improved efficiency of irrigation water use: a south african framework

IRRIGATION AND DRAINAGE

Irrig. and Drain. 62: 262–272 (2013)

Published online 30 May 2013 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ird.1742

IMPROVED EFFICIENCY OF IRRIGATION WATER USE: A SOUTH AFRICANFRAMEWORK†

FELIX B REINDERS1*, ISOBEL VAN DER STOEP2 AND GERHARD R BACKEBERG3

1Institute for Agricultural Engineering, Agricultural Research Council (ARC), Pretoria, South Africa2South African Irrigation Institute (SABI), Pretoria, South Africa

3Water Utilisation in Agriculture, Water Research Commission (WRC), Pretoria, South Africa

ABSTRACT

Irrigated agriculture plays a major role in the livelihoods of nations all over the world and in South Africa it is not different.With the agricultural water use sector being the largest of all water use sectors in South Africa, there have been increased ex-pectations that the sector should increase efficiency and reduce consumption in order to increase the amount of water availablefor other uses.

In a recent study on irrigation efficiency, the approach is that irrigation efficiency should be assessed by applying a waterbalance to a specific situation rather than by calculating various performance indicators such as conveyance efficiency or ap-plication efficiency. Unfortunately the concept of irrigation efficiency is frequently misunderstood leading to the widespreadbelief that water just disappears with low irrigation efficiencies and re-appears with improvements. The purpose of an irrigationsystem is to apply the desired amount of water, at the correct application rate and uniformly to the whole field, at the right time,with the least amount of non-beneficial water consumption (losses), and as economically as possible. The fraction of the waterabstracted from the source that can be utilised by the plant, can be called the beneficial water use component and optimisedirrigation water supply is therefore aimed at maximising this component. It implies that water must be delivered from thesource to the field both efficiently (with the least volume for production along the supply system) and effectively (at the righttime, in the right quantity and at the right quality). Optimising water use at farm level requires careful consideration of the im-plications of decisions made during both development (planning and design), and management (operation and maintenance),taking into account technical, economic and environmental issues.

The SouthAfrican framework covers four levels of water management infrastructure: -the water source, bulk conveyance system,the irrigation scheme and the irrigation farm. The water balance approach can be applied at any level, within defined boundaries, oracross all levels to assess performance within the whole Water Management Area. Copyright © 2013 John Wiley & Sons, Ltd.

key words: Water balance; Irrigation efficiency; Water framework

Received 7 February 2013; Revised 26 February 2013; Accepted 26 February 2013

RÉSUMÉ

En Afrique du Sud, comme ailleurs dans le monde, l’agriculture irriguée joue un rôle majeur dans la vie des nations. Le secteuragricole étant le plus grand consommateur d’eau en Afrique du Sud, il y a de plus en plus d’attentes pour que ce secteuraugmente son efficacité et réduise sa consommation afin d’augmenter la quantité d’eau disponible pour d’autres usages.

Une étude récente défend que l’efficacité d’irrigation doit être évaluée en appliquant un bilan hydrique à une situationspécifique plutôt qu’en calculant différents indicateurs de performance tels que l’efficacité du transport, ou l’efficacité desapplications. Malheureusement, le concept de l’efficience d’irrigation est souvent mal compris et conduit à la croyancelargement répandue que l’eau disparaît quand l’efficacité de l’irrigation est faible et réapparaît avec les améliorations. Le butd’un système d’irrigation est d’appliquer au bon moment et sans pertes la quantité d’eau désirée, au taux d’application uniformeet correct sur l’ensemble du domaine, et aussi économiquement que possible. La fraction de l’eau prélevée à la source qui peut être

* Correspondence to: Mr. Felix Reinders: Programme Manager: Agricultural Water Resources and Conservation, Institute for Agricultural Engineering,Agricultural Research Council (ARC), Pretoria, South Africa. E-mail: [email protected]† Le cadre Sud-Africain d’amélioration de l’efficacité de l’utilisation d’eau d’irrigation.

Copyright © 2013 John Wiley & Sons, Ltd.

263IMPROVED EFFICIENCY OF IRRIGATION WATER USE

utilisée par la plante peut être appelée la composante bénéfique de l’eau; dès lors une utilisation optimisée d’alimentation en eaud’irrigation vise donc à maximiser cette composante. Ceci implique que l’eau doit être livrée de la source vers le champ de façon àla fois efficace (avec le plus faible volume de production tout au long du système d’approvisionnement) et efficiente (au bon mo-ment, avec une quantité et une qualité adéquates). Optimiser l’utilisation de l’eau au niveau des exploitations nécessite un examenattentif des conséquences des décisions prises lors du développement (planification et conception) de la gestion (exploitation etmaintenance), en tenant compte des aspects techniques, économiques et environnementaux.

Le cadre sud-africain couvre quatre niveaux de l’infrastructure de gestion de l’eau: la ressource en eau, le transport, lesystème d’irrigation et l’irrigation de la ferme. L’approche du bilan hydrique peut être appliquée à n’importe quel niveau, dansles limites définies, ou à tous les niveaux ensemble pour évaluer la performance de gestion de l’eau de tout le système.Copyright © 2013 John Wiley & Sons, Ltd.

mots clés: bilan hydrique; efficacité de l’irrigation; Cadre Sud Africain sur l’eau

INTRODUCTION

Irrigated agriculture plays a major role in the livelihoods ofnations all over the world and in South Africa it is not differ-ent. With the agricultural water use sector being the largestof all water use sectors in South Africa, there have been in-creased expectations from government that the sector shouldincrease efficiency and reduce consumption in order to in-crease the amount of water available for other uses, and inparticular for human domestic consumption. Great emphasishas been placed on how an increase in efficiency will lead toreduced consumption by agricultural users and thereby ’re-lease’ some of the annual water yield for use by the domes-tic sector. In the framework on Water for Growth andDevelopment (Department of Water Affairs and Forestry,2008) it is stated that inefficient water use in commercial ir-rigation must be urgently addressed. Recommended actionsinclude measurement of the quantity of water distributedand applied at specific times; preparation of water use effi-ciency and risk management plans; and a reduction of thequantity of water used for irrigation by existing farmersthrough investment in appropriate technology. Water mustbe used more productively to meet demands for food and fi-bre and terminology for intra- and inter-sectorial analysismust be unambiguous across sectors so that interventionsand their impacts are properly understood (Perry, 2011).

In a recently completed Water Research Commission(WRC) research project (Reinders et al., 2010) on improvedefficiency of irrigation water use, the approach is that irriga-tion efficiency should be assessed by applying a waterbalance to a specific situation, rather than by calculatingvarious performance indicators such as conveyance effi-ciency or application efficiency. Unfortunately the conceptof irrigation efficiency is frequently misunderstood leadingto the widespread belief that water just disappears withlow irrigation efficiencies and re-appears with improve-ments. The purpose of an irrigation system is to apply thedesired amount of water, at the correct application rate anduniformly to the whole field, at the right time, with the leastamount of non-beneficial water consumption (losses), and as


economically as possible. When using water to producecrops, it should be considered both as a scarce and valuableresource and an agricultural input to be used optimally. Notall the water that is abstracted from a source for the purposeof irrigation, reaches the intended destination where theplant can make best use of it – the root zone. The fractionof the water abstracted from the source that can be utilisedby the plant, can be called the beneficial water use compo-nent. Optimised irrigation water supply is therefore aimedat maximising this component and implies that water mustbe delivered from the source to the field both efficiently(with the least volume for production along the supplysystem) and effectively (at the right time, in the right quantityand at the right quality). Optimising water use at farm level re-quires careful consideration of the implications of decisionsmade during both development (planning and design), andmanagement (operation and maintenance), taking intoaccount technical, economic and environmental issues.

THE WATER BALANCE APPROACH

At the beginning of the research, the objective was todevelop an efficiency framework consisting of performanceindicators that aimed to include or make provision for allpossible levels of water management and possible scenariosthat can be found in irrigated agriculture. The objectiveswere formulated as follows: To evaluate appropriatemeasurement tools, propose best management practicesand formulate guidelines to improve conveyance, distribu-tion, on-farm surface storage, field application, soil storageand return flow efficiencies of irrigation water use.

However, the standardisation of components within the largerange of water supply and management systems was found tobe problematic. Thewide variety of performance indicators thatwere identified internationally and nationally made the assess-ment process cumbersome. Interpretation of the performanceindicators without benchmarks was nearly impossible, and thenumber of benchmarks required would have been too greatand impractical to implement on the ground.

Irrig. and Drain. 62: 262–272 (2013)

264 F. B. REINDERS ET AL.

Significant international research developments havetaken place since 2005 which have changed the way theirrigation (and water in general) community look at wateruse efficiency. To name but a few, the concepts of waterfootprints and virtual water became more widely recognised(Hoekstra and Hung, 2002), and secondly there was a moveaway from efficiency indicators towards a water balanceapproach (Perry, 2007), and the water balance approachwas also used for accounting of the inputs and outputs ofwater (Ritter, 2006)

The water footprint of an individual, business or nation isdefined as the total volume of fresh water that is used toproduce the goods and services consumed by the individual,business or nation. In order to give a complete picture of wateruse, the water footprint includes both the water withdrawnfrom surface and groundwater and the use of soil water (inagricultural production). It ties in with the concept of waterbalance. The water footprint concept was introduced in orderto have a consumption-based indicator of water use that couldprovide useful information in addition to the traditionalproduction-sector-based indicators of water use.

The water footprint concept is closely linked to the virtualwater concept. Virtual water is defined as the volume of wa-ter required to produce a commodity or service. The conceptwas introduced by Allan in the early 1990s when studyingthe option of importing virtual water (as opposed to realwater) as a partial solution to problems of water scarcity inthe Middle East. Allan elaborated on the idea of using vir-tual water import (through food imports) as a tool to releasethe pressure on scarce domestic water resources. Virtualwater import thus becomes an alternative water source, nextto endogenous water sources. Imported virtual water has there-fore also been called ’exogenous water’ (Haddadin, 2003).

These concepts provide the link between water use,production and financial returns that were previously notalways possible. Now it is possible to use crop productionfunctions and it is used widely. They can of course also beapplied equally well at farm, Water User Association(WUA) or Water Management Area (WMA) level.

A paper by Perry (2007) presented the newly developedframework for irrigation efficiency as approved by theInternational Commission on Irrigation and Drainage (ICID).In the paper, the author describes in detail the history andsubsequent confusion surrounding the calculation and interpre-tation of so-called irrigation or water use ’efficiency’ indicators.The framework and proposed terminology is scientificallysound, being based on the principle of continuity of mass,and promotes the analysis of irrigation water use situations orscenarios in order to expose underlying issues that can beaddressed to improve water management, rather than simplythe calculation of input–output ratios as done in the past.

The basis of the framework is that any water withdrawnfrom a catchment for irrigation use contributes either to


storage change, to the consumed fraction, or to the non-consumed fraction at a point downstream of the point ofabstraction. The water that is consumed will either be tothe benefit of the intended purpose (beneficial consumption)or not (non-beneficial consumption). Water that is not con-sumed but remains in the system will either be recoverable(for re-use) or non-recoverable (lost to further use). Theboundaries are as explained in Figure 1.

In order to improve water availability in the catchment, therelevant authority needs to focus its attention on reducing non-beneficial consumption and non-recoverable fractions: the ac-tivities undertaken to achieve this result can be called the bestmanagement practices. The ICID water balance framework,based on Perry’s model, is shown schematically in Figure 1.

In order to apply this framework to irrigation areas, typicalwater infrastructure system components are defined whereindifferent scenarios may occur. In South Africa, most irrigationareas consist of a dam or weir in a river from which water isreleased for the users to abstract, either directly from the riveror in some cases via a canal. Water users can also abstractwater directly from a shared source, such as a river or dam/res-ervoir, or the scheme-level water source could be a groundwa-ter aquifer. Once the water enters the farm, it can eithercontribute to storage change (in farm dams), enter an on-farm water distribution system or be directly applied to thecrop with a specific type of irrigation system.

The South African framework presented here covers fourlevels of water management infrastructure, (as shown inTable I): i.e., the water source, the bulk conveyance system,the irrigation scheme and the irrigation farm, and the relevantwater management infrastructure (Reinders et al., 2010).

The different water balance framework system compo-nents (used on a scheme basis) and their classificationaccording to the ICID framework, for whichever water man-agement infrastructure may be encountered in the field, areshown in Table II. Although care has been taken to includeall possible system components and water destinations,practitioners are encouraged to customise the frameworkfor their specific circumstances. The abbreviations used toclassify the framework components are declared in Figure 1.

In order to improve water use efficiency in the irrigationsector, actions should be taken to reduce the non-beneficialconsumption (NBC) and non-recoverable fraction (NRF).Desired ranges for the NBC and NRF components havebeen included in Table II to help the practitioner evaluatethe results obtained when first constructing a water balance.Due to the fact that Table II has been drawn up from an ir-rigation system perspective there is not much that the prac-titioner can do to recover water in some of theinfrastructure components, hence it is indicated as NRF.

The values shown here (desired range as a % of inflow)are based on actual results obtained from eleven irrigationschemes and 75 irrigation systems during the course of the

Irrig. and Drain. 62: 262–272 (2013)

Table I. Four levels of water management infrastructure (Reinderset al., 2010)

Water management level Infrastructure system component

Water Source Dam/Reservoir AquiferBulk conveyance system River CanalIrrigation scheme On-scheme dam

On-scheme canalOn-scheme pipe

Irrigation farm On-farm damOn-farm pipe / canalIn-field irrigation system

Figure 1. ICID water balance framework for irrigation water management (after Perry, 2007)


project and can be adjusted if more accurate, locally relevantdata is available in a particular area. However, as circum-stances differ greatly from one irrigation area to the next,it is recommended that water managers at all levels assessa specific system component’s performance against thesame component’s previous years’ data in order to achievecontinuous improvement, rather than against other (seem-ingly similar) system components from different areas.

When trying to quantify the different components, one isfaced with the dilemma of the lack of data available. It is,however, possible to construct a water balance with limiteddata by presenting the results for combined water destinations.For example, at the irrigation system level, it is often easier to


first measure or calculate the beneficial consumption andrecoverable fraction in combination (transpiration, leachingrequirement, drainage water, etc.) and then to determine orcalculate the non-beneficial (NBC) or non-recoverablefractions (NRF) – by constructing the water balance. Theframework classification, as indicated in the second lastcolumn of Table II can therefore be decided on according tothe actual measurements of a specific scheme or systems.

Finally, it is recommended that the water user’s lawful al-location is assessed at the farm edge, in order to encourageon-farm efficiency. At scheme level, conveyance, distribu-tion and surface storage losses need to be monitored bythe WUA or responsible organisation, acceptable rangesset, and agreement obtained with the Water regulator(Department of Water Affairs), where in the system provisionshould be made to cover the losses.

APPLICATION OF THE WATER BALANCEAPPROACH

The field work undertaken in the course of the projectconsisted of various approaches and strategies applied ateach of the identified irrigation schemes, in order to quantifythe water use components. As the application of a water bal-ance approach was an outcome of the research, the schemeswhere field work was undertaken, the system components

Irrig. and Drain. 62: 262–272 (2013)

Table

II.Water

balancefram

eworkallocatio

nof

typicalirrigatio

nsystem

components(Reinderset

al.,2010)

Water

balance

fram

ework

system

component

(based

oninfrastructure)

Inflow

ofwater

into

system

component

Possiblewater

destinations

with

inthe

system

component

Fram

ework

classificatio

nDesired

Range,

%of

inflow

Dam

/reservoir

Totalam

ountof

waterreleased

from

storage

Increase

flow

inbulk

conveyance

system

(river

orcanal)

SC

Operatio

nallossesatthepointo

frelease

NRF

<5

River

bulk

conveyance

system

(from

on-river

dam

toscheme/

farm

edge)(ifapplicable)

Totalam

ount

ofwaterentering

theriver

On-schemesurfacestorage

BC

On-schemedistributio

nsystem

BC

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

Evaporatio

nfrom

water

surface

NBC

<5

Seepage

inriverbed

NRF

<10

Transpiratio

nby

riparian

vegetatio

nNBC

<5

Unlaw

fulabstractions

NRF

0Operatio

nallosses

(unavoidable)

NRF

<10

Canal

bulk

conveyance

system

(from

on-river

dam

toscheme/

farm

edge)(ifapplicable)

Totalam

ount

ofwaterentering

themaincanal


BC


nsystem

BC

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

Evaporatio

nfrom

canal

NBC

<1

Seepage

incanal

NRF

<5

Unlaw

fulabstractions

NBC

0Operatio

nallosses

(unavoidable,eg

filling

canal,tailends)

RF

<10

Operatio

nallosses

(inaccuratereleases,

spills,breaks,etc.)

NRF

0


Totalam

ount

ofwaterentering

aschemedam

Increase

volumeof

water

stored

SC


nsystem

(release

from

dam)

BC

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

Evaporatio

nfrom

dam

NBC

<1

Seepage

from

dam

NRF

<1

Operatio

nallosses

(spills)

NRF

<1

Shared

(schem

e-level)groundwater

aquifercompartment

Total

aquiferrecharge

Increase

groundwater

storage

SC

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

On-schemecanaldistributio

nsystem

(ifapplicable)

Totalam

ount

ofwaterentering

theon-schem

ecanal

distributio

nsystem

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

Evaporatio

nfrom

canal

NBC

<1

Seepage

incanal

NRF

<5

Unlaw

fulabstractions

NRF

0Operatio

nallosses

(unavoidable,eg.

filling

canal,tailends)

RF

<10

Operatio

nallosses

(inaccuratereleases,

spills,breaks,etc.)

NRF

0

(Contin

ues)


Copyright © 2013 John Wiley & Sons, Ltd. Irrig. and Drain. 62: 262–272 (2013)

Table

II.(Contin

ued)

Water

balance

fram

ework

system

component

(based

oninfrastructure)

Inflow

ofwater

into

system

component

Possiblewater

destinations

with

inthe

system

component

Framew

ork

classificatio

nDesired

Range,

%of

inflow

On-schemepipe

distributio

nsystem

(ifapplicable)

Totalam

ountof

waterentering

the

on-schem

epipe

distributio

nsystem

Farm

edge

(on-farm

surfacestorage,

distributio

nsystem

orirrigatio

nsystem

)BC

Operatio

nallosses

(unavoidable)

RF

<5

Leaks

NRF

0On-farm

surfacestorage

Totalam

ountof

waterentering

afarm

dam

Increase

volumeof

water

stored

SC

On-farm

distributio

nsystem

(release

from

dam)

BC

Irrigatio

nsystem

(abstractio

nfrom

dam)

BC

Evaporatio

nfrom

dam

NBC

<1

Seepage

from

dam

NRF

<1

Operatio

nallosses

(spills,leaks)

NRF

<1

Operatio

nallosses

(unavoidable)

RF

<5

On-farm

distributio

nsystem

Totalam

ountof

waterentering

theon

-farm

pipelin

esor

canals

Irrigatio

nsystem

BC

On-farm

distributio

nsystem

leaks

NRF

0In-fieldsystem

(from

fieldedge

toroot

zone)Intended

destination

ofthewater

released.

Totalam

ountof

waterentering

the

irrigatio

nsystem

(Gross

Irrigatio

nRequirement(G

IR)

plus

precipitatio

n)

Increase

soilwater

content

SC

Transpiratio

nby

crop

BC

In-fieldevaporation(beneficial)

BC

Frostprotectio

nirrigatio

nwater

BC

Leaching(intended,

beneficial

butnon-

recoverable)

BC

Interceptio

n(beneficial

butnon-

recoverable)

BC

In-fieldevaporation(non-beneficial,

excessive)

NBC

0

In-fielddeep

percolation(non-intended,

non-recoverable)

NRF

0

In-fieldrun-off(uncontrolled)

NRF

0Drainagewater

(surface

andsubsurface,

recoverable)

RF

Operatio

nallosses

(unavoidable)

NRF

<5


Copyright © 2013 John Wiley & Sons, Ltd. Irrig. and Drain. 62: 262–272 (2013)


could be assessed using the water balance approach.Table III shows the irrigation schemes where field workwas undertaken, together with the system components thatwere assessed at each scheme.

RESEARCH OUTCOMES

The research activities undertaken and the outcomesimplemented were done in four phases:

• Baseline study phase

The various performance indicators previously availablewere reviewed, and irrigation systems evaluated to obtaininformation on the current status of irrigation schemes andsystems. The outcome of this phase was a decision to intro-duce the water balance approach in which the frameworkcomponents have to be defined and quantified for the bound-ary conditions selected, using standardised measurementsrather than the performance indicator approach;

• Assessment phase

During this phase, existing best management practices wereused to assess the current status of irrigation schemes andsystems and to identify which components of the water bal-ance framework improvements can be made. This may be atWater Management Area (WMA) scheme or farm levelwhere different sources of information are available forassessment;

• Scenario development phase

During this phase, alternative scenarios were developed forthe components requiring change, and the feasibility ofimplementing the changes was assessed from technical,

Table III. Irrigation schemes where field work took place and system co

Irrigation Scheme Bulk ConveyanceOn-schemedistribution

Or

Breede River √ √Dzindi √Gamtoos √Hartbeespoort √Hex RiverKZN scheme √ √Loskop √Nkwalini √ORWUA √ √SteenkoppiesVaalharts √Worcester East


environmental and economic perspectives. Models wereused for feasibility assessment, making use of availablecomputer programs and data sets;

• Implementation phase

In this phase, recommendations were made forimplementing feasible changes, and guidelines were devel-oped. These guidelines should be promoted amongst alllevels of stakeholders (WMA, scheme and farm), as a meansof influencing the way in which water use efficiency isreported at the different management levels, for example inwater use efficiency accounting reports, water managementplans and water conservation plans.

With this the main outcome has been developed: Guide-lines for improving irrigation water use efficiency. Thestructure and content of the guidelines are based on the les-sons learnt locally and internationally during the course ofthe project. Hence, a set of performance indicators withbenchmarks was moved away from and a water balance ap-proach is instead being promoted as a more meaningful andsustainable approach to improving water use efficiency.

The ’Guidelines for improved irrigation water manage-ment from dam wall release to root zone application’ areaimed assisting both water users and authorities to achievea better understanding of how irrigation water managementcan be improved, thereby building human capacity,allowing targeted investments to be made with fewer socialand environmental costs.

The guidelines consist of four modules:

• Module 1: Fundamental concepts. This module intro-duces the concepts of optimised water use, irrigationsystem performance and the water balance. It alsotouches on lawfulness of water use, demand manage-ment and appropriate technologies;

mponents were assessed

n-schemeeturn flow

Irrigation system(application)

Irrigation management(Soil storage)

√ √√√ √√√√ √√√

√ √ √√

√ √√

Irrig. and Drain. 62: 262–272 (2013)


• Module 2: In-field irrigation systems. This module ad-dresses the water balance approach at field level, anddescribes how each decision made during the planning,design and management of irrigation systems influ-ences the amount of water required to irrigate the cropsuccessfully;

• Module 3: On-farm conveyance systems. This moduleaddresses the water balance approach at farm level,and describes how the on-farm water distribution sys-tem should be planned, designed and managed to opti-mise water and energy requirements;

• Module 4: Irrigation schemes. This module introducesthe water balance approach at irrigation scheme level,and describes how technologies such as the WAS,iScheme and water measuring devices can be used toensure greater reliability of supply to all water userson a scheme.

In South Africa, reliance on irrigation water for food pro-duction is important due to the arid and semi-arid climate inlarge parts of the country. Although the National Water Act(NWA) (Act 3 of 1998) does not make provision for waterconservation and water demand management (WC/WDM),as part of the implementation of the National WaterResources Strategy (NWRS) various interventions are consid-ered to reconcile demand with supply (Backeberg, 2007).These include the following:

• Demand management – implementing cost recoverythrough consumer tariffs and user charges to influencethe behaviour of water users and to install technologieswhich reduce waste and losses of water such asundetected leakages;

• Resource management – regulation of streamflowthrough storage; control of abstractions and releases;and assessment of the groundwater resource at specificlocalities;

• Re-use of water – recycling of return flows and treat-ment of water;

• Control of alien invasive vegetation – clearing of in-vading alien vegetation and controlling the spread ofsuch vegetation to increase surface runoff;

• Re-allocation of water – enable gradual transfersbetween use sectors with differential benefitsthrough compulsory licensing, supported by waterdemand management and trading of water useauthorizations.

The WC/WDM strategy for agriculture provides a frame-work for ’regulatory support and incentives designed to im-prove irrigation efficiency . . .. in order to increaseproductivity and contribute to reducing income inequalitiesamong people supported by farming activities’.


A plan of action is envisaged which must present the fol-lowing strategic outputs:

• appropriate measures that reduce wastage of water;• progressive modernization of water conveyance, distri-bution and application infrastructure, equipment andmethods;

• preventative maintenance programmes;• water allocation processes that promote equitable andoptimal utilization of water;

• generation of sufficient irrigation information which isaccessible to all stakeholders;

• implementation of water audits from the water sourceto the end user.

In the case of five of these action points, conditions andregulations for WC/WDM for water use sector authorizationhave been published and are currently being reviewed(Backeberg, 2007). For irrigation and agricultural wateruse the emphasis is on five categories: (1) measuring devicesand information systems; (2) water audits, accounting andreporting to the responsible authority; (3) water manage-ment planning and WC/WDM measures; (4) managementof return flows; and (5) education and raising awareness.

CONTRIBUTIONS TO NEW KNOWLEDGE INSOUTH AFRICA

The guidelines developed as part of this project contain infor-mation on aspects of irrigation water use efficiency that is ei-ther new or deviates from previously available information.

The ICID framework was applied by the project team tore-assess the system efficiency indicators typically used byirrigation designers when making provision for losses in asystem and converting net to gross irrigation requirement.A new set of system efficiency (SE) values for design pur-poses was therefore developed. These values are illustratedin Table IV and are considerably more stringent than thepresent system design norms. This values must not be con-fused with Table II’s values because Table II provide thewater balance framework from a holistic point of view andTable IV provide only the irrigation system efficiencyvalues.

System efficiency defines the ratio between net and grossirrigation requirements (NIR and GIR). NIR is therefore theamount of water that should be available to the crop as a re-sult of the planned irrigation system and GIR is the amountof water supplied to the irrigation system that will be subjectto the envisaged in-field losses.

In Table IV, while the different water use components atthe point of application with a specific irrigation systemhas each been allocated a column under ’Losses’. The

Irrig. and Drain. 62: 262–272 (2013)

Table IV. Default system efficiency values

Irrigation system

Losses

Default systemefficiency

(net to gross ratio) (%)

Non-beneficialspray evaporationand wind drift (%)

In-fieldconveyancelosses (%)

Filter andminor

losses (%)Total

Losses (%)

Drip (surface and subsurface) 0 0 5 5 95Microspray 10 0 5 15 85Centre Pivot, Linear move 8 0 2 10 90Centre Pivot LEPA 3 0 2 5 95Flood: Piped supply 0 3 2 5 95Flood: Lined canal supplied 0 5 2 7 93Flood: Earth canal supplied 0 12 2 14 86Sprinkler permanent 8 0 2 10 90Sprinkler movable 10 5 2 17 83Travelling gun 15 5 2 22 78

Adapted from Reinders et al., 2010


approach makes provision for the occurrence of non-beneficial spray evaporation and wind drift, in-field convey-ance, filter and other minor losses. The sum of all theselosses makes up the value in the column ’Total losses’.The default system efficiency values in the last column wereobtained by subtracting the total losses from 100%. Withthis in mind the system must also function optimally andmanaged correctly to obtain these required results. Similardefault values were obtained in a study carried out by TerryHowell of the United States Department of Agriculture onIrrigation efficiencies. Irrigation efficiency is an importantengineering term that involves understanding soil and agro-nomic science to achieve the greatest benefit from irrigation(Howell, 2003).

When an irrigation system is evaluated, the system effi-ciency value can be compared with these default values,and possible significant water loss components identifiedas areas for improvement. The approach is therefore moreflexible and easier to apply than the original efficiencyframework where definitions limited the applications.

It should always be kept in mind that a system’s water ap-plication efficiency will vary from irrigation event to irriga-tion event, as the climatic, soil and other influencingconditions are never exactly the same. Care should thereforebe taken when applying the SE indicator as a benchmark, asit does not make provision for irrigation management prac-tices. The SE values make therefore only provision for theinfield system’s performance and does not make provisionfor the functionality or management practices.

It is recommended that system efficiency be assessed interms of the losses that occur in the field. This can bedetermined as the ratio between the volume of water lostto non-beneficial spray evaporation and wind drift, in-fieldconveyance, filter and other minor losses, and the volumeof water entering the irrigation system, for a specific period


of time. The losses can also be expressed as a depth of waterper unit area, rather than a volume. Improvements cantherefore only be made by improved management practicesand functionality.

IMPROVEDUNDERSTANDINGOFDISTRIBUTIONUNIFORMITY

Irrigation uniformity is a characteristic of the type of irriga-tion system used, together with the standard to which agiven system has been designed, is operated and ismaintained. It can also be affected by soil infiltration charac-teristics and by land preparation.

The traditional approach to accounting for the distributionuniformity of the lower quarter (DUlq) has likely resultedin the default irrigation efficiencies customarily referred to,e.g., that furrow irrigation is assumed to be 65% efficientand centre pivot irrigation is assumed to be 85% efficient.

Unfortunately, the rationale for these assumed efficien-cies, i.e. the typical or assumed non-uniformity, is seldomconsidered, and water is often thought to just ’disappear’with the assumed low efficiencies. However, once the waterbalance approach is applied, it is realised that the water doesnot ’disappear’ but contributes to increased deep percolationwhich may eventually appear as return flow further alongthe drainage system. This water is therefore recoverablefrom a schemes perspective but non recoverable from an ir-rigation system perspective.

The bottom line is that assuring high irrigation uniformityis of primary importance, and should be the goal of good de-sign and maintenance procedures. It is very unlikely thatlow crop yields caused by non-uniform irrigation water ap-plications will be improved by assuming low irrigation effi-ciencies and increasing the water applications accordingly.

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If poor uniformity results in low crop yields, the uniformityneeds to be corrected in order to improve system performance.Simply applying more water to compensate for the part of thefield that is being under-irrigated is unlikely to result in im-proved crop yields - large parts of the field will now sufferfrom over-irrigation, and the risk of long term problems devel-oping due to a raised water table will increase.

The preferred recommendation in this case would be to dealspecifically with the problem of poor uniformity. For planningpurposes, the GIR at the field edge should therefore be calcu-lated as the product of the NIR and system efficiency.

IMPROVED UNDERSTANDING OF ENERGYCOSTS AND THE EFFECTS OF COST

INCREASES

Energy costs influences the selection, design and operationof an irrigation system. The effect of making various deci-sions regarding irrigation system design and operation wasinvestigated and reported on. The effects of system lay-out, emitter selection, standing times and ESKOM’s elec-tricity tariff structures on the capital and operational costof an irrigation system were documented, and various calcu-lation tools were developed.

A CROP WATER USE MODULE FOR THE WASPROGRAMME

The Water Administration System (WAS) was designed as amanagement tool for irrigation schemes and water manage-ment officers wanting to manage their water accounts andwater supply to users through canal networks, pipelinesand rivers. The WAS program is currently in use at all themajor irrigation schemes and a number of smaller irrigationboards throughout South Africa.

During the early stages of the project, a Crop Water Usemodule was developed for the WAS to calculate the waterusage per crop between two specified dates for all theplanted crops on a scheme based on the plant date, the areaplanted and the crop water use curve. The crop yield (ton/ha)can be captured at the end of a growing season and used to cal-culate the total yield (ton) and the yield in (kg/m3).

A summary of water used for a specified period can easilybe generated per crop type. All the crop water use informationcan easily be linked to a geographic information system (GIS).

ISCHEME INFORMATION SYSTEM

The iScheme information system for irrigation schemes wasdeveloped as part of this project and subsequently adaptedand adopted by DWA to develop ’water use efficiency


accounting reports’ (WUEA reports) at irrigation schemes,replacing the previously used disposal reports.

It was recognised that it is a simple and effective way tokeep track of water losses on a scheme or part of a schemeshould be used. It is important to keep the reporting of waterlosses simple; past experience has shown that complicatedreports such as the previous so called disposal report fromthe DWA were either incorrectly used, or not used at all.The calculation of water losses on a scheme should addvalue to water distribution management, providing a toolto help minimise water losses.

iScheme is an information system for irrigation schemesthat contains a list of all irrigation schemes throughoutSouth Africa. Every irrigation scheme is linked to a specificWater Management Area (WMA) and a region. This featuremakes it possible to filter the information in the databaseaccording to scheme, WMA, region and nationally. One ofthe uses of iScheme is to archive WUEA reports for allschemes on a national basis. The iScheme database is ide-ally suited to import, manage and report on WUEA reportson a scheme, WMA, region and national levels.

CONCLUSION AND RECOMMENDATIONS

The activities undertaken during the course of the projecthave contributed to local knowledge on issues regarding ir-rigation water use efficiency. The outcomes deviate from theoriginal envisaged outcomes, in that:

• efficiency refers to the state of a water balance for a de-fined spatial and temporal area rather than to the valueof a performance indicator. The water balance ap-proach is therefore applied holistically to the irrigationscheme and the system efficiency values only to the onfarm system to determine the amount of water thatshould be available to the crop;

• improved efficiency is achieved through a process ofassessment and targeted actions with a water balanceapproach, rather than general practices.

The resulting approach not only complies with an im-provement process of ’measure; assess; improve; evaluate’,but it also promotes an investigative approach to improvingefficiency.

The main output of the project was the compilation ofguidelines for improved irrigation water management fromdam wall release to root zone application. The guidelinesare aimed at assisting both water users and authorities toachieve a better understanding of how irrigation water man-agement can be improved, thereby building human capacity,allowing targeted investments to be made with fewer socialand environmental costs. Using lessons learnt during the

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WRC project, best practices and technologies were intro-duced and illustrated. This contribute to better understand-ing of the realities and potential for efficient irrigationwater use across all levels of water management, and en-courage the adoption of the water balance approach.

REFERENCES

Backeberg GR. 2007. Allocation of water use rights in irrigated agriculture:Experience with designing institutions and facilitating market processesin South Africa. USCID 4th International Conference on Irrigation andDrainange, October 2007, Sacramento, California.

Department of Water Affairs and Forestry. 2008. Water for Growth andDevelopment, Version 7, Department of Water Affairs, Pretoria.

Haddadin MJ. 2003. Exogenous water: A conduit to globalization of waterresources. In: Hoekstra, A.Y. ’Virtual water trade: Proceedings of theInternational Expert Meeting on Virtual Water Trade’, Value of WaterResearch Report Series No. 12, UNESCO-IHE, Delft, the Netherlands.


Hoekstra AY, Hung PQ. 2002. Virtual water trade: A quantification of vir-tual water flows between nations in relation to international crop trade,Value of Water Research Report Series No. 11, UNESCO-IHE Institutefor Water Education, Delft, the Netherlands. http://www.waterfootprint.org/Reports/Report11.pdf

Howell TA. 2003. Irrigation efficiency.Encyclopedia of Water Science, UnitedStates Department of Agriculture, Bushland, Texas, USA; pp 467–472.

Perry C. 2007. Efficient irrigation, Inefficient Communication, FlawedRecommendations, Irrigation and Drainage Vol 56:4, Elsevier, London,United Kingdom, Wiley Interscience.

Perry C. 2011. Accounting for Water use: Terminology for saving waterand increased production. Agricultural Water Management 98(12):1840– 1846.

Reinders FB, van der Stoep I, Lecler NL, Greaves KR, Vahrmeijer JT,Benadé N, Du Plessis FJ, Van Heerden PS, Steyn JM, Grové B, JummanA, Ascough G. 2010. Standards and Guidelines for Improved Efficiencyof Irrigation Water Use from Dam Wall Release to Root Zone Applica-tion: Main Report. WRC Report No. TT 465/10.

Ritter ME. 2006. The Physical Environment: Introduction to PhysicalGeography, 2013, http:/www.uswp.edu/geo/faculty/ritter/geog101/text-book/title_page

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improved efficiency of irrigation water use: a south african framework

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