Translating the agricultural N surplus hazard into groundwater pollution risk: Implications for effectiveness of mitigation measures in nitrate vulnerable zones

•The overall N surplus hazard decreased significantly during the period of study.•The groundwater status related to NO3− is not improving, but aggravating instead.•In 2016, 33 and 66 % of the area showed respectively high and moderate pollution risks.•GRI complements N surplus in assessing the impact of measures on groundwater quality.•Scenario analysis confirms that targeted measures are more effective than global ones.