How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)
How to use the IRRI-TECH
code for calculating drip irrigation networks
1,2
Samir YAHIAOUI1 Lounes IDIR2
LGEE – Ecole Nationale Supérieure d’Hydraulique de Blida B.P.31 09000 Blida Algerie
Mail : 1 [email protected] ; 2 [email protected];
Presentation:
The IRRI-TECH calculation code allows us to quickly and easily determine the crop
water requirements and calculate the entire drip irrigation network with the characteristics of
the support pump that goes with it, with just a few mouse clicks.
The advantage of using this program is that you can highlight the crop water
requirements taking into account the easily usable soil reserve unlike some programs already
on the market. Add to this the fact that we can have them separately and use them for the
design of any type of network outside the drip network.
It should also be noted that it can work even using sewage.
Data to be entered for programming the calculation code:
The user of the IRRI-TECH calculation program must enter some initial data to estimate
the evaporation (ETP), and then from there, depending on soil data and the type of crops,
estimate the crop water requirements.
After estimating these requirements, the user still needs to enter information about the
plot or the area where the network will be planned, and the choice of variants which he has
chosen, i.e. the hydraulic characteristics of the network.
Once all the information is entered, the program will automatically highlight the
dimensions of the various network compartments and the support pump (which is essential if
the pressure at the worst point doesn’t reach at least 1 bar).
The functioning of the calculation program is shown as follows:
1. Requirements:
 Rainfall: the series to be entered is a series of monthly rainfall.
 Temperature: introduce average temperatures.
 The wind: the wind is in m/s
 Insolation : in percentage for each month
1.1 The evaporation calculation :
It is calculated according to the model of BLANY and CRIDEL which is
interpreted by the following formula:
ETP=(8,13+0,46t)*I
 Rooting depth: according to the vegetative stage of the crop in m.
 The hcc, hpf values: in percentage.
 Y : variable value, i.e. (1/3),(2/3) ,(1/2)
Once your data is entered, simply click on the [calculate] button at the bottom of the
panel, or the [delete] button if you want to add new data.
How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)
Fig .01. The evaporation calculation
1.2. Calculation of the easily usable reserve (RFU):
It is determined according to the following model:
RFU= ((Hcc-Hpf)/100)*Y*Z




Z: depends on the vegetative of the crop for each month.
Hcc: moisture at field capacity.
Hpf: soil moisture at wilting point.
Y : Coefficient depending on irrigated soil and crop.
Once your data is entered, simply click on the [calculate] button at the bottom of
the panel, or the [delete] button in case of problems or new data.
Fig.02.Calculation of the easily usable reserve.
1.3. Calculation of crop water requirements:
To assess these requirements, the water balance is calculated as follows:
B = ETR-(Peff+RFU).
ETR = ETP*Kc.
 Kc: crop coefficient which depends on the vegetative stage of the crop.
 Peff: the effective rainfall is calculated as follows: Peff=P*Kc.
How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)
Once your data is entered, simply click on the [calculate] button at the bottom of the
panel, or the [delete] button if you want to add new data.
Fig.03. Calculation of crop water requirements.
2. Doses, frequencies and durations of irrigation
 For the calculation formulae, we use:
 Clean dose = ((Hcc-Hpf)/100)*Y*Z*(P/100).
 Raw dose = (Clean dose/ (Eeff*Cu)).
 Irrigation frequency = (clean dose/bjl)
 Irrigation time = ((Db*Ea*Er)/ (Gpar arbre*dripper flow).
With:
 CS: Crop soil cover.
 Eeff : irrigation efficiency, depends on soil texture.
 Cu: uniformity coefficient.
 G per tree : Number of distribution points per tree;
 Ea : Distance between two neighboring points of the same tree ;
 Moistened strip : width of the moistened strip ;
 Er: tree row spacing= irrigation line spacing.
Once your data is entered, simply click on the [calculate] button at the bottom of the
panel, or the [delete] button if you want to add new data
How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)
Fig.04.Calculation of irrigation doses
2. Sizing of drip irrigation network:
1. Irrigation lines and header lines :
To size a drip irrigation network, several parameters come into play:
 Length and width of the plot: in m.
 Length of the irrigation line and header line: in m.
Once your data is entered, simply click on the [calculate] button at the bottom of the
panel, or the [delete] button if you want to add new data.


Number of irrigation lines = (width of the plot /Er)
Number of trees = (length of the irrigation line/ trees spacing)* number of irrigation
lines
 Number of drippers in an irrigation line = number of trees in a row* number of
drippers for each tree.
 Flow of the irrigation line: expressed in (l/h), it’s the flow accumulation for all
trees in the same row.
The irrigation line flow = number of drippers in an irrigation line* flow of a
dripper.
 Flow of the header line: expressed in (l/h), the sum of flows of each line.
Flow of the header line= flow of a line *number of lines
Fig.05. Calculation for irrigation line and header line.
3. Calculation of diameters:
How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)

Diameter of the irrigation line : calculated from the following model:
Ør(cal)=  P.d.c (r)  2,75 


1,75
 0,478  Q(r) L(r) 
-
1
4,75
By standardizing the diameter depending on the marketed diameters
The head loss is calculated from the following formula
1.75
0,478
4.75
Pdc=
. D .Q .L
2,75

Diameter of the header line : estimated according to the following model:
Øpr (cal) =  P.d.c (pr)  2,75 


1,75
 0,478  Q(pr) L(pr) 
-
1
4,75
The diameter is standardized from the marketed diameters, then the head loss is calculated
according to the following formula
0,478 4.75 1.75
Pdc=
.
.
.L
2,75 D Q
Fig.06. Calculation of diameters
4. Main pipeline and pump:
4.1. Main pipeline: the parameters of the main pipeline are determined after the calculation
of all the parameters of irrigation lines and header lines. The flow, diameter and head loss are
the essential elements for sizing the pipeline.


Length : expressed in (m) , it is a value that must be introduced
Flow rate: the flow rate of the main pipeline is estimated by adding all the flow
rates of header lines.
Diameter: it is calculated as the diameters of lines and header lines by the
formula:


Ør(cal)=  P.d.c (r)  2,75 


1,75
 0,478  Q(r) L(r) 
-
1
4,75
The head loss is calculated according to the following model
How to use the IRRI-TECH calculation code……………………..Prepared by Mr. YAHIAOUI. S and Mr. IDDIR.
L (LGEE-ENSH)
Pdc=
4.2. Pump:
1.75
0,478
4.75
. D .Q .L
2,75
 HG: static head, an input value, expressed in (m).
 Flow rate : expressed in (h/l)
 Hmt : the total dynamic head (m)
Fig .07. Calculation of the main pipeline and the pump characteristics
All these steps resulted in a comprehensive program that calculates whether the
requirements with all their parameters or the sizing of the drip irrigation network.
The following figure shows the comprehensive program:
Fig.08. The IRRI-TEC calculation code.