The role of the South Australian Department of Agriculture/PIRSA
Most horticultural, viticultural and vegetable crop production in South Australia is dependent on irrigation to provide crop water requirements, deliver economic yields and satisfy consumers quality demands. The largest production region, the Riverland, is fully dependent on irrigation as rainfall (average around 250 mm per year) is insufficient for crop production. Water is supplied from the River Murray and used predominately on grapevines, stonefruits, almonds and citrus, some other perennial crops and to a lesser extent vegetables. There are areas of pasture on the Lower Murray, downstream of Mannum.
Around 400 Gl of water is diverted to irrigate around 40,000ha of crops and pasture. The actual volume diverted in any year is dependent on climatic conditions, the volume allocated on SA River Murray water entitlements; and the volume traded from interstate entitlements. Elsewhere in the state most irrigation districts are groundwater dependent, and to a lesser extent, use surface waters from local catchments for supplementary irrigation. Pipeline schemes also transfer River Murray water, and reclaimed effluent water, into some districts.
Irrigation from the River Murray requires:
- pumping water from the river to supply a water distribution system and deliver water to each property in an irrigation district. Earliest irrigation development was on the floodplain or on re-claimed wetlands (swamps) where water could be supplied by gravity or by the pumping technology then available to lift water at a head of a few metres to river terrace (floodplain) soils. Later development of the mallee highland soils became possible once reliable pumping systems were developed that could lift water up to 30 metres above the river valley. Early pumping systems were usually steam powered, later replaced by diesel or electric powered pumps. The expansion of the electricity grid through the Riverland in the 1950’s to 1980’s facilitated the expansion of irrigation.
- a suitable water distribution system to supply each farm in an irrigation district. Early distribution systems were open channels, and while usually concrete lined were prone to leakage and water loss. The gravity channel supply system also meant large areas of land above the channels could not be irrigated. From the 1960’s, all new developments and redevelopment of older districts utilised pipelines, thus minimising water losses and when connected to pressurized on-farm irrigation commanded all available land, including that above the supply channels.
- a suitable method within the farm to distribute water to each crop plant. Early systems were entirely flood or furrow irrigation, but from the 1950’s sprinkler, and from the 1970’s micro-sprinkler and drip systems were adopted. Today irrigation water is almost entirely applied to crops through some form of pressurized system, with minor exceptions for some irrigated pastures that may be flood irrigated where soils and gradients are appropriate.
- decisions on when to irrigate, and how much water to apply. Early irrigation was on some form of fixed roster administered by the water supplier; current irrigation is generally by the individual irrigator utilizing some form of decision support to determine an efficient irrigation schedule.
History of irrigation development in the Riverland
Irrigation of horticultural crops in the Riverland commenced in a significant way with the establishment of Renmark by the Chaffey Brothers in 1887. Such large scale irrigation was dependent on pumps that could lift water a few metres from the river to channels, through which water could be supplied (on roster) to each farm in the district. The Chaffey’s had themselves developed new steam powered pumps, which they had built in England where the necessary skills and engineering resources were available. When installed at Renmark (and at Mildura in Victoria) these pumps were world-leading technology. Within farms water was distributed along channels, by gravity, and applied to crops by furrow or flood irrigation.
Subsequently, as other irrigation districts were developed in the first half of the 20th century, a similar framework was utilized. This comprised a pumping facility on the river, steam, diesel or, later, electric powered, lifting water to a community irrigation district (generally 20-30 metres above the river) which may have some hundreds of farms. Water was distributed using a gravity dependent channel system to each farm, and gravity distribution and application within the farm.
Apart from Renmark, which was managed by a Trust, and the Village Settlements of around 1894, generally the South Australian Government constructed and operated the water supply schemes that delivered water to each farm in the community irrigation districts. Individual farmers were responsible for their on farm irrigation infrastructure (for a history of irrigation development along the River Murray see Irrigation Settlement – some historic aspects in South Australia on the River Murray 1838 – 1978, DB Mack, 2003, and Irrigation and Settlement in the South Australian Riverland, BJ Menzies and PN Gray, Department of Agriculture Technical Paper 7, 1983).
The village settlements were: Gillen, Pyap, Lyrup, Murtho, New Era, Waikerie, Ramco, Holder, Kingston, Moorook (all established in 1894) and New Residence (established in 1895). Most of the settlements had difficulty in pumping water from the river; some were abandoned, while some absorbed into subsequent State Government developed irrigation districts. Lyrup continues today; and despite enormous difficulties demonstrated that village settlement irrigation schemes could be successfully established.
After 1909 the South Australian Government developed irrigation districts, and installed pumps and water distribution systems, at Waikerie (from 1909), Berri (from 1910), Moorook (from 1911), Cobdogla (from 1912), Kingston (from 1913), Mypolonga (from1913), Cadell (from 1919), and Chaffey (from 1922). After World War 2, the Commonwealth Government established irrigation districts at Cooltong and Loxton.
Downstream of Mannum from around 1881, semi-permanent wetlands adjacent to the river were re-claimed by both private developers and the South Australian Government, for irrigated pastures.
Photo 1: Irrigation in the Berri Irrigation District, circa 1980. Areas of salinized land due to shallow watertables can be seen in the centre of the photograph.
By the mid 2000’s all irrigation districts managed by the State Government had been rehabilitated (that is, supply channels replaced by pipelines and the water distribution pumps replaced or upgraded) and were self-managed, through the Central Irrigation Trust.
Private investment has also been significant. From the 1950’s (some development occurred earlier), private development utilised electric pumps to lift water to pipeline water distribution systems and applied water through sprinkler or drip irrigation systems. Private development includes both individual irrigation farms (pumps, distribution system and irrigated land as one entity) and community development (where the pumps and distribution system provide water to a number of farms, that may be separately owned).
Until the 1970’s little effort or resource was applied to farm level irrigation management, or to research, development or extension. An early attempt in 1905 to establish a Government Experimental Orchard at Waikerie as an annex to Roseworthy Agricultural College failed (Roseworthy didn’t develop comprehensive irrigation training or courses until the 1980’s). Samuel McIntosh, appointed in 1910 as Director of Irrigation in the newly established Department of Irrigation and Reclamation, prepared advisory material some of which was published by the Department of Agriculture (for example see Bulletin 58 (1910) Hints to Intending Irrigationalists – Erection of Pumping Plants). In 1928 the Director of Agriculture (Arthur Perkins) enquired of both the Council for Scientific and Industrial Research (CSIR) and the Waite Institute of their interest in placing a soil chemist at the Berri Experimental Farm (presumably due to salinity and soil concerns). However, the responses received indicated that services would be developed at other Centres (including Merbein, Griffith and Waite) and that a scientific officer with broader responsibilities would be a more appropriate Riverland appointment. CSIR, and later CSIRO did undertake a number of soil surveys in the irrigation districts, but there was little local scientific support to farmers in irrigation technology or water management.
Irrigation management problems - salinity
Salinisation of irrigated soils is a problem encountered in many irrigated districts worldwide, and the Riverland has been no exception. The problem arises when irrigation volumes are applied in excess of requirements and as a result shallow water tables develop, soils are saturated, and evaporation leaves salt residue in the surface soils and rootzones.
Riverland soils are derived either from floodplain deposits, (for example, Renmark, parts of Cobdogla, and the reclaimed swamps of the Lower Murray), or from calcareous windblown material (the mallee dune and swale soils of the highland irrigation districts). The mallee soils are generally shallow and sandy or light textured, with a low water holding capacity, and are often underlain by heavy clay (Blanchetown Clay) that restricts rootzone drainage and can perch drainage water. The subsoils, and the regional groundwater, are often saline, due to the accumulation of salt over the previous geological history of the region.
The combination of shallow, sandy textured rootzones with low waterholding capacity, the roster irrigation delivery system forcing irrigators to take water when available rather than when needed (and generally at rates that exceeded the waterholding capacity of the rootzone soils), the use of flood and furrow irrigation with inherent water application inefficiencies, and the clay subsoils all contributed to rising watertables and salinisation at the soil surface due to evaporation from the saline watertable.
Anecdotal evidence suggests that more than half the applied irrigation water could be lost to drainage. Even by the early 1980’s with sprinklers and some capacity to order water, irrigators were still wasting half of their water.
Photo 2: Furrow irrigation of a Riverland vineyard, showing excessive water application (late 1970’s). Poor crop health is also evident.
Serious salinity problems were frequently evident in irrigation districts (as early as 1899 saline seepage was reported in low lying areas of the Lyrup Village Settlement) with the solution being abandonment of lower lying land and the installation of subsurface drains to remove excess water. Irrigation could only continue with the construction of comprehensive drainage schemes through most of the irrigation districts. From the early 20th century reduced water application was recognised as being necessary to manage the salinity problem, but the water supply and irrigation technologies available could not support efficient irrigation.
Private irrigation development was generally sprinkler irrigated (later drip) and often did not develop the same drainage problems as the community districts, suggesting better and more efficient water manage-ment, although many of these developments later developed some water table problems.
Photo 3: Undertree sprinkler irrigation (1980’s). This system offered greater scope for efficient water application, but many design and equipment problems needed to be resolved.
Even the Loxton irrigation district, developed in the late 1940’s as a soldier settlement scheme and laid out using detailed soil surveys and sprinkler irrigation on the sandier soils, developed shallow water tables within a few years. This required installation of sub-surface drainage over most of the district.
The irrigation equipment available at the time of development was not necessarily suitable for the crops or soil types. Sprinkler irrigation led to more uniform water application and was increasingly used from the 1950’s, especially on sandier, lighter textured soils. However, without pressurised internal pipelines on each farm this system of irrigation could not be used.
Sprinkler technology was developed primarily in the USA from the 1930’s. Loxton Irrigation Area, constructed in the late 1940’s, was the first Riverland district to be at least partially pipelined and utilised fixed overhead sprinklers on higher elevation land (sand-dunes) that could not otherwise be readily supplied with water. Generally, grapevines were grown on lower-lying land with heavier textured soils, and furrow irrigated, while tree crops were placed on higher land with lighter textured soils and irrigated by furrow, or later, by sprinkler systems. The use of sprinkler systems was later facilitated by the development of lower cost plastic piping.
Overhead sprinkler irrigation systems initially used proved unsuitable at times of high salinity in the River Murray, due to foliar uptake of salt. After the high salinity year of 1967 when some trees were defoliated by the high salinity water (in the 42 months from Jan 1965 to June 1968, the salinity level in the River Murray at Morgan was above 800 EC for 31 months and peaked at 1400 EC in February 1968) there was a conversion from overhead sprinkler irrigation to low level or undertree systems.
In the 1960’s the Department of Agriculture did some work on sprinkler irrigation, related to more effective operation (including rootzone soil water relationships and pressure checking at sprinkler heads). Milton Spurling, Bill Harris and Max Till were the key people engaged in these early investigations.
Photo 4: Trevor Slugget measuring water pressure at an overhead sprinkler (circa 1980). Such data allowed for assessment of the operational performance of the irrigation system.
From around 1970 drip and micro-irrigation systems were developed. Plastics manufacturing companies with factories in Adelaide drove this initiative (rather than demand from irrigators). These plastic irrigation systems offered potential for much greater water application precision, and the Department of Agriculture embarked on some trial work at this time (for example, Max Till conducted research on drip irrigation on a citrus farm at Waikerie in 1971). Other innovations from the plastics Industries included plastic pipelines that could be easily installed, was relatively low cost, and was integral to the development of new, on farm, sprinkler, micro sprinkler and drip irrigation systems.
A new approach
Significant programs related to the management of water on farms were initiated by the Department of Agriculture from the 1970’s. For the first time serious effort was applied to resolving irrigation management on the farm with a new focus on irrigation equipment, irrigation scheduling, and better matching of irrigation application volumes to the soil water deficit.
In 1971 the Department of Agriculture opened the new Loxton Research Centre laboratory and office complex, and made a number of new staff appointments. While the initial focus was on horticultural crop production technology, there was an interest in expanding services to irrigation industries.
From the late 1960’s the Horticulture Branch operated a leaf analysis laboratory (the former Loxton Flour Mill laboratory) that could analyse the salinity content of plant leaf tissue, and irrigated soils. It was from around this time that salinity data from the blocks was used to help guide an irrigator’s management decisions. Soil Conservation Branch Soils Officer Ken Wetherby was studying mallee soils and his work improved the understanding of subsoil water transmission and the importance of the regional stratigraphy in drainage and water table development.
In 1970 Keith Watson, a recent graduate, was appointed to a new advisory position in irrigation. This was a significant and important new initiative. The position was notable because it was the first irrigation extension officer in Australia and the first real recognition of the importance of irrigation management to horticulturalists. From 1972 Phil Cole, another recent graduate, was located at Loxton to undertake research into irrigation management and crop production.
By 1972, a new Department of Agriculture core group with interest in irrigation and water management was developing which included Adelaide based Max Till and Ben Robinson, who worked in conjunction with Loxton based Keith Watson, Phil Cole, Trevor Glenn (chemist) and Ken Wetherby. This team was supported by the Loxton laboratory providing plant and soil analyses for water and salinity for field programs.
Photo 5: Keith Watson using tensiometers to assess soil water, 1973. Measurement of the water content of soils was crucial to understanding crop water use and for the appropriate timing and volume of irrigation applications.
The investigations of the early 1970’s for the first time monitored soil water content in a number of farms over the irrigation season, and for each irrigation event. Many irrigated properties exhibited excess water in the rootzone, due to application of water volumes much in excess of the soil water deficit, and as a result root systems were in poor health. The research linked crop production decline to poor irrigation management, in particular excess water application. The solution of installing subsurface drainage to remove excess water was not effective in remediating the problems.
Excess irrigation application over many decades generated groundwater mounds beneath the irrigation districts; the underlying clay layers. Low permeability subsoils led to perched water tables; and the low unsaturated hydraulic conductivity of the subsurface layers limited the drainage of water to underlying tile drains. Drainage by tile drains did not appear to provide a ready solution, and for the first time attention seriously moved to consideration of modifying irrigation practices.
In the mid 1970’s the Department of Lands (administering the irrigation districts) provided funds for a re-construction of part of the furrow irrigation system on one Loxton property (Hendrick’s) and for a field assistant (Robert Ziersch) and laboratory assistant (Joy Atze). Drip, sprinkler and furrow irrigation management using a climate and soil tensiometer based irrigation application decision system were trialed. This work, and related district level operational and policy considerations, led to a complete rethink on irrigation management, and over time led to the adoption of improved irrigation practices, improved water use efficiency and improved productivity. This approach was facilitated at the Executive level in the Department as Jim McColl, then Director, had previously worked in irrigation management and had a strong appreciation of the water management problems faced by irrigators.
Photo 6: Phil Cole (on right) in one of the first drip irrigated vineyards in the Riverland, circa 1973.
By the late 1970’s sufficient experience had been gained to suggest a new whole of system approach based on a new understanding of soils (in particular soil water holding properties), new irrigation equipment and technologies (which now included low level sprinklers, micro sprinklers and drip), soil water monitoring, irrigation scheduling, and soil surveys (soils, systems and scheduling). This lead to much improved water management.
At the same time the South Australian Government, with funding assistance from the Commonwealth, and later an irrigator contribution, commenced rehabilitating the water distribution systems in the community irrigation districts, with pipelines replacing channels. This provided a new opportunity to move away from the roster water delivery system to a water order as required system (although initially the rationale for district rehabilitation had not considered this significant opportunity or benefit).
The Department would say, for the first time, to the Public Works Committee investigating new drainage disposal basins that while it supported engineering investment for salinity management, the solution (to salinity management) was largely to be found in better irrigation management at the farm level (McColl and Till (1979) Noora Drainage Disposal Scheme - Department of Agriculture submission to Public Works Committee). The regionalisation of the Department’s programs was at the same time bringing the Department much closer to industry, and increased the influence of the regional leadership (Geoff Thomas) in negotiations with other agencies and in interaction with industry.
In 1978, as a direct result of advice provided by the Department’s Loxton irrigation officers to the salinity and drainage investigations undertaken by the River Murray Commission and the Australian Government, a major research and extension program in irrigation and salinity commenced (RMISIP, the River Murray Irrigation and Salinity Investigation Program) with themes that included irrigation efficiency, salinity management; irrigation extension, irrigation equipment, and crop and irrigation system survey. This was a major initiative for the Department and further supported major change in water management in the Riverland. Max Till and Geoff Thomas had key roles in negotiating the program with (in particular) the Commonwealth and the Engineering & Water Supply Department and, jointly provided high level program overview and direction.
At Loxton, staff levels increased by around 15 people; new facilities and specialist laboratories were developed at the Loxton Research Centre. The Riverland program was initially managed by Don Plowman, and later by Phil Cole. Programs were also developed for the Lower Murray Reclaimed Swamps, with staff support based in Adelaide.
The development of the new irrigation technology ‘package’ by the Loxton team required solutions to a number of key matters, including:
Appropriate soil information.
The soils of many of the Riverland irrigation districts had been mapped, mostly by CSIR and later CSIRO, between 1930 and 1950. The published maps were at a district scale, providing information on soil texture and depth. However, there was limited data that could be used at the farm, or planted block level that was useful for water management.
In 1973 Cole and Watson resurveyed the Kingston irrigation district and developed a new methodology that provided data at the planted block level, allowed for estimation of the depth of rootzones, and incorporated new subsoil understanding derived from the investigations on mallee soils undertaken by Wetherby. This methodology generated ‘profile description sheets’ and later refinements led to the inclusion of soil water information, including plant available water.
The expansion of facilities at Loxton Research Centre in the early 1980’s included a soil physics laboratory, managed by Tony Zimmermann. Laboratory equipment and field soil sampling equipment needed to be developed, but this was successfully done (and became routine after the new laboratories at Loxton are built in 1982). Greg Cock also produced a set of soil water release curves for Riverland soils.
For the first time adequate soil information that could inform the design of irrigation systems and the management of water application was readily available. Subsequently most irrigation development and redevelopment was preceded by a new soil survey based on this approach.
Photo 7: Greg Cock soil sampling in a drip irrigated vineyard (1982). Adequate soil data was necessary for the determination of rootzones and water availability to crops. Tensiometers (the white box) have also been installed.
Efficient irrigation management also required precise knowledge of root zones such that good irrigation systems could be designed and so these could then be managed such to only replace the soil water deficit at each irrigation.
Estimation of crop water use:
Two approaches were followed.
Climatic data was used to calculate crop water use through a potential evapotranspiration approach. Evaporation pan data was initially available from Loxton Research Centre and Golden Heights (Waikerie). This was useful for planning purposes, and while low cost, was found to have many limitations for practical irrigation management at the farm or irrigated block level. However, electronic weather stations were later established across the region to provide data for a range of requirements for crop protection and these also assisted with more accurate estimation of crop water use.
The second approach was direct measurement of soil water content. This required suitable instruments, and consideration of spatial variation and sampling density. The approach taken at Loxton was to develop a direct measurement methodology. Initially tensiometers were used. Although labour intensive, they proved reliable and suitable for research purposes, and monitoring sites were established on many properties. Soil water release curves (derived from the laboratory data) were used to convert the tensiometer data (soil water potential) to soil water content, from which crop water use could be calculated. The data collected by Jill Sinclair and her team over three years from around 1980 showed that significant water loss occurred in many vineyards even when apparent good practices were followed. Neutron moisture meters were also used as a research tool to directly measure soil water content, but could not be widely utilized or operated by farmers.
The Loxton team (Peter Buss and Keith Watson) saw a need for new soil moisture measurement technology and instruments that could replace both tensiometers and neutron moisture meters. Later when both had moved to the private sector they were involved in developing an electronic capacitance based system, which was commercialised (Sentek) and marketed worldwide. These were some of the first commercialized instruments in the world based on capacitance soil moisture measurement. The instruments could be left in situ, data could be transmitted to an analysis centre, and farmers could operate them.
Computer programs to make data handling more efficient were also developed locally (initially by a Renmark irrigator, Peter Weir, who was contracted to the program) and have been continually refined and remain in use today.
The fundamental irrigation questions are how much water to apply to the crop, and when to apply the water. The direct soil water measurement approach, based on soil water content change, could estimate crop water use and to support a real time irrigation scheduling approach. The program developed the methodology, instrumentation, and application approaches that could be used for irrigation scheduling and that would overcome the problem of applying excess water.
Photo 8: Peter Weir collecting soil water information for irrigation scheduling (1984).
Better irrigation equipment, and irrigation equipment standards
A close liaison with the irrigation equipment manufacturing, import, design and supply industry was established, primarily through Keith Watson and Trevor Slugget. A local equipment testing facility was established on Loxton Research Centre, based on ISO and ICWA standards for measurement and evaluation. This facility undertook uniformity measurement of small low-level sprinklers, outside evaluation of larger overhead and undertree sprinklers, and a test rig over a swimming pool to look at the effect of particulate matter in irrigation water on the life of micro sprinklers.
Computer synthesis programs (Peter Weir) were written to simulate water application uniformity at various water operational pressures and system designs. The irrigation equipment manufacturing industry in the USA and Israel had developed equipment evaluation, testing and standards. No such services were available in Australia.
Photo 9: Murray Harvey operating the sprinkler wetting pattern test rig, Loxton Research Centre (1984). This set-up was the forerunner to the Australian Irrigation Technology Centre later established at the Levels Campus of the University of South Australia.
Initially the equipment to measure sprinkler wetting patterns was set up at Loxton Research Centre. Later, in conjunction with the irrigation manufacturing industry and importers, a new dedicated testing facility was opened at the University of SA Levels Campus in 1989 (the Australian Irrigation Technology Centre, Jeremy Cape, Manager; today continues as the Australian Irrigation and Hydraulic Technology Facility run by the University of South Australia). This effort led to a significant improvement in the standard of the sprinkler and drip irrigation equipment available, its design at site specific levels, and its operation.
Keith Watson and Ken Smith (E&WS) also established a series of ongoing meetings between the two Departments and the irrigation industry (represented mainly by local retailer/system designers and equipment manufacturers), aimed at upgrading and making better use of irrigation equipment.
Knowledge and training
In the 1970’s and 1980’s, there was limited irrigation science and technology education and training resources in Australia. To improve officer skills and to access appropriate technologies, an officer exchange was initiated around 1980 with the Israeli Ministry of Agriculture (including the Soils and Irrigation Field Service, and Sprinkler Testing services). This aimed to introduce relevant technologies, learnings from irrigation equipment testing, and soils and irrigation field services. It assisted development of the Australian Irrigation Technology Centre, the Irrigated Crop Management Service, and salinity management in horticulture.
A similar approach after 1984, with the United Stated Department of Agriculture (Agricultural Research Service Water Management Laboratory at Fresno, California) assisted development of better estimation of crop water use, district water balances and irrigation scheduling.
An extension service for soil survey, irrigation system design, and irrigation scheduling (the Irrigated Crop Management Service) was set up to transfer the irrigation management technology to irrigators. This included aspects of fee for service, and led to establishment of a number of commercial services providing irrigation management advice to irrigators. These businesses continue to provide these services to irrigation industries across south eastern Australia.
Landcare groups also developed programs (the WaterCare program) to take the technology (in particular soil moisture measurement) onto farms.
The program developed at Loxton that focused on water management at the farm level, was complemented by the rehabilitation and pipelining of the Government irrigation districts that enabled water supply on demand rather than roster; and the conversion of area based to volumetric water allocation to irrigators. This encouraged irrigators to become more water use efficient, with water savings being used for additional production that provided economic benefits for irrigators and the community. At the district scale the volume of drainage water decreased and the area irrigated increased while at the farm scale water was scientifically managed and delivered real productivity and quality outcomes.
The success of this program was very much due to the extent of cooperation created between the Department of Agriculture, the Engineering and Water Supply Department, and to an extent the Department of Lands. This cooperation occurred at two or three levels and involved:
- Heads of Departments Jim McColl and Keith Lewis;
- senior staff including Geoff Thomas, Don Plowman, Max Till and Jim Killick (E&WS); and Phil Cole, Keith Watson, Lance Gladigau (E&WS), Campbell McKnight (E&WS) and Chas Allen (E&WS).
The irrigation industry in the Riverland and Lower Murray in South Australia underwent a transformation over the 20 year period from around 1980. The area under irrigation expanded, with around 500 Gl of water (at full allocation) used annually. While the volume of water available had not increased (apart from a small volume traded from interstate) the area irrigated (particularly of high value horticultural crops) had increased as had production, in both $ terms and $/Ml of water. The irrigation management programs implemented through the Department of Agriculture/PIRSA and the research and extension initiatives developed at that time were major contributors to this growth.
This article has been prepared by Phil Cole with contributions and assistance from Keith Watson, Greg Cock, Gerrit Schrale and Don Plowman.