Validation of salt dilution method for discharge measurements in the upper valley of Aniene river (central Italy)

Stream discharge can be measured using several methods, which can be influenced by the natural streaming characteristics of the river. The conventional approach to measuring stream flow is the current meter method, based on determining the mean discharge using the velocity and the cross sectional area. This method allows quick stream flow measurements, but in mountain streams, during turbulent flow conditions, or in case of flow depths, smaller than the recommended performance limits for conventional current meters, can give unreliable measurements. An alternative method of stream flow measurement is the salt dilution method that involves injecting an artificially tracer (usually NaCl) and determining its dilution, following complete mixing into the flow, by means of integration of the electrical conductivity as a function of time. This technique is available for use in mountain streams where the other procedures are more problematic. This paper deals with the preliminary results referred to the validation of the salt dilution method in the Upper Valley of Aniene River (Central Italy), in the aim if defining a reliable methodology for the evaluation of discharge in mountain streams, where turbulent flows make difficult apply the conventional current meter method. In the following they are presented the preliminary results of stream discharge measurements, coming from three different campaigns driven from September to October 2014, executed in one of the sections of Aniene River. The comparison of these elaborations, carried on by the application of both methods, is useful to define the reliability and accuracy of discharge measurements carried out by salt dilution method.