Seminare

Bio: Brandon Goeller is an Early Career Researcher with experience in applied catchment ecology, hydrology, biogeochemistry, and GIS mapping. Brandon’s research during his PhD (2015-2018) at the University of Canterbury, NZ, until present at the National Institute of Water and Atmospheric Research (NIWA) has examined how multifunction riparian buffers, constructed wetlands, and other interceptive diffuse pollution mitigations can improve water quality and improve ecosystem health. Prior to his work in NZ, Brandon was a Fulbright and DAAD scholar at the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) (2010-2012) and worked as an environmental policy consultant at Ecologic Institut in Berlin (2012-2014). Brandon specialises in catchment ‘systems thinking’, which crosses multiple scales and involves processes from interactions between flowing waters and soils, to the decisions that land managers make at field- to farm-scales, to understanding the context of regional and national policy drivers.

Abstract: Freshwater ecosystem health is impaired in agricultural landscapes where degraded streams are treated as drains that receive excess sediment, nutrients, faecal pathogens, and agricultural chemicals. In particular, the clearance of riparian vegetation and drainage of wetlands has crippled the ability of these critical land-water interfaces to filter runoff and attenuate diffuse pollution. To assist landowners, their communities, and rural industries to rehabilitate agricultural waterways, improved practical guidance on the design and implementation of riparian buffers, wetlands, and other ecological engineering measures, underpinned by a robust scientific evidence base, is urgently needed.

Surface-flow constructed wetlands (CWs), comprised of vegetated shallow channels or a series of impoundments, are the most suitable and lowest-cost type of wetland to construct for intercepting and attenuating diffuse pollution. Their simplicity and robustness under highly variable flow conditions makes them widely applicable across a range of farm types and landscape settings, and they can enhance multiple ecosystem services. Based on a review of international and New Zealand data, provisional estimates for NZ suggest that, as their relative size increases from 1-5% of their contributing catchment, CW median annual removal efficacies will increase from ~50-90% for Total Suspended Solids, ~26-48% for Total Phosphorus, and ~25-53% in for Total Nitrogen in warm regions and ~17-38% for Total Nitrogen in cool regions. However, field-scale information to quantify CW efficacy in relation to wetland size across different landscapes, flow pathways, and climatic zones is limited.

To address these knowledge gaps, NIWA are working in partnership with regional governments, rural industries, and farmers to quantify and demonstrate the field-scale performance of CWs for reduction of sediment, nutrients, and faecal microbial contaminants from mixed surface runoff and groundwater inflows. Our work has created a ‘demonstration network’ of well-designed and rigorously monitored CWs to rehabilitate agricultural subcatchments. These wetlands benchmark the diffuse pollution attenuation of CW and serve as educational platforms that showcase the practical application, benefits, and fit of wetlands within a range of diverse farm systems and landscapes. Further research at these sites is recommended to benchmark the ancillary benefits of CW and feed this back into improved, more cost-effective designs that also enhance e.g., biodiversity, carbon sequestration / greenhouse gas reductions, and moderate effects of droughts and floods on catchment hydrology.

See in addition this background document on the topic provided by Jacob von Bonin