Edge-of-field and flow path mitigation options can complement in-field management of agricultural land-use to reduce diffuse contaminant losses to surface waters. They can provide farmers and land and water managers with an additional range of tools to manage contaminant losses and achieve nutrient limits. Some mitigations such as riparian buffers and constructed wetlands can also provide other valuable ecosystem services, reducing greenhouse gas emissions and flooding, and enhancing biodiversity and aesthetics.
The pathways by which run-off and associated contaminants travel from land to water determines the types of contaminants mobilised, their form (e.g., dissolved or associated with particulates), where they can be intercepted and the suitability of different mitigation options. Each mitigation option has its niche in terms of contaminant(s) and flow path(s) able to be targeted, efficacy, cost, longevity, operation and maintenance requirements, ancillary benefits and disbenefits, landscape fit, and consenting requirements. However, it is often not clear to users which mitigation option is appropriate for their situation, where it could be located, what contaminant reductions and benefits can be achieved, and what it would cost to implement, maintain and operate.
This talk will overview these factors for 7 mitigation options that have wide applicability on pastoral farms to guide decision making by farmers, restoration practioners and land-water managers. The mitigation options considered are grass filter and planted riparian buffers, constructed wetlands, woodchip bioreactors, filamentous algal nutrient scrubbers, sediment traps and detainment bunds. Practical guidance will be provided to assist identification of appropriate suites of mitigations for specific situations and needs.