Revision of maximum allowable nitrogen inputs applicable for the Danish River Basin Management Plan 2021-2027 (RBMP3): A follow-up on the international evaluation

This report constitutes a follow-up to the International Evaluation of the Scientific and Legal Basis for Nitrogen Reduction in the 3r^d Danish River Basin Management Plan (RBMP3), which was finalised in October 2023. Two of the issues identified by the international evaluation panel included 1) the use of Chl-a target values in open intercalibrated water bodies and 2) the applicability of eelgrass depth limit in shallow water bodies leading to alternative methods for estimating Maximum Allowable nutrient Inputs (MAI) to Danish coastal waters. In addition, the methods for estimating riverine nutrient inputs to coastal waters have been revised, resulting in updated data for nitrogen loadings. In this report we assess the implications of updates for the MAI estimations and revise the MAI estimations used for the RBMP3 taking into account the scientific updates and alternative solutions resulting from the international evaluation.

This report is financially supported by the Danish Environmental Protection Agency (DEPA) under the project “Second opinion phase III, strengthen model foundation”. While DEPA has commented a previous draft of the report, the content and recommendations are the sole responsibility of the authors.