Coping with drought: Lessons learnt from research

on improved irrigation efficiency

Felix ReindersARC-Institute for Agricultural Engineering

SA 2016 ANNUAL CONFERENCE18-19 April 2016

Water and Rain

Conclusion

Introduction

Irrigationefficiency

Introduction

South Africa is a semi-arid country where

water is of critical strategic importance

and has a potential limiting effect on all

future development in the country.

With the high population densities and

significant competition of available water

resources, this situation is exaggerated.

CONTRASTS

DamsInSA

Extensive Water Resource Development

>4400 dams

Province Nett FSC million

m^3 This Week (%) Last Week (%) Last Year (%)

Eastern Cape 1833 74 74 81

Free State 15971 54 53 84

Gauteng 115 88 89 97

Kwazulu-Natal 4669 52 52 72

Lesotho* 2376 52 52 78

Limpopo 1508 62 62 88

Mpumalanga 2539 65 66 89

North West 887 66 67 66

Northern Cape 146 70 60 88

Total 31834 50 50 80

Status of Dams

Provincial summary

Nasionale Water Wet (Wet 36 of 1998)

Dikteer dat water

moet word op ‘n volhoubare en regverdige wyse.

bewaargebruik

ontwikkelbeskerm

bestuur en beheer

Rainfed

16 000 000 ha

Irrigation

1 600 000 ha

Agriculture depends on Water

ANNUAL RAINFALL

857 mm

WORLD

80 % in5

MONTHS

495 mm

SOUTH AFRICA

10 000 mm

HAWAII

1930 1933 1944 1949 2012 2015 Average

519 544 544

Worst drought in 112 years

Decrease in vegetation Northern Cape

Vaalharts irrigation scheme 27%

decrease

Kruger NationalPark37%

decrease

Free state50%

decrease

Vaalharts irrigation Kruger National ParkFree state

Biomass Measuredfor Aug to Jan

Source: eLeaveNetwork 24

National water act (Act 36 of

1998)

Dictates water has to be

protected

used

developed

conserved

managed and

controlled

in a sustainable and equitable manner.

improved irrigation efficiency

Agricultural water use sector is the largest of all water use sectors in South Africa using an estimated 60% of surface and groundwater

yields annually Competition for our scarce resource

Increasing pressure from government that water must be re-allocated to other water use sectors

Great expectations existed that an increase in efficiency will lead to reduced consumption by agricultural users and thereby “release” some of the annual water yield for use by other sectors

The importance of water:

•Water is the key to food security– without water, crops simply cannot grow.

•Water is not just for primary production – it plays a vital role at all stages along the agricultural value chain

•Water for agriculture connects us all together – In times of scarcity we all have a responsibility to use water wisely, efficiently and productively.

We need to be more ‘water smart’.

Water Research Commission Project “Standards and guidelines for improved

efficiency of irrigation water use from dam wall release to root zone application”

Overall objective: To evaluate appropriate measurement tools,

propose best management practices and formulate guidelines to improve conveyance, distribution, on-farm surface storage, field application, soil storage and return-flow efficiency of irrigation water use

Issues that had to be addressed: Confusion regarding the definition of “efficiency” Inconsistent application of existing performance

indicators Lack of data to quantify performance indicators Lack of benchmarks to compare recorded data

with Improved efficiency ≠ reduced consumption

This is still not fully understood by many More often:

Improved efficiency = increased consumption!

A set of performance indicators with benchmarks was not developed - rather a water balance approach is being promoted as a more meaningful and sustainable approach to improving irrigation water management

Guidelines have been developed for improving irrigation water management, based on the lessons learnt locally and internationally during the course of the project

Project outcomes

A new approach to defining efficient use of irrigation water:

Irrigation Efficiency

Water source

Irrigation scheme

Farm

Field

Crop

Ensuring that most of the water taken from the source

reach the intended target– the crop –

by minimising losses along the way.

On-scheme losses

On-farm losses

In-field lossesA water balance approach

The water balance approach is more flexible than calculating ratios

It takes into account: the intended destination of water taken from a

resource, and how the water is used along the way.

It encourages a better understanding of water management at all levels

Based on the water use efficiency framework recommended by the ICID as published in an article by Chris Perry in 2007

Irrigation efficiency

Water balance frameworkWithdrawal for irrigation use:

Water abstracted from streams, groundwater or storage

Storage change:

(SC)Flow to or from

aquifers, in-system tanks, reservoirs, etc.

With no significant

change in water quality between the in and out

flows

Consumed fraction: Non-consumed fraction

Beneficial consumption

:(BC)

Water evaporated

or transpired for the

intended purpose –eg. crop

transpiration

Non-beneficial

consumption:

(NBC)Water

evaporated or transpired for purposes

other than the intended

– eg. evaporation from dams,

riparian vegetation.

Recoverable fraction:

(RF)Water that

can be captured and re-used – eg.

drainage water from irrigation

fields

Non-recoverable

fraction:(NRF)

Water that is lost to

further use –eg. flows to

saline groundwater aquifers, flow

to the sea.

(Perry 2007)

Four levels of water management infrastructure

Water management level Infrastructure system component

Water Source Dam/Reservoir

Aquifer

Bulk conveyance system River CanalIrrigation scheme

On-scheme dam

On-scheme canal

On-scheme pipeIrrigation farm

On-farm dam

On-farm pipe / canal

In-field irrigation system(Reinders, et al,2010)

Field work

IrrigationScheme

Bulk Conveyance

On-scheme distribution

On-scheme return flow

Irrigation system (application)

Irrigation management (Soil storage)

Breede River X X X XDzindi X XGamtoos X X XHartbeespoort X XHex River XKZN scheme X X X XLoskop X XNkwalini X XORWUA X X X X XSteenkoppies XVaalharts X X XWorcester East X

Irrigation schemes where field work took placeand system components were assessed

Gamtoos Irrigation Scheme

System component Inflow DestinationComponent Units of water Component Units of water

On-schemeconveyance system

Waterreleased fromstorage daminto canal

167 Evaporation from canalSeepage in canalLeakages in pipesUnlawful abstractionsOperational losses (unutilised)Return flows (unutilised)

NBCNRFNBCNBCNRFRF

210251684

On-farmconveyance system(from farm edge tofield edge)

Waterdelivered atthe farm edge

102 On-farm system leaks NRF 2

In-field applicationsystem (from fieldedge to root zone)– Centre pivot

Water appliedon the field

100 In-field evaporationTranspiration by cropIn-field deep percolationInterceptionRun-offChange in soil water content

BC/NBCBC

NRFNRFRFSC

5347330-6

Water balance – Gamtoos Irrigation Scheme

MEASURE

MODEL

EFFICIENCY GUIDELINES

We have to find ways of reducing the non-beneficial consumptive and non-recoverable fractions of water use within the areas that we control

How?

Optimising water use

Australian water use efficiency framework (Purcell and Currey, 2003)

• Applied at different levels

• During design AND

management

Implementing the water balance approach

Fundamental concepts: Lawful water use Water and energy

demand management Systems approach Water balance Appropriate technologies

Guidelines - Module 1

Efficient in-field irrigation systems are: Planned with available resources and the water

user in mind, Designed to apply water uniformly and with low

energy requirements, Consists of quality irrigation equipment, Operated according to specifications, Maintained according to recommendations, and Regularly evaluated for early problem detection

Guidelines - Module 2

Efficient on-farm conveyance systems are: Planned with capital and operating costs in mind, Designed to provide the most economical solution, Consists of quality irrigation equipment with high

energy efficiencies, Operated according to design specifications, Maintained according to recommendations, and Regularly evaluated for early problem detection

Guidelines - Module 3

Efficient irrigation schemes are ones where: All stakeholders have access to information regarding

water availability and quality, Water use is properly planned not to exceed

availability, Accurate and reliable measuring devices are

installed, O&M takes place according to specifications, A regularly updated WMP is in place supported by an

effective water use charging policy, and Regular evaluations for early problem detection take

place.

Guidelines - Module 4

In-field: More accurate scheduling Improved soil health Awareness of salt / nutrient movement

On-farm: Earlier detection of irrigation maintenance needs Optimised on-farm water use

On-scheme: Prioritisation of repairs and improvements to

infrastructure Improved scheme operation More fair and equitable water allocation

Benefits – through better understanding:

Irrigation system Losses Newdefault system efficiency (net to gross ratio)

(%)

Non-beneficial

spray evaporation

and wind drift (%)

In-field conveyance

losses (%)

Filter and minor losses

(%)

TotalLosses

(%)

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 83Traveling gun 15 5 2 22 78

Present design norms and the new default system efficiency values

Conclusion

South Africa is a semi-arid country where water is of critical strategic importance and has a potential limiting effect

on all future development in the country.

For efficient irrigation application we need to implement a water balance which require:

Standardised measurements

Accurate record keeping

Practical models

Effective implementation plans

Skilled persons