Mouton Citrus: 135 ha Drip Irrigation Design

Mouton Citrus had acquired a large farm with a reliable gravity-fed water supply, an established canal system and a substantial buffer dam. What they did not have was any irrigation infrastructure.

The plan was to develop 135 ha of mixed citrus in two phases: 93 ha first, with a further 42 ha to follow. The challenge was bigger than designing for the first phase alone. The infrastructure needed to work efficiently at each stage of development without forcing the farm to redesign or replace major components as more hectares came online.

What the farm needed

The system needed to do four things well:

• Deliver reliable irrigation across the full 135 ha development
• Use water and energy efficiently
• Operate efficiently as the farm expanded in phases
• Leave a clear path toward future automation and fertigation

Rather than sizing the system around the first phase alone, Ant designed the infrastructure around the farm's current requirements and likely future operating conditions.

The design approach

The system was built around four priorities:

• Reliability: design for consistent performance even when one component is under strain or offline.
• Energy efficiency: size pumps and pipelines around lifecycle cost rather than lowest initial capital cost.
• Water quality protection: use filtration suited to the source water and the sensitivity of drip irrigation.
• Future flexibility: allow the farm to expand and change how it operates without having to start again.

That resulted in a complete irrigation design covering the infield system, mainlines, pumping, filtration, fertigation, controls and pumphouse infrastructure.

What we designed

The design covered the full irrigation system from the pumphouse to the infield dripperlines across all 135 ha, including the pump station, filtration, fertigation infrastructure, mainlines, manifolds and infield irrigation layout.

The key design decisions were driven by how the farm needed to operate as it developed, rather than by the requirements of the first phase alone.

Pumping and energy efficiency

The pumping system uses two pairs of identical pumps, with each pair covering a different range of operating conditions. Variable speed drives allow the system to adjust to changing demand, operating between 35 and 55 Hz to match output to the farm's requirements at each stage of development.

Running an oversized pump at reduced output for years is inefficient and expensive. The variable speed drives and pump pairing avoid that.

Any pump can feed any rising main, allowing different pump combinations to be used as demand changes. This was particularly important for a phased development. The infrastructure could support the early stages without being locked into a configuration that would become restrictive once the full 135 ha were in production.

Pipe sizing and lifecycle cost

Mainline pipe diameters of 200 mm and 250 mm were selected using lifecycle cost analysis rather than minimum capital cost.

Larger pipes require more capital upfront, but they reduce friction losses as water moves through the system. Lower friction reduces the energy required for pumping over the life of the infrastructure.

For a 135-hectare development, that trade-off is significant enough to warrant proper analysis. The objective was to find the point where additional capital investment was justified by the operating cost it could avoid over time.

Filtration and water quality

Drip irrigation is sensitive to water quality, so filtration was designed around the characteristics of the farm's water source and the requirements of the irrigation system.

The system uses 130-micron filtration, with capacity planned around the full development rather than only the initial phase. Filter banks can be brought into operation progressively as the farm develops, with automated backflushing incorporated into the design.

This protects the dripperlines while keeping filtration practical to operate as the system grows.

Fertigation

The fertigation plant was designed with 80,000 ℓ of fertiliser storage, mixing tanks and provision for specialised applications.

The layout allows fertiliser to move by gravity from storage to the mixing area, reducing unnecessary pumping between stages of the process.

Four fertigation groups allow the farm to manage nutrient applications across defined irrigation areas while keeping the operating arrangement straightforward.

Infield irrigation design

The 135-hectare development is divided into four fertigation groups, with each group operating in two shifts.

The infield system is designed to accommodate the orchard as it develops, with dripperlines running up to 190 m and the ability to move from one to three dripperlines per tree row. This gives the farm a defined path for increasing irrigation capacity as the crop develops without requiring the infield layout to be redesigned as demand increases.

Valve clusters are centralised to keep the control infrastructure accessible and reduce the amount of equipment distributed throughout the field. This makes the system easier to inspect, maintain and operate.

The result is a 135 ha irrigation system designed to support the farm through each stage of development, not only the first phase.

The system can expand from one to three dripperlines per tree row as the orchard develops. Multiple pump combinations, fertigation groups and operating shifts give the farm flexibility to match irrigation capacity to changing demand as more hectares come into production. Filtration capacity was planned around the development requirements so the system can expand without having to rethink the entire filtration arrangement.

The value of this project is not in any single pump, filter or piece of pipe. It is in how the system was considered as a whole. Water supply, pumping, pipelines, filtration, fertigation, field layout, energy use and future expansion all affect one another. A decision made in isolation in one part of the system can create a constraint somewhere else.

For Mouton Citrus, the objective was to build infrastructure that works for the farm as it develops, with the flexibility to adapt as operating requirements change.

That is what fit-for-purpose irrigation engineering looks like.