Sampling from larger bodies of water

Samples from reservoirs, ponds and lakes are taken from various localities and various depths, usually by means of deep sampling devices. It is not recommended to take an average (pooled) sample since substantial differences in the water quality in different positions of the point samples may cause chemical reactions and mispresent the final results. 

Sampling in valley dams over 10 m high is carried out at several predetermined points (profiles) from a boat. Marking of the sampling points by anchored buoys simplifies position fixing. Zonal sampling should be performed to follow the stratification and motion of in-flow water in reservoirs. 

Ponds and small reservoirs with a dam lower than 10 m are sampled from boats, employing series and zonal sampling for various analyses. In some cases, the point samples for a given purpose can be obtained from fixed systems of the dam. 

Sampling of the sea and ocean waters requires well-equipped oceanographic ships. It also includes the collection of plankton and sampling of the sea sediments and upper layers of the sea bottom. 

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