Sampling of running water

The sampling place should represent the whole through-flow profile, or the whole through-flow water quantity. 

The sample is taken from running water, if possible, from the streamline. If the stream has several branches, the sample is taken from the branch with the highest flow rate. In shallow streams, the sample is taken approximately in the upper third or at a depth of about 20-30 cm from the surface in the case of deeper streams the depth for sampling depends on the purpose of the analysis. In some cases, zonal sampling is performed across the whole transversal profile with several vertical samplings. 

The depth of small streams (brooks, artificial channels, water mill drives) ranges over tens of cm, the width over several meters. Sampling is simple since the channel usually forms a streamline. However, water quality 

In emergency situations samples are immediately taken above and below the source of pollution so that a sudden change in water composition can be detected. 

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