DOI: 10.5281/zenodo.18538473
title: BMP matrix longlist
title: BMP options matrix for catchments

description: This dataset summarises the “Longlist” of nitrogen (N) and phosphorus (P) mitigation options compiled during the first phase of WP3 in the New‑Harmonica project. See report: https://research.wur.nl/en/publications/the-development-of-a-bmp-matrix-for-mitigation-options-in-nw-euro/

To ensure the Best Management Practices (BMPs) considered across the project were up‑to‑date and suited to the landscapes, land uses, and climatic conditions of the four participating catchments, a comprehensive review was undertaken. Seventy‑two BMP options were identified by drawing on previous research programmes (including COST 869/ADAS, Fairway and the Demonstration Test Catchments), existing project outputs, and an extensive literature review. Additional innovative BMPs were incorporated following discussions within catchment teams and consultations with the WP1 Policy Group, aiming to extend the assessment beyond widely implemented measures such as riparian buffer strips.

For each BMP, potential trade‑offs and synergies were evaluated in terms of N and P load reduction, gaseous emissions, and soil carbon sequestration. The compiled Longlist was presented to the catchment working groups, who then shortlisted the most relevant measures for scenario development in subsequent work packages. This shortlisting process was supported by informal engagement with local stakeholders—farmers, NGOs, policymakers and unions—who provided insights into the feasibility, cost‑effectiveness, adoption potential and environmental trade‑offs of each measure.

Following discussions held during the first year of the project the following categories were added to the longlist matrix:Name of BMP evaluated (including a brief description and a cross-refence to (i) the ADAS Newell-Price (2011) BMPs; ii) “FS#” which are the numbered Factsheets referred to in Schoumans et al (2014) originally obtained from the COST action 869 project). The Longlist is divided into blocks depending on the source of the BMP, the last block (highest numbers) were measures suggested by the catchment teams in late 2023.Target: Following the standard classification of Source, Receptor and Pathway used for point and diffuse source mitigation classification. One, two or all three targets can be addressed by the specific BMP.Scale (of BMP) field > farm > catchment, where a “farm” contains multiple fields and a “catchment” one or many farms.Impact on diffuse nutrient loads in rivers from the BMP (N and P). The impact is assumed to reduce these relative to baseline conditions unless indicated by a “+” sign. Here, C may be included at a later date if the literature supports C being treated as a pollutant or nutrient causing issues in freshwaters but this has not been flagged up to date (except in the Wye) as a potential pressure).Impact on soil nutrient balance from the BMP (positive or negative, i.e. increasing or decreasing the quantity of the nutrient in question in the upper soil relative to baseline conditions).Impact on losses of nitrate to groundwater from the BMP, either “Shallow” or “Regional”. The definition of these categories was: “Shallow” being groundwater which then flows back into the local streams within the catchment and thus contributes to the nutrient loading at the monitored outlet; whereas “Regional” groundwater may flow out of the catchment or even discharge to coastal waters.Timescale for effectiveness (Short or Long) of the BMP, “Short” would be to achieve an effective, demonstrable solution in less than 5 years (although this is subjective and open to debate).Impact on Gaseous emissions (N and C only) due to the BMP, the main emissions from agricultural catchments being: ammonia, nitrous oxides and methane (positive or negative changes to the fluxes of these pollutants under baseline conditions)Risk of Pollution Swapping (N and C only), this is related to the previous category and to the risk of an aqueous nutrient discharged (e.g. nitrate) being converted or “swapped” by the BMP to a gaseous pollutant (e.g. ammonia), or vice-versa.Supporting Literature including websites and reports (in terms of the citeable papers and reports - these have been reviewed above).

Datasets, for example catchment monitoring data to support the effectiveness of riparian fencing.These categories were elucidated in the matrix by a simple “Y” or “N” or “+ -“ indicator rather than a full quantitative assessment, and some categories are rather subjective and open to debate, especially if new evidence from BMP studies comes online during the next few years (for example to clarify if constructed wetlands several decades old can become a source of P if they become full of sediment and are not maintained properly). The COST869 Factsheets provided a useful summary of each BMP for most of the categories listed above and can be accessed here: https://www.cost869.alterra.nl/Fs/List_of_options.htm. A short description of specific changes brought about by the BMP has been included (for example if a particular form of gaseous N is associated with the BMP). Arguably, an additional column could be added for “unexpected consequences”, which is similar to pollution swapping but relates to the BMP causing a different pollutant to be emitted to the “baseline” conditions. This could for example represent pollution swapping from releasing soluble reactive P under baseline conditions to releasing ammonia gas after the BMP is introduced (according to Kleinman et al., (2022)).