This publication is a result of the Coordinated Research Project (CRP) F32008 "Global Monitoring of Nitrogen Isotopes in Atmospheric Waters" implemented by the IAEA’s Isotope Hydrology Section in 2018-2023. The CRP was focused on the determination of the spatio-temporal distribution of nitrogen isotopes in precipitation as a potential source of nitrogen pollution of water resources, especially of aquatic systems sensitive to eutrophication stressors. The principal method was based on the combined application of nitrogen isotopes with atmospheric chemistry and hydrometeorological techniques to better understand wet deposition processes and to characterize the origin and transformations of inorganic nitrogen loadings. This publication was supported by specialists in isotope hydrology, atmospheric and water sciences from a range of different countries around the world. Examples of their isotope applications have been provided to give context to the guidelines and recommendations made by this publication.