A framework for applying interceptive mitigations for diffuse agricultural pollution

Abstract

ABSTRACT Interceptive mitigation options implemented at the edge of agricultural fields and along run-off and drainage flow-paths can complement preventive in-field management actions to reduce diffuse contaminant losses to surface waters. However, it is often unclear to users which interceptive mitigation option is appropriate for their situation, where it should be located, what contaminant reductions and other benefits can be achieved, and what it would cost to implement, maintain, and operate these practices. We outline a framework for selecting and applying eight interceptive diffuse pollution mitigation practices potentially applicable on New Zealand farms: riparian grass filter, planted and multifunction buffers; constructed wetlands; woodchip bioreactors; filamentous algal nutrient scrubbers; sediment traps; and detainment bunds. The framework provides users with a semi-quantitative evaluation of the relative benefits and costs of the best suited mitigations across a range of farmed landscapes. It highlights where each mitigation has its niche in terms of the landscape fit, flow-path(s) intercepted, contaminant(s) targeted, efficacy, associated co-benefits, relative cost, operation and maintenance requirements, longevity, and consenting requirements. Testing and refinement of this framework is encouraged, using data from field-scale implementation, to better quantify efficacy in practice, and inform empirical models and decision making across farm and catchment scales.