The following information has been supplied by the Manning Water Users Association to provide information to the general community about irrigation practices in the Manning.
What farms in the Manning irrigate?
Many different farms in the Manning River catchment irrigate, including dairy and beef producers and citrus and vegetable growers. Some farms irrigate almost all year round; some small ‘hobby’ farms irrigate only for a few days every year. There are some 180 irrigation licence holders along the rivers and creeks which make up the Manning catchment but only a relatively small number (perhaps 30 or so) are irrigating regularly throughout the year.
Why is irrigation necessary?
Irrigation helps fill the ‘gap’ between rainfall events. Historically, most of the Manning’s rainfall occurs in February-April (sometimes in damagingly heavy falls). In spring, when pastures and many crops are demanding water to thrive, it is often dry and summers can be very hot and dry, so established pastures and crops can be damaged if they cannot be given a supplementary ‘drink’ with irrigation.
What types of irrigation systems are used in the Manning?
Different farms use very different irrigation systems. You might see ‘travelling’ irrigators, which comprise a big ‘gun’ on a frame winching itself along a steel cable anchored at one end of a paddock. Or ‘bikeshift’, low-pressure sprays close to the ground and moved in a star pattern using motor bikes. Sometimes aluminium pipes are laid out end-to-end; these have spray nozzles along one side. ‘Lateral’ and ‘pivot’ irrigators have large frames from which are hung many individual spray nozzles; they are self-propelled along the width of a paddock (‘lateral’) or in circles (‘pivot’). Citrus and vegetable growers and others use drip irrigation techniques.
Dairy farmers in particular often irrigate out of their effluent ponds, to recycle nutrients to paddocks away from the river. Various spray types are used for this so you cannot tell if it is effluent water being used just by looking at the irrigation system.
One irrigation technology you won’t see in the Manning is ‘flood irrigation’: laser-levelled paddocks that are periodically flooded for a period and then drained. This style of irrigation, often seen in the Murray-Darling basin and elsewhere, is not suited to the topography and soil types of the Manning.
I see some irrigation happening during daylight hours or on windy days: isn’t this wasteful, shouldn’t irrigation happen overnight or when it is still?
It depends on the irrigation technology and the circumstances of the individual farm. All irrigation is very costly: electricity or diesel for pumps; capital costs of pipework and equipment; maintenance costs; and labour to move irrigation around a farm. So farmers are highly motivated to not waste their irrigation water. Most farms do try to irrigate overnight or in the early morning/late afternoon when evapo-transpiration losses are lowest...but at certain times of the year (cooler months) or in certain weather conditions (high humidity), this is less important. Different irrigation technologies are more sensitive to wind: for example, big ‘gun’ travelling irrigators are not usually operated when it is very windy, but this is less important for low-pressure ‘bike shift’ irrigation. Finally, farm economics and safety factors come into play: for those with electric pumps, the availability of off-peak power is an important consideration when timing irrigation. And if staff are manually re-locating irrigation infrastructure around a farm, it may not be possible to do this safely at night.
Who licences irrigators and determines how much water they can extract?
In NSW, DPI Water licences irrigators. Licences set out how much water can be taken; and what size pumps and other equipment can be used; and precisely where pumps can be located and where water can be applied. MidCoast Council, the water supply authority for the Manning, Great Lakes and Gloucester areas, is not involved in licensing, regulating or supervising irrigation works in the Manning.
What are the current cease to pump arrangements for irrigators?
The Manning Water Users Association adopted cease to pump parameters in November 2014. They are - when the flow in the Manning River is:
1. >41ML but <51 ML for four consecutive days: cease pumping on weekends with no increase in normal weekday daily pumping times (if unmetered) or volumes (if metered) OR alternatively and at the farmer's discretion, pump only between the hours of 5pm and 8am (i.e. overnight).
2. >30ML but <41ML for four consecutive days: reduce pumping by 50 per cent (if metered) or to every second day with no increase in normal daily pumping times (if metered).
3. <31ML for four consecutive days: cease pumping
4. In any of the above circumstances, members recommence pumping only when flows are >50ML for four consecutive days
What is the Manning Water Users Association and how does it operate?
The Manning Water Users Association (WUA) is a voluntary group comprising irrigators from throughout the Manning catchment, including people who draw water from the Manning, Upper Manning, Avon, Gloucester and Barrington rivers and from Dingo Creek. The WUA meets from time to time throughout the year to discuss topics related to river health and irrigation practices. The WUA meets more frequently (sometimes weekly!) during times of threatened or low water flow to agree on reduced-pumping or cease-pumping flow levels and re-commence points. Although these points are determined formally by DPI Water, the Manning WUA has a history of voluntarily imposing restrictions on members before these official restriction points are reached. The WUA invites anyone with an interest in the health of the Manning catchment to attend its meetings (though only licensed irrigators can vote and stand for committee positions); MidCoast Water Services is a valued participant in most WUA deliberations.
Interested in more information?
The Manning WUA can be contacted by writing to:
The Secretary, Manning Water Users Association, 400 Bungay Road, WINGHAM NSW 2429.