A groundwater perspective on the river basin management plan for central Portugal - developing a methodology to assess the potential impact of N fertilizers on groundwater bodies

The Water Framework Directive establishes that the river basin management plans must have a summary of the pressures and impacts of human activities, such as agriculture, on the chemical and quantitative status of groundwater bodies. In order to identify those areas where a potential impact from agricultural activities on groundwater bodies exists, but currently lacking groundwater monitoring data, a methodology was developed that combines the use of gross nitrogen balance values with the results of a specific vulnerability assessment index. A farm management efficiency parameter is added, to identify the factors that contribute to nitrogen use efficiency and to assess the near-future scenarios. This methodology allows the identification of significant pressures that may be responsible for a groundwater body failing good status where there is no representative monitoring network.