Ashburton Lyndhurst Irrigation Scheme

Ashburton Lyndhurst Irrigation Ltd along with Mayfield Hinds Irrigation Ltd and Valetta Irrigation Ltd irrigate 75,000 hectares of farmland in mid-Canterbury and are the three irrigation company shareholders of Rangitata Diversion Race Management Ltd (RDRML).  Ashburton District Council along with Trustpower are the two, non-irrigation scheme shareholders.

The Ashburton Lyndhurst Irrigation Scheme was developed in the late 1940’s to provide borderdyke irrigation via gravity fed open channels. The scheme was originally designed to provide enough water to irrigate 60% of farmland, which at that time was considered to be sufficient.

The Rangitata Diversion Race Management Ltd (RDRML) company was incorporated on 22 September 1989 with farmers subscribing for shares (2/ha) to fund the start-up capital to get the business operational, for things such as employing staff, buying plant and machinery, funding easements and water supply agreements. From 1989 to 1992 the Company negotiated the acquistion of the scheme from the Crown.

RDRML was a dream of pioneering farmers in mid-Canterbury when the 750,000 acre plain was first farmed in the mid-19th century.  It took the massive unemployment of the 1930’s depression to provide the catalyst for the work to start on what would become the RDR.

John van Polanen is chairman of the Ashburton Lyndhurst part of the scheme and more recently chair of the Rangitata Diversion Race, which is the “parent” water scheme.  He is currently in the process of converting a 380 ha plus sheep and beef farm into dairy.

The Stage One work was on John’s part of the scheme, piping water to around 3,800 ha of the Ash/Lind’s 25,000ha. John says it worked really well and that was an encouragment to proceed with Stage 2.

Farmers in the Ashburton Lyndhurst scheme, like others on the RDR, get their water via a supply contract with RDR.

18 December 2007 shareholders approved the $8 million Stage 1 Piping Proposal and in 2008 the project got underway. The concept was to use the natural fall of the land within the open channel irrigation scheme to generate pressurised water at the farm gate, by piping the water from the RDR to each individual farm.  Sufficient pressure would be generated to spray irrigate without pumping.

30km of pipeline, supplying 37 properties to irrigate around 4,000ha was installed.  The design pressure allowed a minimum of 40 metres (58psi) to each property, sufficient for centre pivots, laterals, travelling irrigators & sprinklers.

The advantages of Stage 1 include energy savings, improved water efficiency, including a 15% saving in water by eliminating losses of open channel system; increased irrigated area, minimum of 50 year design life, and very low maintenance costs.

After the Stage 1 Piping Scheme was completed, the 5 farmers just below the RDR could see the advantages of scheme pressurised water, however were too close to the RDR and could not use gravity to generate pressure.  The solution was to use water powered turbines to generate the pressure.

Two turbines were installed on the main race of the ALIL scheme, 1 km below the RDR race. These got underway in December 2009, supplying water to over 940ha.  One turbine drives a high pressure pump supplying water to five big gun irrigators and the other turbine drives a low pressure pump supplying seven centre pivots.

The capital cost was approximately $580,000, however the annual electricity saving for the 5 farmers is around $125,000 annually.  The two turbines operate high and low pressure pumps independently.  The high pressure pump outputs 110 l/sec @ 80m head, the low pressure 235 l/sec @ 40m head.

1n November 2012 the shareholders of the scheme voted in favour of progressing with the Stage 2 upgrade project which will enable 5 ponds to be created and the pressurised pipe system to be extended out to the rest of the scheme. The extension is estimated to cost $110M, funded from new share applications.

John van Polanen says significant water savings, delivery of water under pressure and increased reliability, along with the necessity to keep pace with environmental pressures were behind the major upgrade.

The energy saved by piping the scheme will be equivalent to the energy used by 2,000 homes.

The minimum design pressure is 40 metres (58 psi) to each property, with the potential 18% saving in water allowing an additional 4,000ha to be irrigated.

The 3 year project is to be completed by September 2017.

Water is delivered to 244 shareholders whose farms are west and north of Ashburton

Borderdyke irrigation has been developed over the years, from originally a totally manual system of wild flooding, to the wide border system with digital clocks allowing flood irrigation to be set up for at least a 24 hour period.  Up until 10 years ago, 90% of the schemes shareholders used borderdyke irrigation, this presently sits at around 30%, with approximately 7% of shareholders converting to spray irrigation annually.

Spray irrigation has been used in Ashburton Lyndhurst for at least 30 years, but recent times have seen a dramatic shift from borderdyke, with efficiencies constantly improving.  The latest systems were designed to apply water with millimeter accuracy to meet the plant’s requirements with use of soil moisture probes.

Land use over time has continued to change.  Currently 45% is applied to dairy, 23% dairy support, 17% arable, 14% sheep & beef and 1% other.  The area has predominately medium to light soils.

The Land and Water Regional Plan (LWRP) divides Canterbury into separate groundwater zones and the LWRP process is setting nutrient limits for each of these zones.  Part of this process requires all properties (greater than 5ha and losing more than 20 kg/N/ha) to have a Farm Environment Plan (FEP) completed in 2016 or 2017.

Part 1 of the FEP has recently been rolled out, which requires an on-line survey to be completed.  Shareholders will be required to provide information including, farm area, farm land use, irrigation, nutrient management & supply of a farm map.

Completion of the FEP is a consent requirement for all shareholders being supplied with RDR Water.  During the next 2 years shareholders will also be required to complete FEP – Part 2, which includes risk assessment and management within land management units and management practices against FEP objectives and targets.  History has shown the FEP process helps many farmers to increase the efficiency of their water and nutrient use to give an increase in productivity and profit.