This document discusses a case study analyzing the effect of using single versus dual crop coefficients on crop water requirements under different irrigation methods for wheat crops in the command area of the Choral River Irrigation Project in India. The study finds that considering dual crop coefficients and adopting drip irrigation could increase the area under wheat crops by about 8% while saving water. Specifically, it calculates crop water requirements for wheat using single and dual crop coefficients under sprinkler, furrow, and drip irrigation. It determines that drip irrigation requires the least water and furrow irrigation requires less than sprinkler irrigation. Overall, the study concludes dual crop coefficients and drip irrigation could enhance water use efficiency and yield per unit of available water.

1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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WATER USE MANAGEMENT CONSIDERING SINGLE AND DUAL CROP
COEFFICIENT CONCEPT UNDER AN IRRIGATION PROJECT: A CASE
STUDY
Sunil Ajmera
Associate Professor, SGSITS, Indore
Dr. Rakesh Kumar Shrivastava
Professor, SGSITS, Indore
ABSTRACT
An attempt has been made in the present study to work out the effect of single and dual crop
coefficient under different methods of Irrigation on the crop water requirement. The result shows that
area under Wheat crop can be increased by about 8 % considering Dual Crop coefficient and
adopting Drip Irrigation Practice. The results can be utilised in increasing the area under crop so as to
increase water use under a Canal Irrigation Project for enhancing overall yield and its efficiency.
Keywords: Reference crop evapotranspiration (ETo), Crop evapotranspiration (ETc), Crop
coefficient(Kc), Exposed Soil fractions, Basal crop coefficient (Kcb), Irrigation method, Efficiency.
I. INTRODUCTION
Population growth is resulting into increase of water requirement and reduction in availability
of water and land for agriculture sector. Poor water management is certainly one of the most
important factors for low performance of irrigation system.. Therefore, water management in the
canal command area is very essential to improve the performance of irrigation project.
Water is required for the growth of crop. Availability of water in the reservoir depends upon
annual rainfall. In the low rainfall years, availability of water in the reservoir is less compared to
designed capacity of reservoirs. This results into reduction of area under crop. Deficit availability of
water ultimately results in reduction of overall yield i.e. crop production.
Water losses occur by evapotranspiration, which is combination of two processes Water is
lost, on one hand from the soil surface by evaporation and on the other hand from the crop by
transpiration and is referred to as evapotranspiration (ET). Evapotranspiration from plant varies with
crop growing stage viz. initial stages, development stage, mid stage, end stage. Consumptive use
comprises of crop Coefficient and evapotranspiration. Reference crop evapotranspiration ETo can be
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calculated using Penman-Monteith method. Experimentally determined ratios of ETc/ETo, called
crop coefficients (Kc), are used to relate ETc to ETo or ETc = Kc*ETo. The values of Crop coefficient
varies by using single and dual crop coefficients approach under different methods of irrigation so
that crop water requirement will reduce to certain extent.
Objective of the present study is to work out the effect of methods of Irrigation and single
and dual crop coefficient on the crop water requirement for wheat crop under Choral Irrigation
Project. The results can be used for deciding area under the crop considering the availability of water
in the reservoir.
II. STUDY AREA
The Choral River Project situated near Mhow Tehsil of Indore under Water Resources Deptt.
of M.P. has been considered as a case study for evaluating the effect of Single and Dual Crop
coefficients in the command area of Choral Project. The. 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 “Figure 1”. 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 28.04m is constructed across the river
having gross storage of 23.92Million cubic meters (MCM) with live storage capacity of 19.23 MCM
and Dead storage capacity of 4.69MCM. The cropping pattern under the project is given in
“Table 1”.
Figure 1. Choral River Project

3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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Table 1. Details of Crop Pattern in Command Area under study
Particulars
Area in
Hectares
Particulars
Area in Hectares
Kharif Crop: Rabi Crop:
Maize 20 Wheat 2145
Jower 15 Gram 234
Ground Nut 5 Potato 585
Vegetable 7 Onion 78
Vegetable 78
III. SINGLE AND DUAL CROP COEFFICIENT APPROACHES
Crop coefficient (Kc) is defined as the ratio of crop evapotranspiration (ETc) and reference
evapotranspiration (ETo).The effect of both crop transpiration and soil evaporation are integrated into
a single crop coefficient. The Kc coefficient incorporates crop characteristics and average effects of
Evaporation from the soil. While predicting for the effects of specific wetting events on the value of
the crop coefficient (Kc), the solution consists of splitting Kc into dual crop coefficient, one for crop
transpiration, i.e., the basal crop coefficient (Kcb), and one for soil evaporation (Ke): The dual crop
coefficient (Ke and Kcb) approach is more complicated and more computationally intensive than the
single crop coefficient (Kc) approach. The procedure is conducted on a daily basis and is intended for
applications using computers. .The dual crop coefficient approach calculates the actual increase in Kc
for each day as a function of plant development and the wetness of the soil surface.
Crop coefficient obtained for four growth stages of crop growing periods. The four growth
stages of crop growing periods are as follows:
1. Initial period – planting to 10% ground cover
2. Crop development – 10% ground cover to effective cover i.e., flowering
3. Mid-season – Effective cover to start maturity
4. Late season – Start of maturity to harvest.
The values of Single crop coefficient and Basal crop coefficient for Wheat crop as detailed in FAO
56 are given in “Table 2” and “ Table 3”.
Table 2: Single Crop Coefficient
Table 3: Basal Crop Coefficient
Crop
Crop Coefficient
Kcini Kcdev Kc mid Kc end
Wheat 0.4 0.775 1.15 0.35
Crop
Basal Crop coefficient
Kcini Kcdev Kc mid Kc end
Wheat 0.32 0.35-1.0 1.0 1.0-0.30

4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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a. Effect on Kc with Irrigation Practices
There are various methods of irrigation adopted by farmer to irrigate crops. Irrigation
practices like surface, subsurface and drip irrigation are used. Crop coefficient varies due to exposed
and soil wetted fraction. Exposed fraction depends upon crop cover and crop stage. Wetted soil
fraction depends upon method of irrigation used to irrigate crops.
b. Wetted Soil fraction
Common values of fraction of soil surface (fw) wetted by irrigation or precipitation acquired
from FAO56 are given in “Table 4”
Table 4: Common values of fraction fw of soil surface wetted by irrigation
c. Exposed Soil Fraction
The value of Exposed Soil fractions covered by vegetation (fc) and (1-fc) as available in FAO
56 are given in “Table 5”.
Table 5: Common values of fractions covered by vegetation (fc) and exposed to sunlight (1-fc)
d. Soil Water Characteristics
Common values of soil water characteristics has been adopted from Table 19 of FAO56
IV. ANALYSIS AND COMPUTATION
a. Calculation of Reference Crop Evapotranspiration
The FAO Penman-Monteith method (Allen et al., 1998) is used for the computation of
Reference crop evapotranspiration (ETo) using meteorological data available in the vicinity of the
Project Area from 1996-2009.
b. Calculation of Crop Coefficient.
Crop Coefficient taken from FAO 56 are modified considering the values of minimum
Relative Humidity (RHmin) and the wind speed at 2 m height (U2) using equation recommended by
Wetting events Fw
Sprinkler irrigation 1.0
Furrow irrigation(Alternate furrow) 0.5
Drip irrigation 0.3
Crop growth stage Fc 1-fc
Initial stage
Crop development stage
Mid-season stage
Late season stage
0.0 - 0.1
0.1 - 0.8
0.8 - 1.0
0.8 - 0.2
1.0 - 0.9
0.9 - 0.2
0.2 - 0.0
0.2 - 0.8

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FAO56. The Determination of daily values for Kcb at different stages is also obtained by using the
guideline and equations recommended by FAO 56.
The values of the soil evaporation coefficient, Ke, are is also calculated by daily water
balance computation for the surface soil layer for the calculation of the cumulative evaporation or
depletion from the wet condition as per the guidelines and equations recommended by FAO 56.
The calculation of Crop Coefficient as above were made for the determination of Crop
coefficients using above mentioned procedure and using the fraction fw of soil surface wetted by
irrigation and fractions covered by vegetation (fc) and exposed to sunlight (1-fc) for Sprinkler,
Furrow and Drip Irrigation Practices. Results of single and dual crop coefficient for Sprinkler
irrigation practices are shown in “Table 6”.
Table 6. Single and Dual Crop Coefficient for various Irrigation Practices
c. Crop Water Requirement
The estimated values of ETo have been further multiplied by calculated values of crop
Coefficient Kc to get the crop evapotranspiration (ETc) for individual crops. “Crop Water
Requirements” have been worked out for the Wheat crops for the project area. Estimation of the
irrigation water requirement involves the determination of Special needs (SPL), Crop
evapotranspiration (ETc), Crop Coefficient (kc), Reference crop evapotranspiration (ETo) effective
rainfall( ER) Surface water contribution (ds) and Groundwater contribution(Gwc) to meet the crop
water requirements for optimum growth. The SPL value for individual crops has been determined
using prevailing practice in the Water Resources Department, Govt. of M.P. ER, ds and Gwc is
assumed as zero in the present study for determination of Net Irrigation requirement(NIR). Gross
Irrigation requirement is obtained by using following formula.
GIR ൌ
NIR
Ea
‫כ‬ 100
Where Ea = Project efficiency which is taken as 58% in the present study.
Results of water requirement for Wheat Crop are given in “Table 7”. Comparison of Water
Saved by the use of dual crop coefficients using different Irrigation Practices for Wheat Crop is
shown in “Table 8”.
Irrigation Method Single Crop Coefficient Dual Crop Coefficient
Kcini Kcdev Kc mid Kc end Kcini Kcdev Kc mid Kc end
Sprinkler Irrigation 0.4 0.775 1.15 0.35 1.22-0.32 0.35-1.23 1.15-1.0 0.95-0.30
Furrow irrigation 0.2 0.77 1.15 0.35 1.22-0.32 0.35-1.11 1.04-1.0 0.95-0.30
Drip irrigation 0.12 0.77 1.15 0.35 1.22-0.32 0.35-1.17 1.06-1.0 0.95-0.30

6. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308
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Table 7: Water requirement for Wheat crop
Practices
adopted for
wheat crop
Net Irrigation
requirement
(cm/ha)
Area(Ha)
Net Irrigation
requirement
(MCM)
Gross water
requirement at
canal Head
(cm/ha)
Gross water
requirement at
canal Head
(MCM)
Single
Kc
Dual
Kc
Single
Kc
Dual
Kc
Single
Kc
Dual
Kc
Single
Kc
Dual
Kc
Sprinkler
irrigation
35.72 32.38 1100 3.572 3.238
71.94 66.17 7.194 6.617
Furrow
irrigation
34.85 31.61 1000 3.485 3.161
70.43 64.85 7.043 6.485
Drip
irrigation
34.50 31.15 1000 3.45 3.115
69.84 64.05 6.984 6.405
Table 8: Water Saved by the use of dual crop coefficients using different Irrigation Practices
for Wheat Crop
V. CONCLUSION
Based on results obtained it is found that considerable amount of saving in water is possible if
water is supplied considering dual crop coefficient concept. It is further found that furrow Irrigation
consumes less water compared to sprinkler Irrigation. Further Drip Irrigation consumes minimum
water. Thus the overall efficiency of water can be increased under deficit supply of water and area
under Wheat crop can be increased by about 8 % considering Dual Crop coefficient and adopting
Drip Irrigation method, which will further increase overall yield i.e. Crop production per unit
availability of water
Practices adopted for Wheat
Crop
Gross Water requirement
(MCM)
Water
saved
(MCM)
Water saved in %
Single Kc Dual Kc
Sprinkler irrigation 7.194 6.617 0.577 8.02
Furrow irrigation 7.043 6.485 0.558 7.92
Drip irrigation 6.984 6.405 0.579 8.29

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