Technical points to know before making drip irrigation design

Hello everyone,
After my first post on basics of drip irrigation design, Now I am going further to technical aspects of drip irrigation design and another method to draw a drip irrigation design for a field.
Before deicide a particular drip irrigation design for any field one have to take several points in to consideration. This points are,

• Head (mtr)
• Discharge (Q) of the water (m3/hr.)
• Irrigation Rate (mm/hr.)
• Irrigation Time for one shift (hr.)
• Water requirement in Field/ No. of Shifts a day
• Area Flow (m3/hr.)
• Irrigation time for one shift
• No. of shifts a day

Note: I’ve explained the meaning of all the above aspects in detail in my previous thread.

Now I am proceeding to the further details,

1.Total Head (mtr):

Head contains various aspects like, suction of the pump, delivery and availability of water etc.

So first you have to calculate the head for operating your drip irrigation system. You can calculate it by the following method,

Total Head = Head of System + Depth of water level (mtr) + Distance of water source from the field

Where, System Head = Suction + Lift + Head of Pipes (main & sub main) + Head of Lateral

2. Discharge Q (m3/hr):

It is the water available from the main water source. We can calculate it by the following formula,

Discharge (Q) =     Motor HP X 75 X Pump Efficiency (%)

                            --------------------------------------------

                      TOTAL HEAD (mtr)

Where,

• Pump efficiency (%) = 50 to 60 (if using electric motor)
• Pump efficiency (%) = 60 to 65 (if using submersible pump)

“Please note that the discharge we can get from the formula above is approximate. The actual flow may vary according to water availability in the particular season.”

3. Irrigation Rate (mm/hr):

Irrigation rate is the amount of water supplied to one hector of land in a single watering period.

Irrigation rate can be drawn from the following formula,

Irrigation Rate =             Dripper discharge (LPH)

                              -------------------------------------------------------

                                Lateral Spacing (mtr) X Emitter Spacing (mtr)

4. Water Requirement of field:
For running perfect and effortless irrigation system we must have to know the actual water requirement of our field and the water available to our water source. If one get more water then the water required in the field than you have to divert water according to the exact need of your field and wise a versa.
For this we have to divide our field in to the shifts. So all the area of the field can irrigate with the proper amount of water. We can decide the field shift with the following formula,

Water Requirement =        Irrigation Rate  X 10 X Area (ha)
(No. Of shifts)                     ---------------------------------------------
                                                   Discharge (m3/hr)

Note: If you get the figure like 1.2 then the no. of shift will be 2. Always move to the next figure from the first figure.

The above method for calculating shift may be vary according to the type of field. It is possible that you have to put more shifts in a uneven land or typical elevated field.
To calculate the water requirement of the particular Shift, one can get if from the formula below,

Shift Flow (m3/hr) = Area (ha) X 10 X Irrigation Rate

Note: Always set the total flow of shifts irrigated at the same time, lesser than the available flow at the water source.

5. Irrigation Time for one Shift:
  After all the above calculation we have to still count a major part of the design and that is,how much to irrigate a shift ? It is depend upon the water requirement of the crop you have grown and the area of the shift.
You can get the peak period water requirement of mostly grown crops in India from the following chart,

Sr. No.	Name of the Crop	Water Requirement(mm/day)
1	Mango	2.30
2	Sapota	2.30
3	Coconut	2.5
4	Sweet Orange	3
5	Acid Lime (Lemon)	3
6	Citrus	2.91
7	Aonla	1.85
8	Guava	3.5
9	Papaya	6
10	Cashewnut	3
11	Grapes	5.5
12	Pomegranate	4.9
13	Custard Apple	3
14	Banana	6.5
15	Ber	3.3
16	Vegetables	6.5
17	Medicinal & Aromatic Plants	7
18	Patchouli	4
19	Mulberry	5
20	Sugarcane	7
21	Castor	6
22	Cotton	6
23	Groundnut	6
24	Pulses	5
25	Tobacco	6
26	Potato	5
27	Strawberry	7.6
28	Onion	7.6

You can find out the irrigation time from one shift by the following formula,


Irrigation Time =    Evaporation Equivalent of the Crop
                         ------------------------------------------------
                                         Irrigation Rate

For Example:
If we have Evaporation Equivalent of 6.0 mm /day and Irrigation rate of 3.57 mm/hr, then

Irrigation Time =  6 / 3.57  = 1.68 hrs.

“But how can you find out how much time is equal to 1.68 hour ? “

Note that the Value we get from irrigation time is always in fraction of 100. So we have to convert it in to the hour format. For this you have to do the following,
1.68 = 1 + 68 * 60/100
       = 1 + 4080 / 100
       = 1 + 40.8
       = 1 hour 40 minutes

6. Total No. of Shifts a day:
After getting all the necessary information on designing a drip irrigation system. Still we have a question that if we have limited power source and we have large field that how can we irrigate a field at the same time?
Well for this we have to count the total number of shifts per day to irrigate the particular part of the field. You can simply find out numbers of shift according to power availability in your region by following,

No. of shifts per day =     Time available for Irrigation
                                ------------------------------------------
                                    Irrigation time of one shift

Some more necessary information
Well that’s all about the drip irrigation design aspects but some more information you have to needed is,
How much plants are there in the field?
No. of plants in the field =
(Total area * 10,000) / lateral spacing  *  Emitter Spacing

Conversations
LPS= (m³/hr. X 1000) / 3600
LPM = (m³/hr. X 1000) / 60
M³/hr. = (LPM X 60) / 1000

How many laterals are going to be used in the field?
Lateral Length = Area (sq. mtr) / Row spacing

Distance Measures:

1 m	=	3.28 feet
1 hector	=	2.47 Acre or 10000 Sq. mtr.
1 m³	=	1000 ltr

These are the basic things to decide and draw a suitable drip irrigation design for your field. You can use some of the Software like Auto cad for this.

All the above calculations are bit hectic, So I've prepared an excel sheet for easy calculations.

You can download it from HERE (Irrigation Data Calculator).

Lets see it in details as under,

Irrigation data calculator looks like below,

 You can get almost all the necessary data with this calculator sheet. for this you have to enter some details like,

• Area of the plot/ field (in hector)
• Lateral spacing / Spacing between two rows of crop (in meter)
• Spacing between two emitters / drippers (in meter)
• Emitter discharge (LPH)
• Motor/Engine HP
• Water source depth (in meter)

This will give all the data like available flow, total number of plants in the field, required flow by the crop in the field, number of shifts to irrigate the field, irrigation rate etc.

You have to select your crop in the crop cell to get peak water requirement and operation hours per shift like below,

Other parts like Water carrying capacity of PVC, Hydraulic Calculation are explained in the posts below,

1. Basic aspects of drip irrigation system design
2. Drip Irrigation Component Installation
3. Head loss & Velocity in irrigation pipes
4. Video Tutorial on drip irrigation systems design
5. Water carrying capacity of irrigation pipes

Or scan a QR code here,

I am a professional trainer on MIS system design, for training cost & other details please contact me on the mail address below,

- Hardip Gajjar
  (hrdpgajjar@hotmail.com)

Drip Irrigation Design basics

Hi everyone,
As we know Drip irrigation is the only best available option for the farmers to save water and get higher production. Here i am trying to explain how to select the proper drip irrigation system for the field.
There are few steps in the selection of the proper drip irrigation design and material for your field, which are,
1. Survey of the field
2. Emitter/ dripper selection
3. Input- Output matching
4. Lateral Selection
5. Sub main line selection
6. Main line selection
7. Filter selection
8. Pump selection / check

Now i am going to explain the aspects above.
1. Field Survey:
In this step, one has to measure the whole field, either manually or with the help of GPS or any other method. After measuring draw a rough diagram or map of the field on a blank paper with all the measurements. Also don't forget to mention the "North" Direction. (You can find it simply by, facing towards the sun at this time your left hand side is NORTH).
After completing the diagram fill out the following details, as we are going to need it in the next steps, viz,
For Online drip

• Crop:
• No. of Emitters per plant:
• Discharge of each emitter:

For Inline drip

• Crop
• Lateral Spacing (mtr)
• Emitter Spacing (mtr)
• Discharge of each emitter

2. Emitter/ Dripper Selection
It is different from country to country, for INDIA inline drippers are used for close spacing crops like Cotton, Castor, Potato, Vegetables etc. and online drippers are used widely for Plantation, horticultural crops like, Mango, Sapota, and Custard Apple etc.
3. Input- Output matching
This is the main part of any drip irrigation system design here one can need to calculate some data.
No. of sections / Valves = Input (Total water requirement of the field)
                                    ---------------------------------------------------
                                       Output (water available at the pump set)
For ONLINE drippers,
INPUT = No. of Plants X No. of Emitters per plant X Discharge of each emitter in LPH
For Inline drippers,
INPUT (LPH) = No. of emitters X Discharge of each emitter (LPH)
Where,
Lateral length (mtr) =  Area (Square meter)
                             ----------------------------------
                                  Row Spacing (mtr)

No. of emitters =  Lateral length
                       ----------------------------
                           Emitter spacing

Now with all this data you can find out how many sections you will need in your field to irrigate the whole field with the drip irrigation system.
4. Lateral selection
5. Sub main line selection
6. Main line selection
all above aspects are depend on the water flow available for your system, for sub main and main lines the selection of pipes will depend on the flow listed below,
Water holding capacity of PVC pipe:

• 63 mm (2") - 0 to 18 m3/hr.
• 75 mm (2.5") - 0 to 25 m3/hr.
• 90 mm (3") - 0 to 32 m3/hr.
• 110 mm (4") - 0 to 40 m3/hr.

Note: Above details are approximate figures.

7. Filter Selection

In this section one should have to select the appropriate filter for the drip irrigation system. Selection of filter is depending on the water source. One can select the filter with the help of the following,

Open Well - Sand filter with backup, Screen filter/ Disc filter

Open Tank - Sand filter with backup, Screen filter/ Disc filter

Stream - Sand filter with backup, Screen filter/ Disc filter

Bore well with silt - Screen / Disc filter

Bore well with river sand - Hydro cyclone filter with Back up Mesh/ Screen filter

8. Pump selection / Check
You have to check the total head and discharge of the pump set.
For well-designed drip irrigation system the discharge of the pump set should be equal to the discharge of the each section in the field.
Total Head (mtr) = Suction
Elevation
System operating pressure
Friction Loss in Head unit / filter
Friction loss in main line
Friction loss in sub main line
Friction loss in lateral line
Friction loss in Fittings
Others
Where,
System Operating Pressure = Minimum pressure required at emitting point of the emitter.
Selection of pump:
Pump Horse Power (H.P.) =      Q X H X 100
                                         ----------------------
                                              75 X n (%)
Where,
Q = Maximum Sectional Discharge (lps)
H = Total Dynamic Head (mtr)
n = Efficiency of the pump
Efficiency of the pump:
For Mono-block pump set 65 to 70 %
For Coupled pump set 60 to 65 %
For Submersible pump set 50 to 55%
This is the most common aspects to choose a proper drip irrigation system in the field, i hope you all find useful information from this article.

You can find more information in details in the topics below,

1. Technical aspects of drip irrigation
2. Drip Irrigation component Installations
3. Head Loss & Velocity in irrigation pipes
4. Video tutorial on drip irrigation design
5. Water carrying capacity of irrigation pipes

or scan a QR code here,

I am a professional trainer in MIS system designs, for cost and other details please mail me on the below address,

Cheers!

Hardip Gajjar
(hrdpgajjar@hotmail.com)