🌿 Sampling of rivers and streams — programme, choice of cross-section and point, handling of the sample (PN-EN ISO 5667-6)

Environment PN-EN ISO 5667-6

Overview

SCOPE, TRANSLATED FROM THE TEXT OF THE STANDARD: this part of ISO 5667 establishes the principles to be applied to the design of sampling programmes, sampling techniques and the handling of water samples from rivers and streams for physical and chemical assessment.

FOUR EXCLUSIONS — EACH REFERS ELSEWHERE. The standard does NOT apply to the sampling of estuarine or coastal waters. It does NOT apply to sampling for microbiological testing — procedures for this are given in ISO 19458, described separately in this database. It does NOT concern the examination of sediments, suspended solids or aquatic organisms. Nor is it applied to passive sampling of surface waters, for which ISO 5667-23 is appropriate. The standard also draws attention to a borderline case: where natural or artificial dams cause water to be retained or stored for several days or longer, the stretch of river or stream concerned should be treated as still water — and ISO 5667-4 is appropriate for sampling it.

WHY THE PLAN IS MORE IMPORTANT THAN THE EQUIPMENT. The standard opens the clause on the programme with a sentence worth quoting in translation: sampling is usually the first step of an investigation and to a large extent determines the quality of the whole investigation. Therefore it is recommended to prepare a detailed sampling strategy, often based on a preliminary investigation in which the relevant aspects have been identified. The manner of sampling follows both from the purpose of the investigation and from the situation in the field.

WHAT THE SAMPLING PLAN SHOULD CONTAIN — EIGHT GENERAL POINTS. The standard lists: the purpose of the investigation; the parameters to be determined for each sampling point; the measurements made at the sampling point together with an indication of the methods — for example temperature, dissolved oxygen, pH or flow rate; the frequency and times of sampling and the type of sample; the sampling location and the number and position of points; the sampling equipment; quality assurance procedures; transport, preservation and storage of samples.

WHAT THE PLAN SHOULD TAKE INTO ACCOUNT REGARDING FIELD CONDITIONS — FIVE POINTS. Safety; the hydrodynamic and morphological characteristics of the water; local circumstances, such as water depth, floating layers, vegetation and accessibility of the site; sampling depths; the expected composition and quantity of the water, including the presence of floating or sediment layers.

FACTORS THAT GOVERN THE BEHAVIOUR OF POLLUTANTS IN A RIVER. The standard lists: temperature, turbidity, depth, velocity, turbulence, slope, changes in direction and cross-section and the nature of the bed. And it adds an explanation that shows why these factors cannot be ranked by importance: the slope and the roughness of the channel affect the depth and velocity of flow, and these together govern turbulence; turbulence in turn affects the rate of mixing of effluents and tributaries, aeration, the sedimentation or scouring of suspended solids, the growth of attached forms and the rate of self-purification. Added to this are chemical and biological processes — photosynthesis, respiration, metabolic transformations.

CHOICE OF SITE: TWO DECISIONS, NOT ONE. The standard divides the choice of sampling site into two questions: where the measurement cross-section lies in the catchment, river or stream, and which exact point in that cross-section. The purpose of the investigation often determines the site directly — for example when assessing the quality of an effluent discharge — but sometimes gives only a general idea, as when characterising the quality in a catchment.

CHANGING THE SAMPLING POINT IS A DECISION, NOT A TRIFLE. The standard states explicitly that practical considerations, for example accessibility, may make the ideal sampling point impracticable — but any change of the designated point, for whatever reason, must be discussed and agreed with the person commissioning the sampling programme. The outcome of these arrangements is recorded in the sampling point record, which contains the route, the exact location of the point, the sampling method and details such as the keys needed and health and safety matters.

WHAT WE DO NOT GIVE. We have a preview of the text of the standard covering the scope, clause 4 on the design of the programme and the beginning of clause 5 on the choice of site; the further clauses — preparation for sampling, sampling techniques, sampling under ice, handling of samples — are in the inaccessible part. We therefore DO NOT GIVE: sampling techniques at individual depths, requirements for samplers, rules for sampling under ice or conditions for preserving and storing river samples.

HOW MANY LABORATORIES THE TAB WILL NOT SHOW (23.09.2026). Measurement (23.09, copy of the scopes, matching by the beginning of the value): "PN-EN ISO 5667-6" stands at the beginning of the value in 123 entries at 119 laboratories; at 7 FURTHER laboratories the designation appears only in the middle of the value and the tab will not show them. HERE, HOWEVER, THE SECOND CAUSE IS MORE IMPORTANT, CONTRARY TO THE OTHER SAMPLING STANDARDS: 25 MORE LABORATORIES DROP OUT BECAUSE OF THE FORM, because they recorded the sheet without the "EN" element — "PN-ISO 5667-6:2016-12" (20 laboratories) or "PN EN-ISO 5667-6" (1). IN TOTAL 32 ARE INVISIBLE: 7 because of POSITION, 25 because of FORM — i.e. for this entry it is not the order in the value that is the main loss, but the split in notation conventions. The cause is as for other sampling standards: several sheets of the 5667 series entered in one value, for example "PN-ISO 5667-5:2017-10 PN-ISO 5667-4:2017-10 PN-EN ISO 5667-6:2016-12 z wyłączeniem…". These notations have no common beginning, so they cannot be fixed with the key; a fix would require matching by the content of the value, i.e. a change in the program.

EDITION (state of the PKN card on 23.09.2026). PN-EN ISO 5667-6:2016-12 is in the English version (42 pages, KT 119 Water Quality - Basic Problems), implements EN ISO 5667-6:2016 and ISO 5667-6:2014 [IDT] and replaced PN-ISO 5667-6:2003 — the Polish version; there is no Polish version of the 2016-12 edition in the catalogue. The card lists the additional element PN-EN ISO 5667-6:2016-12/A11:2020-10 (English version); whether this amendment concerns the content of the guidance — WE HAVE NOT ESTABLISHED.

Method principle

A sample from a river is to represent the water flowing in the given cross-section, not a random place at the bank. Therefore the standard leads from the purpose of the investigation to the plan, from the plan to the cross-section, and only then to the point and the sampling technique. Turbulence and mixing decide whether in a given cross-section a discharge is already mixed with the river water — and on this depends whether one sample is sufficient or whether several must be taken across the cross-section. Impounded stretches are treated as still water, because the assumptions about flow cease to apply there.

Applications

• Monitoring of the quality of rivers and streams — physical and chemical testing
• Assessment of the impact of an effluent discharge on the receiving water: cross-sections upstream and downstream of the outlet
• Characterisation of water quality in a catchment — multi-point programmes
• Design of sampling programmes on the basis of a preliminary investigation
• Keeping sampling point records: route, location, method, keys, safety

Key parameters

Standard

Standard number

PN-EN ISO 5667-6:2016-12 (wersja angielska; wprowadza EN ISO 5667-6:2016 [IDT] i ISO 5667-6:2014 [IDT])

Title (PL)

Jakość wody -- Pobieranie próbek -- Część 6: Wytyczne dotyczące pobierania próbek z rzek i strumieni

Title (EN)

Water quality — Sampling — Part 6: Guidance on sampling of rivers and streams

Step-by-step procedure

1. Establishing the purpose of the investigation

   The purpose determines the manner of sampling. A preliminary investigation is recommended, in which the relevant aspects are identified.

2. Preparing the plan

   Eight general aspects and five concerning field conditions — listed in the description. The plan also includes quality assurance procedures.

3. Choice of cross-section

   Position of the measurement cross-section in the catchment, river or stream. Check whether the stretch is impounded — in that case the standard on still waters is appropriate.

4. Choice of point in the cross-section

   A second, separate decision. Take account of turbulence and the degree of mixing, depth, floating layers and accessibility.

5. Agreeing deviations

   If the designated point is impracticable, the change is discussed and agreed with the person commissioning the programme, and the arrangements are recorded in the sampling point record.

6. Measurements at the sampling point

   Temperature, dissolved oxygen, pH, flow rate — in accordance with the methods indicated in the plan.

7. Sampling, transport and preservation

   In accordance with the plan. WE DO NOT GIVE SAMPLING TECHNIQUES, REQUIREMENTS FOR SAMPLERS AND PRESERVATION CONDITIONS — these clauses of the standard are outside the available preview.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Safety is the first point of the list of field conditions in the standard itself — not an addition to the plan
• Sampling from the bank, from a bridge and from a boat — risk of falling into the water, high water and strong current
• Sampling under ice requires a separate risk assessment — the standard devotes separate clauses to it
• Rivers downstream of effluent discharges — contact with microbiologically contaminated water despite the chemical purpose of the investigation
• SUBSTANTIVE NOTE: this standard is not applied to microbiological testing — PN-EN ISO 19458 is appropriate

Frequently asked questions