IRRIGATION PROBLEMS IN DEVELOPING COUNTRIES Optimization Of Drip And Sprinkler... · 4.1.4 EPANET Design On Dripline ... presented is a thesis for Master Degree in “Irrigation Problems

ISTITUTO AGRONOMICO

PER L 'OLTREMARE

UNIVERSITÀ DEGLI STUDI DI FIRENZE

FIRST LEVEL MASTER DEGREE IN

IRRIGATION PROBLEMS IN DEVELOPING COUNTRIES

Design Optimization Of Dr ip And Spr inkler System Using VEPROLGS And EPANET Softwares

Supervisor I Dr . Ivan Solinas Student Name Inocêncio Oliveira Mulaveia Supervisor I I Dr . Graziano Ghinassi

A.A. 2012/2013

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DEDICATION

To My Parents, My Brothers And My Girlfriend For Supporting Me

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ACKNOWLEDGEMENT

I Want To Express My Gratitude To The Staff of Institute Agronomico Per

Lol’ tramare (IAO), Who Made Possible The Master Especially To:

The General Director Of Istituto Agronomico Per Lol’ tramare (IAO), Dr.

Giovanni Totino

Technical and Scientific Tutor, Dra. Elisa Masi

Ex-Master Tutor, Dr. Paolo Enrico Sertoli

Administrative And Logistic Coordinator, Dr. Andrea Merlin

For The Reception, Welcoming And Patience Always Showed

The Master Coordinator at University Deli Study Di Firenze Drab Elena Brescia

The Master Coordinator at Institute Agronomic Per Lol’ tramare Dr. Tiberio

Chiari

For Orientation And Support Throughout The Master

To My Supervisors Dr. Ivan Solinas And Dr. Graziano Ghinassi

For Technical And Scientific Monitoring Support Given During The Thesis

Elaboration

And Finally To Universita Degli Studi Di Firenze

For Allowing Me, To Make Part Of Unique Academic Family

My Academics Salutes

Warm Thanks

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TABLE OF CONTENTS

1. Introduction...………………………………………………………………1

2. State Of Art.………………………………………………………………..2

2.1 Drip Irrigation……….……………………………………………………2

2.2 Sprinkler Irrigation……………………………………………………….5

3. Study Area And Methodology……………………………………………..6

3.1 Presentation Of The StudyArea…………………………………….…….6

3.1.1 Geographic Location…………………………………………….....…..6

3.1.2 Physical-Geographic Aspects……………………………...…….….….7

3.1.2.1 Geology and Geomorphology…………………………………….…..7

3.1.2.2 Soils………………………………………………………….………..8

3.1.3 Climate characteristics……………………………………….….….…..9

3.1.3.1 Temperature………………………………………………………….10

3.1.3.2 Precipitation Characteristics………………………………………....11

3.1.4 Agriculture………………………………………………….………….13

3.1.5 Infrastructure Regulating Floods…………………………..…………..13

3.2 Methodology…………………………………………………..…..……..13

3.2.1 Data Collection……………………………………………..…………..13

3.2.2 Choice Of Plot……………………………………………..…………..16

4. Results And Discussion………………………………………...………….16

4.1 Results and Discussion for Drip Irrigation…………………...………....16

4.1.2 Crop Water Requirement………………….……………………...…….16

4.1.2.1 Results………………………………………………………………...16

4.1.2.2 Discussion………………………………………….…………………16

4.1.3 Dripline Design....………………………………………..………...…..17

4.1.3.1 Results……………………………………………….………………..17

4.1.3.2 Discussion…………………………………………….……………….18

4.1.4 EPANET Design On Dripline………………………….……………….19

4.1.4.1 Results…………………………………………………..…………….19

4.1.4.2 Discussion……………………………………………………………..21

4.2 Results And Discussion on Sprinkler System….…………………….…..22

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4.2.1 Crop Water Requirement……………………………………...……….22

4.2.1.1 Results………………………………………….……………………..22

4.2.1.2 Discussion………………………………………...…………………..22

4.2.2 EPANET Design On Sprinkler…………………….…………...………22

4.2.2.1 Results…………………………………………….…………………..23

4.2.2.2 Discussion………………………………………….…………………24

5. Conclusion……………………………………………….….……….…….27

References……………………………………………...…….…..…….….…28

Appendix……………………………………………...……….………….….30

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ABSTRACT

Agriculture in Mozambique essentially is constituted by the family sector that

practice subsistence farming, which depends mainly on rainfall and so far the

results achieved have proved to be not satisfactory at all due to many factors.

However in recent years, the country had a significant improvement of

production, and this improvement has been attributed mainly to the expansion

of cultivated areas. However this improvement must be followed by an

investment of new irrigation techniques, which will allow to make a change

from subsistence agriculture (where the most producers use surface irrigation)

to commercial agriculture (with sprinkler and drip irrigation) turned to profit,

that has the major urban centers and agro-processing industry as market.

Therefore the study proposes to perform a design regarding to the sprinkler and

drip irrigation performance, providing therefore a broad vision to the producers

on the management and factors to take into consideration in choosing of these

of irrigation methods.

Then using tools like GOOGLE EARTH, to locate the area of study,

determining the latitude and longitude, the elevation of the field, CLIMWAT

2.0, to generate data through Meteorological Station that comes close of the

study area, Harmonized World Soil Database (HWSD) and SPAW Hydrology

to determine Soil Water Characteristics in the field, and Crop Water

Requirement for determination of Water Requirement Of Crop, it was possible

to design a drip irrigation system using VEPROLGS to modeling water

distribution along the drip lines and Plot and EPANET for dimensioning the

system, from the water intake to the plot head and Sprinkler irrigation system

using EPANET for dimensioning the system, from the water intake to the plot,

namely main pipes, secondary, laterals until the sprinklers.

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ABBREVIATIONS

TIA - Trabalho de Inquérito Agrícola

SADC - Southern African Developing Community

FAO - Food And Agriculture Program For United Nations

HWSD - Harmonized Water Soil Database

SPAW HIDROLOGY - Soil Plant Atmosphere Water Pond&Higrology

CHO - Control Head Orifice

H - Head

Q - Flow Rate

MW - Mega Watts

O C - Celsius Degrees

o - degrees

m.w.c - meter water column

m - meter

mm - millimetres

hr - hours

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1. Introduction

Agriculture in Mozambique essentially is constituted by the family sector that

practice subsistence farming, which depends mainly on rainfall. To give an

idea of the importance of this sector for the country, data from surveys

conducted by TIA (2000), indicate that in rural areas, family farming consists

mainly small farms (those who cultivate less than 5 ha) and this sector accounts

for about 99% of agricultural production (3.090.197 family units) and occupies

over 95% of the cultivated area of the country.

According to Bart van den Boom (2011), despite the importance of this sector

it faces various problems, and the main is low productivity with decreasing

trend due to factors such as the uneven distribution of rainfall, low use of

technologies improved, poor state of road infrastructure, especially the weak

link between the south and north of the country, and relatively few investments

made in agriculture.

To the factors above it is associated, the weak agricultural extension services

due to lack of technicians with a proper formation that can guarantee

acceptable levels of adoption in agricultural programs ongoing in the country.

In recent years, the country had a significant improvement of production, and

this improvement has been attributed mainly to the expansion of cultivated

areas. However this increase in agricultural production as a reflex of a more

openness areas of cultivation must be followed by an investment of more and

more agricultural inputs, infrastructure and new irrigation techniques, which

will allow to make a change from subsistence agriculture (where the most

producers use surface irrigation) to commercial agriculture (with sprinkler and

drip irrigation) turned to profit, that has the major urban centers and agro-

processing industry as market. Hence the need to perform a study regarding to

the sprinkler and drip irrigation performance, providing therefore a broad

vision to the producers on the management and factors to take into

consideration in choosing of these of irrigation methods. The study here

presented is a thesis for Master Degree in “ Irrigation Problems in Developing

Countries” and it consists in 5 Chapters:


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2. State Of The Art

Irrigated agriculture in most parts of Sub-Saharan Africa has not been

encouraging even with the threat of severe adverse effects of global food and

financial crises and a scourge of the consequences of climate change (Saa

Dittoh et al, 2010), and in the specific case of Mozambique due to its

geographical location, the country is systematically affected by natural

disasters (especially drought, floods and cyclones), and is therefore important

to invest in technologies that target the use of water for irrigation, as part of an

overall strategy of developing the agricultural sector, and Some of the

technologies in which it could invest are drip and sprinkler irrigation.

2.1 Drip Irrigation

Drip irrigation sometimes called trickle irrigation and involves dripping water

onto the soil at very low rates over a long period of time, usually lasting several

hours. The water flows under low pressure through system of small diameter

plastic pipes fitted with outlets called emitters or drippers laid along each row

of plants allowing water to be applied close to plants so that only part of the

soil in which the roots grow is wetted. With drip irrigation water, applications

are more frequent (usually every 1-3 days) than with other methods and this

provides a very favorable high moisture level in the soil in which plants can

flourish, reducing water loss by up to 60 percent.

A drip system presents basic components in which it described just after:

Valve, turns on or off the water flow through a pipe;

Backflow preventer, is a device that prevents dirt from being sucked back into

irrigation water;

Pressure regulator, reduces the water pressure and keeps it at a constant level;

Filter, cleans the water. drip emitters have very small openings that are easily

Clogged;


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Emitters, controls how fast the water drips out onto the soil. most emitters are

small plastic devices that either screw or snap onto a drip tube.

Drip irrigation is compatible with vegetable crops that are grown as annuals, in

rows, and which do not require flooding.

It has long been proven as beneficial and economical on fruit, nut and

vegetable crops throughout the world, but recently growers of field crops such

as alfalfa, corn, cotton, onions, potatoes and processing tomatoes are realizing

the benefits as well in other words it is justified for crops of high market value.

Designing drip systems for operation on hilly ground can be challenging and

the options for attaining good uniformity are highly dependent on the terrain.

Fortunately there are components available that can be used to improve

uniformity, therefore it is adaptable to any farmable slope.

Drip irrigation is suitable for most soils even thus it necessary to considerer

some measures by management of the system in each soil type. It can

determine the soil wetting patterns influencing the depth of the drip tape and

the distance between emitters. The duration and frequency of irrigation are also

determined by the soil type. Over-watering can move nutrients or fertilizer (if

applied) away from the root zone. On sandy soils, water goes primarily

downward rather than horizontally so emitters should be at relatively close

spacing. Spacing between emitters can be greater in heavier soils where there is

considerable movement laterally.

In sandy soils, irrigate more frequently, but run the water for a lesser amount of

time. In heavier soils, irrigate less often, but run the water for a longer duration.

In both cases, this should lessen the chance of leaching nutrients or fertilizers

away from the root zone.

According to C. Wilson and M.Bauer (April 2013), the advantages and

disadvantages of drip irrigation are:


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Advantages

It can delivers water slowly immediately above, on or below the surface of the

soil. This minimizes water loss due to runoff, wind and evaporation. Drip

irrigation can be operated during the windy periods.

The mold spots on house siding and the staining and deterioration of wood

privacy fences experienced with overspray from sprinkler irrigation is

eliminated with the use of drip; because water doesn’ t leave the landscape with

drip irrigation, pavement deterioration associated with sprinkler irrigation

runoff is eliminated.

Properties with old, galvanized steel water service lines where corrosion has

resulted in a narrowed diameter may benefit from a retrofit to drip irrigation;

the low volume requirements of drip irrigation are a good match with restricted

supply lines.

Drip systems can be managed with an AC or battery powered controller;

automated landscape irrigation is an advantage to many people with busy

lifestyles.

Adaptable and changeable over time, drip systems can be easily expanded to

irrigate additional plants if water is available. Emitters can be simply

exchanged or removed and emitter lines eliminated or repositioned; when

plants are removed or die, drip lines should be plugged.

Disadvantages

If emitters are poorly placed, too far apart or too few in number, root

development may be restricted by the limited soil area wetted.

Water seeping at ground level is hard to see and makes it difficult to know if

the system is working properly; an indicator device that raises and lowers a flag

to show when water is flowing is available to overcome this issue.


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Regular maintenance inspections are needed to maintain system effectiveness.

Clogs are much less likely with filtered water and proper pressure regulation

used in combination with self-cleaning emitters.

Drip tubing can be a trip hazard especially for dogs and children but is less

problematic if covered with mulch and fastened with wire anchor pins every 2

to 3 feet; drip lines can also be easily cut while undertaking other landscape

maintenance activities.

2.2 Sprinkler Irrigation

Sprinkler Irrigation is a method in which water is sprayed into the air and

allowed to fall on the ground surface somewhat resembling rainfall. Water is

distributed through a system of pipes usually by pumping. The spray is

developed by the flow of water under pressure through small orifices or

nozzles and it is then sprayed into the air and irrigated entire soil surface

through spray heads so that it breaks up into small water drops which fall to the

ground.

The Basic components of the sprinkler irrigation system are:

Pumping Unit, is required to carry water from the source through the main line

and laterals up to the sprinkler or nozzle from where it is sprayed and applied

to the crops.

Main Lines, carries water from the pumping unit to the various parts of the

field. Main line may be permanent or portable.

Permanent Main Line, is advantageous where field boundaries are fixed and

crops require full season irrigation. Portable main lines are more economical

when a sprinkler system is used for different fields or let out on hire to other

farmers.

It is often buried so that they do not come in way of other agricultural

operations.

Lateral Lines, carry water from the main line to sprinklers or nozzles. Lateral

pipes are normally available in 5 m, 6 m, and 12 m lengths.


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Each length has quick couplings. All couplings are provided rubber gaskets in

female portion, which tightens the coupling and makes it, leak proof.

Nozzle/Sprinkler Head, are the most important component of the sprinkler

system. Their operating characteristics under optimum water pressure and

climatic conditions, mainly wind velocity, will determine their suitability and

the efficiency of the system. Most agricultural sprinklers are the slow rotation

type.

Riser, the riser pipe connects the rotating sprinkler head to the lateral. Usually

the pipe diameter varies from 12 mm to 75 mm with standard pipe threads;

Almost all crops are suitable for sprinkler irrigation, but it is needed to take

into account that it can foster the development of foliar diseases and therefore

is necessary to take some measures to manage the crop when face this type of

constraint.

Sprinkler irrigation is adaptable to different terrain conditions with slope. The

lateral pipes that provide water to the field should always be placed out along

the ground contour lines whenever possible in order to minimize pressure

changes at the nozzles and ensuring uniform irrigation.

3. Study Area and Methodology

3.1 Presentation Of The Study Area

3.1.1 Geographic Location

The Hydrographic Basin of Umbelúzi is International, born in Swaziland and

has major effluents, the rivers Black M'buluzi and White M'buluzi, enters in

Mozambique from a point close to Goba border and is shared by three

countries, namely Swaziland, Mozambique and a small portion by South Africa

(figure 1).

It covers an area of 5600 km2. Of this portion Mozambique occupies about

40% and it is located downstream.


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In Mozambican part of the Basin Umbelúzi River is an area located entirely in

Maputo Province, in the southern part of Mozambique. The major effluents in

Mozambican territory are: the Calichane and Movene River.

Its boundaries are the Incomati Basin in North and Maputo River North in

South, east border the Tembe River. The boundary to the west is the Maputo

Basin.

Figure 1: Geographic Location of Study Area

3.1.2 Physical-Geographic Aspects

3.1.2.1 Geology and Geomorphology

The geology and geomorphology are some factors that influence the dynamics

of runoff depending on the rock type of the area and the slope of the relief.

According to Muiambo (1996), the Umbelúzi Basin geological formations are

distributed in bands with north-south orientation. From the mouth of the river

to the source are distinguished: alluvium, sandstone, basalt, rhyolites, basalts

again, limestones, shale’s, granites and basic rocks.

As for geomorphology in general the Mozambican part of the basin does not

have a remarkable relief, the higher altitudes do not exceed 638 m and are

located in the border area with Swaziland and minimum altitudes range from 1

to 319 m located in the South and Northeast of Basin (figure 2).


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Figure 2: Spatial Variation of Relief

This characteristic of Umbelúzi relief makes it vulnerable to seawater intrusion,

flooding, since a wide area is below the average of the sea level.

3.1.2.2 Soils

The soils study is important because it support human activities as well as

plants, and it is influential factor in the floods in Mozambique (NAPA, 2007).

The predominant soils in the Mozambique portion of Basin derive from

sediments of Karroo, Tertiary and Quaternary. As to texture in east region,

Sandy textured soils predominate in the central region crossed by a belt of

clayey soils, which are predominant at upstream of the basin (figure 3).

Figure 3: Soil Texture


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These soil characteristics make the western down Umbelúzi, and the entire area

that covers the South Africa and Swazi territory be little permeable, with a

retention capacity of water ranging from very poor to poor.

In contrast the central area and coastline down Umbelúzi in Mozambican

territory, the retention capacity of water ranges from average of good to very

good (figure 4).

Figure 4: Capacity of the Soil Water Retention

Therefore the soils of the area down Umbelúzi, offer necessary and sufficient

conditions for agriculture practice.

3.1.3 Climate characteristics

In studies of hydrological character, climatic characterization is essential,

therefore temperature, precipitation, evapotranspiration are some of the most

important elements for studies of this kind. Have been chosen, because they are

preponderant in the climatic analysis conditions, with strong influence on the

flooding analysis process.


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3.1.3.1 Temperature

It is a phenomenon closely related to altitude. Are registered annual averages

around 18 º C to 21 º C in the area Swazi, and between 21 º C to 24 º C in

Mozambique territory (figure 5).

Figure 5: Spatial Distribution of Temperature in Annual Average

The maximum and minimum temperatures monthly average recorded on the

hot (December and January) and cold (June and July) months of the year,

respectively ranging between 9 º C and 32.5 º C (figure 6).

Figure 6: Monthly Average temperature in ° C; Source: Climwat 2.0


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3.1.3.2 Precipitation Characteristics

At Umbelúzi Basin floods are caused essentially by temporal and spatial

distribution of rainfall, concentrated in a single period, and with greater

intensity (figure 8). The distribution of these monthly rainfalls is

characterized by the fact that practically all the rain concentrate during the

summer months (October-April). During the months of May-September is

generally recorded poor rainfall (figure 7).

Figure 7: Average Monthly Precipitation in (mm); Source: Climwat 2.0

In general rainfall is distributed irregularly throughout the year, with 85% of

precipitation occurring between the months of October and April being weak in

the remaining periods (figure 7). In the country the area that receives high

annual rainfall rate is the coastal strip, with values ranging between 900-1364

mm per year (figure 8).

Figure 8: Spatial Distribution of Average Annual Precipitation


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The potential evapotranspiration is a factor of great importance in the

hydrological cycle, so is need to get precise information of their value for

planning water resources in region. Its importance is clear due to the role it

plays in the process of water underground storing.

An example: checks in hot weather and dry when evaporation has a maximum

higher than precipitation, causes the minimum flows in the river.

The ETo recorded throughout the year shows that are verified high rates of Eto

during the months of October to April and low rates in months of May to

September (figure 9).

Figure 9: Average Monthly ETo in (mm/day); Source: Climwat 2.0

The annual potential evapotranspiration average, ranges from 169-1500 mm.

Figure 10: Spatial Distribution of Evapotranspiration Annual Average


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The lower evapotranspiration is verified in South Africa and Swazi territory,

with annual averages ranging from 169 to 350 mm and the highest (1500 mm)

in Mozambique coastal strip (figure 10).

Setting out relationship between precipitation and potential evapotranspiration

in space and within the basin scale, may be noted that the basin has high

potential evapotranspiration and low rainfall, consequently large water deficit.

Theoretically, the use of a cover in large areas would be an effective process of

soil moisture conservation, thereby reducing the penetration of solar radiation

on the ground.

3.1.4 Agriculture

Along the basin is practiced rain fed agriculture in the open prairie, and grazing

in the savanna.

3.1.5 Infrastructure Regulating Floods

The main hydraulic infrastructures are Mnjoli Dam built on the Black M'buluzi

in Swaziland and the Pequenos Libombos Dam built in Mozambique territory.

The Pequenos Libombos Dam was constructed with the following objectives:

Water supply to Maputo City (Mozambique Capital) through an annual

throughput of 76.5* 106 m3 in event more predictably, and 104*106 m3 in

extreme hypothesis, for the irrigation of 13.000 ha, floods deadness and

production of electricity with a maximum power of 1.7 MW (SADC, 2008).

3.2 Methodology

3.2.1 Data Collection

To carry out this study it was necessary to make a data collection, and were

generated software that are described below:


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GOOGLE EARTH, this software was used essentially to locate the area of

study (determining the latitude and longitude, the elevation of the field and the

distances involved).

Then made up using the software CLIMWAT 2.0, to generate climate data

through Meteorological Station that comes closest, specifically the Umbeluzi

Weather Station, located at a distance of approximately 13 km of the study

area.

For the collection of data regarding the soil of the field were used software

such as Harmonized World Soil Database (HWSD) and SPAW Hydrology to

determine Soil Water Characteristics in the field.

For the determination of water requirement in Maize Crop, it was used

CROPWAT 8.0 Software, soil data generated by Harmonized World Soil

Database (HWSD) software and Soil Water Characteristics (SPAW

HIDROLOGY).

Design of Irrigation System

To perform the study two softwares were used VEPROLGS and EPANET 2.0.

The first was used for design and modeling water distribution along the drip

lines and Plot and the second was used for the design and dimensioning of

pipes (pipeline system), from the water intake to the plot head, or to the main

and secondary pipes.

VEPROLGS

Verification and design of drip line and plant areas for saving water and energy

(VEPROLGS) is an application software released in 2003 (first version), that

performs the operation checks dimensioning and design of systems of drip

irrigation, with the aim to increase the uniformity of distribution of irrigation,

to save water and reduce energy consumption. Through this software it is

possible to assess the functioning of entire sectors of irrigated field crops, even

if grown on slopes and strongly with changes in elevation along the row.


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It is already equipped with the operating characteristics of a large number of

drip lines full tested by the National Laboratory of Irrigation within a

Convention between ARSIA and University of Pisa.

Essentially the program allows verification of the operation on the systems

already installed, and identify any changes to improve performance, guide the

design choices in the process of building new plants according to the criteria of

high efficiency, provide useful parameters for plant management.

And finally associated with the evaluation of the functional performance of the

plants to the charges for the amortization of the purchase of drip lines and

energy costs for the distribution of irrigation water.

EPANET 2.0

It was developed by the Water Supply and Water Resources Division of the

U.S. Environmental Protection Agency's National Risk Management Research

Laboratory, and it is software that models water distribution piping systems

and performs extended period simulation of the water movement and quality

behavior within pressurized pipe networks.

EPANET tracks the flow of water in each pipe, the pressure at each node, the

height of the water in each tank, and the type of chemical concentration

throughout the network during a simulation period, water age, source, and

tracing and provides a fully equipped, extended-period hydraulic analysis

package that can:

simulate systems of any size; compute friction head loss using the Hazen-

Williams, the Darcy Weisbach, or the Chezy-Manning formula; include minor

head losses for bends, fittings, etc.; model constant or variable speed pumps;

compute pumping energy and cost; model various types of valves, including

shutoff, check, pressure regulating, and flow control; account for any shape

storage tanks (i.e., surface area can vary with height); consider multiple

demand categories at nodes, each with its own pattern of time variation;


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model pressure-dependent flow issuing from sprinkler heads; base system

operation on simple tank level, timer controls or complex rule-based controls.

3.2.2 Choice Of Plot

The area of 9128 m2, was defined to be a potentially agricultural area, due to

the proximity of Pequenos Libombos Dam, in which the producers practice

agriculture mostly based on surface irrigation.

4. Results And Discussion

4.1 Results and Discussion for Drip Irrigation

4.1.2 Crop Water Requirement

4.1.2.1 Results

Table 1. Maize total gross irrigation

Source: CROPWAT 8.0 Analysis

The total net irrigation is 257.6 mm with daily maximum requirement of 3.5

mm/day for planting date of May 17.

4.1.2.2 Discussion

The maximum daily water requirement is 3.5 mm/day and is registered in

August at mid season stage of the crop, therefore the Dripline Irrigation System

must be able to provide water in the amounts required by the crop.


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4.1.3 Dripline Design

4.1.3.1 Results

The total area is 27.384 m2 and it is divided into 3 plots of 9128 m2 each with a

slope of 0.71 %. By making use of VEPROLGS in each plot, this provide a list

of order drippers ranked according to uniformity distribution as is shown in the

following table.

Table 2. Dripline rank according to uniformity

Source: VEPROLGS Analysis

According to Rank drippers, all features have distribution uniformity above

90%.

Table 3. Operate under Turbulent Twin wall 8mil d.16 q. 0.89 s.0,3 (2000)



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Operating under Turbulent Twin wall 8mil d.16 q. 0.89 s.0,3 (2000) dripline,

provides uniformity on line of 97.2 %, with a inlet pressure of 3.2 m.w.c, and

irrigation intensity of 1.9 mm/hr.

Table 4. Plot Checking under Turbulent Twin wall 8mil d.16 q.0.89 s.0.3 (2000)


A checking area under Turbulent Twin wall 8mil d.16 q.0.89 s.0.3 (2000) dripper,

evidences that uniformity is 97.2 % in the plot and the flow rate is 4.9 l/s

(17.64 m3/hr).

4.1.3.2 Discussion

Ten of drippers presented in rank by the software, they all feature a uniformity

over 90% and according Larry S. (2013), drippers in a field (annual crops) with

uniform topography and slope less than 2% of uniformity of emitters ranging

between 80-90%, and in the specific case of Turbulent Twin wall 8mil d.16

q.0.89 s.0.3 (2000) dripper, provides distribution uniformity of 97.2 % in the

line and in the plot, therefore acceptable for the sizing of drip irrigation system

at this location.


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Turbulent Twin wall 8mil d.16 q.0.89 s.0.3 (2000) dripper, emits an irrigation

intensity of 1.9 mm/hr, smaller compared with the saturation hydraulic

conductivity of the soil which is 7.3 mm/hr, which shows that will not occurs

water losses by runoff.

Besides it is non self-compensating (with smaller diameter), therefore likely

less expensive comparing with self-compensating drippers, therefore more

appropriate to Mozambican reality.

The aspects above, proved to be quite relevance to the choice of this dripper.

Turbulent Twin wall 8mil d.16 q.0.89 s.0.3 (2000) operates at inlet pressure of

3.2 m and the flow rate required at plot area is 17.64 m3/hr. However when

selecting the pump, it is needed to estimates head losses due to friction to add

at inlet pressure.

4.1.4 EPANET Design On Dripline

Will be carried the dimensioning of the irrigation system based on EPANET

software from the reservoir next to the Dam, until the mainfold in the plot. Will

be selected the pipe size, enabling to provide a flow rate and pressure required,

thereby ensuring optimum performance of dripline. The system scheme is

shown at figure 12 and system operating at figure 13.

4.1.4.1 Results

Table 5 .System Components Characteristics System Components Length (m) Diameter (mm) Roughness

PR Valves 2&5 _ 100 _

Pipe 3 177 96.8 140

Pipes 4&6 65.2 96.8 140

Source: EPANET Analysis


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Figure 11. Irrigation System Layout; Source : EPANET 2.0 Analysis

Pump characteristics H=3.75 m ; Q=17.64 m3/hr

Figure 12. Pump curve; Source : GRUNDFOS DATA BOOKLET

Figure 13. System Operating ; Source: EPANET 2.0 Analysis

Plot Area 9128 m2

Plot Area 9128 m2


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4.1.4.2 Discussion

Through the software is possible to verify that a is delivered at plot a flow rate

of 17.64 m3/hr, with a velocity of 0.62 m/s (figure 13) at a pressure of 3.75

m.c.w, slightly higher than had been predicted by VEPROLGS on the plot

which was 3.2 m.c.w, meaning that the pump can compensate the head losses

due to friction in the system which is 0.55 m and also can face the slope

displayed by the field (0.7 %).

The diameters applied to the pipes (96.8 mm) was with the aim to result in a

lower velocity of water and securing the pressure demanded by dripper, besides

the plots have the same area (9128m2), then the pump will provide water for all

area, each plot at time therefore it was necessary to have the same diameter.

The distances applied between driplines in VEPROLGS Software was 1 m, in

order to cover two crop lines (distance between crop lines is 0.5m), allowing

save money in cost related to buy driplines. Since the soil is sandy loam the

distances between drippers in the driplines and thus it could provide water

distribution uniformity, however the plot will be irrigate more often, but

running water for short periods of time in order to reduce the possibility of it

leaching of nutrients from the root zone.

The height of water at the Dam is 47 m and field has an elevation of 29 m, in

other words the difference between water height at the Dam and the elevation

of the field is 18 m. Since the total head required at plot by the pump is 3.75

m.c.w, it allows to say with certainty that it is possible to provide water to the

field by gravity (without use a pump). Therefore it will allow saving money on

purchasing costs, fuel/energy, and maintenance of a pump.

For such it is considered that the Dam has Constant Head Orifice (CHO)

Turnout installed at bottom. This device will allow to control and regulate the

pressure until the desired levels providing to the plot the required flow.


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According Crop Water Requirement, the daily maximum net irrigation is 3.5

mm and the precipitation intensity of dripper is 1.9 mm/hr, meaning that to

irrigate one plot it will take 1.8 hrs and to irrigate all field will take 5.4 mm/hr.

4.2 Results And Discussion on Sprinkler System

4.2.1 Crop Water Requirement

4.2.1.1 Results

Table 6. Maize Total Gross Irrigation

Source: CROPWAT 8.0 Analysis

The total gross irrigation is 286.2 mm with daily maximum requirement of 3.7

mm/day for planting date May 17.

4.2.1.2 Discussion

The maximum daily water requirement is 3.7 mm/day and is registered in

August at mid season stage of the crop, therefore the Sprinkler System must be

able to provide water in the amounts required by the crop.

4.2.2 EPANET Design On Sprinkler

Through a pump water can be conveyed from the reservoir up to the field, and

it has to be directed to the distribution pipes and from here to sprinklers which

are distributed throughout the field. This irrigation system scheme can be

shown through EPANET Software as illustrated below in figure.14 and the

system components characteristic at table 7.


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4.2.2.1 Results

Table 7.System Components Characteristics

System Components Length (m) Diameter (mm) Roughness

Valve 2, 4-14&122 _ 75 _

Pipe 3

Pipes 15& 104-113

177

17

79.2

96.8

100

100

Pipes 16-121 17 66 100

Source: EPANET Analysis

Figure 14. Irrigation System Layout; Source: EPANET Analysis

Pump Characteristics (H = 5.06 m; Q=11.44 m3/hr)

Figure 15. Pump curve; Source: GRUNDFOS DATA BOOKLET


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Figure 16. System Operating; Source: EPANET Analysis

4.2.2.2 Discussion

According to the irrigation system layout (figure 14) it is possible to observe

the sprinklers disposition in the field with a distance of 17 m between them.

The other components characteristics of the system can be consulted on the

table 7 and in annex 1 (for sprinklers).

The Sprinkler (funny) applied at this system has the advantage to adjustable

according to the angles sectors, meaning that the first lateral located at the edge

of the field (as shown in figure 14), sprinklers will be adjusted to provide water

in sectors as described just below:

Sprinklers positioned in the corners will have watering sector of 90o, and

middle sprinklers will have a watering sector of 180o; going out from the edges

towards the interior of field, sprinklers that had watering sector of 90o (which

were located in the corners) will be adjust to have watering sector of 180o, and

the remaining will work normally with a angle of 360o.

This management measure is to ensure distribution uniformity of water by

overlapping of wetted area of the sprinklers, chiefly at edge of the field.


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In practice the system will work with one lateral with 9 sprinklers, so each

lateral has a valve at the entrance in ways that when a lateral is working the

others will be closed.

Therefore it will be assembled valve, pipe and sprinklers corresponding to a

single lateral. Meaning that to perform irrigation operation these components

(valve, laterals fitted with sprinkler) will be installed and after irrigate the plot,

it will be removed and installed on the next line so on until the all field is

irrigated.

Such management action will allow save on purchasing of other components,

but it will be needed to ensure manpower for mounting and dismounting the

components along the field, and in the specific case of Mozambique it is

possibly find manpower available.

Using EPANET simulation with a Funny sprinkler from Sime, it is show that

the system operating can provide to each sprinkler a flow that ranges between

1.26 to 1.30 m3/hr, values considered to be acceptable given that in the field

sprinklers demand a flow of 1.2 m3/hr (Appendix C).

Therefore the Groundfos NB/NK 40-125 4-pole, 50 Hz /129 is the curve pump

(figure15).

Therefore since from selected diameters either in the main pipe (96.8 mm)

either in laterals with sprinklers (66 mm), the system is able to feed the last

point in the field delivering the demanded flow and also because from this

pump it is possible have a head that can cope the head losses due to friction and

the slope displayed in the field, therefore the total head was H=5.06 m to a total

flow of Q=11.44 m3/hr. However the difference between the water heights

contained in the Dam and altitude of the field and 18 m.


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Although the field is at distance of 177 m from the Dam, it is possible to state

with certainty that will not be needed a pump, since with 18 m.c.w (greater

than the pump head, H=5.06) it is possible guarantee the flow demanded in the

field, simply by mounting Constant Head Orifice (CHO) Turnout on the

bottom of Dam to control and regulate the pressure until desired levels.

It will allow irrigate by gravity and save money on purchasing of a pump,

energy/fuel and maintenance.

According to Crop Water output, the daily crop water requirement is 3.7 mm,

therefore to irrigate all the field (12 laterals/lines) will be needed 44.4 mm,

meaning that it will take 12 hrs to irrigate a plot correspondent one laterals/line.


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5. Conclusion

Through the softwares Google Earth, Climwat, Cropwat was possible to

generate data and support mechanism that led to design of drip and sprinkler

irrigation system that was suitable to the study area. However is worth to let

lessons learned from the performance of the system and how to improve it, in

way that could contribute to a judgment during of adoption of these two types

of irrigation systems in accordance with Umbelúzi Basin reality.

Despite cost of drip irrigation components, it operates with small capacity

pump (H=3.75 m.c.w) with small water need (Q=17.64 m3/hr), allowing water

to be provided to irrigate others fields or others purpose.

For sprinkler system is necessary considerable amounts of water to irrigate a

field, but with some management measures it is possible to get high

performances. By making the system work with one lateral line and moving it

to the next line after finishing, although requires manpower for mounting and

dismounting the lateral, this measure has proved to be extremely important,

because the system can works with a smaller capacity pump (H=5.06) which

demand a small amount of water (Q=11.44m3/hr) resulting in system

optimization.

The both systems can work in regions or seasons with water scarcity (therefore

suitable to cash crop).

Due to proximity of the field and difference of water height at the Dam and

field elevation (18 m), the two systems can work without a pump to deliver

water to the field, it is guaranteed by the height of water in the Dam.

This design of the two systems was made next to Pequenos Libombos Dam at

Umbeluzi Dam, however this approach can be applied to other crops in

different region of the country.


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References

MADER. 2000. Relatório Geral Do TIA. Maputo, Mozambique: Ministry of

Agriculture and Rural Development. Available at:

http://fsg.afre.msu.edu/mozambique/iiam/rr_3p.pdf. Accessed 15 May 2013

Boom, B., 2011

Análise da pobreza em Moçambique. Available at:

http://www.sow.vu.nl/pdf/Mozambique/Analysis%20of%20Poverty%20in%20

Moz%20March%202011%20Port.pdf. Accessed 20 May 2013

Sime, SIME IDROMECCANICA.

Available at: www.sime-sprinklers.com/pdf/CG/10%20Funny.pdf. Accessed

15 June 2013

Muiambo, A.A., 1996

Impacto da Barragem dos Pequenos Libombos nos Recursos Naturais do

Distrito de Boane. Universidade Eduardo Mondlane. Available at:

http://www.saber.ac.mz/bitstream/10857/2511/1/Gt-032.pdf. Accessed 5 June

2013

Programa para Acção Nacional para Adaptação as Mudanças Climáticas, 2007.

Ministério para a Coordenação para Acção Ambiental, Moçambique. Available

at:

http://www.legisambiente.gov.mz/index.php?option=com_docman&task=doc_

view&gid=141. Accessed 3 June 2013.

Schwankl, L.: 2013

Maintenance of Micro irrigation Systems. University of California.

Available at: http://micromaintain.ucanr.edu/. Accessed 7 June 2013.


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Crescimento Económico Necessário Mas Deve Ser Sustentável, 2008.

A comunidade para o Desenvolvimento da África Austral Hoje (SADC Hoje).

Available at:

http://www.sardc.net/Editorial/sadctoday/documents/portv10n6.pdf

Accessed 29 May 2013.

Dittoh, S., Akuriba, M. A., Issaka, B. Y.; and Bhattarai, M. 2010.

Sustainable Micro-Irrigation Systems for Poverty Alleviation in The Sahel: A

Case for “Micro” Public-Private Partnerships? Joint 3rd African Association of

Agricultural Economists (AAAE) and 48th Agricultural Economists.

Association of South Africa (AEASA) Conference. Available at:

http://ageconsearch.umn.edu/bitstream/97045/2/122.%20Sustainable%20Micro

%20Irrigation%20in%20the%20Sahel.pdf. Accessed 3 June 2013.

Wilson, C., Bauer, M. 2013.

Drip Irrigation for Home Gardens. Colorado State University Extension.

Available at: http://www.ext.colostate.edu/pubs/garden/04702.html.

Accessed 30 May 2013


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Appendix

Appendix A, Harmonized World Soil Database Of The Field

Appendix B, Soil Water Characteristics Of The Field


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Appendix C, Sime Sprinkler


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Appendix D

Documents

IRRIGATION PROBLEMS IN DEVELOPING COUNTRIES Optimization Of Drip And Sprinkler... · 4.1.4 EPANET Design On Dripline ... presented is a thesis for Master Degree in “Irrigation Problems