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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. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-020-11998-0.

Some basic approaches to modeling nonpoint-source nitrate contamination in ground water are reviewed including statistical models, reservoir models, analytic models, and numerical transport models. Ongoing studies in Nebraska are used to illustrate several modeling approaches. Although there are a range of models that could be useful in modeling nitrate pollution in Nebraska, the data base limits the choices to relatively simple models in most cases.

Nitrate problems related to ground and surface waters in the Izmir area of Turkey have been investigated in this study. It has been found that heavily polluted rivers also contribute to the nitrate contamination of ground water.

The conversion of nitrate to nitrogen gas by denitrification has been shown to be highly active in riparian-zone organic soils. Nonpoint-source nitrate pollution of streams and lakes can be reduced by utilizing the renovative capacity of these riparian zones. The factors controlling denitrification in riparian zones are reviewed, focusing on the role of carbon supply. Results from a number of recent New Zealand studies are used to illustrate the magnitude of the riparian-zone denitrification process and the factors controlling its rate.

Management issues concerning fertilizer and water application in irrigated agriculture are reviewed with respect to controlling nitrate pollution. The impacts of different types of nitrogen fertilizers and of different agricultural practices on nitrate leaching are analyzed. Irrigation scheduling and methods, and surface and subsurface drainage practices are reviewed in relation to the water management issue of nitrate leaching as a result of excess water supply. Existing knowledge of fertilizer application, water management, and agricultural practices can be applied to improve nitrate pollution control, and corresponding best management practices are proposed.