Groundwater quality trend and trend reversal assessment in the European Water Framework Directive context: an example with nitrates in Italy

Eleonora Frollini,Nicolas Guyennon,Elisabetta Preziosi,Nicoletta Calace,Stefano Menichetti,Emanuele Romano,Maurizio Guerra,Marco Marcaccio,Stefano Ghergo

doi:10.1007/s11356-020-11998-0

Abstract

Groundwater resources are of utmost importance in sustaining water related ecosystems, including humans. The long-lasting impacts from anthropogenic activities require early actions, owing to the natural time lag in groundwater formation and renewal. The European Union (EU) policy, within the implementation of the Water Framework Directive (WFD), requires Member States to identify and reverse any significant and sustained upward trend in the concentration of pollutants, defining specific protection measures to be included in the River Basin Management Plans (RBMP). In Italy, official guidelines for trend and trend reversal assessment have been published recently. Statistical methods, such as the Mann-Kendall test for trend analysis and the Sen’s method for estimating concentration scenarios, should be applied at the fixed terms stated by the WFD implementation cycles to identify upward trends, while the Pettitt test is proposed for the identification of trend reversal. In this paper, we present an application of a slightly modified version of the Italian Guidelines to a groundwater body in Northern Italy featuring nitrate pollution and discuss its advantages and limitations. In addition to Pettitt test, for the trend reversal analysis, we apply the Mann-Kendall test in two sections and compare the results. We conclude that this method seems more reliable than Pettitt test to identify a reversal point in quality time series. The overall procedure can be easily applied to any groundwater body defined at risk across Europe, for the assessment of the upward trends of pollutants and their reversal, even with little chemical monitoring data. Although focused on the EU legislative framework, this procedure may be relevant for a wider context, allowing to individuate upward trend as early warning for contamination processes in an integrated water resources management context.

Highlights

Groundwater plays an important role in drinking water supply: about 50% of the world’s human consumption is sustained by groundwater, being the primary source for 1.5– 2.8 billion people (Giordano 2009)
In order to preserve and/or improve the quality of groundwater, the assessment of the chemical status and of upward trends of pollutants is fundamental for the identification of those groundwater bodies (GWB) in which protective measures are most needed
We describe the methodological approach proposed by the Guidelines (“Materials and methods”) and present an application of this procedure, slightly modified, to a groundwater body in Emilia-Romagna (Po Plain, Northern Italy) (“Results”)

Summary

Introduction

Groundwater plays an important role in drinking water supply: about 50% of the world’s human consumption is sustained by groundwater, being the primary source for 1.5– 2.8 billion people (Giordano 2009). In Europe, the share of groundwater needed nationally to meet the total demand for freshwater ranges from 9% up to 100% (Scheidleder et al 1999), and in Italy, more than 85% of the drinking water is supplied by aquifer exploitation from wells and springs (Onorati et al 2006; ISTAT 2017). In order to preserve and/or improve the quality of groundwater, the assessment of the chemical status and of upward trends of pollutants is fundamental for the identification of those groundwater bodies (GWB) in which protective measures are most needed. Since the positive effects of actions to improve the quality of groundwater can be detected after some years from their implementation, it is necessary to identify upward trends of the pollutants in advance (Craig and Daly 2010)

Methods

Results

Discussion

Conclusion