Constructing weirs on Serpentine agricultural drains

PHCC Program Manager Neil Dixon with enthusiastic landholders Karen and Bernie Miller.

Improved river water quality, a boost to biodiversity and increased farm productivity are all in the pipeline for landholders in WA’s Peel-Harvey region.

The Better Collaborative Drainage Management project, being led by the Peel-Harvey Catchment Council (PHCC) with funding from the Regional Estuaries Initiative (REI), will see the construction of weirs on agricultural drains, which run into rivers and estuaries in the Peel-Harvey catchment.

The first weir to be built under the project will be constructed in a Water Corporation drain that runs into the Serpentine River. The new weir will simultaneously hold water back in the landscape and also funnel some of it into a nearby artificial wetland that has been constructed by local landholders, where natural cycling should bring big reductions in sediment and nutrients in the water.

The weirs will also reduce the impact of the ‘first flush’ at the start of winter, which is typically the most harmful runoff event of the year, according to Peel-Harvey Catchment Council chairman Andy Gulliver.

“The project will improve the health of the local rivers and the downstream environment, including the Peel-Harvey Estuary,” Mr Gulliver said.

“It will help cut the risk of algal blooms and allow for native plants and animals to flourish in our waterways.”

“Though there are many environmental wins with this project, landholders will also benefit from the weir as it will help retain water in the landscape for a few extra weeks into summer, providing habitat for waterbirds, as well as boosting pasture growth and farm productivity.”

The REI project builds on from a pilot of the weir concept carried out in the Mayfield Sub-Catchment area, where monitoring by the University of WA showed significant reductions in nutrients running-off from the property.

The project will launch its first weir in the Serpentine Catchment with local landholders Karen and Bernie Miller. Up to 10 structures in total are expected to be implemented to improve water quality throughout the Peel-Harvey Catchment over the next two years.

For the Miller’s new weir, the project is targeting a 25 per cent drop in phosphorus travelling through the drain over a 12-month period and a fall in total nitrogen levels by at least 5 per cent, based on reductions achieved in similar projects, including Jenkin’s Weir and the Waroona wastewater treatment swale.

All up it’s a win-win for both the environment and landholders participating in this project, which the Miller family are looking forward to.

“It’s a pleasure to be involved in this project and I enjoy helping improve our environment,” Mr Miller said.

For more information or to get involved with the Better Collaborative Drainage Management project, please contact the Peel-Harvey Catchment Council on 6369 8800 or email