Following several discussions about our results, AgResearch scientists were interested in following up and doing some further analysis. They suggested, that fortnightly sampling might not present an accurate picture of what is really going on in these wetlands, so they undertook a three-year trial measuring inflows and outflows under different flow patterns, such as during dry times and heavy rainfall.
The results showed that the size of the wetlands were small compared to their contributing catchment area, but that still resulted in some reductions to contaminants with reductions in sediment (53%), phosphorus (31%) and E.coli (10%) for the wetland on a sheep and beef property, but limited reductions on the wetland on a dairy farm. The full results can be read here.
Wetland Trials
The Pomahaka Water Care Group have several trial sites where we're working to assess the effectiveness of sediment traps and wetlands to remove contaminants leaving land and entering water.
From January 2019, Otago Regional Council began testing water from four mitigation sites fortnightly, this testing programme was completed in June 2020. The results are shown below.
