Constraints
Si = the storage volume in the reservoir at the beginning of period i, ha-m Continuity equation Qi = the inflow in the reservoir due from canal during Si (1-ai) + Qi –Li -Di ≥ Si+1(1+ai) period i, ha-m for all i Di = demand of water for irrigation during period i, the inflow is assumed to be repetitive ha-m Li = losses in the reservoir during period i, ha-m Si+1 = the final storage volume in the reservoir at the Storage capacity end of the period i, ha-m. a= surface area per unit active storage or slope of the Si ≤ K for all i straight line segment with water surface area (yNon negative constraint axis) plotted against reservoir storage (x-axis) Si ≥ 0 for all i ei = evaporation rate during the period i, mm. T is the last period in the sequence. j = index for the year. Spilli
= Si (1-ai) + Qi– Li -Di - Si+1(ai) – K, = 0,
if positive otherwise
Different layouts of microirrigation system
L2S2 layout
L2S4 layout
L4S2layout
L6S2layout
(Other options upto L10 S 8 )
Design Criteria: Pressure variation in sub unit - 20 per cent
•lateral size : 12 mm and 16 mm •submain and main: 32 mm to 110 mm diameter • emitters: 4 Lph average rated discharge
the optimal layout among all the feasible options is the one with minimum cost of lateral, submain and main (fixed + operating cost).
Optimization Technique for Solution to Pipe Network Design ď Ž
Objective function . .
where,
annual fixed cost on pipe and accessories and operating cost including maintenance, repairs, taxes and insurance costs, Rs E ( Dop ) = annual energy costs, Rs. P ( Dop ) = contribution towards annual fixed cost on pumping unit, Rs. Dop = pipe diameter of a link. C ( Dop ) =
ď Ž
Annual fixed costs PWc(Dop)= crf w y
= = =
present worth of pipe and accessories, Rs. capital recovery factor interest rate and the number of years the cost will be incurred in future
Annual energy costs cef= Qop= Hop= r= Taop= Rp= Ρp=
cost escalation factor discharge through the link, lps total pressure requirement, m annual rate of escalation annual hours of operation cost of power, Rs/KWh pump efficiency
Contribution towards annual fixed cost on pumping unit B=minimum cost of the pumping unit, Rs Rpu=cost of the pumping units, Rs/HP Constraints: Conservation of mass
Qop=discharge requirement of the link op K=subscript for all the links joining to the junction o K=total number of links joining to the junction o
Conservation of energy for communicating links
for primary links
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
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
Conclusions
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 %.
THANK YOU