Scientists worked for three years to test inflows and outflows from the site and the Pomahaka Water Care Group has collaborated with the Phosphorus Mitigation Project to run several field days throughout this time.
The preliminary results show about 80% of sediment was being trapped by the bund including about 70% of phosphorus and 60% of nitrogen.
You can read a great write up about this work here.
The Phosphours Mitigaiton Project have developed a Detainment Bund guide, where they describe what a detainment bund is:
A Detainment BundPS120 (DB) is a low earth berm placed across an ephemeral storm water flow path on a farm to temporarily detain storm water run-off for water quality objectives. DBs are usually located on valuable and productive pasture paddocks as these areas are often where ponding opportunities can be optimised with the least earthwork requirements. They are generally not located on permanently flowing waterways.
You can find out more about Detainment Bunds here.
Detainment Bund
The Phosphorus Mitigation Project has been undertaking a trial on a Pomahaka property to assess how effective detainment bunds are a mitigating contaminant movement on our heavier clay soils.
There has been a large amount of work illustrating the effectiveness of detainment bunds in other parts of the country, however there was a limited amount of trialing done on different types of soil. The Pomahaka Water Care Group was approached by the Phosphorus Mitigation Project to see if we could help find a farmer who would be willing to have trial site on their property.
We managed to find a farmer and a suitable site.
