DEPARTMENT: WATER AFFAIRS AND FORESTRY Dam/5. Irrigation Planning Design... · REPORT NUMBER: P WMA 10/C31/00/0908 DEPARTMENT: WATER AFFAIRS AND FORESTRY Directorate: Options Analysis

REPORT NUMBER: P WMA 10/C31/00/0908

DEPARTMENT: WATER AFFAIRS AND FORESTRY

Directorate: Options Analysis

Lead Consultant: In association with:

JULY 2008 - Final

VAAL RIVER SYSTEM: FEASIBILITY STUDY FOR

UTILIZATION OF TAUNG DAM WATER

IRRIGATION PLANNING AND DESIGN

Feasibility Study for Utilisation of Taung Dam Water

PWMA 10/31/00/0908 Irrigation Planning and Design July 08

FEASIBILITY STUDY FOR UTILISATION OF TAUNG DAM WATER

MAIN REPORT

PHASE 3

Supporting Report 9

CONVEYANCE SYSTEM SCENARIOS AND

ECONOMIC ANALYSIS

P WMA 10/C31/00/1308

Supporting Report 10

REGIONAL AND NATIONAL ECONOMY

P WMA 10/C31/00/1408

Supporting Report 11

EIA AND PUBLIC PARTICIPATION

P WMA 10/C31/00/1508

PHASE 2

Supporting Report 8

EXISTING AND PROPOSED INFRASTRUCTURE

P WMA 10/C31/00/1208

PHASE 1

Supporting Report 5


P WMA 10/C31/00/0908

Supporting Report 6

WATER DEVELOPMENT AND SUPPLY PLANS

P WMA 10/C31/00/1008

Supporting Report 7

WATER QUALITY STATUS OVERVIEW AND

MODELLING

P WMA 10/C31/00/1108

Supporting Report 1

DEMOGRAPHICS

P WMA 10/C31/00/0508

Supporting Report 2

WATER DEMANDS AND USE

P WMA 10/C31/00/0608

Supporting Report 3

YIELD AND SYSTEM ANALYSES

P WMA 10/C31/00/0708

Supporting Report 4

GROUNDWATER RESOURCES OF NALEDI, TAUNG AND PHOKWANE

P WMA 10/C31/00/0808


PWMA 10/31/00/0908 Irrigation Planning and Design July 08

LIST OF REPORTS

REPORT NO DESCRIPTION REPORT NAME

P WMA 10/C31/00/0408 Main Feasibility Report FEASIBILITY STUDY FOR UTILIZATION OF TAUNG DAM WATER: MAIN REPORT

P WMA 10/C31/00/0508 Supporting Report 1 DEMOGRAPHICS

P WMA 10/C31/00/0608 Supporting Report 2 WATER DEMANDS AND USE

P WMA 10/C31/00/0708 Supporting Report 3 YIELD AND SYSTEM ANALYSES

P WMA 10/C31/00/0808 Supporting Report 4 GROUNDWATER RESOURCES

P WMA 10/C31/00/0908 Supporting Report 5 IRRIGATION PLANNING AND DESIGN

P WMA 10/000/00/1008 Supporting Report 6 WATER DEVELOPMENT AND SUPPLY PLANS

P WMA 10/C31/00/1108 Supporting Report 7 WATER QUALITY STATUS OVERVIEW AND MODELLING

P WMA 10/C31/00/1208 Supporting Report 8 EXISTING AND PROPOSED INFRASTRUCTURE

P WMA 10/C31/00/1308 Supporting Report 9 CONVEYANCE SYSTEM SCENARIOS AND ECONOMIC ANALYSIS

P WMA 10/C31/00/1408 Supporting Report 10 REGIONAL AND NATIONAL ECONOMY

P WMA 10/C31/00/1508 Supporting Report 11 EIA AND PUBLIC PARTICIPATION

REFERENCE

This report is to be referred to in bibliographies as:

Department: Water Affairs and Forestry, South Africa, 2007. Feasibility Study for Utilisation of Taung Dam Water: Irrigation Planning and Design: prepared by Golder Associates.

Report No.: P WMA 10/C31/00/0908

Project No.: WP8950 Project File: 14/2/C300/2/2

Feasibility Study for Utilisation of Taung Dam Water (i)

PWMA 10/C31/00/0908 Irrigation Planning and Design July 08

EXECUTIVE SUMMARY

The Taung area has a high agricultural potential, restricted primarily by limited and erratic rainfall.

In the absence of irrigation, some subsistence agriculture is taking place and livestock such as

goats are kept. Communal land ownership does result in over grazing, exacerbated by the

absence of a camping program and fencing.

At present 3 764 Ha are developed for irrigation with 411 farmers. Centre pivots take 2 756 Ha

and sprinklers 1 008 Ha. No surface irrigation is practiced (cf Vaal Harts).

In order to ascertain the potential for expansion, a reconnaissance level survey of areas outside of

the present irrigated lands was undertaken. The survey looked at land potential and also

considered climate and possible crops. In general, the 1:50 000 topographic series mapping was

used as a base map. No existing detailed level soil maps of these areas could be found.

It was found that 3 315 Ha of land were probably acceptable for irrigation development. Eight

separate sites were identified, and arbitrarily named sites 1-8, from north to south (see

Annexure A).

The cropping potential of Taung was considered in respect of soils, land capability and climate.

Existing irrigated cropping patterns were examined and constraints to yield and crop choice were

noted.

A number of crops were short listed for further consideration – based on the inherent agricultural

potential and the choices of the local Department of Agriculture’s staff and the existing farmers.

Water requirements for these crops were then calculated and are shown in Table 3 in the main

body of the report. Table 4 considers the water requirements for two commonly practised crop

rotations, maize-barley – which produces good returns, and lucerne. Lucerne has a very high

potential in the area, and good results have been achieved both at Taung and Vaal Harts.

In order to quantify the amount of water that an expansion of 1 750 Ha would entail, a series of

calculations were undertaken for a maize/barley rotation as well as for perennial lucerne, in terms

of the three possible irrigation methods. System specific efficiencies were used.

These figures, derived from the SAPWAT computer program, gave what can be described as the

‘ideal’ situation, where water is supplied to meet the theoretical crop water demand. However, the

Taung Irrigation Scheme gets its water from the Vaalharts canal system – the conveyance capacity

of which is based on an allocation of 8 417 m³ per hectare per annum. The difference between the

Feasibility Study for Utilisation of Taung Dam Water (ii)


ideal practice and the existing practice is in the order of 56% (i.e. the existing is 56% of the

theoretical requirements).

It was understood that under the water scarce conditions of the Taung area, water use efficiency

was an important aspect. However, also important was the operating costs of the irrigation

systems and the technology employed. Although border strip irrigation was seen to be the least

water efficient of the systems considered (65% as opposed to 75% for sprinkler and 80% for pivot),

it had been shown at Taung that the small farmers have been crippled by high pumping costs

(sprinkler and pivot).

Furthermore, the existing pivot irrigators and pump stations are in a bad state of repair, indicating

that the technologies employed were probably unreasonably complex for most of the small

farmers. It was considered that over-irrigation under border strip irrigation would also help leach

salts from the soil.

For all irrigation types, however, it was felt important that subsurface drains be installed

simultaneously with the irrigation development. This would ensure that the water table is controlled

from the beginning and salinisation is prevented.

A recurrent theme as emphasised to the consultants during their site visit was the expectation of

the “expansion” of Taung Irrigation Scheme. The Department of Agriculture officials and the

community have been anticipating for some time, the expansion of Taung Irrigation Scheme to

cater for persons excluded from the redesign activities in the late 1970’s. During that period the

existing flood irrigation scheme was converted into a centre pivot scheme, with the subsequent

exclusion of 175 persons. Apparently these persons, and in some cases their relatives or

descendants, have been ‘waiting’ all along for restitution. As the re-constituted flood scheme was

designed on the basis of 10 Ha per person, the expectations are for similar areas to be their

allocation if, and when, expansion is effected. This would be a total of 1 750 Ha. The local people

considered in the past that the Taung Dam would be the source of water for this expansion.

This irrigation study therefore assumes that water will eventually be supplied to the 175 farmers for

their 1 750 ha via the standard Taung scheduled rate of 8 417 m³ per hectare, or 14 729 750 m³ in

total.

A further concern expressed during consultations was that of “dry weeks”, a term coined by the

existing farmers for periods when no water reaches them – it being fully abstracted by upstream

Vaal Harts farmers. This is mentioned here in view of the allocation pressures pertaining to Taung

Dam water.

Power costs have been cited as crippling to some farmers.

Feasibility Study for Utilisation of Taung Dam Water (iii)


The study has revealed that Taung Dam would probably be fully subscribed in the provision of

domestic and other primary water users. It has also revealed that additional water is still available

for Taung Irrigation Scheme expansion, also via the Vaalharts main canal and balancing dams.

A request was made, however, to investigate an alternative area to the South East of Taung (Ba-

Ga-Maida) where, using Taung Dam water, irrigation under gravity might be possible. A soil

survey of the Ba-Ga-Maida area had shown 6568ha to be irrigable. This area did not form part of

the Vaalharts or Taung Irrigation Schemes and had no current water allocation from the Vaalharts

Irrigation Scheme.

The capital cost to provide irrigation to this area was subsequently calculated so as to formulate an

opinion as to whether it would be financially viable to implement (should water from the Taung

Dam be available). Six scenarios in respect of water delivery system were investigated.

The total irrigation development costs were found to range between R151,494 and R256,000 per

ha (including bulk and infield infrastructure costs) depending on the scenario. If these amounts

were amortised over a 20 year period with an interest rate of 12% per annum the annual cost

would be R21,000 to R34,000 per ha respectively. Even in respect of high value crops these costs

are economically not viable.

A financial analysis was undertaken on the selected enterprises and on the different irrigation types

proposed. The selected enterprises included:

• Maize

• Barley (in rotation with maize)

• Lucerne

A production programme for the selected enterprises was compiled. From these production

programmes gross margins for the selected enterprise were estimated. Gross margins represent

income from the sale of the crop less all direct costs that can be allocated to the production of the

specific enterprise. The main assumptions for the gross margins are as follows:

Different farmer models have been compiled for the selected rotations for the different irrigation

models. The main cost driver from the irrigation types has been taken from Table 6 included in

Section 5. The areas that can be cropped for each enterprise, assuming optimum irrigation

requirements are also taken from Table 6. The tables below give a summary of the farmer

models.

Feasibility Study for Utilisation of Taung Dam Water (iv)


Farmer Models for Different Irrigation Types for Lucerne

Centre Pivot (4.5 ha cropped)

Sprinkler (4.2 ha cropped)

Border Strip (3.6 ha cropped)

Gross Income 93 960 87 696 75 168

Production Costs 46 370 45 445 31 415

Gross Margin 47 590 42 251 43 753

Overhead Costs 31 476 31 476 31 476

Net Income 16 114 10 775 12 277

Capital Costs 120 000 100 000 80 000

IRR 14.25% 10.15% 17.25%

Farmer Models for Different Irrigation Types for a Maize Barley Rotation

Centre Pivot (4.5 ha cropped)

Sprinkler (4.2 ha cropped)

Border Strip (3.6 ha cropped)

Gross Income 121 815 113 694 97 452


Gross Margin 39 547 34 685 37 470

Overhead Costs 31 476 31 476 31 476

Net Income 8 071 3 209 5 994

Capital Costs 120 000 100 000 80 000

IRR 3.37% -4.25% 4.75%

An internal rate of return for each farmer model was estimated so that the models can be

compared with each other on a financial basis.

It should be noted that these are real returns and exclude inflation. A real return of under 5%

would be considered unviable, between 5 – 10% marginal and above 10% would be considered

viable depending on the risk factor, i.e. the higher the risk, the higher the rate of return. A typical

irrigation scheme would require between 10 – 12% IRR (at least) depending on assumptions (i.e.

costs) included in the financial model.

As a result of the higher capital and pumping costs centre pivot and sprinkler irrigation are less

viable than border strip irrigation. Border strip irrigation is more viable even if it is on a smaller

area. In terms of water use efficiency this is taken into account in financial terms as the model

assumes that 10 Ha is costed (water tariff), however only 3.6 Ha is cropped.

Feasibility Study for Utilisation of Taung Dam Water (v)


In terms of enterprises, lucerne is more viable than the maize/barley rotation however it is more

capital intensive. For resource poor farmers the maize barley rotation may be more affordable. It

should be noted that maize grown on its own is not a viable option.

Feasibility Study for Utilisation of Taung Dam Water (vi)



Table of Contents PAGE

EXECUTIVE SUMMARY ................................................................................................................. (i)

1. INTRODUCTION................................................................................................................ 1.1

2. AGRICULTURAL POTENTIAL ......................................................................................... 2.1

2.1. GENERAL.......................................................................................................................................... 2.1

2.2. RECONNAISSANCE LEVEL SURVEY............................................................................................. 2.1

2.3. CROPPING........................................................................................................................................ 2.3

2.4 WATER CONSUMPTION.................................................................................................................. 2.6

3. LAND ISSUES ................................................................................................................... 3.1

4. PLANNING AND DESIGN ................................................................................................. 4.1

4.1. WATER AVAILABILITY ..................................................................................................................... 4.3

5. COSTING ........................................................................................................................... 5.1

6. FINANCIAL ANALYSIS..................................................................................................... 6.1

6.1. GROSS MARGINS ............................................................................................................................ 6.1

6.2. FARMER MODEL.............................................................................................................................. 6.2

7. CONCLUSION ................................................................................................................... 7.1

Feasibility Study for Utilisation of Taung Dam Water (vii)


TABLES Table 1 : Consideration of Available Land In Respect Of Irrigation Potential

Table 2 : Crops Selected

Table 3 : Crop Factors And Water Requirements For Range Of Possible Crop Types For Taung (Rainfall Not Allowed For)

Table 4 : Water Requirements For Two Cropping Scenarios

Table 5 : Block And Plot Areas Adjusted For Application Of Scheduled Water Amounts And With Irrigation At Peak Theoretical Demand

Table 6 : Taung Small Farmer Irrigation Plot Operating Costs

Table 7 : Summary Gross Margin For Selected Enterprise

Table 8 : Farmer Models For Different Irrigation Types For Lucerne

Table 9 : Farmer Models For Different Irrigation Types For A Maize Barley Rotation

Feasibility Study for Utilisation of Taung Dam Water (viii)


ANNEXURES

Annexure A Map of potential irrigable areas

Annexure B Eight potential areas showing different irrigation system layouts

Annexure C Standard 10 Ha irrigation units possible for Taung

Annexure D Suggested layouts for the irrigation systems on the 8 blocks of land

Annexure E Soil analysis results

Annexure F Gross Margins

Feasibility Study for Utilisation of Taung Dam Water 1.1


1. INTRODUCTION

This report covers Task 5: Irrigation, under Phase 1: Determination of Dam Yield and

Water Demand.

Currently the Taung Dam water resource is not utilised at all, and simply impounds

some of the flow of the Harts River, providing a large surface area from which water is

lost to the atmosphere by evaporation. The main aim of Task 5 was to determine

whether opening up new irrigation areas in Taung Irrigation Scheme using water from

Taung Dam will be economical and sustainable. The modern approach to

sustainability considers whether social, economic and environmental components are

sufficiently balanced to ensure long-term viability. If any of these components are

under pressure then the planned development is unlikely to succeed in the long-term.

From an environmental perspective, parts of the neighbouring Vaalharts Irrigation

scheme are severely salinised, and care needs to be taken to ensure that any new

irrigation areas in Taung Scheme have sufficient drainage and leaching water flows to

maintain crop productivity. The National Department of Agriculture has embarked on a

strategy to improve the network of drains to enable leaching of the salts in both

Vaalharts Irrigation Scheme and the existing area under irrigation in the Taung

Irrigation Scheme. The additional water required for leaching of salts down to an

acceptable salinity level will also increase pressure on the total water demand for the

Taung Scheme basic natural resource scoping.

The Taung area was examined in respect of its natural resources – particularly

regarding the potential agricultural usage of Taung Dam water. This included survey of

lands available and the cropping potential. The Taung Dam, which is the expected

source of water, was visited. The existing water source (Vaal Harts North Canal) and

the existing canals and associated infrastructure were inspected. Data in respect of

climate was obtained and calculations made in respect of cropping potential. Some

soils were sampled for nutrient status and texture from Site 2 and 4a (see

Annexure E). Soil fertility recommendations were done for irrigated lucerne, maize

and tomato. Site 4a is approximately central to the proposed new irrigated areas. The

sampling was intended to gain an understanding of the chemical and physical status of

‘typical’ Taung soils. It must be emphasised that a comprehensive soil survey has not

been undertaken. Should the irrigation development/expansion, or some part of it be

given the go-ahead, then a detailed soil survey should be carried out of the probable

irrigable areas.



The soil samples taken in Site 4a were analysed for particle sizes within the clay, fine

silt and coarse silt and sand classes. The results indicate sandy clay loam soils of

800 mm depth. Clay contents increased from 21 % in the 0 – 250mm layer to 33 % in

the 500–800mm layer, with coarse silt and sand fractions of 71 and 57 %, respectively.

These sandy clay loam soils are unlikely to present drainage limitations within the 0 –

800mm layer, which is considered an adequate rooting depth for most field crops.

With irrigation, the Taung scheme should be capable of matching the high unit

agricultural output of the adjacent Vaalharts Irrigation scheme. The climate is suitable

for a variety of crops, such as maize, barley, sunflower, cotton, groundnut and lucerne,

and orchard crops such as olives, grapes, citrus and pecan do well.



2. AGRICULTURAL POTENTIAL

2.1. General

The Taung area has a high agricultural potential, restricted primarily by limited and

erratic rainfall. In the absence of irrigation, some subsistence agriculture is taking place

and livestock such as goats are kept. Communal land ownership does result in over

grazing, exacerbated by the absence of a camping program and fencing.

At present 3 764 Ha are developed for irrigation with 411 farmers. Centre pivots take

2 756 Ha and sprinklers 1 008 Ha. No surface irrigation is practiced (cf Vaal Harts).

The choice for installing centre pivots was made in the late 1970’s (under Agricor).

The objective was an attempt to militate against the rising water tables in the existing

surface irrigation scheme. It was felt that the greater application efficiency of pivots

over flood irrigation would minimise losses to deep percolation, so controlling and

eventually lowering the water table.

However, it has been shown over the years that the water table has not receded and in

most cases has continued to rise (local communication), albeit at a slower rate.

The results under pivots are mixed, with some excellent cropping occurring under

some pivots, and no cropping evident under others. In some circumstances the pivots

are standing – unserviceable and not in use.

The problems associated with the existing scheme vary from land ownership problems

to vandalism.

2.2. Reconnaissance Level Survey

In order to ascertain the potential for expansion, a reconnaissance level survey of

areas outside of the present irrigated lands was undertaken. The survey looked at land

potential and also considered climate and possible crops. In general, the 1:50 000

topographic series mapping was used as a base map. No existing detailed level soil

maps of these areas could be found.

Factors such as land slope, texture, stoniness, wetness, flooding potential, soil-depth

and erosion hazard were considered. This site analysis was augmented by

examination of 1:10 000 ortho-photos. Satellite imagery was used to identify

potentially wet areas.



All the land examined was first indicated to the consultants as being available for

development by the Extension Staff and the Tribal Authority.

It was found that 3 315 Ha of land were probably acceptable for irrigation development.

Eight separate sites were identified, and arbitrarily named sites 1-8, from north to south

(see Annexure A).

Table 1 shows the identified land together with positive and negative aspects of each:

Table 1: Consideration of Available Land in Respect of Irrigation Potential

Area #

Gross Area Ha

Positive Aspects Negative Aspects 1st Choice Ha

2nd Choice Ha

1 300 Medium to good quality land Greatest distance from source

300

2 442 Good quality land Some distance from source

442

3 73 Elongated and follows canal closely

High elevation – above existing canal

73

4 221 In command of dam 7; good quality land

Divided into relatively small blocks

221

5 488 Low elevation; below dam 7 Medium quality land; possible minor drainage problem

488

6 534 Low elevation Medium quality land; possible drainage problem

534

7 766 Below existing canal; medium to good quality land

Slightly steep (1:400) 766

8 491 Low elevation; below dam 6 Medium quality land; possible drainage problem

491

3315 1917 1398

3315

It must be emphasised, however, that before any detailed planning takes place, a

detailed soil survey should be carried out on these identified ‘potential’ areas, so as to

confirm the reconnaissance work.

The particle size analysis for the soil samples taken at Site 4 a (discussed under

Section 1 and presented in Annexure E) indicates sand clay loam soils to 800mm

depth. These sandy clay loam soils have adequate rooting depth for most agronomic

crops and are unlikely to present drainage limitations, making them suitable for

irrigated crop production.



The possible irrigable land was mapped (Annexure A) with 1:50 000 topographic

maps as base.

2.3. Cropping

The cropping potential of Taung was considered in respect of soils, land capability and

climate. Existing irrigated cropping patterns were examined and constraints to yield

and crop choice were noted.

A number of crops were short listed for further consideration – based on the inherent

agricultural potential and the choices of the local Department of Agriculture’s staff and

the existing farmers.

Table 2: Crops Selected

Crop Season Reason for Inclusion

Barley Winter Grown on contract with South African Maltsters (SAM)

Lucerne All year Widely grown, markets with feedlots/dairies, ideal climate for cutting and baling

Tomato Summer Popular on local market in Taung

Onion Winter Popular on local market in Taung

Pumpkin Summer Popular on local market and low-tech storage required (in open)

Maize Summer Grown on contract with South African Maltsters (SAM)

Potato Autumn Popular on local market in Taung

Groundnut Summer Market through Groundnut International (GNI)

Sunflower Summer Good market for oil pressing, good for nutrient cycling being deep rooted

Cabbage Winter Popular on local market in Taung

Water requirements for these crops were then calculated. The water requirements for

these crops are shown in Table 3. Table 4 considers the water requirements for two

commonly practised crop rotations, maize-barley – which produces good returns, and

lucerne. Lucerne has a very high potential in the area, and good results have been

achieved both at Taung and Vaal Harts.



Table 3: Crop Factors and Water Requirements for Range of Possible Crop Types for Taung (Rainfall Not Allowed For)

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total

Days 31 28 31 30 31 30 31 31 30 31 30 31 Water Reqs

Ref Et 7.00 5.90 4.90 3.90 3.00 2.60 2.80 3.80 5.10 5.90 7.00 7.40 (mm/annum)

Barley 0.55 0.77 1.11 1.10 0.66

43 67 131 168 121 530

Lucerne 0.85 0.85 0.85 0.81 0.71 0.66 0.66 0.69 0.76 0.82 0.85 0.85

184 140 129 95 66 51 57 81 116 150 179 195 1445

Tomato 1.09 1.09 0.20 0.59 0.77 0.97 1.09

237 180 30 90 141 204 250 1132

Onion 0.42 0.45 0.71 0.86 0.83 0.72 0.15

64 53 66 67 72 85 23 429

Pumpkin 0.68 0.27 0.58 0.74 0.88 0.84

148 45 89 135 185 193 794

Maize 0.93 0.46 0.40 0.76 1.14 1.14

202 76 61 139 239 262 979

Potato 0.47 0.94 1.09 1.05

71 110 101 82 365

Groundnut 1.14 0.79 0.66 0.39 0.60 1.03

247 131 100 71 126 236 912

Sunflower 1.10 0.55 0.20 0.38 0.91

239 91 30 80 209 648

Cabbage 0.54 0.86 0.99 0.96

82 101 92 75 350

Crop Factor

0.55 Part month - planting/harvesting

0.71 Full month



Table 4: Water Requirements for Two Cropping Scenarios

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Days 31 28 31 30 31 30 31 31 30 31 30 31 365

Rainfall mm/Month 66 72 55 19 4 25 50 49 340

Reference Et mm/Day 7.00 5.90 4.90 3.90 3.00 2.60 2.80 3.80 5.10 5.90 7.00 7.40

Maize Barley Rotation

Maize Cf 0.93 0.46 0.40 0.76 1.14 1.14

201.8 76.0 0.0 0.0 0.0 0.0 0.0 0.0 61.2 139.0 239.4 261.5 979 mm

Barley Cf 0.55 0.77 1.11 1.10 0.66

0.0 0.0 0.0 0.0 0.0 42.9 66.8 130.8 168.3 120.7 0.0 0.0 530 mm

Summer & Winter Total 201.8 76.0 0.0 0.0 0.0 42.9 66.8 130.8 229.5 259.7 239.4 261.5 1,508 mm

Lucerne (Perennial)

Lucerne Cf 0.85 0.85 0.85 0.81 0.71 0.66 0.66 0.69 0.76 0.82 0.85 0.85

Total 184.5 140.4 129.1 94.8 66.0 51.5 57.3 81.3 116.3 150.0 178.5 195.0 1.445 mm

In the revised planning of Taung Irrigation Expansion – with water supply being based

on the existing fixed water quota, the ‘demand’ side of the water balance has, as a

consequence, also been affected.

A basic assumption of the revised water allocation change (from ‘theoretical maximum’

to ‘basic quota’) was that a smaller area would be grown (irrigated) under the reduced

allocation. This assumption acknowledged that the economics of the farming

operations would continue to be analysed in terms of cropping performance being at

maximum potential (full irrigation). This was similar to the previous analysis where

water was ‘not limited’.

However, it is most probable that farmers would grow a greater area than that dictated

by the ‘high-potential minimum’. The allocated farm area of 10 Ha might not be fully

planted, but it might be greater than the reduced ‘maximum potential’ area of, say,

4 Ha.

Where the extent of the irrigated area is not known, water demand calculations

become problematic and can be misleading. The assumption has therefore been

adopted that supply (fixed) and demand volumes are the same, (at least for this

exercise where water and not land is limiting).



Rainfall does not easily fit into this assumption, and it would be unlikely that farmers

would plan to alter their ‘fully irrigated’ area on the possibility of rain.

Furthermore, with irrigation in a semi arid area (only 250 mm effective rainfall) and with

high variability – both spatially and temporally, the addition of rainfall would not serve

to increase accuracy of planning.

Basically therefore, with or without rainfall the same water demand will apply

(equivalent to quota) and the area allocated to full irrigation will also be unchanged.

Thus the supply infrastructure will be unaffected by the addition of rainfall, and the core

economic calculations of returns per fully irrigated unit of land will also be unaffected.

Rainfall has therefore been excluded from the water demand calculations in respect of

the revised planning based on water quotas.

The only effect that rainfall will have for the farmer will be for him to increase his overall

planted area in summer (with the attendant risk). For the water supply authority, the

rainfall effect would be to allow cut-back on rotational streams during the rainy period,

but the farmer would require his total balance to be made up over the longer term.

Infrastructure design would be based on peak demand and would not include rainfall.

2.4. Water Consumption

In order to quantify the amount of water that an expansion of 1 750 Ha would entail, a

series of calculations were undertaken for a maize/barley rotation as well as for

perennial lucerne – in terms of the three possible irrigation methods. System specific

efficiencies were used.

These figures, derived from the SAPWAT computer program, gave what can be

described as the ‘ideal’ situation, where water is supplied to meet the theoretical crop

water demand. However, the Taung Irrigation Scheme gets its water from the

Vaalharts canal system – the conveyance capacity of which is based on an allocation

of 8 417 m³ per hectare per annum. The difference between the ideal practice and the

existing practice is in the order of 56% (i.e. the existing is 56% of the theoretical

requirements).

The calculations carried out for the irrigation water requirements for Taung expansion

had then to take into account the differences between the theoretical crop water

requirement and the scheduled water.



The following assumptions were made:

• The theoretical demand for lucerne is 14 450m³/ha/annum and for maize/barley

rotation, 15 080 m³/ha/annum

• Only 8 417 m³/ha is available (55% and 58% of requirement respectively)

• The scheduled amount is a gross figure – requiring that efficiency losses are

subtracted from it - as applicable to each irrigation method. The net irrigation

figure will be substantially less than the gross scheduled figure. It is assumed,

however, that the scheduled amount is a ‘field edge’ figure, and that all

conveyance losses have been subtracted. This has therefore been excluded

from our calculations.

• The total water available to the expansion will be based on the 175 farmers each

with 10 Ha of land; therefore the total scheduled volume for Taung expansion is

14 729 750 m³.

• As the supply will be less than the demand in respect of the 10 Ha of irrigation,

the farmer will have the choice of using the lesser amount over his full 10 Ha, or

to apply the theoretical amount over a smaller area. However, water will still be

supplied at the required rate and will in the end comprise the scheduled amount

of 84 170 m³ per 10 Ha farm.

• The calculations to accommodate the use of scheduled irrigation water have used

reduced area (within each 10ha farm) as the variable leaving the scheduled

volumes and theoretical demands unaltered.

• Slightly improved irrigation efficiencies are used as it is assumed that a greater

care will be taken of the lower applications – and wastage will be limited.

• Effective rainfall has not been included in the water requirement calculations as

with the partially covered lands it is difficult to calculate. It also will not affect the

total water supplied as per schedule – unless surplus rainfalls are experienced

over the seasons. However, rainfall will certainly assist the farmers with possible

crop production increases if the full areas are planted.

As it is impossible to accurately calculate the economic returns on a farm using both

variable water applications and variable planted areas - the attached economic

analysis has been carried out as follows:

• Each farm is analysed on the basis of using the theoretical peak production

amounts of water per hectare.



• The possible area to be planted under the circumstance of water curtailment has

been calculated, and has been used for each farm under the various irrigation

types. (See tables).

• The farmer may risk planting a greater area (with perhaps a lower yield), but this

has not been included in the calculations.

Five tables in Annexure B show monthly water requirements for three irrigation

systems and for two crop rotations and have been adjusted to take cognisance of the

scheduled irrigation amounts.

The tables also show the calculations carried out to determine the maximum amount of

land area that could be cropped and irrigated on a 10 Ha farm using the total crop

water requirement as calculated in the previous section, but restricted to the scheduled

amount for the full 10 Ha allocation. The various irrigation efficiencies have also been

taken into account.



Table 5 below quantifies the land that can be irrigated under the two proposed

cropping systems and in terms of the three irrigation systems.

Table 5: Block and Plot Areas Adjusted for Application of Scheduled Water Amounts and with Irrigation at Peak Theoretical Demand

Surface Sprinkler Pivot

Block # Net

Irrigated Area

Irrigated Areas

Ha/Plot #

Net Irrigated Area Ha

Irrigated Areas

Ha/Plot #

Net Irrigated Area Ha

Irrigated Areas

Ha/Plot #

Reg. Volume

Per Block (10³m³)

1 0 0 0 0 0 0 0

2 106 3.6 122 4.2 130 4.5 2,450

3 0 0.0 0 0.0 0 0.0 0

4 51 3.6 59 4.2 63 4.5 1,183

5 131 3.6 151 4.2 161 4.5 3,041

6 120 3.6 139 4.2 148 4.5 2,788

7 182 3.6 210 4.2 224 4.5 4,224

8 47 3.6 55 4.2 58 4.5 1,098

Maize/Barley

Total 637 3.6 735 4.2 784 4.5 14,783

1 0 0 0 0 0 0 0

2 106 3.6 122 4.2 130 4.5 2,346

3 0 0.0 0 0.0 0 0.0 0

4 51 3.6 59 4.2 63 4.5 1,133

5 131 3.6 151 4.2 161 4.5 2,912

6 120 3.6 139 4.2 148 4.5 2,670

7 182 3.6 210 4.2 224 4.5 4,045

8 47 3.6 55 4.2 58 4.5 1,052

Lucerne

Total 637 3.6 735 4.2 784 4.5 14,157

NOTE: The net irrigated area has been adjusted to reflect the difference between the scheduled water allocated per hectare and the water requirement calculated using SAPWAT.



3. LAND ISSUES

The recurrent theme as emphasised to the consultants during their site visit was the

expectation of the “expansion” of Taung Irrigation Scheme. The Department of

Agriculture officials and the community have been anticipating for some time, the

expansion of Taung Irrigation Scheme to cater for persons excluded from the redesign

activities in the late 1970’s. During that period the existing flood irrigation scheme was

converted into a centre pivot scheme, with the subsequent exclusion of 175 persons.

Apparently these persons, and in some cases their relatives or descendants, have

been ‘waiting’ all along for restitution. As the re-constituted flood scheme was designed

on the basis of 10 Ha per person, the expectations are for similar areas to be their

allocation if, and when, expansion is effected. This would be a total of 1 750 Ha. The

local people considered in the past that the Taung Dam would be the source of water

for this expansion

Thus it was the point of departure for the consultants to survey the surrounding tribal

areas to determine whether or not irrigable lands of this scale existed.

Another concern expressed during consultations was that of “dry weeks”, a term

coined by the existing farmers for periods when no water reaches them – it being fully

abstracted by upstream Vaal Harts farmers. This is mentioned here in view of the

allocation pressures pertaining to Taung Dam water.

The choice of centre pivots by Agricor for the re-formatting of Taung may not have

been appropriate in the first place, as the pivots have to be shared by the farmers in

order to make up the required number of allotments. Each farmer has 10 Ha under

irrigation – with, for example, four farmers working the 40 Ha pivots and two farmers

the 20 Ha machines. This shared farming approach causes problems in respect of

operating costs, cropping programs and harvesting.

Power costs have been cited as crippling to some farmers. In other cases, only part of

the circle is cropped, one or more of the farmers skipping a crop on their portion. In

many cases, the farmers hire out their land and pivot irrigator to non-resident

commercial farmers, mainly from the Vaalharts scheme. This results in ‘tenant

agriculture’, with the associated minimal interest of the lessee in the conservation of

the land resource. The owners usually pay for electricity and water; the tenant sharing

the returns on the crops produced. This practice does not encourage local farmers to

embrace the role and responsibilities of commercial agriculture.



4. PLANNING AND DESIGN

Three possible methods of irrigation were considered, namely:

• Centre Pivot

• Sprinkler

• Surface – border strip

These three methods were looked at primarily for the following reasons:

1. They are currently in use at Taung (familiar to the local farmers)

2. The centre pivots are at present the system of choice (ease of operation)

3. Border strip has been successful in the past – and it uses the least energy

Typical layouts of these three systems are shown in Annexure C.

Each method was examined from the aspects of water use efficiency, capital cost,

operating cost, ease of maintenance, labour requirement and local experience.

It was considered important to examine carefully any recommendation for future

developments in the light of prevailing constraints – as outlined above.

For all irrigation types considered, it was felt important that subsurface drains be

installed simultaneously with the irrigation development. This would ensure that the

water table is controlled from the beginning and salinisation is prevented.

Some comments on the three possible irrigation methods follow:

Centre pivot

This is the dominant system that exists at Taung at present. Most farmers appear to

be satisfied with this system, but there are a number of drawbacks. Pivots have a

relatively high capital cost, and their operating costs, with respect to electricity are also

high.

They are subject to wind drift and runoff at the ends, where high precipitation rates

occur. There is a problem at present with maintenance, with the Department of



Agriculture being committed to meeting these costs. Future developments would have

to carefully examine the support interventions.

They do benefit from labour saving, and this is probably the main reason for their

appeal. If well managed, they have good application efficiency.

When considering centre pivot design, the ‘nesting’ of the circles was problematic – as

is often the case - with considerable land being occluded at the ‘corners’. In order to

make up the 1 750 Ha, some land unsuitable for pivots (180 Ha) was included in the

total – blocks 3 and 4 in this case.

Where irrigated areas of less than ten hectares are planted – due to the scheduling

restrictions, the farmers will have to plan with their pivot partners how water will be

distributed. E.g. the two farmers could plant their reduced hectarages side by side –

reducing the ‘dead’ area that the pivot will have to travel.

Border strip irrigation

The installation of sub surface drains would permit a return to surface irrigation

systems – which pre-dated the existing centre pivots. Border strip irrigation would be

the best option as it can be used to irrigate most of the existing and favoured crops.

Border strip is practised widely at Vaal Harts. This system reduces the operating costs

of irrigation – principally electricity, which was cited as a major cause of failure

amongst the farmers. It is the least expensive to implement, but does require more

labour than the other systems. However, with the high unemployment levels in the

area, this might be a positive factor. Efficiency losses are a concern, with well

managed systems operating at about 70% efficient and about 60% efficient under less

able management. Most water is lost to either deep percolation or run-off at the end of

the run. Good design will minimise unnecessary losses. Deep percolation can,

however, be useful in reducing salt build-up – where sub-surface drains are installed -

and can be considered to have a positive role in those circumstances.

Sprinkler Irrigation

There is a limited area under sprinkler at Taung at present. The main disadvantage

with sprinklers is the necessity to move the sprinklers to new positions on a regular

basis. This requires labour and supervision. Whilst the sprinkler moves may be carried

out by family members, this is a tedious operation, and it is usual to buy in labour –

which will be a cost to the small farmer. Apart from the moving of pipes/sprinklers,



there is an energy requirement which constitutes a further disadvantage to the small

farmer. It also suffers poor efficiency in windy conditions.

The suggested layouts of the various irrigation systems are shown in Annexure D. It

should be noted that the 10 Ha sprinkler and border strip blocks have the same

dimensions (500 x 200m) so only border strip blocks are shown – together with centre

pivots. The layouts demonstrate the difficulty of fitting the pivot circles into the same

areas of land that the rectangular border strip and sprinkler blocks occupy.

Drip irrigation was not considered owing to its high capital cost (+/-R 25 000/Ha) and

the complexity of the system – requiring a high level of management and/or

supervisory input.

4.1. Water Availability

The study has revealed that Taung Dam would be fully subscribed in the provision of

domestic and other primary water users. The study has also revealed that additional

water is available for Taung Irrigation Scheme expansion - it also being sourced via the

Vaalharts main canal and balancing dams.

This irrigation study therefore assumes that water will eventually be supplied to the

175 farmers for their 1 750 Ha via Vaalharts at the scheduled rate of 8 417 m³ per

hectare, or 14 729 750 m³ in total.

The type of irrigation employed would depend largely on the factors previously

mentioned – including capital cost, operating cost, ease of use, and efficiency

potential.



5. COSTING

The operating costs of the three irrigation systems were calculated. These are shown

below. It should be noted that sprinkler has the highest costs in terms of Rand per

millimetre applied, and border strip the highest water duty requirement.

With respect to capital costs, the cost per hectare for centre pivot is about R12 000 and

sprinkler about R10 000. Border strip will rely on careful land levelling using laser

guided equipment, costs depending on the state of the land at present. Ridge forming

will be a further minor cost. A total cost per hectare of about R8 000 can be expected

for border strip.

Table 6: Taung Small Farmer Irrigation Plot Operating Costs

Irrigation System

Area (ha)

Maximum Water Duty

(24h) (I/sec/ha)

Maximum Water Duty (10h)

(I/sec/ha)

Flow required at field edge

(I/sec)

Annual Power

Requirement (kWh)

Cost of Irrigation (R/ha/an)

Cost of Irrigation (R/mm)

No. Man-days

Per ha Per

Annum (#)

(maize/barley)

Centre Pivot

4.5 0.98 8 13,038 1,922 1.04 280

(Per Farmer)

4 6,519 1,922 1.04 140

Sprinkler 4.2 0.98 4 15,583 2,265 1.38 280

Border Strip

3.6 0.98 1.96 20 0 1.172 0.59 280

Notes:

The centre pivots are costed as a single 20 Ha machine. However, each unit will accommodate two farmers of 10 Ha each.

Assumptions

1000m of mainline at friction losses of 1m/100m. 3m static head from pump station to fields (pivot extra 2m).

Cost of water 5c/m³ Cost of electricity 33c/kWh

All border strip lands are under command of a secondary canal.



6. FINANCIAL ANALYSIS

Given the above information a financial analysis was undertaken on the selected

enterprises and on the different irrigation types proposed. The selected enterprises

include:

• Maize

• Barley (in rotation with maize)

• Lucerne

6.1. Gross Margins

A production programme for the selected enterprises was compiled. From these

production programmes gross margins for the selected enterprise were estimated.

Gross margins represent income from the sale of the crop less all direct costs that

can be allocated to the production of the specific enterprise. The main assumptions

for the gross margins are as follows:

• The gross margins are based on an average farmer in the area and attempt to

be representative of a typical farming operation in the region. However in

reality, there is a wide range of expertise and experience in farming which

results in a wide variation in actual income and costs of enterprises.

• Gross income is based on representative yields and a long-term price projection

for the enterprise.

• The gross margin costs include:

- input costs such as seed, chemicals and fertilizer,

- contract mechanical operations such as ploughing and spraying,

- all directly allocated labour costs

- transport costs,

- packaging costs,

- a contingency amount of 5% of total costs to allow for miscellaneous

expenses.

A summary of the gross margin for the selected crops is given in Table 7. A detailed

Gross Margin analysis for the selected enterprises is given in Annexure F.



Table 7: Summary Gross Margin for Selected Enterprises

Maize Barley Lucerne (Est.)

Lucerne (2 – 5 years)

R/ha (Sprinkler Irrigation)

Price (R/ton) 1 800 2 200 1 200 1 200

Yield (tons) 10 4 15 18

Gross Income 18 000 9 070 (+ straw) 18 000 21 600

Variable Cost 11 535 7 276 10 821 10 820

Gross Margin 6 465 1 794 7 179 10 780

The above table indicates that lucerne has the highest return, however it is more

capital intensive as the establishment costs are relatively high. The next step in the

analysis is to develop farmer models.

6.2. Farmer Model

Different farmer models have been compiled for the selected rotations for the

different irrigation models. The main cost driver from the irrigation types has been

taken from Table 6. The areas that can be cropped for each enterprise assuming

optimum irrigation requirements are also taken from Table 6. The main assumptions

of the models are as follows:

• The farm models are estimated over a 10 year period

• The models are undertaken in constant 2008 Rand values

• It is assumed that the farm will be developed in the first year of operations.

• 20% of lucerne is re-established every year

• Water cost (tariff) included

• No finance (interest) costs included

• Income and production costs are derived from the gross margin estimates.

• All initial capital costs are included

• Overhead costs have been estimated for each farmer model and included in the

analysis. These include management salaries, general repairs, bank charges,

auditing fees etc. These have been standardised across the enterprise and



irrigation types so that the result of the model will reflect enterprise and irrigation

type efficiency.

Table 8 gives a summary of the various farmer models.

Table 8: Farmer Models for Different Irrigation Types for Lucerne

Centre Pivot (4.5 Ha cropped)

Sprinkler (4.2 Ha cropped)

Border Strip (3.6 Ha cropped)

Gross Income 93 960 87 696 75 168


Gross Margin 47 590 42 251 43 753

Overhead Costs 31 476 31 476 31 476

Net Income 16 114 10 775 12 277

Capital Costs 120 000 100 000 80 000

IRR 14.25% 10.15% 17.25%

Table 9: Farmer Models for Different Irrigation Types for a Maize Barley Rotation

Centre Pivot (4.5 Ha cropped)

Sprinkler (4.2 Ha cropped)

Border Strip (3.6 Ha cropped)

Gross Income 121 815 113 694 97 452


Gross Margin 39 547 34 685 37 470

Overhead Costs 31 476 31 476 31 476

Net Income 8 071 3 209 5 994

Capital Costs 120 000 100 000 80 000

IRR 3.37% -4.25% 4.75%

An internal rate of return for each farmer model was estimated so that the models

can be compared with each other on a financial basis.

It should be noted that these are real returns and exclude inflation. A real return of

under 5% would be considered unviable, between 5 – 10% marginal and above 10%

would be considered viable depending on the risk factor, i.e. the higher the risk, the

higher the rate of return. A typical irrigation scheme would require between 10 –



12% IRR (at least) depending on assumptions (i.e. costs) included in the financial

model.



7. CONCLUSION

As a result of the higher capital costs and pumping costs centre pivot and sprinkler

irrigation are less viable than border strip irrigation. Border strip irrigation is more

viable even if it is on a smaller area. In terms of water use efficiency this is taken into

account in financial terms as the model assumes that 10 Ha is costed (water tariff),

however only 3.6 Ha is cropped. In terms of enterprises lucerne is more viable than

the maize/barley rotation however it is more capital intensive. For resource poor

farmers the maize barley rotation may be more affordable. It should be noted that

maize grown on its own is not a viable option.



ANNEXURE A

MAP OF POTENTIAL IRRIGABLE AREAS





ANNEXURE B

MONTHLY WATER REQUIREMENTS FOR THREE IRRIGATION SYSTEMS AND FOR TWO CROP ROTATIONS















ANNEXURE C

TYPICAL LAYOUTS FOR 3 IRRIGATION SYSTEMS







ANNEXURE D

SUGGESTED LAYOUTS FOR THE IRRIGATION SYSTEMS ON THE 8 BLOCKS OF LAND

















ANNEXURE E

SOIL ANALYSIS RESULTS





ANNEXURE F

GROSS MARGINS







Documents

DEPARTMENT: WATER AFFAIRS AND FORESTRY Dam/5. Irrigation Planning Design... · REPORT NUMBER: P WMA 10/C31/00/0908 DEPARTMENT: WATER AFFAIRS AND FORESTRY Directorate: Options Analysis