SIST ISO 5667-6:2007
(Main)Water quality -- Sampling -- Part 6: Guidance on sampling of rivers and streams
Water quality -- Sampling -- Part 6: Guidance on sampling of rivers and streams
This part of ISO 5667 sets out 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. It is not applicable to the sampling of estuarine or coastal waters and has limited applicability to microbiological sampling. This part of ISO 5667 is not applicable to the examination of sediment, suspended solids or biota. In cases where naturally occurring or artificially constructed dams result in the retention or storage of water for several days or more, it might be better to consider the stretch of the river or stream as a standing water body for sampling purposes. ISO 5667-4 provides guidance for sampling in these circumstances.
Qualité de l'eau -- Échantillonnage -- Partie 6: Lignes directrices pour l'échantillonnage des rivières et des cours d'eau
Kakovost vode - Vzorčenje - 6. del: Navodilo za vzorčenje rek in vodnih tokov
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МЕЖДУНАРОДНЫЙ ISO
СТАНДАРТ 5667-6
Второе издание
2005-07-15
Качество воды. Отбор проб.
Часть 6.
Руководство по отбору проб из рек и
потоков
Water quality – Sampling –
Part 6: Guidance on sampling of rivers and streams
Ответственность за подготовку русской версии несёт GOST R
(Российская Федерация) в соответствии со статьёй 18.1 Устава ISO
Ссылочный номер
ISO 5667-6:2005(R)
©
ISO 2005
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ISO 5667-6:2005(R)
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ISO 5667-6:2005(R)
Содержание Страница
Предисловие .v
Введение .vii
1 Область применения .1
2 Нормативные ссылки .1
3 Термины и определения .1
4 Составление программы отбора проб.3
4.1 Выбор точки отбора проб.3
4.2 Частота и время отбора проб .6
5 Подготовка к отбору проб.7
6 Отбор проб в указанных местах.7
6.1 Отбор проб с мостов.7
6.2 Отбор проб из ручьев.8
6.3 Отбор проб с берега.8
6.4 Отбор проб с катера.8
6.5 Отбор проб при наличии льда.8
7 Методы отбора проб.8
7.1 Отдельные дискретные пробы .8
7.2 Отбор проб с конкретных глубин.9
8 Оборудование для отбора проб.9
8.1 Отдельные дискретные пробы .9
8.2 Отбор проб из поверхностных слоев для легких неводных жидкостей (например,
масел) или поверхностных пленок.10
8.3 Устройства для отбора проб с конкретных глубин.10
8.4 Устройства для автоматического отбора проб.10
8.5 Другое оборудование для отбора проб.11
8.6 Обеспечение хранения пробоотборного оборудования и проб перед доставкой в
аналитическую лабораторию .11
9 Отбор пробы.12
9.1 Прибытие на место .12
9.2 Промывка оборудования.12
9.3 Прямой отбор проб .12
9.4 Непрямой отбор проб с помощью сосуда для отбора проб .13
9.5 Отбор проб через лед.13
9.6 Отбор проб поверхностных слоев или пленок .13
9.7 Отбор точечных проб .13
9.8 Добавление консервантов на месте отбора .13
9.9 Маркировка .14
10 Стабилизация, транспортировка и хранение проб.14
10.1 Стабилизация .14
10.2 Транспортировка .14
10.3 Безопасность и контролируемость проб при хранении и доставке.15
11 Качество .15
11.1 Исключение возможности загрязнения .15
11.2 Идентификация проб и записи .15
12 Отчеты .16
12.1 Аналитические отчеты .16
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ISO 5667-6:2005(R)
12.2 Протоколы отбора проб . 16
13 Сертификация/регистрация/аккредитация . 17
14 Контроль качества. 17
15 Меры предосторожности . 17
Библиография . 18
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ISO 5667-6:2005(R)
Предисловие
Международная организация по стандартизации (ISO) является всемирной федерацией,
объединяющей национальные органы по стандартизации (комитеты-члены ISO). Работа по разработке
международных стандартов, как правило, ведется в технических комитетах ISO. Каждый комитет-член,
заинтересованной в разработке теме, ради которой был образован данный технический комитет,
имеет право быть представленным в этом комитете. Международные организации, правительственные
и неправительственные, поддерживающие связь с ISO, также принимают участие в ее работе. ISO
тесно сотрудничает с Международной Электротехнической Комиссией (IEC) по всем вопросам
стандартизации в области электротехники.
Международные стандарты разрабатываются в соответствии с правилами, приведенными в Части 2
Директив ISO/IEC.
Основное назначение технических комитетов заключается в разработке международных стандартов.
Проекты международных стандартов, принятые техническими комитетами, рассылаются комитетам-
членам на голосование. Для опубликования международного стандарта требуется собрать не менее
75 % положительных голосов комитетов-членов, принявших участие в голосовании.
Обращается внимание на тот факт, что некоторые элементы настоящего документа могут являться
предметом патентных прав. ISO не несет ответственность за идентификацию части или всех подобных
патентных прав.
ISO 5667-6 разработан Техническим комитетом ISO/TC 147, Качество воды, Подкомитетом SC 6,
Отбор проб (общие методы).
Настоящее второе издание отменяет и заменяет первое издание (ISO 5667-6:1990), которое было
пересмотрено в техническом отношении.
ISO 5667 состоит из следующих частей под общим наименованием Качество воды. Отбор проб:
1
— Часть 1. Руководство по составлению программ и методик отбора проб
1
— Часть 2. Руководство по методам отбора проб
— Часть 3. Руководство по сохранению и обработке проб воды
— Часть 4. Руководство по отбору проб из озер, естественных и искусственных
— Часть 5. Руководство по отбору проб питьевой воды из очистных сооружений и
трубопроводных распределительных систем
— Часть 6. Руководство по отбору проб из рек и потоков
— Часть 7. Руководство по отбору проб воды и пара в котельных
— Часть 8. Руководство по отбору проб мокрых осаждений
— Часть 9. Руководство по отбору проб морских вод
1
Стандарты ISO 5667-1 и ISO 5667-2 в данный момент подвергаются совместному пересмотру и будут
опубликованы как ISO 5667-1.
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ISO 5667-6:2005(R)
— Часть 10. Руководство по отбору проб сточных вод
— Часть 11. Руководство по отбору проб грунтовых вод
— Часть 12. Руководство по отбору проб донных осадков
— Часть 13. Руководство по отбору проб осадков станций очистки сточных вод
— Часть 14. Руководство по обеспечению качества при взятии и обработке проб природных вод
— Часть 15. Руководство по сохранности и обработке проб осадков и отложений
— Часть 16. Руководство по биотестированию проб
— Часть 17. Руководство по отбору проб взвешенных наносов
— Часть 18. Руководство по отбору проб грунтовой воды на загрязненных участках
— Часть 19. Руководство по отбору проб морских отложений
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ISO 5667-6:2005(R)
Введение
Понимание цели отбора проб является важной предпосылкой для определения принципов, которые
должны быть применяться в решении конкретной проблемы отбора проб. Примерами целей программ
отбора проб обычно используемых для рек и ручьев могут быть:
а) определение пригодности воды из реки или ручья в бассейне реки по качеству для конкретного
использования, например:
1) в качестве источника питьевой воды,
2) для сельскохозяйственного использования (например, все типы ирригации, для питья
скота),
3) для поддержки и/или развития рыбных хозяйств,
4) для эстетического пользования (например, для водных видов спорта и плавания);
b) оценка воздействия человека на качество воды, например:
1) исследование воздействия сброса сточных вод или аварийных разливов на дренирующий
водоток,
2) оценка воздействия землепользования на качество реки или ручья,
3) оценка воздействия накопления и сброса веществ, включая загрязняющие вещества из
донных отложений на аквабиоту в водной массе или в донных отложениях,
4) изучение воздействия отвода, регулирования стока речного бассейна и переброса воды
из одной реки в другую на химическое качество рек и их аквабиоту,
5) изучение воздействия работ по регулированию рек на качество воды (например,
постройка/разрушение плотин, изменение структуры русла/дна).
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МЕЖДУНАРОДНЫЙ СТАНДАРТ ISO 5667-6:2005(R)
Качество воды. Отбор проб.
Часть 6.
Руководство по отбору проб из рек и потоков
1 Область применения
В данной части ISO 5667 содержатся принципы, которые должны применяться для составления
программ отбора проб, методов отбора проб и обращения с пробами воды из рек и ручьев для
физического и химического анализа.
Это неприменимо к отбору проб эстуарных или береговых вод и ограниченно применимо к отбору проб
для микробиологического анализа.
ПРИМЕЧАНИЕ Процедуры для отбора микробиологических проб описаны в международном стандарте ISO 19458.
Данная часть ISO 5667 неприменима к исследованию отложений, взвешенных твердых частиц или
биоты.
В тех случаях, когда естественные или искусственно созданные плотины вызывают удержание или
накопление воды в течение нескольких дней или дольше, возможно лучше рассмотреть расширение
русла реки или ручья для создания непроточного водоема для целей отбора проб. В международном
стандарте ISO 5667-4 содержатся указания оп отбору проб в таких ситуациях.
ПРЕДУПРЕЖДЕНИЕ – Внимание в данной части стандарта ISO 5667 сосредоточено на отборе и
целостности проб воды. Отбор этих проб может быть опасным, поэтому внимание
привлекается к существованию в некоторых странах законодательных требований к
безопасности персонала.
2 Нормативные ссылки
Следующие справочные документы необходимы для применения данного документа. Для ссылок с
датами применимо только указанное издание. Для ссылок без дат применимо последнее издание
справочного документа (включая любые поправки).
ISO 5667-18:2001, Качество воды. Отбор проб. Часть 18. Руководство по отбору проб грунтовой
воды на загрязненных участках
ISO 6107-2:1997, Качество воды. Словарь. Часть 2
3 Термины и определения
Для целей данного документа термины и определения даны в документе ISO 5667-18 и ISO 6107-2 с
учетом следующего.
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ISO 5667-6:2005(R)
3.1
автоматический отбор проб
automatic sampling
процесс, при котором пробы отбираются дискретно или непрерывно, независимо от участия человека и
в соответствии с предварительно заданной программой
[ISO 6107-2:1997]
3.2
точечный отбор проб
incremental sampling
метод, в котором отбираются малые пробы из-за низкой скорости потока (с возможностью загрязнения
донными отложениями) или из-за ограниченного доступа (например, когда проба отбирается
устройством с малым отверстием); затем эти малые пробы соединяются и образуют смешанную пробу
ПРИМЕЧАНИЕ Используется вся жидкость, содержащаяся в малых пробах, в отличие от смешивания аликвот
при составлении усредненной по потоку (flow-proportional) пробы (см. 8.4).
3.3
изокинетический отбор проб
isokinetic sampling
метод, в котором проба из водного потока поступает в отверстие пробоотборника с той же скоростью,
что и скорость потока в непосредственной близости от пробоотборника
[ISO 6107-2:1997]
3.4
легкая неводная жидкость
light non-aqueous-phase liquid
LNAPL
органические соединения, имеющие низкую растворимость в воде и плотность ниже плотности воды,
например нефтепродукты
[ISO 5667-18:2001]
3.5
выборочный отбор проб
random sampling
вид отбора проб, при котором вероятность получения различной концентрации определяемого
компонента в точности равна той, которая определяется гауссовым распределением данного
компонента
3.6
река
river
природное тело из непрерывно или периодически текущей воды с хорошо определенным
направлением движения к океану, морю, озеру, внутриконтинентальной впадине, болоту или другому
водоему
[ISO 6107-2:1997]
3.7
участок для отбора проб
sampling site
общая область в водном пространстве, в которой отбираются пробы
[ISO 6107-2:1997]
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ISO 5667-6:2005(R)
3.8
точка отбора проб
sampling point
точное положение в месте отбора проб, в котором отбираются пробы
[ISO 6107-2:1997]
3.9
поток
stream
вода, текущая непрерывно или периодически с хорошо определенным курсом, как и река, но обычно
меньших размеров
[ISO 6107-2:1997]
3.10
подпроба
sub-sample
часть, отобранная из пробы и считающаяся представителем этой пробы
3.11
систематический отбор проб
systematic sampling
отбор проб, при котором пробы отбираются через заранее установленные промежутки времени, часто
равномерно распредёленные во времени
4 Составление программы отбора проб
4.1 Выбор точки отбора проб
4.1.1 Общие положения
Обычно перед тем, как отбирать пробы, рассматриваются следующие факторы. Практические вопросы,
такие как доступность, могут сделать идеальную точку отбора проб непригодной. Любые изменения
выбранной точки отбора проб на любом основании следует обсудить и согласовать с составителем
программы отбора проб. Результаты обсуждения могут быть записаны в файл обора проб, который
содержит указания по месту отбора, подробное описание расположения точки отбора, метод отбора и
конкретные подробные сведения (например, необходимые ключи и вопросы техники безопасности).
Можно отдельно отметить эквивалентные точки отбора проб, которые могут использоваться, если,
например, меняются условия течения реки. Также можно указать тип отбора пробы, например, глубину
погружения.
4.1.2 Выбор участка для отбора проб
При выборе точного расположения точки, в которой должны отбираться пробы, обычно
рассматриваются два аспекта:
а) выбор участка для отбора проб (т.е. расположение сечения отбора проб в бассейне реки, реке или
потоке);
b) определение конкретной точки на этом участке.
Часто выбор участка определяется целью отбора проб (например, в случае определения качества
сброса сточных вод), но иногда цель определяет только общее направление поиска участка отбора
проб, например, в случае получения характеристик качества бассейна реки.
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ISO 5667-6:2005(R)
Выбор участков для отбора проб для отдельных станций отбора проб обычно несложен. Например,
можно выбрать станцию мониторинга в качестве базовой для определения качества воды, чтобы
использовать обычный мост или чтобы отводимые сточные воды или приток хорошо успели
перемешаться в горизонтальном направлении до станции. Положение точек отбора на станциях
мониторинга системы водоснабжения необходимо зафиксировать в узких пределах.
В областях с сезонными дождями, где имеются длительные периоды без дождей, количество воды в
реках очень сильно меняется, и участки для систематического использования следует выбирать таким
образом, чтобы они были доступны и удобны для пробоотбора в периоды минимального и
максимального наполнения.
Если необходимо выполнять отбор проб зимой из-подо льда, следует выбирать участок для отбора
возможно более близко к участку, который используется для отбора проб во все остальные времена
года. Если отбор проб должен производиться рядом с мостом, участок должен находиться достаточно
далеко вверх по течению, чтобы исключить загрязнение проб песком и солью с дороги. Отклонения от
обычной точки отбора проб должны быть зарегистрированы в результатах анализа как часть набора
данных.
4.1.3 Важность перемешивания
Когда изучается влияние притока или сброса сточных вод на качество воды на конкретном участке
реки или в основном потоке, необходимо выбрать по меньшей мере два участка для отбора проб; один
должен находиться непосредственно выше по течению, чем место слияния, а второй – достаточно
далеко вниз по течению, чтобы гарантировать полное перемешивание.
Расстояния, необходимые для полного перемешивания сливов с основным потоком, в значительной
степени определяются физическими характеристиками русла реки.
Смешивание в потоке происходит в трех направлениях, а именно:
а) вертикально (от поверхности к дну);
b) горизонтально (от одной стороны к другой);
с) в продольном направлении (выравнивание пиков и спадов в концентрации компонентов стоков
по мере прохождения воды вниз).
Расстояния, на которых происходит перемешивание в этих трех направлениях, должны учитываться
при выборе участков и точек обора проб; они зависят, среди прочего, и от скорости течения реки. Для
изучения процессов смешивания и проведения измерений полезно использовать введение меток
красителей в поток.
ПРИМЕЧАНИЕ Использование метода меток может потребовать разрешения органов, ответственных за
водоснабжение, так как при этом возможны проблемы с выбросом химических веществ в окружающую среду.
Если это так, то для изучения процессов перемешивания проще использовать уже имеющиеся характеристики,
такие как рН, температура или электропроводность.
Обычно стоки в большинстве потоков полностью перемешиваются вертикально в пределах километра.
Обычно пробы можно отбирать только на одной глубине, хотя расслоение может иметь место в реках и
ручьях с медленным течением в результате термических и других эффектов, влияющих на плотность.
В таких случаях может потребоваться отбор проб на нескольких глубинах. Необходимо также провести
предварительные испытания, чтобы оценить степень расслоения (см. указания в 4.2).
Расстояние, необходимое для полного горизонтального перемешивания, обычно зависит от наличия
относительно резких изгибов, островков или валунов, и оно измеряется километрами (а не метрами).
Поэтому для получения представительных проб их необходимо отбирать в двух или более точках,
расположенных вдоль ширины реки, на участках, находящихся по течению ниже сброса стоков или
впадения притока.
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ISO 5667-6:2005(R)
Вопрос расстояний, необходимых для продольного перемешивания, может быть важен при
определении частоты отбора проб. Чтобы получить достоверные результаты непосредственно после
нерегулярного сброса, потребуется более частый отбор проб, чем если его проводить ниже по течению,
когда продольное перемешивание будет в значительной степени завершено.
Расстояние в метрах, l, для полного перемешивания, с точностью до 1 % однородности,
приблизительно рассчитывается по следующей формуле (опубликована в ISO 555-2):
2
0,13bc(0,7c+ 2 g )
l=
gd
где
b средняя ширина потока в метрах;
c коэффициент Шези для потока (15 < c < 50);
g ускорение свободного падения, в метрах на секунду в квадрате;
d средняя глубина потока реки в метрах.
Следующий пример иллюстрирует влияние различных значений коэффициента Шези на продольное
перемешивание в потоке.
ПРИМЕР Рассмотрим два потока, каждый шириной по 5 м и глубиной 1 м, но с предельными значениями
коэффициента Шези, один равный 15 (очень шероховатое дно, т.е. поток очень быстрый и турбулентный), другой
– 50 (очень гладкое дно, т.е. очень спокойный, медленный поток). При расчете по приведенному уравнению
полная однородность в первом потоке будет достигаться через 83 м, а второй станет однородным только через
683 м.
Следует отметить, что по результатам некоторых измерений приведенное выше выражение может
давать заниженное значение расстояния перемешивания для малых потоков, шириной около 5 м и
завышенное – для рек шириной около 50 м. Вероятно, это объясняется тем, что в оценке обычно
используется средняя ширина, средняя глубина и средний коэффициент Шези. Горизонтальное
перемешивание может происходить гораздо медленнее, чем ожидается, а вертикальное – гораздо
быстрее. Имеется большое количество литературных источников, содержащих другие формулы для
расчета расстояний, необходимых для перемешивания (см. Ссылку [15]).
4.1.4 Учет времени пребывания
Время пребывания часто играет важную роль при выборе места для отбора проб. Например, может
потребоваться, чтобы участки отбора проб были приспособлены для отслеживания присутствия
определенных компонентов или загрязняющих веществ в системе, особенно при наличии дискретных
источников загрязнения. Для этого необходимо знать время пребывания в исследуемой системе.
Знание времени пребывания также важно, если пробы отбираются с целью изучения скорости
изменения состояния нестабильных компонентов (например, для исследования самоочистки водной
массы время пребывания может дать информацию о кинетических коэффициентах скорости).
Для определения времени пребывания необходимо использовать один из трех основных методов, а
именно использование поверхностных поплавков (ISO 748), использование маркеров (опубликован в
ISO 555-1, ISO 555-2 и ISO 555-3) или измерение скорости течения при известной площади
поперечного сечения потока (ISO 748 и ISO 1070).
Измерения следует проводить минимум при пяти различных скоростях потока и полученные времена
пребывания для соответствующих скоростей следует нанести на график, по которому затем методом
экстраполяции или интерполяции определять время пребывания для другой скорости. Однако
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ISO 5667-6:2005(R)
экстраполяция больше, чем на 10 % от измеренной скорости потока, может дать неточное значение
времени пребывания.
Также следует отметить, что время пребывания может значительно меняться в зависимости от
времени года в регионах, где имеют место только сезонные дожди.
Общие указания по расчету времени пребывания см. в ISO 5667-1, а инструкции по измерению потока
жидкости в открытых каналах – в ISO/TR 8363.
4.1.5 Участки с неоднородным потоком
Проблемы возникают при выборе подходящих участков для отбора проб, когда определяемые
компоненты распределены в исследуемой водной массе неоднородно. В целом, следует избегать
использования таких участков, за исключением тех случаев, когда сами эти участки представляют
непосредственный интерес, поскольку на них не могут быть представительные пробы основной части
водной массы. Если имеется какая-либо вероятность неоднородного распределения определяемого
компонента на выбранном участке, необходимо провести экспериментальное исследование характера
и масштаба неоднородности по всем трем измерениям. Если в результате исследований выяснится,
что определяемые компоненты распределены равномерно, то можно использовать любую точку
отбора проб. Если нет – следует поискать другой участок, где определяемые компоненты
распределяются равномерно. Если такой участок найти невозможно, необходимо отбирать пробы на
выбранном участке в достаточном количестве точек, чтобы обеспечить получение достоверных
результатов.
Эти пробы часто можно объединять как подпробы, чтобы получить одну усредненную пробу,
отражающую состав воды в месте отбора проб, и не проводить анализ отбельных проб, отобранных к
каждой точке. Однако при этом не будет получена информация о разбросе состава по разным точкам.
Кроме того, объединение подпроб таким образом невозможно, когда отбираются пробы для анализа
растворенных газов и других летучих веществ.
4.2 Частота и время отбора проб
Важно, чтобы программа отбора проб была составлена правильно со статистической точки зрения,
чтобы сводная статистическая информация, полученная в результате анализа, давала оценку
требуемых данных в пределах допуска для целей программы. Если в цели программы не входит
определение порядка допустимой ошибки, то выполнение программы со статистической оценкой
невозможно. Инструкции и рекомендации по использованию статистики для определения частоты
отбора проб приводятся в стандарте ISO 5667-1.
Когда
...
INTERNATIONAL ISO
STANDARD 5667-6
Second edition
2005-07-15
Water quality — Sampling —
Part 6:
Guidance on sampling of rivers and
streams
Qualité de l'eau — Échantillonnage —
Partie 6: Lignes directrices pour l'échantillonnage des rivières et des
cours d'eau
Reference number
ISO 5667-6:2005(E)
©
ISO 2005
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ISO 5667-6:2005(E)
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Published in Switzerland
ii © ISO 2005 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 5667-6:2005(E)
Contents Page
Foreword. v
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Design of sampling programme. 3
4.1 Sampling point selection . 3
4.2 Frequency and time of sampling. 5
5 Preparation for sampling . 6
6 Sampling at specific locations . 7
6.1 Sampling from bridges. 7
6.2 In-stream sampling. 7
6.3 Sampling from the bank side. 7
6.4 Sampling from craft. 7
6.5 Sampling under ice. 7
7 Sampling methods. 7
7.1 Single, discrete samples. 7
7.2 Sampling from specific depths . 8
8 Sampling equipment. 8
8.1 Single, discrete samples. 8
8.2 Sampling of surface layers for LNAPL (e.g. oils) or surface films . 9
8.3 Devices for sampling from specific depths .9
8.4 Automatic sampling devices . 9
8.5 Other sampling equipment . 10
8.6 Provision of storage for sampling equipment and of samples prior to delivery to the
analysing laboratory. 10
9 Taking the sample. 10
9.1 Arrival on site . 10
9.2 Rinsing the equipment . 10
9.3 Direct sampling . 11
9.4 Indirect sampling using a sampling vessel . 11
9.5 Sampling through ice . 11
9.6 Sampling of surface layers or films. 11
9.7 Sampling by increments . 12
9.8 Adding preservatives in the field . 12
9.9 Labelling . 12
10 Stabilization, transport and storage of samples . 12
10.1 Stabilization. 12
10.2 Transportation. 12
10.3 Security and traceability of samples during storage and delivery. 13
11 Quality. 13
11.1 Avoidance of contamination. 13
11.2 Sample identification and records. 14
12 Reports . 14
12.1 Analytical reports. 14
12.2 Sampling protocols . 15
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ISO 5667-6:2005(E)
13 Certification/registration/accreditation. 15
14 Quality control. 15
15 Safety precautions . 15
Bibliography . 16
iv © ISO 2005 – All rights reserved
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ISO 5667-6:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5667-6 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 6, Sampling
(general methods).
This second edition cancels and replaces the first edition (ISO 5667-6:1990), which has been technically
revised.
ISO 5667 consists of the following parts, under the general title Water quality — Sampling:
1)
Part 1: Guidance on the design of sampling programmes
1)
Part 2: Guidance on sampling techniques
Part 3: Guidance on the preservation and handling of water samples
Part 4: Guidance on sampling from lakes, natural and man-made
Part 5: Guidance on sampling of drinking water and water used for food and beverage processing
Part 6: Guidance on sampling of rivers and streams
Part 7: Guidance on sampling of water and steam in boiler plants
Part 8: Guidance on the sampling of wet deposition
Part 9: Guidance on sampling from marine waters
Part 10: Guidance on sampling of waste waters
Part 11: Guidance on sampling of groundwaters
Part 12: Guidance on sampling of bottom sediments
1) ISO 5667-1 and ISO 5667-2 are currently undergoing joint revision, which will be published as ISO 5667-1.
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ISO 5667-6:2005(E)
Part 13: Guidance on sampling of sludges from sewage and water-treatment works
Part 14: Guidance on quality assurance of environmental water sampling and handling
Part 15: Guidance on preservation and handling of sludge and sediment samples
Part 16: Guidance on biotesting of samples
Part 17: Guidance on sampling of suspended sediments
Part 18: Guidance on sampling of groundwater at contaminated sites
Part 19: Guidance on sampling of marine sediments
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ISO 5667-6:2005(E)
Introduction
An understanding of the purpose of sampling is an essential prerequisite to identifying the principles to be
applied to a particular sampling problem. Examples of the purposes of sampling programmes commonly
devised for rivers and streams are as follows:
a) to determine the suitability of the water quality of a river or stream within a river basin for a particular use,
such as:
1) a source of drinking water,
2) for agricultural use (e.g. all types of irrigation, live-stock watering),
3) for the maintenance and/or development of fisheries,
4) for amenity use (e.g. aquatic sports and swimming);
b) to assess the impact of human activities on the quality of water, such as:
1) to study the effects of waste discharge or accidental spillages on a receiving water,
2) to assess the impact of land use on river or stream quality,
3) to assess the effect of the accumulation and release of substances including contaminants from
bottom deposits on aquatic biota within the water mass, or on bottom deposits,
4) to study the effects of abstraction, river regulation and river-to-river water transfers on the chemical
quality of rivers and their aquatic biota,
5) to study the effects of river engineering works on water quality (e.g. addition/removal of weirs,
changes to channel/bed structure).
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INTERNATIONAL STANDARD ISO 5667-6:2005(E)
Water quality — Sampling —
Part 6:
Guidance on sampling of rivers and streams
1 Scope
This part of ISO 5667 sets out 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.
It is not applicable to the sampling of estuarine or coastal waters and has limited applicability to
microbiological sampling.
NOTE Procedures for microbiological sampling are given in ISO 19458.
This part of ISO 5667 is not applicable to the examination of sediment, suspended solids or biota.
In cases where naturally occurring or artificially constructed dams result in the retention or storage of water for
several days or more, it might be better to consider the stretch of the river or stream as a standing water body
for sampling purposes. ISO 5667-4 provides guidance for sampling in these circumstances.
WARNING — The focus of this part of ISO 5667 is the collection and integrity of water samples. The
collection of these samples can be hazardous and attention is therefore drawn to the existence in
some countries of legislative requirements for the safety of personnel.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5667-18:2001, Water quality — Sampling — Part 18: Guidance on sampling of groundwater at
contaminated sites
ISO 6107-2:1997, Water quality — Vocabulary — Part 2
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5667-18 and ISO 6107-2 and the
following apply.
3.1
automatic sampling
process whereby samples are taken either discretely or continuously, independently of human intervention,
and according to a predetermined programme
[ISO 6107-2:1997]
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ISO 5667-6:2005(E)
3.2
incremental sampling
technique in which small samples are taken because of a low flow rate (with the possibility of contamination by
bottom deposits) or because of restricted access (e.g. where a sample is obtained through a small aperture),
these small samples then being aggregated to form a composite sample
NOTE All the liquid contained in the small samples is used, unlike blending of aliquots used to make a
flow-proportional sample (see 8.4).
3.3
isokinetic sampling
technique in which the sample from a water stream passes into the orifice of a sampling probe with a velocity
equal to that of the stream in the immediate vicinity of the probe
[ISO 6107-2:1997]
3.4
light non-aqueous-phase liquid
LNAPL
organic compounds which have low water solubility and a density less than that of water, e.g. petroleum
products
[ISO 5667-18:2001]
3.5
random sampling
form of sampling whereby the chances of obtaining different concentration values of a determinand are
precisely those defined by the probability distribution of the determinand in question
3.6
river
natural body of water flowing continuously or intermittently along a well-defined course into an ocean, sea,
lake, inland depression, marsh or other watercourse
[ISO 6107-2:1997]
3.7
sampling site
general area within a body of water from which samples are taken
[ISO 6107-2:1997]
3.8
sampling point
precise position within a sampling location from which samples are taken
[ISO 6107-2:1997]
3.9
stream
water flowing continuously or intermittently along a well-defined course, as for a river, but generally on a
smaller scale
[ISO 6107-2:1997]
3.10
sub-sample
portion removed from a sample and intended to be representative of that sample
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ISO 5667-6:2005(E)
3.11
systematic sampling
sampling whereby the samples are taken at predetermined intervals, often equally spaced in time
4 Design of sampling programme
4.1 Sampling point selection
4.1.1 General
The following factors are usually considered in advance of the sampling event. Practical sampling issues,
such as accessibility, may make the ideal sampling point impractical. Any change to the designated sampling
point on any grounds should be discussed and agreed with the sampling programme originator. The outcome
of the deliberations may be recorded in a sampling point file which contains directions to the sampling site, the
detailed location of the sampling point, the method of sampling and specific details (e.g. keys required and
health and safety issues). It may differentiate between equivalent sampling points that may be used if, for
instance, river conditions change. It may also specify the type of sampling to be carried out, e.g. the depth to
sample.
4.1.2 Choice of sampling site
In choosing the exact point from which samples are required, two aspects are generally involved:
a) the selection of the sampling site (i.e. the location of the sampling cross-section within the river basin,
river or stream);
b) the identification of the precise point at the sampling site.
The purpose of sampling often defines sampling sites (as in the case of the determination of the quality of an
effluent discharge), but sometimes the purpose only leads to a general idea of the sampling site, as in the
characterization of quality in a river basin.
The choice of sampling sites for single sampling stations is usually relatively easy. For example, a monitoring
station for a baseline record of water quality can be chosen to permit the use of a convenient bridge, or to
allow an upstream effluent discharge or tributary to be well mixed laterally before the station. Stations for
monitoring water supply abstraction points might need to be fixed within narrow limits (i.e. in proximity to the
abstractions).
In regions that receive seasonal rainfall only, and that have long periods without rain, river volumes and flows
can vary tremendously, and sampling sites for regular use should be chosen so as to ensure that they remain
appropriate and practical for sampling during periods of both maximum and minimum flow.
Where it is necessary to carry out sampling through ice in winter, the chosen sampling site should be as close
as possible to the sampling site used during other seasons of the year. If sampling is to be carried out near a
bridge, the site should be located far enough upstream to avoid contamination from road salt and sand.
Deviations from the routine sampling point should be detailed as part of the dataset and recorded with the
analytical results.
4.1.3 Importance of mixing
When the effects of a tributary, or an effluent, on the quality in a particular identified stretch of river or the main
stream are of interest, at least two sampling sites should be chosen; one should be just upstream of the
confluence and the other should be sufficiently far downstream to ensure that mixing is complete.
The physical characteristics of the channels of watercourses largely control distances required for the
complete mixing of effluents with stream flow.
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ISO 5667-6:2005(E)
Effluents mix in three dimensions in a stream, namely:
a) vertically (from top to bottom);
b) laterally (from one side to the other);
c) longitudinally (levelling out of peaks and troughs in the concentration of effluent constituents as water
passes downstream).
The distances over which effluents mix in these three dimensions should be considered in the selection of
sampling sites and points and are affected by, amongst other things, the water velocity. Tracer techniques
using dyes can be useful in studying mixing processes and conductivity measurements can also be helpful.
NOTE The use of tracer techniques might be subject to licensing by the authority responsible for the watercourse, as
there might be concerns over the release of chemicals into the environment. Where this is the case, it might be better to
use determinants already present, such as pH, temperature or conductivity, to study mixing processes.
Effluents discharged into most streams mix vertically completely within a kilometre. Normally a stream need
not be sampled at more than one depth, although stratification can be induced in slow-moving rivers and
streams by thermal and other density effects. In these cases, sampling at several depths might be necessary
and preliminary tests should be carried out to assess the degree of stratification (see 4.2 for guidance).
The distance necessary for complete lateral mixing is generally dependent on the occurrence of relatively
sharp reverse bends, islets or boulders and is measured in kilometres rather than fractions of a kilometre.
Therefore, to obtain representative samples a stream should be sampled at two or more points across its
width at sites downstream from an effluent or tributary discharge.
Consideration of longitudinal mixing distances can be important in deciding on the frequency of sampling. To
give representative results just below an irregular discharge, more frequent sampling will be required than
would be necessary some distance downstream where longitudinal mixing has been completed to a greater
extent.
The distance in metres, l, for complete mixing, to within 1 % of complete homogeneity, should be calculated
approximately using the following formula (originally published in ISO 555-2):
2
0,13bc(0,72)c + g
l =
gd
where
b is the average width of the reach, in metres;
c is the Chezy coefficient for the reach (15 < c < 50);
g is the acceleration due to gravity, in metres per second squared;
d is the mean depth of the reach, in metres.
The following example gives an illustration of the effect of different Chezy coefficients on the longitudinal
mixing of a stream.
EXAMPLE Consider two streams both 5 m wide and 1 m deep but with extreme values of the Chezy coefficient; one
of 15 (very rough bottom, i.e. the stream is very fast and turbulent) and the other of 50 (very smooth bottom, i.e. a very
tranquil, slow-moving stream). When calculated in accordance with the equation given in this subclause, the former will
have reached complete homogeneity after 83 m while the latter will not be homogeneous until it has travelled 683 m.
It should be noted that some tests have shown that the above expression can underestimate the mixing length
for small streams of about 5 m in width and overestimate the mixing length for rivers of over about 50 m in
width. This is most likely due to the fact that the average width, average depth and Chezy coefficient are
4 © ISO 2005 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 5667-6:2005(E)
usually estimates. Lateral mixing can take place much more slowly than expected and vertical mixing more
quickly. There are many literature sources containing alternative calculations that deal with mixing distances
(see Reference [15]).
4.1.4 Consideration of time-of-travel data
Time-of-travel data can often be of relevance to the choice of sampling location. For example, sampling sites
might have to be arranged to allow certain constituents or pollutants to be traced through a system,
particularly from a discrete source of pollution. This necessitates knowledge of the residence time within the
system under investigation (i.e. the time of travel). Knowledge of the time of travel is also important in
sampling studies to investigate the rate of change of unstable constituents (e.g. in the self-purification of a
water body, the time of travel can provide information on kinetic rate coefficients).
In determining the time of travel, one of the three principal methods should be used, namely the use of surface
floats (see ISO 748), the use of tracers (originally published in ISO 555-1, ISO 555-2 and ISO 555-3) or the
measurement of flow rate with knowledge of cross-sectional areas (see ISO 748 and ISO 1070).
Measurements should be made at a minimum of five different flow rates and the resulting times of travel
plotted against the corresponding flow rates, thereby enabling other travel times to be obtained by
extrapolation or interpolation. However, extrapolation outside 10 % of a measured flow rate value can provide
inaccurate information on time of travel.
It should also be noted that time of travel can vary greatly between seasons in regions that experience
seasonal rainfall only.
ISO 5667-1 should be consulted for general guidance on time of travel and ISO/TR 8363 should be consulted
for guidance on the measurement of liquid flow in open channels.
4.1.5 Non-homogeneous sites
Problems arise in selecting suitable sampling sites whenever the determinands are not homogeneously
distributed throughout the water body of interest. In general, such sampling sites should be avoided, except
when the sites themselves are of direct interest, as they might not yield representative samples of the major
part of the water body. If there is any possibility of a non-homogeneous distribution of the determinands of
interest at the chosen site, experimental tests on the nature and magnitude of any heterogeneity in all three
dimensions should be made. If such tests show that the determinands are distributed homogeneously, any
sampling point will suffice. Otherwise another site should be sought where the determinands are
homogeneously distributed. If it is impossible to find such a sampling site, samples should be taken from
sufficient points at the chosen site to ensure representative results.
These samples can often be combined as sub-samples to form one single composite sample representative of
the quality at the sampling location, so that it is not necessary to analyse individual samples taken from each
of the sampling points. However, this provides no information on the variability in quality between the sampling
points. In addition, the combination of sub-samples in this way cannot be undertaken when sampling for
dissolved gases or other volatile constituents.
4.2 Frequency and time of sampling
It is essential that the sampling programme be properly statistically designed in order that the statistical
summary information produced from the analytical results provides an estimate of the required information to
within the tolerance limits of the programme’s objectives. If the objectives do not include a definition of the
magnitude of the tolerable error, a statistically based sampling programme is impossible. Guidance and
recommendations on the application of statistics to sampling frequency are given in ISO 5667-1.
Where cyclic or other persistent variations are present, better precision should be sought in estimating mean
concentrations by systematic rather than by random sampling (for any given number of samples), provided
that the sampling interval is short enough for consecutive samples to reveal the variations.
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ISO 5667-6:2005(E)
When using systematic sampling, it is essential to ensure that the frequency of sampling does not coincide
with any natural cycle present in the system, or with some other time-based effect (e.g. a pump just upstream
starting once an hour), a study of the effects of which are not part of the sampling objectives.
In river systems, regular cyclic variations in water quality can occur with, for example, periods of one day, one
week and one year. W
...
SLOVENSKI STANDARD
SIST ISO 5667-6:2007
01-februar-2007
1DGRPHãþD
SIST ISO 5667-6:1996
.DNRYRVWYRGH9]RUþHQMHGHO 1DYRGLOR]DY]RUþHQMHUHNLQYRGQLKWRNRY
Water quality -- Sampling -- Part 6: Guidance on sampling of rivers and streams
Qualité de l'eau -- Échantillonnage -- Partie 6: Lignes directrices pour l'échantillonnage
des rivières et des cours d'eau
Ta slovenski standard je istoveten z: ISO 5667-6:2005
ICS:
13.060.10 Voda iz naravnih virov Water of natural resources
13.060.45 Preiskava vode na splošno Examination of water in
general
SIST ISO 5667-6:2007 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 5667-6:2007
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SIST ISO 5667-6:2007
INTERNATIONAL ISO
STANDARD 5667-6
Second edition
2005-07-15
Water quality — Sampling —
Part 6:
Guidance on sampling of rivers and
streams
Qualité de l'eau — Échantillonnage —
Partie 6: Lignes directrices pour l'échantillonnage des rivières et des
cours d'eau
Reference number
ISO 5667-6:2005(E)
©
ISO 2005
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SIST ISO 5667-6:2007
ISO 5667-6:2005(E)
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ii © ISO 2005 – All rights reserved
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SIST ISO 5667-6:2007
ISO 5667-6:2005(E)
Contents Page
Foreword. v
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Design of sampling programme. 3
4.1 Sampling point selection . 3
4.2 Frequency and time of sampling. 5
5 Preparation for sampling . 6
6 Sampling at specific locations . 7
6.1 Sampling from bridges. 7
6.2 In-stream sampling. 7
6.3 Sampling from the bank side. 7
6.4 Sampling from craft. 7
6.5 Sampling under ice. 7
7 Sampling methods. 7
7.1 Single, discrete samples. 7
7.2 Sampling from specific depths . 8
8 Sampling equipment. 8
8.1 Single, discrete samples. 8
8.2 Sampling of surface layers for LNAPL (e.g. oils) or surface films . 9
8.3 Devices for sampling from specific depths .9
8.4 Automatic sampling devices . 9
8.5 Other sampling equipment . 10
8.6 Provision of storage for sampling equipment and of samples prior to delivery to the
analysing laboratory. 10
9 Taking the sample. 10
9.1 Arrival on site . 10
9.2 Rinsing the equipment . 10
9.3 Direct sampling . 11
9.4 Indirect sampling using a sampling vessel . 11
9.5 Sampling through ice . 11
9.6 Sampling of surface layers or films. 11
9.7 Sampling by increments . 12
9.8 Adding preservatives in the field . 12
9.9 Labelling . 12
10 Stabilization, transport and storage of samples . 12
10.1 Stabilization. 12
10.2 Transportation. 12
10.3 Security and traceability of samples during storage and delivery. 13
11 Quality. 13
11.1 Avoidance of contamination. 13
11.2 Sample identification and records. 14
12 Reports . 14
12.1 Analytical reports. 14
12.2 Sampling protocols . 15
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13 Certification/registration/accreditation. 15
14 Quality control. 15
15 Safety precautions . 15
Bibliography . 16
iv © ISO 2005 – All rights reserved
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SIST ISO 5667-6:2007
ISO 5667-6:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5667-6 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 6, Sampling
(general methods).
This second edition cancels and replaces the first edition (ISO 5667-6:1990), which has been technically
revised.
ISO 5667 consists of the following parts, under the general title Water quality — Sampling:
1)
Part 1: Guidance on the design of sampling programmes
1)
Part 2: Guidance on sampling techniques
Part 3: Guidance on the preservation and handling of water samples
Part 4: Guidance on sampling from lakes, natural and man-made
Part 5: Guidance on sampling of drinking water and water used for food and beverage processing
Part 6: Guidance on sampling of rivers and streams
Part 7: Guidance on sampling of water and steam in boiler plants
Part 8: Guidance on the sampling of wet deposition
Part 9: Guidance on sampling from marine waters
Part 10: Guidance on sampling of waste waters
Part 11: Guidance on sampling of groundwaters
Part 12: Guidance on sampling of bottom sediments
1) ISO 5667-1 and ISO 5667-2 are currently undergoing joint revision, which will be published as ISO 5667-1.
© ISO 2005 – All rights reserved v
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ISO 5667-6:2005(E)
Part 13: Guidance on sampling of sludges from sewage and water-treatment works
Part 14: Guidance on quality assurance of environmental water sampling and handling
Part 15: Guidance on preservation and handling of sludge and sediment samples
Part 16: Guidance on biotesting of samples
Part 17: Guidance on sampling of suspended sediments
Part 18: Guidance on sampling of groundwater at contaminated sites
Part 19: Guidance on sampling of marine sediments
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Introduction
An understanding of the purpose of sampling is an essential prerequisite to identifying the principles to be
applied to a particular sampling problem. Examples of the purposes of sampling programmes commonly
devised for rivers and streams are as follows:
a) to determine the suitability of the water quality of a river or stream within a river basin for a particular use,
such as:
1) a source of drinking water,
2) for agricultural use (e.g. all types of irrigation, live-stock watering),
3) for the maintenance and/or development of fisheries,
4) for amenity use (e.g. aquatic sports and swimming);
b) to assess the impact of human activities on the quality of water, such as:
1) to study the effects of waste discharge or accidental spillages on a receiving water,
2) to assess the impact of land use on river or stream quality,
3) to assess the effect of the accumulation and release of substances including contaminants from
bottom deposits on aquatic biota within the water mass, or on bottom deposits,
4) to study the effects of abstraction, river regulation and river-to-river water transfers on the chemical
quality of rivers and their aquatic biota,
5) to study the effects of river engineering works on water quality (e.g. addition/removal of weirs,
changes to channel/bed structure).
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SIST ISO 5667-6:2007
INTERNATIONAL STANDARD ISO 5667-6:2005(E)
Water quality — Sampling —
Part 6:
Guidance on sampling of rivers and streams
1 Scope
This part of ISO 5667 sets out 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.
It is not applicable to the sampling of estuarine or coastal waters and has limited applicability to
microbiological sampling.
NOTE Procedures for microbiological sampling are given in ISO 19458.
This part of ISO 5667 is not applicable to the examination of sediment, suspended solids or biota.
In cases where naturally occurring or artificially constructed dams result in the retention or storage of water for
several days or more, it might be better to consider the stretch of the river or stream as a standing water body
for sampling purposes. ISO 5667-4 provides guidance for sampling in these circumstances.
WARNING — The focus of this part of ISO 5667 is the collection and integrity of water samples. The
collection of these samples can be hazardous and attention is therefore drawn to the existence in
some countries of legislative requirements for the safety of personnel.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5667-18:2001, Water quality — Sampling — Part 18: Guidance on sampling of groundwater at
contaminated sites
ISO 6107-2:1997, Water quality — Vocabulary — Part 2
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5667-18 and ISO 6107-2 and the
following apply.
3.1
automatic sampling
process whereby samples are taken either discretely or continuously, independently of human intervention,
and according to a predetermined programme
[ISO 6107-2:1997]
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ISO 5667-6:2005(E)
3.2
incremental sampling
technique in which small samples are taken because of a low flow rate (with the possibility of contamination by
bottom deposits) or because of restricted access (e.g. where a sample is obtained through a small aperture),
these small samples then being aggregated to form a composite sample
NOTE All the liquid contained in the small samples is used, unlike blending of aliquots used to make a
flow-proportional sample (see 8.4).
3.3
isokinetic sampling
technique in which the sample from a water stream passes into the orifice of a sampling probe with a velocity
equal to that of the stream in the immediate vicinity of the probe
[ISO 6107-2:1997]
3.4
light non-aqueous-phase liquid
LNAPL
organic compounds which have low water solubility and a density less than that of water, e.g. petroleum
products
[ISO 5667-18:2001]
3.5
random sampling
form of sampling whereby the chances of obtaining different concentration values of a determinand are
precisely those defined by the probability distribution of the determinand in question
3.6
river
natural body of water flowing continuously or intermittently along a well-defined course into an ocean, sea,
lake, inland depression, marsh or other watercourse
[ISO 6107-2:1997]
3.7
sampling site
general area within a body of water from which samples are taken
[ISO 6107-2:1997]
3.8
sampling point
precise position within a sampling location from which samples are taken
[ISO 6107-2:1997]
3.9
stream
water flowing continuously or intermittently along a well-defined course, as for a river, but generally on a
smaller scale
[ISO 6107-2:1997]
3.10
sub-sample
portion removed from a sample and intended to be representative of that sample
2 © ISO 2005 – All rights reserved
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ISO 5667-6:2005(E)
3.11
systematic sampling
sampling whereby the samples are taken at predetermined intervals, often equally spaced in time
4 Design of sampling programme
4.1 Sampling point selection
4.1.1 General
The following factors are usually considered in advance of the sampling event. Practical sampling issues,
such as accessibility, may make the ideal sampling point impractical. Any change to the designated sampling
point on any grounds should be discussed and agreed with the sampling programme originator. The outcome
of the deliberations may be recorded in a sampling point file which contains directions to the sampling site, the
detailed location of the sampling point, the method of sampling and specific details (e.g. keys required and
health and safety issues). It may differentiate between equivalent sampling points that may be used if, for
instance, river conditions change. It may also specify the type of sampling to be carried out, e.g. the depth to
sample.
4.1.2 Choice of sampling site
In choosing the exact point from which samples are required, two aspects are generally involved:
a) the selection of the sampling site (i.e. the location of the sampling cross-section within the river basin,
river or stream);
b) the identification of the precise point at the sampling site.
The purpose of sampling often defines sampling sites (as in the case of the determination of the quality of an
effluent discharge), but sometimes the purpose only leads to a general idea of the sampling site, as in the
characterization of quality in a river basin.
The choice of sampling sites for single sampling stations is usually relatively easy. For example, a monitoring
station for a baseline record of water quality can be chosen to permit the use of a convenient bridge, or to
allow an upstream effluent discharge or tributary to be well mixed laterally before the station. Stations for
monitoring water supply abstraction points might need to be fixed within narrow limits (i.e. in proximity to the
abstractions).
In regions that receive seasonal rainfall only, and that have long periods without rain, river volumes and flows
can vary tremendously, and sampling sites for regular use should be chosen so as to ensure that they remain
appropriate and practical for sampling during periods of both maximum and minimum flow.
Where it is necessary to carry out sampling through ice in winter, the chosen sampling site should be as close
as possible to the sampling site used during other seasons of the year. If sampling is to be carried out near a
bridge, the site should be located far enough upstream to avoid contamination from road salt and sand.
Deviations from the routine sampling point should be detailed as part of the dataset and recorded with the
analytical results.
4.1.3 Importance of mixing
When the effects of a tributary, or an effluent, on the quality in a particular identified stretch of river or the main
stream are of interest, at least two sampling sites should be chosen; one should be just upstream of the
confluence and the other should be sufficiently far downstream to ensure that mixing is complete.
The physical characteristics of the channels of watercourses largely control distances required for the
complete mixing of effluents with stream flow.
© ISO 2005 – All rights reserved 3
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SIST ISO 5667-6:2007
ISO 5667-6:2005(E)
Effluents mix in three dimensions in a stream, namely:
a) vertically (from top to bottom);
b) laterally (from one side to the other);
c) longitudinally (levelling out of peaks and troughs in the concentration of effluent constituents as water
passes downstream).
The distances over which effluents mix in these three dimensions should be considered in the selection of
sampling sites and points and are affected by, amongst other things, the water velocity. Tracer techniques
using dyes can be useful in studying mixing processes and conductivity measurements can also be helpful.
NOTE The use of tracer techniques might be subject to licensing by the authority responsible for the watercourse, as
there might be concerns over the release of chemicals into the environment. Where this is the case, it might be better to
use determinants already present, such as pH, temperature or conductivity, to study mixing processes.
Effluents discharged into most streams mix vertically completely within a kilometre. Normally a stream need
not be sampled at more than one depth, although stratification can be induced in slow-moving rivers and
streams by thermal and other density effects. In these cases, sampling at several depths might be necessary
and preliminary tests should be carried out to assess the degree of stratification (see 4.2 for guidance).
The distance necessary for complete lateral mixing is generally dependent on the occurrence of relatively
sharp reverse bends, islets or boulders and is measured in kilometres rather than fractions of a kilometre.
Therefore, to obtain representative samples a stream should be sampled at two or more points across its
width at sites downstream from an effluent or tributary discharge.
Consideration of longitudinal mixing distances can be important in deciding on the frequency of sampling. To
give representative results just below an irregular discharge, more frequent sampling will be required than
would be necessary some distance downstream where longitudinal mixing has been completed to a greater
extent.
The distance in metres, l, for complete mixing, to within 1 % of complete homogeneity, should be calculated
approximately using the following formula (originally published in ISO 555-2):
2
0,13bc(0,72)c + g
l =
gd
where
b is the average width of the reach, in metres;
c is the Chezy coefficient for the reach (15 < c < 50);
g is the acceleration due to gravity, in metres per second squared;
d is the mean depth of the reach, in metres.
The following example gives an illustration of the effect of different Chezy coefficients on the longitudinal
mixing of a stream.
EXAMPLE Consider two streams both 5 m wide and 1 m deep but with extreme values of the Chezy coefficient; one
of 15 (very rough bottom, i.e. the stream is very fast and turbulent) and the other of 50 (very smooth bottom, i.e. a very
tranquil, slow-moving stream). When calculated in accordance with the equation given in this subclause, the former will
have reached complete homogeneity after 83 m while the latter will not be homogeneous until it has travelled 683 m.
It should be noted that some tests have shown that the above expression can underestimate the mixing length
for small streams of about 5 m in width and overestimate the mixing length for rivers of over about 50 m in
width. This is most likely due to the fact that the average width, average depth and Chezy coefficient are
4 © ISO 2005 – All rights reserved
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ISO 5667-6:2005(E)
usually estimates. Lateral mixing can take place much more slowly than expected and vertical mixing more
quickly. There are many literature sources containing alternative calculations that deal with mixing distances
(see Reference [15]).
4.1.4 Consideration of time-of-travel data
Time-of-travel data can often be of relevance to the choice of sampling location. For example, sampling sites
might have to be arranged to allow certain constituents or pollutants to be traced through a system,
particularly from a discrete source of pollution. This necessitates knowledge of the residence time within the
system under investigation (i.e. the time of travel). Knowledge of the time of travel is also important in
sampling studies to investigate the rate of change of unstable constituents (e.g. in the self-purification of a
water body, the time of travel can provide information on kinetic rate coefficients).
In determining the time of travel, one of the three principal methods should be used, namely the use of surface
floats (see ISO 748), the use of tracers (originally published in ISO 555-1, ISO 555-2 and ISO 555-3) or the
measurement of flow rate with knowledge of cross-sectional areas (see ISO 748 and ISO 1070).
Measurements should be made at a minimum of five different flow rates and the resulting times of travel
plotted against the corresponding flow rates, thereby enabling other travel times to be obtained by
extrapolation or interpolation. However, extrapolation outside 10 % of a measured flow rate value can provide
inaccurate information on time of travel.
It should also be noted that time of travel can vary greatly between seasons in regions that experience
seasonal rainfall only.
ISO 5667-1 should be consulted for general guidance on time of travel and ISO/TR 8363 should be consulted
for guidance on the measurement of liquid flow in open channels.
4.1.5 Non-homogeneous sites
Problems arise in selecting suitable sampling sites whenever the determinands are not homogeneously
distributed throughout the water body of interest. In general, such sampling sites should be avoided, except
when the sites themselves are of direct interest, as they might not yield representative samples of the major
part of the water body. If there is any possibility of a non-homogeneous distribution of the determinands of
interest at the chosen site, experimental tests on the nature and magnitude of any heterogeneity in all three
dimensions should be made. If such tests show that the determinands are distributed homogeneously, any
sampling point will suffice. Otherwise another site should be sought where the determinands are
homogeneously distributed. If it is impossible to find such a sampling site, samples should be taken from
sufficient points at the chosen site to ensure representative results.
These samples can often be combined as sub-samples to form one single composite sample representative of
the quality at the sampling location, so that it is not necessary to analyse individual samples taken from each
of the sampling points. However, this provides no information on the variability in quality between the sampling
points. In addition, the combination of sub-samples in this way cannot be undertaken when sampling for
dissolved gases or other volatile constituents.
4.2 Frequency and time of sampling
It is essential that the sampling programme be properly statistically designed in order that the statistical
summary information produced from the analytical results provides an estimate of the required information t
...
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