[en] An interregional training course on the Use of Nuclear and Related Techniques to Measure Storage, Flows and Balance of Water in Cropping Systems was organized jointly by the SWMCN Section and the Soil Science Unit (SSU) and held from 1 to 25 October 2007 at the Agency's Laboratories, Seibersdorf. In the first week of the Course participants learned about new developments in soil water monitoring devices and took part in computer laboratory exercises aimed at estimating crop water use. The participants were taught the principles behind the electromagnetic (capacitance) probes and why they do not work effectively. During practical sessions they learned how to use the hydroprobes in the field and also learned how to build their own time domain reflectometry (TDRs). It was emphasized that the soil moisture readings from the neutron probe are currently the best, but the need for better capacitance sensors was advocated. Lectures and practicals during the second week focused on plant water relationships, evapotranspiration and crop water use and requirements. Participants learned about the theory and construction of thermocouples and TDR sap flow sensors and constructed their own thermocouples and TDR sap flow sensors to measure and analyze sap flow in citrus. The use of porometers to measure transpiration and leaf conductance and portable infra red (IR) thermometers for measuring the crop water stress index was also demonstrated. As a follow up to the lectures in the second week, the third week lectures and practical sessions in the third week focused on an introductory lecture which outlined the use of stable isotopes to trace plant source water, leaf water isotope enrichment and transpiration and combining ¹³C and ¹⁸O to understand plant response to a water deficit. Participants had field practicals on isotopic procedures for determining sources and fluxes of water in plants and soil, and isotopic methods for integrating inputs and losses to receiving water bodies. There was also a computer laboratory exercise on interpreting, understanding and presenting data generated from the Mass Spectrometer. The last week of the course was devoted to practical field training both in Seibersdorf and at the BOKU University. proposals for presentation outlining the applicability of the proposed project to their individual developing countries