Water Quality Monitoring

Sewage pipe. Photo © Joe Miller

Water quality monitoring to identify pollutants and their sources is critical for mitigating impacts from sewage. To recognize sewage pollution events, baseline conditions must be established and regularly monitored. Techniques for water quality monitoring vary, ranging from extensive laboratory analysis to real-time field tests. Water quality monitoring is typically done by local government agencies, but efforts are growing to expand capacity for monitoring that include partner organizations and local volunteers.

Sewage Pollution Indicators and Methods

The table below lists indicators used to identify and measure sewage pollution in the ocean. Test methods vary and the provided resources offer detailed methodologies for practitioners.

CaffeineLab test (GC-MS)>24 hours
DNALab test (eDNA metabarcoding or fluorescence quantification)Same day
DO (dissolved oxygen)Field measurementReal-time
Endocrine Disruptors (e.g., estrogen)Lab test (GC-MS)>24 hours
Enterococcus (FIB)Lab test (culture quantification)>24 hours
Chlorophyll aField measurementReal time
Clostridium perfringens (FIB)Lab test>24 hours
Hydrogen SulfideField measurementReal time
MetalsLab test>24 hours
NitrateField measurementReal time
Nitrogen IsotopesLab test>24 hours
pHField measurementReal-time
Chemicals of Emerging Concern (CECs)Lab test>24 hours
SalinityField measurementReal-time
SterolsLab test>24 hours
SucraloseLab test (GC-MS)>24 hours
Total Dissolved Solids (TDS) or turbidity Field measurementReal-time

Water quality testing methods range from involved procedures, undertaken in a lab setting, to simple field measurements. For example, turbidity, an indicator of water clarity to understand the depth sunlight is able to penetrate, can be measured manually using a secchi disk or digitally using a conductivity meter, nephelometer, or photosynthetically active radiation sensor. These portable field measurement tools require maintenance and calibration, but enhance the ability to collect data in real time. Some of the more simplistic and affordable monitoring strategies, such as hydrogen sulfide (H2S) tests that indicate whether fecal indicator bacteria (FIB) are present in water, have increased community engagement with monitoring efforts, leading to improved behavior and sanitation systems in opens in a new windowTanzania.

See the Resources section for more detailed water quality monitoring methodologies for practitioners.

maui water quality

Poor water quality off the coast of Maui. Photo © Bill Rathfon for Hui O Ka Wai Ola

opens in a new windowHui O Ka Wai Ola

Hui O Ka Wai Ola is a citizen science water quality sampling program aligned with Hawai‘i Department of Health, Clean Water Branch standards and protocols. Samples and data collected are used for decision making around water quality standards and management plans. Samples collected in the field are brought to a local high school lab dedicated to water quality monitoring procedures. Data from field sampling efforts are consolidated into a database support ongoing monitoring that are used in analysis, to track pollution events, and to recognize water quality and coral reef trends over time.

This program acknowledges the limitations any one water quality indicator may present. Each water quality indicator contributes to understanding, but no single measurement is sufficiently conclusive. Therefore, strategies that compile measurements of several indicators are more valuable. ref  This is especially important because of the lack of global agreement on pollution thresholds. For instance, enterococcus is the most commonly measured fecal indicator bacteria (FIB) in marine environments used to determine beach closures and advisories. However, another bacteria found in sewage, Clostridium perfringens, is considered a more accurate indicator of sewage pollution in Hawai‘i but is not approved for use nationwide. ref The lack of coordinated understanding of the ocean’s resilience to sewage pollution, as it impacts both marine and human health, necessitates establishing localized baselines and monitoring efforts for effective protection. For more information on this program view the webinar about Hui O Ka Wai Ola.


An emerging monitoring opportunity exists through data analysis, particularly coupled with increasing remote sensing and spatial imagery efforts. opens in a new windowPublicly available data may include algal blooms, coral bleaching events, opens in a new window sea temperature fluctuations, eutrophication potential, and, in some cases, combined with other geographic data, such as locations of sewage treatment plants, these data may provide managers with useful information to understand baseline conditions as well as create methods for monitoring changes over time. opens in a new windowHeal the Bay’s NowCast Beach Report Card, is a model to predict beach water quality in California, USA, and improves public awareness of contamination events.

water quality field measurements

Water quality field measurements by Hui O Ka Wai Ola citizen scientists. Photo © Bill Rathfon

There remains a need for innovative and cost effective measurement and reporting tools to identify sewage pollution. The opens in a new window Ocean Health Index is a project undertaken by NCEAS that presents ocean health scores based on threats and resilience. A data layer specific to sewage pollution in the ocean is in development and will be useful for data analysis and multi-scalar evaluations of the impacts of sewage pollution.

Bubbling sewage effluent

Bubbling sewage effluent. Photo © Matthew Chatfield, Flickr


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