The comparative analysis of the Hungarian and European methodology of discharge measurement

According to the climate change and Water Framework Directive 2000/60/EC (WFD) the analysis od the status of waterbodies and their continuous monitoring has to be carried out based on unified methodologies and standards. Individual prescriptions have to be in harmony with national and international standards, in order to ensure equal scientific value and comparability of the data. The international standard EN ISO 748 entitled „Hydrometry - Measurement of liquid flow in open channels using current-meters or floats” was issued in 2008. This standard is based on the discharge measurement methods in the European Union (EU) and it differs in some aspects from the Hungarian standard (ME-10-231-16:2009). The goal of our study was to identify and answer the questions related to the introduction of this standard into Hungarian practice. The issue is crucial for the hydrometry units of Hungarian Water Directorates, as if the introduction of a new standard is not correctly substantiated the consequences can include avoidable economical burdens and/or changes in the quality of data. The research was initiated and financed by the Hungarian General Directorate of Water management and targeted at the comparative analysis of the measurement and calculation methodologies of the two standards, carried out on watercourses in Hungary. Thus we have executed a series of measurements in 31 cross-sections on 18 different watercourses in Hungary. Based on our results we can state that the difference between the results of the different methodologies generally does not exceed the uncertainties originating from the measurements themselves. Under specific circumstances (e.g. very low flow velocities) the effect of the chosen methodology can be significant.