For many of us water-in-agriculture means irrigation. But! Do we always have irrigation water available??
The majority of agriculture production in Australia does NOT depend on irrigation or indeed has irrigation water available.
Neither can those producers afford such water supplies unless these are collected on site. And please realise, that at this stage most irrigation competes for water with urban populations. In the Bega Valley this is aggravated by temporary population increases during holiday periods.
If water is so important and if most agricultural production depends so much on water, it appears to us absolutely essential, that we make maximum use of the rain we do get. We therefor repeat the things we must do and thus fit into our routine farming and gardening/orchard practices.
We must make certain that we catch and store all rain - whether it falls in a heavy dollop or in lengthy drizzles.
HOW DO WE DO THAT??
1.Make certain that it does not run off!!
Open up the soil - ensure it is not compacted!
Cover soil with some sort of vegetation.
Mulch, mulch, mulch
Obstruct the run-off, work along the contour!
2.Make certain that it stays in the soil!!
Reduce evaporation
Mulch, mulch, mulch
Break the wind - tree lines, hedges, tall grasses, fences.
One can also notice that there are changes afoot in the way we RE-USE water. Urban populations have the potential to make lots of water available for RE-USE.
There are two potentially big supplies and go under the name of sewage and grey water. Here in the Bega Valley we are not attempting to do anything with grey water - yet. (Grey water is all that water coming from a household, excluding sewerage, i.e. from showers, bath or sink.)
In Sydney The Water Board has the monopoly of supplying water to every household. A competitor has turned up to compete for the grey water from Sydney. After a cleaning process this water will be very valuable as irrigation supplies or for toilets and manufacturing processes.
Is it any wonder that there is competition for such a precious resource?
Sewage is special in that it contains some harmful bacteria and other negative items. But it has the advantage of also containing nutrients such as phosphorus and nitrogen, which are highly priced as fertilisers.
Here in the Bega Valley we are starting to organise the recycling of sewage as a valuable irrigation material for cash plant crops.
Soil and plants combined are excellent recyclers of sewage, because in this medium the sewage disappears completely and is converted into plant products.
Sewage on the loose in sea or lake can be a problem with the production of blue-green algal blooms.
Treating sewage as a resource solves a lot a problems for a society and will provide us with more jobs.
Answers to 15 frequently asked questions on reuse and reclaimed water irrigation.
1. Why use reclaimed water?
Reclaimed water, used in place of fresh water where appropriate, is a valuable resource. Not only can its use assist in the preservation of fresh water supplies, it reduces the need to use commercial fertilisers on crops and pastures. Treated effluent contains water, plant nutrients and organic matter, which together improve soil fertility and encourage plant growth.
The use of reclaimed water can have economic benefits, depending on connection fees and charge per volume. This also relies on limiting the use of the water to prevent costly soil structure problems caused by too many nutrients.
The use of reclaimed water can benefit the environment and community as long as the water is managed properly and the resources of the catchment are considered as part of a total network.
2. Is it more difficult to use than fresh water?
Yes and no. The capacity of plants to take up nutrients and other dissolved substances is limited, so irrigation with reclaimed water may need to be restricted to prevent a build-up of nutrients in the soil or excessive loss to groundwater. Ensuring that the water-loading matches the plant requirements can control this. As plant requirements change through the course of their growth, the application of nutrients also needs to change. In using reclaimed water, it is possible to dilute the water during those periods when there is a demand for water but not for additional nutrients.
Reclaimed water can be applied using flood, sprinkler and drip irrigation methods, and can be used on turf, pasture, trees and a range of horticulture and fodder crops. The application rates are the same as for fresh water, and on the same time frame as the irrigation season.
3. Can I use it all the year round?
This depends on the climate of your area. The amount of irrigation is governed by rainfall and evaporation, which together determine the water supply and demand of a pasture or crop. In most of Victoria, evaporation generally exceeds rainfall during the warmer months. At these times soil moisture levels fall and plant growth declines. In the cooler months there is usually enough rainfall to meet the water requirements of growing plants. Reclaimed water produced in the cooler months must be held in storage until the next irrigation season.
In warmer climates it is possible to irrigate all the year round. Irrigation quantities still vary with the seasons and some storage is still required.
4. Won't the use of reclaimed water just add to the salinity problem occuring in the area?
Irrigation with reclaimed water can raise the salt levels around the roots of irrigated plants. Consequently, some leaching is necessary if irrigation is to be sustained. Rainfall usually flushes the salt away causing the leached salt to enter the groundwater. The keys to ensuring no problems occur are good drainage and no salt build-up prior to commencing irrigation. In addition, it is necessary to carry out a site assessment to determine the groundwater level and quality before irrigation begins.
5. Is it possible to have a scheme with prolonged sustainability?
With careful management, suitable crops and an appropriate irrigation site it is possible for a reclaimed water irrigation system to be sustainable in the long-term. The following factors are relevant to ensuring sustainable irrigation practices are undertaken:
The application rate is equivalent to the requirements of the crop, pasture or woodlot.
Surface and subsurface drainage.
Buffer distances should remove the nutrients from the ecosystem. Turf growing and cropping are examples of enterprises that export nutrients.
A properly sized storage lagoon is usually required to ensure that irrigation only occurs when required.
Government regulations encourage sustainable irrigation practices. Land characteristics, groundwater, irrigation methods and land use are basic factors that must be considered.
6. Will the quality of the groundwater be adversely affected?
Excessive irrigation with low quality water involves a risk of pollution of the groundwater. The Draft State Environment Protection Policy (Groundwaters of Victoria) proposes that any discharge of waste to land must give consideration to the impact of rising water tables on the sustainability of irrigation. These factors need to be determined prior to the installation of any wastewater irrigation scheme.
7. Won't run-off from the irrigation site contaminate other sites?
The EPA publication "Guidelines for Wastewater Irrigation" defines the arrangements required for containment on-site. Run-off collection systems are sometimes required to collect run-off and recycle it back onto the irrigation area. This prevents any run-off flowing onto neighbouring properties or to waterways.
A site management plan is usually part of an agreement between the operator and the Authority for the sale of reclaimed water. Run-off control forms a part of this agreement.
8. Will there be an odour associated with the irrigation?
Odour problems are usually the result of either poorly managed treatment and collection systems or overload of these systems. Properly managed irrigation systems of reclaimed water should not produce any odour at all.
9. Will toxic metals accumulate in the soil?
Trace elements are essential for life. It is therefore not surprising that domestic wastewater usually contains small quantities, but these should not pose a threat to the soil quality. The balance of elements and nutrients does need to be monitored as normally occurs in irrigated agriculture.
10. What about the possibility of phosphorus accumulating close to the surface?
Long-term application of nutrient-rich water can result in excessive accumulation, especially of phosphorus, in the soil. This can be dealt with in several practical ways: ensuring the input of nutrients always matches the output; ensuring the reclaimed water is diluted with fresh water during low-growth periods; and ensuring plant matter is removed.
11. What other environmental factors should be considered?
One of the prime objectives of using reclaimed water for irrigation is to divert the discharge from the rivers and streams onto the land. This diversion assists in reducing the levels of nutrients in these streams that can otherwise lead to the growth of blue-green algae.
Care needs to be taken with a diversion to ensure that the amount of water diverted does not leave the receiving environment without an adequate flow. A gradual change to any ecosystem is preferable in order to monitor these changes.
12. What health considerations need to be incorporated in the scheme?
Reclaimed water from sewage treatment facilities is required to meet prescribed microbiological health standards. The treatment of reclaimed water is a very effective method of safeguarding public health.
Factors influencing the survival of pathogenic micro-organisms in soils include moisture, temperature, pH, nutrients, organic matter and the presence of some organisms and toxins. Micro-organisms remaining on exposed surfaces are destroyed by sunlight and desiccation. For this reason there is a withholding period after irrigation before access is allowed to public recreation areas. There are also buffer distances for residential areas from reclaimed water irrigation.
13. Can disease to be transported when recycled water is used on crops and pastures?
Appropriate wastewater treatment and, sometimes, restrictions on produce (e.g. Salad vegetables) are required to prevent the spread of organisms capable of causing disease.
14. Have there been any cases of disease outbreaks attributable to the use of reclaimed water in Australia?
No. The regulations and safety measures applied in Australia have been effective on preventing disease outbreaks caused by reclaimed water use. The Victorian Environment Protection Authority (EPA) is about to release new guidelines for the use of reclaimed water that will cover health-related standards.
15. What are the main advantages and disadvantages of using reclaimed water for irrigation?
Advantages:
Reduced impact of wastewater discharges on the waterways.
Fewer requirements for commercial fertilisers.
Ready supply of irrigation water.
Replaces the use of high quality (drinking) water for irrigation.
Disadvantages:
Reduction of in-stream environmental flows.
Possible problems with sustainability of land uses.
Requires careful management and monitoring.
