Environ 2021 Abstract – Darragh Murphy
Date: 16-18 June 2021
Title of Event: Environ 2021 – 31st Annual Irish Environmental Researchers Colloquium
Location: Online – Co-hosted by Environmental Research Institute (ERI) and Environmental Sciences Association of Ireland (ESAI)
Presentation/poster: Presentation (Accepted)
Presentation Title: The application of Natural Water Retention Measures (NWRM) to attenuate flood and water quality issues in agricultural catchments
Abstract (Accepted): Agricultural catchments are affected by elevated loadings of nutrients and suspended solids, channelization of low-order streams and the presence of complex networks of sub-surface drainage. Such human-driven alterations to the hydro-morphological and biological character of agricultural landscapes have the combined effects of inducing both chronic and flood-driven surges of nutrients and suspended solids to receiving water bodies; bringing about not only degradation of habitats for wildlife, but also jeopardizing the quality of drinking waters for humans and livestock. While legislation such as the Nitrates Directive and the Water Framework Directive may, in certain cases, have aided in the reduction of the flux of water quality pressures to receiving streams, rivers and lakes, water quality continues to degrade both in Ireland and internationally at a worrying pace.
Temporary retention of surface waters on land is known to reduce downstream flood risk and to encourage the deposition of suspended solids and biological uptake of labile nutrients such as Soluble Reactive Phosphorus (SRP) and Dissolved Organic Carbon (DOC). In-stream structures which help to retain Particulate Organic Matter (POM) and enhance interactions between hyporheic microbial communities and nutrients in the water column have also been shown to aid in attenuation of pollutants including fecal indicator organisms (FIOs), which pose a significant risk to drinking waters.
The current study, conducted on a mixed-use farm in Co. Cork is investigating the potential for nature-based solutions, namely Natural Water Retention Measures (NWRM) such as in-stream and offline water retention areas to attenuate floods and entrained water quality pressures. Chemical and hydrological data are being collected from a low-order stream within the farm as it is diverted and temporarily retained on forested and rye-grass dominated retention areas, and as its flow is altered by in-stream structures. Preliminary results indicate that retention of stream water on agricultural grassland for a as few as 6 hours can induce significant reductions in stream-borne ammonium and nitrate concentrations. These types of nature-based solutions can be installed at low-cost and can be knitted seamlessly into the agricultural landscape. The adoption of nature-based solutions to flood risk and water quality issues may offer affective protection to rural communities and natural environments, while preserving the physical infrastructure and livelihoods of rural landowners.
