Evolution and assessment of a nitrate vulnerable zone over 20 years: Gallocanta groundwater body (Spain)

Nitrate pollution from agricultural sources is one of the biggest issues facing groundwater management in the European Union (EU). During the last three decades, tens of nitrate vulnerable zones (NVZ) have been designated across the EU, aiming to make the problem more manageable. The Gallocanta Groundwater Body in NE Spain was declared as an NVZ in 1997, and after more than 20 years, significant improvements in water quality were expected to be observed. In the present study, the spatiotemporal trend of nitrate concentration within the Gallocanta NVZ in the last 38 years was assessed, and the effectiveness of the NVZ implementation was tested. Data from the official Ebro Basin Confederation monitoring network from 1980 to 2018 were used, and the results showed an increasing but fluctuating trend in nitrate concentration since 1980. Although a slight improvement was detected after the NVZ designation in 1997, the low rate of improvement would take decades to reach desirable levels in most of the area. The lack of update and control of action programmes, the inappropriate NVZ delimitation, and the influence of natural factors seem to be the reasons for the failure of the nitrate reduction measures. Currently, nitrate pollution and groundwater management are a matter of concern for the EU, so given the recurring problems in water supply in the area and the nonfulfillment of the goal of good quality status, more demanding measures are needed to be implemented in the short term.

This work was undertaken thanks to a pre-doctoral grant awarded by the Government of Aragon to J. M. Orellana (BOA 20/07/2017). The work received funding from Ministerio de Economía y Competitividad via the Research Project AGRO-SOS (CGL2015–66016-R), and it was also supported by the Juan de la Cierva – Formación program, FJCI-2016-24,920; Research Project CGL2015–64284-C2–1-R awarded to D. Merchán.