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water supply manual

INTRODUCTION

The construction of the Northern Mallee Pipeline system is a cause of significant change on many Mallee farms. The old system of channels and dams is becoming redundant. The new system of tanks and troughs provides farmers with the opportunity to place their watering points anywhere on the property. There are many choices to be made concerning the type, size and location of pipes, tanks and troughs.

Many farmers have not previously designed a water distribution system. If their new system is effective, they will not have to redesign their system for many years to come. The purpose of this manual is to help farmers to make the most of the unique challenges presented by the introduction to the Northern Mallee Pipeline system.

This manual provides information and guidance on the design of piped farm water supply systems. It does not attempt to be an exhaustive water supply design manual. The focus is on the types of systems and the issues that are most prevalent in the northern Mallee.



laying the pipeline
Laying the Northern Mallee Pipeline in the Walpeup area.1

WARMPlan BACKGROUND

This manual has been produced on behalf of WARMPlan 2001. WARMPlan was established as part of a Drought Regional Initiative for the Northern Mallee to assist farmers to achieve the opportunities offered by the Northern Mallee Pipeline (NMP) system, and promote and conduct other activities that could help secure improved levels of drought preparedness, profitability and viability for dryland farms.

The activities of the Project are guided by a Commonwealth-State Agreement, and an Implementation Plan and they are directed by a locally based Steering Committee.

The areas served by the NMP system are used for dryland cropping and grazing. Water for stock and domestic purposes has been supplied to these areas since settlement, by an extensive system of open channels and farm dams. The NMP system replaces this network of channels with a network of pipelines that will deliver water to farm tanks. The pipe and tank system offers several advantages to farmers, when compared to the channel and dam system.

WARMPlan 2001 aims to help farmers to make the most of opportunities presented by the change in the system of water supply.

Since most farmers in the area have limited experience in the design, construction, operation and maintenance of piped systems, WARMPlan 2001 has taken the opportunity to assist farmers by providing a manual which helps them to design efficient, reliable systems. A well-designed and maintained on-farm piped system will maximise livestock production and minimise farm-operating costs. A poorly designed system can be costly a lot to build and then keep on costing, due to wasted water, stock deaths and the need for frequent repairs.

farmers planning water supply systems
Farmers planning their water system
WARMPlan 2001 is helping farmers by providing advice and assistance in starting alternative enterprises in the area. The project also has programs to assist farmers to manage drought risks and to produce their own Whole Farm Plans with particular attention given to the adoption of sustainable farming practices.

THE NORTHERN MALLEE PIPELINE SYSTEM

Victoria’s Mallee region has several features that make the task of providing a reliable water supply for the farms and towns of the area difficult. The sandy soils and low annual rainfall mean that there is no run-off generated within the region in most years. Since there is no harvestable surface water, and the ground water is highly saline, water must be imported from outside the region. Extensive development of this rich cropping and grazing region was only made possible by the construction of a network of open channels which carry water from the Grampians region over 200 km to the south.

This network of channels supplies every farm and town in the region. With the exception of some isolated high spots, the whole system is powered by gravity. Water is conveyed from south of Horsham to north of Ouyen without being pumped once. The furthest point on the channel system is 600 kilometres by channel from the headworks. At the time of its construction, in the first decades of the last century, the Wimmera Mallee stock and domestic channel system represented the best available engineering solution for the water supply problems of the area.

historical view of the channel system
Top Left: Drift sand filling the main Dennying Channel - Walpeup
Top Right: Breakout on Dennying Channel - 1994
Bottom: Clearing drift sand from main channel - 1940's


However, almost as soon as the system was built, it was evident that losses from the channels and dams, due to seepage and evaporation, were very high. Over the years, many schemes to replace the open channels with pipelines were proposed. These proposals were prohibitively expensive. It was not until the early 1970’s that the first large domestic and stock channel system was replaced by a pipeline system.

The Millewa channel system was supplied via a pump at Lake Cullulleraine, west of Mildura. This system suffered the same seepage and evaporation losses as the channel system in the northern Mallee. A pipe system was found to be viable, provided it was designed to provide the flow rate that would satisfy the average daily demand in January. Tanks were required on each farm to provide a buffer between this average flow rate and the peak demands experienced through the day.

Pipeline systems proposed earlier in the century had been sized to deliver water in the same way as the channel system, ie the water required for the whole year would be delivered to dams over a period of a few weeks. These systems would have required huge, enormously expensive pipes. The design concept used in the Millewa system, ie year round supply to tanks, allows the system to utilise small diameter pipes. Since the areas served, and hence the lengths of pipelines, are quite large, the total cost of the system is dominated by the cost of purchasing the pipes. The cost of on-farm tanks is quite modest in relation to the cost of the off-farm pipelines.

If tanks were not required on farms, the capacity of the off-farm pipelines would need to be increased. The increase in the cost of the pipeline system would be much larger than the savings in the cost of the farm tanks.

Following the construction and successful operation of the Millewa scheme, the Rural Water Commission applied the same design concepts to a series of pipeline systems that are replacing the Wimmera Mallee channel system in the northern Mallee.

WATER QUALITY

Several parameters are used to describe water quality. These parameters define the physical content, the chemical content and the biological content of the water. Knowledge of these parameters is useful when deciding to what use water from a particular source could be put. If water from a particular source is not suitable for a desired purpose then either an alternative source or a method of treatment needs to be found.

Water from the NMP system has lower salinity and is ‘softer’ than water from the Wimmera Mallee channel system. Water from the NMP system will be more suitable than water from the channel system, for a range of uses.

Physical content

The two parameters most commonly used to define physical content are colour and turbidity. Turbidity is due to clay particles suspended in the water. Some sediment may settle out of water held in a tranquil state. The chemical content of the water will have a large bearing on whether all the fine clay particles will settle out.

Turbid water can cause problems by clogging up micro irrigation systems and by depositing sediments in pipes and tanks. The effectiveness of some agricultural chemicals, and in particular glyphosate, is reduced if the water used for mixing is highly turbid.

Water can become coloured by organic materials leached from decomposing vegetation. Colour and turbidity can cause staining of clothes washed in the water.

While clear, colourless water will always be more aesthetically pleasing, turbidity alone is almost never high enough to cause health problems for people or stock drinking the water. In fact it is the chemical and biological content that generally determine if water is safe to drink.

Chemical content

All waters (even rainwater) contain some dissolved salts. While there are many different types of salts, the term for the net effect is salinity. The electrical conductivity (EC) of water is the easiest and most frequently used method to quantify salinity. The unit used is microSiemen per centimetre. These units are also called EC units. (1EC unit = 1mS/cm)

The other commonly used unit for quantifying salinity is parts per million. To convert EC units to parts per million multiply by 0.6.

As the salinity of water increases there are less options for which it can be used.

The table below is a guide to the effects of saline water on plants. (Source - Landcare Notes SC0034)
Conductivity (mS/cm)
Suitable uses
<300 Low salinity water suitable for most crops and most soils
300-800 Low to medium salinity water, which can be used to irrigate all crops, however increased leaching may be required for sensitive crops.
800-2500 Medium salinity water, which requires adequate leaching and may be a problem if it used on soils with restricted drainage or on stone fruit using an overhead sprinkler system. The salt-tolerance of plants must be considered.
2500-5800 Medium to high salinity water, which may only be used on permeable, well-drained soils, which provide adequate leaching and with salt tolerant crops. Careful management required.
5800-21500 High salinity water, which is only suitable for high salt tolerant crops on soil with excellent drainage and leaching potential. Adequate winter rains are required to leach salts from the soil. Careful management is required.
>21500 Generally considered too saline for irrigation.
The table below is a guide to the suitability of saline water for stock. (Source Landcare Notes SC0034)
Conductivity (mS/cm)
Magnesium (mg/L)
Suitability for use
<5800 <20 Suitable for watering of all stock
<7500 <200 Unsuitable for poultry
<8500 <400 Unsuitable for poultry and pigs
8500-16500 <600 Unsuitable for poultry or pigs, generally unsuitable for lambs, calves and weaner stock. Caution is required with lactating stock. Suitable for dry mature sheep and cattle.
16500-25000 <600 Suitable only for dry mature sheep and cattle; caution is required for cattle unaccustomed to water of this quality
25000 <600 Unsuitable for watering of stock.


aquaman
Aquaculture is now possible with the improved water quality.


The salinity of water, delivered through the channel system to farms in the northern Mallee ranges from around 200 up to 1600 mS/cm. Evaporation of water from farm dams further concentrates the salts. Water delivered through the Northern Mallee Pipeline system will range between 200 to 800 mS/cm. Since this water is delivered to tanks, there should not be any further increase in the salinity of the water.

Certain salts will cause the clay particles suspended in water to be attracted to each other and form larger particles. These larger particles settle out of the water. Hence the higher the salinity the more likely water will become clear when it is held in a tranquil state.

Biological content

All surface waters contain a range of biological activity. Most of this activity is desirable and presents no risk to those who drink the water. However, some micro-organisms have the potential to cause serious health problems.

Water authorities responsible for providing drinking water conduct tests at regular intervals to check that the concentrations of dangerous micro-organisms in the water they deliver are at safe levels. The water delivered by the Northern Mallee Pipeline (NMP) system to farms is not suitable for human consumption.

The NMP system delivers water to several towns across the northern Mallee. The authority (Grampians Region Water Authority) responsible for the town water systems treats the water in the larger towns under its control to make it safe for human consumption.

The most cost effective and reliable means for farmers to provide water that is safe for human consumption is a system of rainwater tanks.

rainwater tanks
In rural areas rainwater is still the best option for human consumption.


The water delivered by the NMP system is safe for stock to drink. Excessive amounts of algae may grow in the water if it is exposed to the sun. These algae are usually harmless, although the appearance and odour may deter stock from drinking the water. The water is safe for gardens and general domestic use.

NMP SYSTEM CONDITIONS OF SUPPLY

Pressure

The NMP system is designed so that there will be sufficient pressure to deliver water to tanks placed on the highest hills throughout the supply area. This makes it possible for water to be distributed within each farm without the need for further pumping.


diagram of home water plan
Pipeline, tanks, troughs and homes in the landscape


On-farm systems can be designed on the assumption that the minimum head at the water meter will be 10 metres greater than the elevation of the highest hill in the allotment. Since the minimum head will be present on the hottest days, when demand is at its highest, pipe sizes should be selected to be adequate in this situation.

In reality the pressure in the pipeline may drop below the minimum design head for some periods on the hottest days resulting in lower than expected flows into tanks. Flow, however, will increase again and fill the tanks as the demand decreases during the night.

Maximum pressures in the NMP system vary in different parts of the network. They will be experienced when the demand on the system is low and as a result of surges generated by pumps stopping and starting. The pressure rating of pipe on-farm, between the water meter and the tank, must match the rating of the NMP system at the meter. Most of the NMP system is either Class 6 or Class 9 pipe. There is some Class 12 pipe and even a small section of Class 15 pipe. For an explanation of pipe pressure ratings see the section on selecting pipes in “Hydraulic Design”.

The pressure rating of the NMP system at each meter should be checked with Wimmera Mallee Water prior to designing your system.

Pipelines that run away from farm tanks will only be subjected to the head of the tank. Class 6 or Rural B poly pipe will be suitable in those situations.

Flow rates

The NMP system has been designed to be capable of supplying all the homes that currently exist in the area as well all the stock that might be run in the future. The stocking rate used in the design is quite a bit higher than the current stocking rate.

The standard water meters (20 mm) used in the system are capable of passing up to 20,000 litres per day (0.2 l/s) without incurring excessive head losses. If a higher flow rate is required, WMW should be contacted. It may be feasible to pass a higher flow rate through a standard meter, or a larger meter may be required.

Storage and Back-flow Prevention

The NMP system is designed to deliver water to tanks. Tanks provide the buffer between the very high, short term, demands that are experienced on each farm, and the low, constant flow rate delivered by the NMP system. Tanks also provide security in the event that supply through the NMP system is interrupted, due to planned maintenance or breakdowns.

Farmers are required to have tanks with sufficient capacity to last at least 3 days, at the hottest time of the year, with no supply from the NMP system. This requirement must be satisfied for each tank. It is the farmer’s responsibility to calculate the peak daily demand on each tank and install a tank with 3 days capacity.

Tanks must be impervious, ie made from steel, polyethylene, fibreglass or concrete. Water must not be put into dams.

A float valve must be used to control the flow from the NMP system into each tank. The float valve inlet must be positioned at least 50mm above the level of the tank overflow pipe. This is to ensure there is always an air gap between the float valve and the surface of the water in the tank. The air gap makes it impossible for water from the tank to siphon back into the NMP system when pressure is lost in the NMP system.

WMW will only install each service connection after a tank of the required size has been correctly installed.

Service Connections

Most service connections are installed by WMW at no charge to the farmer, if connected within two years of the last dam fill in the area. The number of service connections that can be installed at no charge is calculated by dividing the total area of the farm by 250 ha and rounding up to the nearest whole number.

The farmer has some discretion about where he locates this number of connections. If extra connections are required or the connections are required after the two-year period expires, then a charge applies. The charges that apply in the 1999/2000 financial year a listed below. Property owners are required to contact WMW’s Northern Mallee Pipeline Project Office for more recent charges.
25000 Situation
25000 Charge
Meter is on the same side of the road as the NM pipeline. $340
Meter is separated from NM pipeline by a road reserve without a sealed road. $450
Meter is separated from NM pipeline by a road reserve with a sealed road. $775

If a railway or a road crossing is required to provide the service connection, separate charges depending on the actual cost to WMW will apply.

In most rural areas the meter can be installed anywhere along the boundary of an allotment which is “fronted” by a NM distribution pipeline. An allotment is “fronted” if a NM pipeline runs parallel with the boundary, either inside the allotment or in the allotment on the opposite side of the road reserve. There are restrictions to this situation. They include:

  • The main pipeline will only be tapped if no other option exists.
  • Meter connections that require the crossing main sealed roads and railway lines will not be authorised if other options exist, or they may be restricted to designated points. In these circumstances always check with the WMW Pipeline Project Engineer.

It makes sense to place meters where they can be easily read and where the length of on-farm pipelines is minimised.

The picture below shows how the water meter will look. It is installed close to the fence line. The pipe-work installed by WMW ends with a length 25mm diameter polyethylene pipe extending from the meter assembly. The farm system connects to this pipe.

In order to have a service connection installed farmers should take the following steps.

1. Design the farm pipeline system; the use of a professional designer is recommended if the system is extensive or complex.

2. Send a “service connection application form”, to the WMW District Manager – Ouyen, PO Box 116, Ouyen 3490, or fax it to (03) 5092 1637.
Blank forms are normally posted out to farmers as each section of the NMP system is built. Extra forms can photocopied or requested from the NMP Project Engineer on (03) 5092 1613 or the District Manager – Ouyen on (03) 5092 1411.

3. Purchase and install tanks, and commence installing the remainder of the farm system.

4. WMW’s contractor will contact each farmer by phone prior to installing each service connection. The contractor will verify the required location for the service connection and ask if tanks have been installed. Service connections will not be carried out until tanks have been installed.

5. Once the service connection is installed, the farmer may connect the farm system to it and commence using water.

Tariffs and Charges

The WMW tariff for properties supplied from the Northern Mallee Pipeline has a component based on the area of the property and a component based on the volume of water delivered through the meter.

For the 1999/2000-year the charges are $2.02 per Hectare plus $0.56 per kilolitre. For properties where the total area of the enterprise owned by the farmer is smaller than 110 ha, the minimum area charge of $218 applies.

DESIGNING YOUR SYSTEM

When designing a farm water distribution system it is useful to tackle the problem in two phases. The first is functional design. That means deciding on what you want the system to do, ie where do you want the water to go and what will the water be used for at each site.

The second phase is hydraulic design. This means deciding how you will get the water to the places where you want it. After working through the hydraulic design you may find some parts of the system to be impractical or too expensive. You can then go back and review the functional design with the aim of making it a bit more practical or less costly.

Thus the design process goes around a few cycles before the final design is selected. It is best to start with the functional design so that the widest range of possibilities can be examined. Starting with the functional design should also help to keep you focused on ensuring that, at the end of the day, the system will work. After all, it is pointless having something that is easy to build, but which does not work.

FUNCTIONAL DESIGN

Farm layout

The ideal time to review your Whole Farm Plan is just before you start your water distribution system design. If you haven’t already worked on a Whole Farm Plan, then it is a good time to start developing one. Contact WARMPlan or DNRE to get help to organise a Whole Farm Planning group in your area. The abandonment of the channel system is another factor that makes this a good time to review the Whole Farm Plan.
  • Channels will no longer need to subdivide paddocks. Farmers will have more freedom to subdivide paddocks in ways that suit them.
  • Consideration should be given to farming your property according to soil capability and designing your water system using sustainable farming principles.
  • Opportunity will exist to eliminate pest plants and animals that found harbour along the old channels.
  • The location of watering points will not be governed by the route and elevation of the channel
  • Access tracks will no longer need to go to channel crossing points or curve around channel loops.
  • Channels and adjacent seepage areas will be brought back into production.

Construction of the new farm pipe system and filling in the old channels will take time and cost money. The Whole Farm Plan should also address the timing of new works and cash flow.

The layout of stock troughs and fences has a strong influence on the way grazing pressure is spread across the paddock. Ideally stock should not be forced to walk more than 1 to 1.5 km to water. Do not place troughs where heavy trafficking by stock is likely to start sand hills drifting. Troughs should be placed on heavier ground, which is less subject to erosion

Planning Approval

Before clearing native vegetation that may result from planned installations or the backfilling of channels, farmers should first contact the local municipal council to clarify their obligations regarding planning permits.

Trough locations

Don’t place troughs near fences. Do place them where they can be easily checked. If there is only one clump of trees in a paddock and that clump is a popular camping spot for stock in the summer, then it is desirable to place a trough near the trees. It is not a good idea to place the trough right in the trees, as sheep will then lay down all about the trough, preventing much of the mob from having a turn at drinking.

Identify troughs that may be required at yards, sheep dips, shearing sheds and stock containment areas.

Other water uses

Consideration could be given to setting up outlets that can be used for filling spray tanks. Such outlets need to provide a high flow rate and are usually placed at tanks. It is worth planning where water would be accessible for fire fighting.

Significant quantities of water will be required at homes. The layouts of pipe systems on allotments containing homes will be centred on the homes. You could make allowance for any planned developments on the property – without looking too far into the future. An advantage that pipeline systems have over dams is that they can be substantially modified at a later date for relatively little cost.

HYDRAULIC DESIGN

Selection of tank sites and pipe routes

It is important to remember that selection of tank sites is not part of the functional design. Tank sites are selected to suit the trough locations, not the other way around.

Pipe routes leading from the water meter to the tank, then from the tank to the stock trough, home or other demand point must be selected.

When selecting pipe routes, keep in mind:
You will want to find the pipe again after it is buried – either because you suspect there is a leak, because you want to connect another pipe to it, or because you need to dig or rip in the area for some other reason. So try to lay the pipe in straight lines between points that will be permanently marked, or parallel with fence lines.

You don’t want the pipe to become exposed over time, so avoid routes over sand hills with a history of big movements or areas of sheet limestone, which may prevent the pipe layer from penetrating.

Try to avoid going over rises that might result in the pipe trapping air. Air can accumulate at local high spots in the pipeline and effectively throttle the flow of water as shown in the diagram below. (See air valves)
diagram2

Water flowing through a small pipe will flush the air out the end of the pipe provided the velocity of the water is great enough.
Flushing velocities for various size pipes are shown in the table below.
Pipe internal diameter Flushing Velocity (m/s) Flushing Flow (l/s)
12 mm ½" 0.33 0.04
20 mm ¾" 0.43 0.14
25 mm 1" 0.48 0.24
32 mm 1¼" 0.54 0.43
40 mm 1½" 0.61 0.77
50 mm 2" 0.68 1.34
(Source – Garret et al. (1976, p.3.4.5)

Make sure that there is no point on a pipe leading from a tank that is higher than the tank.
Tanks should be placed to minimise the total length of pipe. As a rule of thumb, pipe costs will usually be minimised when the tank is placed centrally among the troughs it serves. If it only supplies one trough, it should be close to the trough.

This is because the pipe from the water meter to the tank can deliver the daily demand over a full 24-hour period. In addition, there is at least 10m head of water available to push this relatively small flow rate. As a result the pipe from the meter to the tank will be smaller in diameter and thus less costly as a result.

The pipe from the tank to the trough must deliver the daily demand in only 4 hours and the available head is the difference in elevation between the tank and the trough (this may be only 2-4m). This pipe needs to be short or large in diameter.

A tank serving a house needs to be placed on the hill closest to the house, or even on a dam bank. Since most homes will use an electric pressure pump to pump water for the house and garden, the tank only needs to be high enough to provide a flooded suction for the pump and to provide a little head in the event of a power blackout or a pump breakdown.

Apart from being central and elevated to some extent, tanks need to be placed so that they will not suffer damage as a result of erosion. Tanks are best placed on heavy ground or among trees. If they must be placed on an exposed sand hill, the area around the base of the tank must be protected against wind erosion.

The tank overflow pipe must be arranged to direct water away from the tank. Many tanks have been destroyed when float valves have stuck and overflow water has eroded and softened the soil beneath the tank.

If a tank is likely to be used for filling spray tanks then it needs to be placed where it is accessible.

Calculating demands and tank sizes

The least confusing approach to designing pipe systems is to work out the design capacities for each tank and the pipe supplying the tank, and then to work out the design capacities for the pipes leading away from the tank.

The table below provides information on the peak daily requirements for stock and other uses. Tanks and pipelines need to be designed with a capacity to satisfy these peak daily requirements.

Peak Daily Demand L/head/day Source
Sheep
Lactating ewes 9 1
Dry sheep 7 1
lambs 2.5 1
Cattle
Lactating cows 70 1
Dry cows & steers to 500kg 45 1
Cattle over 500kg 68 1
calves 25 1
Horses
Grazing 45 2
Working 70 2
Pigs
Lactating sows 30 2
Mature pigs 15 2
Piggery average daily wash down 15L/m2 of concrete surface 2
Poultry
Laying 40L/100 2
Non-laying hens 23L/100 2
Turkeys 70L/100 2
Source 1- Wimmera Mallee Water (1995), 2 – Heck (1995)
Crop Spraying
Most herbicide spraying occurs in the cooler months, when stock demand is very low. The capacity of the pipeline supplying the tank should be checked to ensure that it will keep up to spraying requirements over a 24 hour period. The daily requirement will be the volume of the spray tank times the number of tanks put out in a day, divided by 24 hours.

Since the farm tank will be much larger than the spray tank there is no need to design the pipe from the meter to the tank to refill the farm tank as each spray tank is emptied. The farm tank will simply be drawn down to some extent during the day.

Look at each tank and list the things that it must supply. Then calculate the peak daily requirements for each of those things.

Example

Tank 1 supplies:
1 house and garden 7,000 L/day
One mob of up to 500 ewes with lambs in either one of the two paddocks served by the tank 500 x 7 L/day = 3,500 L/day
Total peak daily requirement 10,500 L/day

Since the tank must have the capacity to last three days at the time of peak demand, the required tank size is 3 x 10,500 L = 31,500 L

The pipe leading from the meter to the tank must have a design capacity of 10,500 L/day (0.12 L/second)

Flow rates for pipelines are usually quoted in L/s. To convert from L/day to L/s divide by the number of seconds in a day, ie 24 x 60 x 60 = 86,400

The next step is to work out the design capacities for the pipes leading away from the tank.

Stock Demand

The peak daily demand at each stock trough needs to be calculated using the figures from the table above and the maximum likely mob size. The pipe supplying each trough must have a design capacity that will allow the peak daily demand to be delivered in only 4 hours. This is because stock do not drink at a steady continuous rate over a full 24 hours. The pipe to the trough needs to keep up as the stock are drinking.

sheep
Sheep move to the trough as a mob.
Even though there may be more than one trough in a paddock, each trough needs to have the design capacity to satisfy the demands of the entire mob. That is because sheep and cattle will usually stay in one mob and one mob will drink from one trough at a time.

If a pipe branches to supply two troughs, then the design capacity of the pipe before and after the branch will be the same.
For example

The biggest likely mob size that will be run in this paddock is 500 ewes with lambs. There are three troughs in the paddock arranged as shown below.

diagram3
The design capacity for the pipe between the tank and trough A is:
Design capacity - tank to trough A = 500 x 7 /(4 x 60 x 60) = 0.24 L/s Design capacity - tank to Tee between trough B and trough C = 0.24 L/s Design capacity - Tee to trough B = 0.24 L/s Design capacity - Tee to trough C = 0.24 L/s

You may have a tank and pipe system that supplies troughs in more than one paddock. You must now answer the question, Will there be stock in adjoining paddocks at the same time?

Where troughs in adjoining paddocks are served by the same pipeline, and it is your practice to never put different mobs in adjoining paddocks at the same time, then calculating the required flow for each trough is done the same way as the examples above. That is, there is one mob and the whole mob is supplied from one trough on any given day.

If adjoining paddocks are stocked at the same time then the calculation of flows becomes a little complicated. The mobs in each paddock will act independently of each other. They will drink from their own troughs and they may or may not drink at the same time as each other. For a very large system serving many different points, a factor would be applied to account for the fact that not all the stock will want to drink at exactly the same time.

The problem of multiple independent demands is beyond the scope of this manual. There will be very few systems in the northern Mallee that will serve more than two mobs at the same time. In calculating the design capacities of pipes in a system serving two mobs, it is best to adopt a conservative approach and assume that the two mobs will want to drink at exactly the same time. Therefore, pipelines serving both mobs will need to have a design capacity that will satisfy the requirements of both mobs at the same time.

Domestic demand

In an average house with three occupants the peak usage of water within the house is around 960L/day. This is water used for dishwashing, laundry, bathroom and toilet. This figure does not include water for drinking or cooking or for watering gardens. If more people live in a home, the amount of water that is used within the home goes up a bit. It is safe to allow 1000 L/day for water used within the home plus another 1000L/day for an evaporative air conditioner, regardless of how many people live in the house.


garden
Improved water quality and supply is reflected in pleasant home gardens.
The biggest component of domestic demand, and the one that varies the most from house to house and month to month, is water used on the garden and lawns. It has been calculated that, in the northern Mallee, in January, an average of 5000 L/day will maintain a garden containing lawn and other wet climate plants. This is the size of garden that would fit on a ¼ acre (1,000m2) block, excluding the area occupied by an average sized 3 bedroom house, carport, driveway and paths. (Source – Water Engineering Design Services (1992, p. 10)

A ¼ acre block is 32m x 32m or 25m x 40m. The area occupied by the house etc is 400 square metres, leaving 600 square metres of garden and lawns. If the area of garden and lawns watered is larger than 600 square metres then the average January daily requirement will be higher in proportion. Therefore, one method of calculating the garden’s January water requirement is to measure the actual area of garden and lawns watered, divide the area in square metres by 600, and multiply by 5000 L/day.

If the garden consists of plants adapted to an arid climate then the watering requirement will be lower.

Looking at the area of garden watered is one method of calculating the garden water requirements. This method should give good estimates of average requirements over a whole month. However this method could under estimate the peak daily flow rate or the flow rate of a pressure pump.

If the pressure pump that drew water from the dam is going to be used with the new pipeline system, then it will be useful to measure the actual output of this pump. First check the pump operator’s manual to see if it specifies the output of the pump. If the manual can’t be found then measure the output of the pump by turning on all the sprinklers that would normally be used to water the garden, directing the flow into a container of known volume, and measuring how long it takes to fill the container.

The pipe from the tank to the pressure pump will need to be designed for this flow rate.

To determine the peak daily garden requirement, multiply the measured flow rate by the total time the sprinklers would be run on the hottest days of the year. This is the figure that should be added to the in-house requirements (1000 or 2000 L/day) to give the peak daily domestic requirement. This figure is then used when determining tank size and when designing the pipeline that leads from the meter to the tank.

If a new pump and associated pipe-work will be needed in order to change over to the new pipeline system then another method must be used to calculate peak flows.

The method generally recommended by suppliers of domestic pressure pumps is based on the number of taps that need to run at one time. The table below gives the rate of flow that would normally be expected from different types of outlets around the house with the system at 140 kPa.

Shower or bath or laundry 14 L/minute
Kitchen sink 11 L/minute
Toilet 7 L/minute
Garden tap 14 L/minute
(Source – Hislop (1998, p. 19)

The pump is selected by first deciding how many outlets must be able to operate at the same time without a significant drop in pressure. The flow rates for all the outlets are then added up to give the peak flow rate. The pump and pipes are then selected to deliver the required peak flow rate.
For example;
Through the hottest days of summer you might need to run two garden hoses for much of the day. While they are running, the toilet needs to refill while the washing machine does a load and someone has a shower.
Peak flow rate = 2 x 14 + 7 + 14 + 14 = 63 L/minute = 1.05 L/s

Selecting Tanks

Tanks are available in a range of materials. For many years concrete and corrugated galvanised steel were the only options available. In the last decade they have been superseded by new materials, offering lower cost and longer life.

Polyethylene and fibreglass are popular materials because they are durable and available in a variety of colours. If they need to be relocated, they are light enough to be moved without the use of a crane. Prefabricated concrete tanks are very durable provided the quality of the materials and manufacturing process are high. There is some variation in the expected life of tanks produced by different manufacturers. The prices for fibreglass, polyethylene and concrete tanks are all very competitive. Prices generally include delivery to site. Since concrete tanks are difficult to move without the right equipment, you need to have your site ready before they arrive.


well established tank
A well established tank with a limestone base.

Poured-on-site concrete tanks provide a low cost option where a storage volume exceeding 45,000 L (10,000 gallons) is required. To limit the growth of algae and to prevent the entry of birds, leaves etc., it is well worth making sure all tanks have a roof. Prefabricated tanks always include a roof, while a roof is an extra for a poured-on-site tank.

When ordering a tank it is possible to specify customised outlets. It is worth considering a 2” outlet, even if the pipes leading away from the tank are only 1”. A Tee can be connected to the 2” outlet. The branch should include a ball or gate valve and reduce down to the size of the pipe leading away to the trough. A 2” ball or gate valve should be installed on the other line. A fitting suitable for connecting to a hose used for filling spray tanks should follow the 2” valve. Alternatively, a fitting allowing quick connection to CFA appliances could follow the 2” valve. The local CFA should be consulted regarding the preferred fitting.

Selecting troughs

There are several different types of stock troughs on the market. The type of trough you use will have a lot to do with personal preference. Many types of trough are suitable only for sheep.

Sheep troughs generally stand about 400 mm high, while cattle troughs stand 500 to 600 mm high. Cattle can drink from sheep troughs, but sheep will struggle trying to drink from cattle troughs. Sheep troughs made with thin sheets of galvanised steel; polyethylene, fibreglass or fibro cement, will be destroyed by cattle when they step in them. If you have both sheep and cattle, then you need to use concrete sheep troughs.

For rectangular troughs, 1 metre of length is required per 30 head of cattle or 130 head of sheep. For circular troughs, 1 metre of circumference is required per 15 head of cattle or 65 head of sheep. The numbers of stock that can successfully watered by some common trough sizes are given in the table below.

Rectangular trough lengths Sheep Cattle
8' 2.4 m 310 70
12' 3.6 m 470 110
16' 4.8 m 620 140
Circular trough diameters
4' 4" 1.29 m 260 60
4' 9" 1.42 m 290 70
6' 8" 1.99 m 410 90
10' 3.05 m 620 140


These numbers should be used as guide. Of course it will be impossible to have exactly the right number of stock for the size of trough. However, if stock numbers are low, water in the troughs will tend to foul more quickly with algae. If you have multiple troughs and only a small mob in a particular paddock, it may be worth turning off the water for some of the troughs.

Round troughs have the advantage of being more stable. When soil is lost from around the trough, a round trough will not tip or crack. Rectangular troughs made up of sections that sit on little pedestals are prone to developing leaks or overflowing when the soil under the pedestals is lost.

Rectangular, single piece, concrete troughs are as robust and as stable as round concrete troughs.

Concrete troughs are heavy, and require the use of a fork-lift for safe handling. Sheep troughs made of low weight materials can be handled manually. This is very useful if they need to be relocated.

Selecting pipes

A key component of the design of the system is the selection of pipe type, size and pressure rating.
Pipe type
For the range of pressures and flow rates that will be experienced on farms in the northern Mallee, polyethylene (poly) pipe is the cheapest and most convenient suitable pipe type. Where the required pipe size is larger than 50 mm, PVC pipe may be marginally cheaper. However there will be very few instances where farmers in this area will require 50 mm pipes

Polyethylene pipes come in coils and can be installed with a pipe laying attachment on a suitable ripper. This makes them quick and relatively easy to install. For all types of pipes, the joints between pipes are the points where leaks are most likely to occur. Because polyethylene pipes come in coils of 100 – 200 m, there are very few joints, and hence very few potential problem points.
Pressure rating
The pressure rating of a pipe defines the pressure that the pipe can safely withstand over a long period. In order to achieve higher-pressure ratings, pipes are made with thicker walls. Thicker walls mean more material is used to make the pipes and hence the pipes cost more. Thicker walls also result in the internal diameter of the pipe being reduced, hence for a range of pipes with the same nominal size; the pipes with the higher-pressure rating will pass less water. There is no point in buying pipes with a higher pressure rating than is necessary.

PVC water pipes can be class 4.5, class 6, class 9, class 12 or class 15. Class 4.5 pipes have a safe working pressure of 450 kPa or 45 metres of water. Class 6 is safe with 600 kPa; class 9 is safe with 900 kPa, etc.

When designing water supply pipelines it is convenient to use metres of water to define pressures. If you had a tank full of water that was 45 m high, and you measured the pressure of the water at ground level, the pressure would be 450 kPa.

The pressure ratings for metric polyethylene pipes are PN 8, PN 10, PN12.5 etc. PN 8 has a safe working pressure of 800 kPa.

A large proportion of the polyethylene pipe installed on farms is made to the old imperial standard. This class of pipe is Rural B. This pipe has a safe working pressure of 600 kPa.

The pressure rating of pipes, which connect the water meter to the farm tank, must be high enough to handle the maximum pressure expected in the NMP system. WMW can advise you of the maximum expected pressure in each part of the NMP system.

Rural B poly pipe is suitable for all parts of the farm system downstream of the tank. Most pipes carrying water that gravitates from a tank will never experience a pressure over 10 m or 100 kPa. Domestic pressure pumps are usually adjusted to deliver around 20 m or 200 kPa. This is well within the limits of Rural B poly pipe.
Pipe size
The sizes of Rural B poly refer to the internal diameter of the pipe. The internal diameter of 1" Rural B pipe is 1". The sizes of metric poly pipe refer to the outside diameter of the pipe. 25 mm metric poly is not equivalent to 1" Rural B poly. In fact the internal diameter of 25 mm metric poly is around 20 mm. The fittings used for metric poly and Rural B poly are generally not compatible, so be careful when specifying and purchasing pipes and fittings.

The actual internal diameter of metric poly depends on the pressure rating of the pipe. As the pressure rating increases, the internal diameter decreases.
Head
Water will move through a pipe from a place of high potential energy to a point of lower potential energy. The term we usually use instead of potential energy is “head”. Head is the sum of pressure and elevation and the units used to quantify it are metres of water. The bigger the head difference between the ends of a pipe, the faster water will flow through the pipe.

If we were only concerned with moving water about in pipes on a horizontal plane, then we would only need to talk about pressure. The pressure difference between each end of a pipe would be the head difference and we could use that to calculate how much water would flow through the pipe.

But we need to look at water flowing from an elevated tank down to a stock trough. The pressure of water in the tank, measured at the surface of the water is 0 kPa (0 m of water). The pressure of the water that falls out of the float valve at the stock trough is 0 kPa (0 m of water). The head difference between the water in the tank and the float valve on the trough is the difference in elevation between the water level in the tank and the float valve.

If the head difference is known and the length of the pipe is known, then the amount of water that will flow through a pipe can be determined using a chart from a pipe manufacturer or the tables below.

The head difference divided by the pipe length is the hydraulic gradient. In engineering calculations it is given the symbol "S”. The table set out below, expresses hydraulic gradient as metres per 1000 metres. To express a hydraulic gradient as m/1000m, divide the head-difference (m) by the length of pipe (m) and then multiply by 1000.

Flow verses hydraulic gradient for Rural B poly pipe
Nominal Size ¾” 1” 1 ¼” 1 ½” 2”
Internal Diameter 19.0mm 25.4mm 31.7mm 38.1mm 50.8mm
S (m/1000m) Flow (L/s)
4 0.05 0.11 0.19 0.31 0.67
6 0.06 0.13 0.24 0.39 0.83
8 0.07 0.16 0.28 0.46 0.97
10 0.08 0.18 0.32 0.51 1.10
15 0.10 0.22 0.39 0.64 1.36
20 0.12 0.26 0.46 0.75 1.59
25 0.14 0.29 0.52 0.84 1.80
30 0.15 0.32 0.57 1.98
40 0.17 0.37 0.67 1.09 2.32
50 0.20 0.42 0.76 1.23 2.61
60 0.22 0.47 0.83 1.35 2.88
80 0.25 0.54 0.97 1.58 3.37
100 0.29 0.61 1.10 1.78 3.80


Flow verses hydraulic gradient for PN 10 metric poly pipe
Nominal Size 25mm 32mm 40mm 50mm
Internal Diameter 20.8mm 26.8mm 33.6mm 42.0mm
S (m/1000m) Flow (L/s)
4 0.06 0.12 0.23 0.41
6 0.08 0.15 0.28 0.50
8 0.09 0.18 0.33 0.59
10 0.10 0.20 0.37 0.66
15 0.13 0.25 0.46 0.83
20 0.15 0.30 0.54 0.97
25 0.17 0.33 0.61 1.09
30 0.19 0.37 0.67 1.20
40 0.22 0.43 0.78 1.40
50 0.25 0.49 0.88 1.58
60 0.28 0.54 0.97 1.75
80 0.32 0.63 1.14 2.04
100 0.36 0.71 1.28 2.30

Flow verses hydraulic gradient for PN 12 metric poly pipe
Nominal Size 25mm 32mm 40mm 50mm
Internal Diameter 20.0mm 25.8mm 32.0mm 40.2mm
S (m/1000m) Flow (L/s)
4 0.06 0.11 0.20 0.36
6 0.07 0.14 0.25 0.45
8 0.08 0.16 0.29 0.52
10 0.09 0.18 0.32 0.59
15 0.12 0.23 0.40 0.74
20 0.14 0.27 0.47 0.86
25 0.15 0.30 0.53 0.97
30 0.17 0.33 0.59 1.07
40 0.20 0.39 0.69 1.25
50 0.23 0.44 0.77 1.41
60 0.25 0.49 0.86 1.56
80 0.29 0.57 1.00 1.82
100 0.33 0.64 1.13 2.05


Flow verses hydraulic gradient for Series 1 PVC pipe
Nominal Size ¾” 1”
Internal Diameter 19.0mm 25.4mm
S (m/1000m) Flow (L/s)
4 0.83 2.48
6 1.03 3.09
8 1.20 3.61
10 1.36 4.07
15 1.69 5.07


The procedure for selecting pipe size is:
1. Determine required flow rate for the pipeline.
2. Determine the required pipe pressure rating.
3. Measure the available head difference either from contour maps or survey.
4. Measure the required pipe length either from survey or a map.
5. Calculate “S”, the hydraulic gradient.
6. Find the table for pipes with the appropriate pressure rating.
7. Select a pipe size from that will deliver the required flow (or a bit more) with the available hydraulic gradient.

When selecting the pipe that leads for the water meter it should be assumed that there is 10 m of head available. At most times of the year the NMP system will have much more head available, but a design based on the minimum guaranteed figure should always be able to deliver the required flow.

Pumps

The Northern Mallee pipeline system is designed to deliver water to tanks. Tanks can be placed on hills so that water will gravitate from the tanks to troughs in the flats. There is generally no need to pump water to troughs. If a trough must be placed some distance from the NMP system, then the lowest cost method of supplying the trough will be to place a tank near the trough and run a pipe from the meter to the tank. This will be the best solution even if the trough is several kilometres from the meter.

Because the NMP system has sufficient pressure to deliver water anywhere on a farm, there is no need to pump water for stock. Windmills are a common site in most grazing districts across Australia. However, in the area served by the NMP system they are becoming redundant.

There is a need to pump water at homes. Around our homes we have become accustomed to water coming out of the taps with plenty of pressure. Good pressure is most appreciated when it comes to watering the garden. Garden sprinklers will water a large area when there is good pressure. When the pressure is poor, sprinklers must be moved many times.

Most homes on Mallee farms draw their water from a nearby dam with an electrically powered pressure pump. Pressure pumps are usually set to turn on when the pressure in the domestic system drops to 140 kPa and turn off when the pressure reaches 275 kPa.
Direct Connections
It is impractical to utilise all the pressure of the NMP system by making a direct connection between the meter and the house for three reasons.

1. A volume of water equivalent to three days of consumption must be stored. When water from the NMP system runs into a tank, the only pressure remaining is the head of water in the tank. If the tank were on a 14 metre-high hill or tank stand, then the head from the tank would give good pressure at the home. However, 14 metre high stands are quite expensive, and most sand hills in the Mallee are between 4 and 6 metres high.

2. It is technically possible to have tanks with 3 days storage capacity, which are filled from the NMP system and then bypassed. The home would then be directly connected to the NMP system until there was an interruption to supply. The tanks would then be used until the NMP system came back on-line.

This system would satisfy WMW requirements if suitable back-flow prevention devices were installed near the meter and the pressure rating of all the pipes in the domestic system matched the pressure rating of the NMP system in that area. However, much of the NMP system has a higher pressure rating than the pipes generally used in domestic plumbing.

3. An important practical problem with tanks that are usually bypassed is the smell. Water delivered by the NMP system contains small amounts of organic matter. If this water is put in a tank and then left, with no inflow or outflow, for several weeks, the organic matter will rot and the dissolved oxygen will be consumed. When the water is finally released it will have a strong “rotten egg gas” smell.
Using existing pumps
The most cost effective way to set up most homes when they are connected to the NMP system is to use the same pressure pump that drew water from the dam. Tanks are installed next to the pressure pump and connected to the pump suction. (It is worth putting the tanks on a small rise or a dam bank so that when the power is off some flow will still gravitate to the house.) The remainder of the domestic system remains unchanged.
Relocating pumps
It is worth considering if the tank and pump should be relocated when the connection to the NMP system is made. Unless the dam can be converted into a catchment dam, it will never be used again. It might be possible to get rid of a private overhead power line or eliminate some inefficient pipes by placing the tank and pressure pump closer to the house.

The cost of installing the pressure pump at a new location will be minimised if electrical power is already available at the site. In fact, the location of a suitable power point is generally what governs the selection of a pump site. It will always be cheaper to install new pipes to a pump site near power than it will be to install new power lines to a pump site near water.

A tank supplying a pump can be located some distance from the pump. Priming problems will be eliminated if the connecting pipe is designed so that there will be a positive pressure at the inlet to the pump, even when the pump is running at its maximum capacity. A pump that always has positive pressure at its inlet is said to have “flooded suction”.

The connecting pipe also needs to be installed so that there are no local high points along the way. The pipe should fall from the tank to the lowest point and then rise to the pump.
Replacement Pumps
If the pressure pump is reaching the end of its life then there are some things to consider when buying a replacement.

Pressure pumps used to draw water from dams are usually shallow-well jet pumps. Occasionally deep-well jet pumps are used. Both types of pumps are self-priming and can operate where there is a significant suction lift.

When a pump is set up with a tank so that it can operate with a flooded suction, the pump does not need to be self-priming. A single stage or multi stage centrifugal pump can be used. These pumps are simpler and more efficient than jet pumps. They can be purchased as a pressure pump, with the same pressure tank and pressure switching gear as a pressure pump based on a jet pump.
pump
Pressure pumps can maintain a regular pressure for the house.

Troughs supplied by pump

Pumps are needed to give good pressure around the house and garden. They can also be used to supply stock troughs. It does not make good economic sense to buy a pump for the sole purpose of supplying stock troughs, when the NMP system can deliver water to any point on a farm. However, if a pump is needed to supply a home, there is nothing wrong with running some stock troughs off the home system.

Since most domestic pressure pumps set to turn on at 140 kPa, this is the pressure that should be used when calculating the available head for the pipeline to each stock trough. With this pressure, it is possible to provide an adequate flow to a stock trough up to 2 km away, using 1” pipe.

Air valves

If possible, new pipelines should be laid out with no local high points that will collect air. Air is present in pipelines before they are first filled with water. There are also small amounts of air dissolved in water. As water flows through a pipe, some air comes out of solution, forming small bubbles. Either way, there has to be a way for air to be expelled from the pipeline.

Local high points are easy to avoid if the troughs are fairly close to the tank and the land falls from the tank to the trough. For longer pipelines the need to cross over hills and small rises may be unavoidable.

A local high point in a pipeline might collect air. The resulting air lock will restrict the flow of water.

If the rise is very slight, the water may push all the air ahead of it. For a long, small diameter pipeline on reasonably flat country, it can be difficult to predict whether or not air locks will be a problem.

For such pipelines it is best to see how they perform before deciding if air valves should be added. When the pipeline is installed, the line should be carefully marked so that it can be found again later. Ideally it should be laid parallel with a fence line or a tree line, so that if air valves are needed, they can be placed on the fence line and protected from damage.

Air valves are installed on the branch of a Tee installed in the pipeline at the high point. The branch can rise vertically from the pipeline so that the air valve is located just above ground level, directly above the pipeline. Alternatively, elbows can be used to take the air valve pipe across to a fence line. The air valve pipe should be not quite horizontal, so that it rises all the way to the air valve.
diagram4
An air valve should not be installed on the suction side of a pump. Air valves let air in and out of a pipe. If negative pressure were created in a suction pipe, an air valve would allow air to enter the pipe and cause the pump to loose prime.

Survey techniques

There are three key numbers that are needed before the best pipe size can be selected. They are required flow rate, available head and pipe length. The last two numbers are determined by survey.

A qualified surveyor has a choice of several techniques for measuring the relative heights of tank and trough sites and for measuring the distances between them. A pair of Global Positioning System (GPS) receivers could be used. The more common technique is to use a Total Station. This device is mounted on a tripod and measures the time taken for light to travel from the Total Station to a reflecting prism held at the next point of interest and back. The Total Station also measures the horizontal and vertical angles to the prism.

A less high-tech instrument is the surveyor’s Automatic Level. This is a telescope, which, when set up correctly, has a precisely level line of sight. The surveyor looks through the telescope to a staff held at the next point of interest. The number on the staff that lines up with the cross hair on the telescope is the difference in height between the telescope and the ground on which the staff has been placed. With this technique, horizontal distance is usually measured with a tape or a measuring wheel.

If you are contemplating building several tank and trough systems then it would be a good investment to engage a designer who will, as part of the service, survey the relative heights and distances between the key points.

If you feel capable of handling the design calculations, they you could engage a surveyor just to survey the relevant points. You will get the best value for money if you can tell the surveyor exactly which points must be surveyed, and which points are connected to each other.

For example, you may have a tank site and two trough sites in Paddock No 1 and a tank and a trough in Paddock No 2. The systems in each paddock are separate and so are the surveys. You do need to know the heights and distances between the points in Paddock No 1 relative to each other. You do not need to know the heights and positions of these points in Paddock No 1 relative to the points in Paddock No 2, or relative to sea level or any other external datum. If you can clearly tell your surveyor which points must be connected and which must not, you will save time and money.

It is impossible to estimate the height of a hill or the relative heights between two points, with any sort of accuracy, just by looking at them. The only technique that can be used to estimate relative heights, without the use of surveying instruments, relies on the fact that the line of sight from your eye to a distant horizon is approximately horizontal.

If you stand at a proposed trough site and look to the proposed tank site and you can see a distant horizon behind the tank site, then the height difference between the two sites is less than the height of your eyes above the ground (around 1.7m). If you have to stand on top of the cabin of your ute before you can see a horizon behind the tank site, then you know the height difference between the two sites is the height of your eyes above the ground (perhaps 3.3m).

If the hill is higher than 3.3 metres you can try looking in the opposite direction. Sit on the hill and get someone to hold up a pole with a tape measure attached at the trough site. When the top of the pole appears level with the far horizon wave your arms and get them to read the height of the top of the pole above ground level.

Horizontal distances can be measured using a vehicle odometer or a long tape measure, or by pacing.

Costing and revision of design

Once all the pipes, tanks troughs and pumps have been selected, the cost of the system needs to be worked out. If this cost exceeds expectations then the design may need to be changed.

The exercise of listing all the components of the system and the cost of each component makes apparent which items are the most expensive. In order to reduce the cost of the system, it is best to look at ways of eliminating or reducing the most expensive items.

The table below gives an indication of prices for various components of pipeline systems. These prices were current early in 2000. You will need to get quotations from your preferred suppliers.

Pipes Available in; Price
25mm PN 10 PE 200m coils $0.68/m
25mm PN 12.5 PE 200m coils $0.75/m
32mm PN 10 PE 200m coils $1.35/m
32mm PN 12.5 PE 200m coils $1.50/m
¾” Rural B PE 200m coils $0.27/m
1” Rural B PE 200m coils $0.32/m
1¼” Rural B PE 150m coils $0.49/m
1½” Rural B PE 150m coils $0.63/m
2” Rural B PE 100m coils $1.10/m
50mm Class 9 PVC 6m lengths $3.07/m
80mm Class 6 PVC 6m lengths $4.15/m
Stock Troughs Size Price
Poly sheep trough 2.4m long $235
Poly sheep trough 3.6m long $368
Poly sheep trough 4.8m long $441
Concrete sheep trough 2.4m long $266
Concrete sheep trough 4.8m long $411
Concrete sheep trough 1.4m diameter $140
Concrete sheep trough 2.0m diameter $205
Concrete sheep trough 3.0m diameter $450
Concrete cattle trough 1.3m $140
Concrete cattle trough 2.0m $290
Concrete cattle trough 3.0m $495
PE Tanks Price
500 gallons 2300 litres $390
1000 gallons 4500 litres $585
1100 gallons 5000 litres $585
1500 gallons 6800 litres $955
2000 gallons 9100 litres $1170
3000 gallons 13600 litres $1500
5000 gallons 22700 litres $1900
7000 gallons 32800 litres $2420
10000 gallons 45400 litres $3620


In addition to the items listed above, an allowance should be made for valves, fittings and installation costs.

Good quality float valves designed for use on low-pressure systems on stock troughs will cost around $150 each. 2” ball valves for tank outlets cost around $50 each. Tees, joiners and reducers for pipelines will cost about as much as the pipes.

The cost of installing pipes is difficult to quantify since most farmers will use their own labour and equipment. It is useful to factor in an installation cost when making comparisons between options that involve different lengths of pipe. Installation costs will be around $1.50/m for pipes that are ploughed into the ground. Where stony soils or PVC pipes call for an open trench, the cost will be around $3.00/m.

A table or a computer spreadsheet should be used for calculating the cost of the system. An example is given below. In the example, it has been assumed that the cost of fittings is equal to the cost of pipes. You can list each different fitting, but the exercise becomes complex, even with a spreadsheet.

Estimate of cost
CA 76, Parish of Pipeland
Item Size Unit Rate$/unit Amount Cost$
Tank 5000 gallon each 1900 0 0
Tank 3000 gallon each 1500 1 1500
Tank 1500 each 955 0 0
Concrete sheep trough 2.4m long each 266 2 532
PE pipe 25mm PN 10 m 0.68 380 258
PE pipe 1 ¼” Rural B m 0.49 0 0
PE pipe 1” Rural B m 0.32 170 54
PE pipe ¾” Rural B m 0.27 0 0
Fittings item 312
Pipe laying m 1.50 550 775
TOTAL 3431


For the example given in the table a few things could be tried to see if the cost of the system could be reduced.

The cost of the tank is almost half the cost of the entire system. Could this system be combined with the system in an adjoining block so that one tank is shared between the two blocks?

Could the length and size of pipes be reduced, by placing the tank closer to the troughs?

Could the length of the PN 10 metric PE pipe be reduced by placing the troughs, and hence the tank, closer to the meter?

BUILDING AND MAINTAINING THE SYSTEM

Troughs

Troughs should be located on heavy ground with low erosion risk. The area around each trough should be protected against erosion by the placement of a 150mm thick layer of limestone rubble. This layer should be maintained on a regular basis.

As an alternative to limestone, old car tyres can be laid on the ground around troughs and then filled with soil.

Float valves in troughs should be designed for low-pressure operation. High-pressure valves will restrict flow and may be more likely to stick. Brass float valves manufactured by Alderdice are suitable.
troughfloat
Good quality fittings are essential.

Floats, valves and any pipes leading to the valves must be protected from stock by suitable covers. The pipe leading to the trough should rise vertically from an elbow 450 mm below the ground to an elbow at the point where the float valve is mounted, as shown in the diagram below.
diagram5

Troughs should be placed at least 20 away from any fence in order to prolong the life of the fence. Troughs may be placed closer to fences, providing for example, the fence is reinforced with sheets of Riverina mesh.

Water in troughs, can become contaminated by algae, dung, leaves, dust, bees and dead birds. Contamination is really only a problem if the stock refuse to drink it. The contaminants listed above are rarely be toxic. Stock troughs must be cleaned out periodically to remove contaminants. If a trough needs cleaning too often then it may be wise to introduce measures to reduce the amount of contaminants entering the trough.

Algae need two things to grow – sunlight and nutrients. The water delivered through the pipe system has enough nutrients in it for algae to survive. If dung and dust blow into the water then nutrient levels will rise. Consider placing the trough in a location where sheep are less likely to camp. More dung and dust are created where sheep camp. Sunlight can be reduced by building a shade structure over the trough or placing something in the trough that shades some of the water surface.

well placed trough
Trough centrally located trough near shelter and with a base of limestone.
trough on concrete foundation
Trough with a concrete foundation and a well-protected ball valve.


Large round troughs have a big water surface compared to a narrow rectangular trough. Theoretically, round troughs will collect more sunlight than a rectangular trough with the same circumference. This may translate into more algae growth.

At certain times and locations troughs can become clogged with dead bees. Bees need to drink water, but end up drowning in most troughs. The way to stop bees drowning in your trough is to provide them with a safe place to drink and a place to get out of the water should waves knock them in. Bees need secure footholds at the water’s edge. This can be provided by putting plastic containers, partially filled with water, and covered by a stocking in the trough. The containers float in the trough. The stockings have a texture that the bees can hang on to.

Pipes

Ideally, pipes should be buried at least 450 mm below the ground. This is particularly important in areas where the surface may erode, for example, around troughs, in gateways, beside tree lines, along tracks on sandy ground, and around tanks.

Spare pipe fittings particularly joiners, should be kept on hand so that breaks and leaks can be repaired promptly. The hydraulic design of the system may call for a wide range of different pipe sizes. In order to reduce the number of different spares that must be carried, it might be prudent to reduce the number of different pipe sizes in the design. A larger size pipe can be substituted for a smaller size. 1” pipe can be used instead of ¾” pipe with a negligible increase in costs.

Ploughing in pipes

The most widely used method for installing pipes on Mallee farms is ploughing in. A pipe plough can be made, by attaching a curved steel tube to the back of a ripper tyne. Polyethylene pipe is fed down through the steel tube as the tyne is pulled through the soil by a tractor. Some sellers of PE pipe have three point linkage mounted pipe ploughs available for loan. Several Landcare groups in the Mallee have modified rabbit rippers so that they can be used to plough in PE pipes.
When ploughing in PE pipes:
  • Inspect the tube that feeds the pipe into the ground to ensure there are no sharp edges or points that could score the pipe.
  • Rip the line once or twice before installing the pipe to ensure the ripper tine goes to the maximum depth.
  • Try to install the pipe when the air is cool and the sun is not shining. When the sun shines on PE pipe, it warms up and expands. When the pipe goes into the ground it cools down and tries to contract. As a result the pipe will be permanently in tension. This tension will not break the pipe, but it might cause some joints to fail.
  • Unroll the pipe from the coil and lay it out beside the ripper line so that it can be fed up and then down into the plough tube as the tractor moves along the line. Take care to guide the pipe into the tube without kinking it.
  • Do not leave any pipe lying on the ground with an open end. Mice will get into an open pipe and cause a blockage.

Tanks

The area around tanks needs to be protected against wind erosion. Either by a thick layer of limestone rubble extending 3 metres out from the side of the tank in all directions, or by a sheep, cattle and rabbit-proof fence placed 3 metres out from the tank all the way around.
Water Tank in a high but sheltered area
Water Tank in a high but sheltered area with a limestone base


The tank must be fitted with an overflow pipe that will direct any overflow away from the base of the tank. The float valve delivering water from the WMW system should be designed for high-pressure operation. A float valve designed for low-pressure operation may not shut off completely once the tank is full. Any above ground pipe-work at the tank must be protected from stock.

It is useful to have all tanks fitted with a 2” outlet. A 2” Tee can then be connected to the outlet. One branch can be reduced down to whatever size pipes run to stock troughs or homes. The other branch will run straight to a 2” ball valve (or a gate valve). This valve can then be used to fill spray tanks or fire tankers.

Reclaiming the old channels

Farmers are understandably eager to fill in the old channels once the NMP system comes into service.
Please consider:
  • It is dangerous to attempt filling in a channel using a tractor without a Rollover Protective Structure. One farmer has been killed in the northern Mallee when his tractor rolled over while he was attempting to fill in a channel.
  • There are contractors in the area with suitable equipment for safely filling in channels. Their rates are reasonable, especially when farmers cooperate and arrange for a channel passing through many farms to be filled-in in one go.
  • In most of the farming areas across the northern Mallee, less than 5% of the native vegetation cover remains. Do not use the exercise of filling in channels as an excuse to remove more native vegetation. It is state wide planning policy that: "A planning permit is required to remove, destroy or lop native vegetation on any land in a holding of 0.4 hectare or greater in size.” Some exceptions may apply for minor land clearing associated with domestic or rural practices. Landholders can check with their local shire to ascertain any requirements, before undertaking any native vegetation clearance
  • Once channels are filled in, the control of weeds and removal of rabbit harbour will be made much easier.

Water conservation

The Northern Mallee Pipeline system has been built with the primary objective of saving water. Around 70 to 90 % of the water was lost to seepage and evaporation from the old system of channels and dams. The pipeline system delivers close to 100% of the water that is pumped out of the Murray River.

There is also much that can be done on-farm to conserve water.
Saving water on the farm
(Source - Wimmera Mallee Water (1995))
    Take care when setting up new troughs to reduce the chances of breaks or sticking float valves wasting water.
  • Place the trough on a firm foundation and refill the area around the trough from year to year.
  • Arrange pipe-work so that it cannot be knocked, squashed, tugged or hooked by stock.
  • Use a float valve designed for low-pressure operation.
  • Protect the float valve from interference by stock.
When a new pipe or trough is installed, check for leaks. The best way is to put a pressure gauge on the system. Pressurise the system with a pump or the NMP system and then isolate it by closing a valve or the meter tap. Monitor the pressure gauge for a couple of hours. If there are no leaks the pressure should drop by less than 10% in two hours.

If a pressure test is not possible then carefully inspect the pipeline, tanks and troughs for signs of a leak. On sandy soils a slow leak may not cause a wet patch on the surface. Eventually weeds growing over the leak will show great vigour.

Read water meters regularly, and keep a record of the readings and the dates. Also record the number of stock being supplied with water through the meter. From these readings you can calculate the litres/head/day for different times of the year. Then if a reading does not fit the pattern, it may indicate a leak somewhere in the system.

If there is no stock in a paddock and one of the wheels on the meter is moving, then there is a leak in the system. A leaking joint or an overflowing trough can waste thousands of litres, if unnoticed.
Saving water in the garden
Select plants that use less water. Most native plants require little water and maintenance.

Slowing down the wind will reduce water use by plants. Tall trees, shrubs and fences can all act as wind breaks, as well as providing shade.

Group plants with similar watering requirements in the one area. This will reduce the work associated with watering and allow all plants to receive the correct amount of water.

A shade house will protect plants from strong winds and the hot sun. Plants grown in a shade house will need less water.

Lawns use a lot of water so keep the area of lawn to a minimum. Consider the use of alternatives such as bark chips, paving or ground covers. Select hardy lawn species, such as couch grass, kikuyu or buffalo grass.

    If you want to have a green lawn and save water too:
  • Toughen it by only watering it once or twice a week.
  • Aerate the soil.
  • Do not mow the grass shorter than 3cm.
  • Use a timer system with sprinklers.
using a timer saves water
Spray and dripper controller saves water


Use mulch in the garden. Mulch reduces evaporation loss from the soil and reduces weeds that compete with garden plants for moisture. Straw, newspaper, lawn clippings and bark are all suitable as mulch. Well-rotted compost makes ideal mulch and will also improve soil structure. Remember to place mulch away from the trunk of trees and shrubs to prevent collar rot.
Saving water in the house
Keep showers to about five minutes. Ten to twenty litres of water can be wasted every unneeded minute. Installing a water-saving showerhead or a flow-restrictor are cheap and effective ways of saving water.

A full bath uses 200 litres so don’t fill it to the brim. By reducing the water level by 5cm you save 20 litres. A partially filled bath uses less water than a long shower.

Check your toilet for leaks. A leaking cistern can waste thousands of litres per year.

A normal toilet uses about 11 litres per flush. A duel flush toilet means a half flush can be used. Alternatively, the amount of water used for every flush can be reduced by carefully bending the float arm on your cistern down or by placing a clean brick or a plastic bottle filled with water in your cistern.

A washing machine uses 100-200 litres of water per load. Wash a full load at a time or reduce the water level for smaller loads. Laundry water can be recycled. Catch the rinse water in a trough and use it for the next load or put it on the garden.

Don’t fill the sink or run the dishwasher for a small number of dishes. Wait until you have a full load rather than doing several small loads per day.

Glossary

air valve
A device that allows air to escape from a pipeline. The valve comprises a chamber containing a float. When the chamber contains water the float rises to the top of the chamber and seals against a small hole. When the water in the chamber is displaced by air from the pipeline, the float drops down and uncovers the small hole. The water pressure in the pipeline then expels the air in the chamber. Once the chamber is full of water again the float rises and closes the hole.

available head
The maximum possible head difference between two ends of a pipeline.

Back-flow prevention
Devices or methods used to prevent water flowing from the farm pipe system back into the NMP supply system in the event that the head in the NMP system drops below the head in the farm pipe system. One-way valves and air gaps are the most common methods of preventing back-flow.

ball valve
A valve that can be turned by hand to open or close a pipeline. A 90° turn of the handle takes the valve from fully open to fully closed.

design capacity
The amount that you need. Components are selected so that the meet or exceed the design capacity.

direct connection
The connection of two pipe systems without a tank. The pressure from the supply system is carried right through into the receiving system.

domestic and stock
A description used by Water Authorities for the classification of certain water supply systems. Water used for domestic and stock purposes is used for washing, toilet flushing and garden watering in and around homes and for stock to drink. This classification does not include water used for commercial irrigation or drinking water.

float valve
A valve with a float attached to an arm that shuts the valve once the water in a tank or trough reaches a certain level.

flooded suction
The condition where the water at the inlet of a pump is under positive pressure.

flow rate
The volume of water delivered through a pipe in a given period of time.

gate valve
A valve that can be turned by hand to open or close a pipeline. Several turns of the hand wheel are required to take the valve from fully open to fully closed.

head
The total energy of the water at a particular point. It is the sum of pressure and elevation. Pressure is converted to metres by dividing kPa by 10.

hydraulic gradient
The head loss along a section of pipe divided by the length of the pipe.

leaching
The process where water moving through the soil profile dissolves salts and other chemical compounds and hence removes them.

peak daily demand
The maximum volume of water required over a 24 hours period.

peak demand
The maximum instantaneous flow rate required. This flow rate will be much higher than the peak daily demand.

pressure
The compressive stress within water. It has the units of kilo Pascals (kPa).

pressure pump
A pump with a control system that holds the pressure of water on the discharge side of the pump within certain limits by starting and stopping the pump.

pressure rating
The safe long term working pressure for a pipe.

Rural Water Commission
A Victorian state government instrumentality responsible for the provision of water supply and drainage across rural Victoria. This organisation was split into a number of regional bodies in 1994.

service connection
The point where the farm water system is connected to the NMP system. It includes a water meter.

tariff & charge
The tariff defines the structure used by Wimmera Mallee Water to calculate water bills for each property. The tariff structure is reviewed infrequently and involves a process of customer consultation. Charges are reviewed annually by the Board of WMW and may change by a few percentage points.

Whole Farm Planning
An approach to planning the physical layout of a farm and farming operations that takes into account landforms, soil types and sustainable farming principles. The term Property Management Planning is also used to describe the same approach.

Wimmera Mallee Water
A successor body to the Rural Water Commission.

Bibliography

Cummings, D. 1994, Water conservation on rural properties, Landcare Notes SC0007, Natural Resources and Environment, Melbourne, Vic

Cummings, D. 1997, Water quality for farm water supplies, Landcare Notes SC0034, Natural Resources and Environment, Melbourne, Vic

Garrett, B., Nelson, K., Pyke, W., Stirling, A. & Thomas, P. 1976, Farm Water Supply for Stock and Domestic Use, Soil Conservation Authority, Kew, Vic (unpublished)

Heck, B. 1995, Water requirements Stock and domestic purposes, DNR Water Facts W36, Department of Natural Resources, Brisbane, Qld

Hislop, D. 1998, Farm Water, NSW Agriculture, Paterson, NSW

Mansfield, B. 1998, Water requirements of beef cattle, Agnote DAI/18, NSW Agriculture, Paterson, NSW

Southorn, N. 1995, Farm Water Supplies, Inkata Press, Chatswood, NSW

Water Engineering Design Services 1992, Northern Mallee Pipeline Project Outline Design, Rural Water Corporation, Armadale, Vic.

Wimmera Mallee Water 1995, Making Every Drop Count - A Guide to Saving Water around your Property, Wimmera Mallee Water, Horsham, Vic (leaflet)

Wimmera Mallee Water 1995, Northern Mallee Pipeline Information, Wimmera Mallee Water, Swan Hill, Vic (leaflet)

Contact Details:

NRE Bendigo
BENDIGO DELIVERY CENTRE, 3554
Telephone 03 5430 4524
Facsimile 03 5448 4982

Department of Natural Resources and Environment:
-First Floor, Fire Station Arcade, MILDURA, 3500.
(P.O. Box 905 – 3502)
Tel. 03 5022 4300
-Pickering Street, OUYEN, 3490. (P.O. Box 89)
Tel. 03 5092 1322
-324 Campbell Street, SWAN HILL, 3583. (P.O. Box 501)
Tel. 03 5033 1290

Wimmera Mallee Water
District Manager – Ouyen,
PO Box 116, Ouyen 3490,
Telephone 03 5092 1411
Facsimile 03 5092 1637

NMP Project Engineer
PO Box 116, Ouyen 3490
Telephone 03 5092 1613
Facsimile 03 5092 1214

Channel Filling Contractors –
Look in the Yellow Pages under “Excavating &/or Earth Moving Contractors”

Design Consultants –
Look in the Yellow Pages under “Irrigation &/or Reticulation Systems”

Acknowledgements

Cummings, D. 1997, Water quality for farm water supplies, Landcare Notes SC0034, Natural Resources and Environment, Melbourne, Vic

Garrett, B., Nelson, K., Pyke, W., Stirling, A. & Thomas, P. 1976, Farm Water Supply for Stock and Domestic Use, Soil Conservation Authority, Kew, Vic (unpublished)

Heck, B. 1995, Water requirements Stock and domestic purposes, DNR Water Facts W36, Department of Natural Resources, Brisbane, Qld

Hislop, D. 1998, Farm Water, NSW Agriculture, Paterson, NSW

Water Engineering Design Services 1992, Northern Mallee Pipeline Project Outline Design, Rural Water Corporation, Armadale, Vic.

Wimmera Mallee Water 1995, Making Every Drop Count - A Guide to Saving Water around your Property, Wimmera Mallee Water, Horsham, Vic (leaflet)

Wimmera Mallee Water 1995, Northern Mallee Pipeline Information, Wimmera Mallee Water, Swan Hill, Vic (leaflet)
Healthy Viable Mallee Farms

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