Approaches to Water Quality Monitoring

Deborah Chapman,

UNEP GEMS/Water Capacity Development Centre,

University College Cork, Ireland

Overview: Approaches to Water Quality Monitoring

• Aim: to stimulate discussion around three themes occurring in the

workshop:

• monitoring ambient water quality from national to global scales;

• monitoring and managing the freshwater ecosystem;

• monitoring in relation to guidelines or targets

• What we understand by “water quality” and “monitoring”

• Overview of physical, chemical and biological monitoring approaches

• Choosing the right water quality monitoring approach

What do we mean by water quality?

• Water quality is defined by the characteristics or properties

of the water

• The characteristics of water govern its suitability for

different uses

• “Uses” include: drinking water, irrigation, assimilating

wastewaters, natural fisheries/aquaculture, aquatic

ecosystem, etc.

What do we mean by water quality?

Each use has its own set of water quality requirements in order to

reduce the levels of treatment needed, e.g.:

• drinking water should have low levels of pathogens and toxins

• irrigation water should be low in salts

• water for some industrial processes should be low in suspended

materials

Water quality can be determined and classified in different ways using

the physical, chemical and biological characteristics of the water

What do we mean by monitoring?

Water quality is characterised through scientific

studies and monitoring

Monitoring is the systematic collection of data over temporal or spatial scales in order to define:

• Current environmental conditions

• Past environmental conditions (historical monitoring)

• Repeated collection of data over long time scales can

indicate trends

Years

1960 1970 1980 1990 2000

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Mean Ptot concentration

Management objective

Start of phosphateremoval in STP

Ban of P in textilewashing products(CH)

Possible media for sampling or analysis in water quality programmes

• Water (filtered or unfiltered)

• Particulate matter (suspended or sedimented)

• Biota (filter feeder, predator, sedentary, mobile)

Choosing what to monitor

• Basic parameters

• Characterise the geological and climatological influences on the water body – provides a

baseline

• Ecosystem-related parameters

• Demonstrate potential human influence on the whole aquatic ecosystem

• Contaminants

• Demonstrate specific waste emissions, potential for ecosystem damage, potential risk for

human uses

Some naturally occurring elements/substances can be damaging to water bodies

if their levels are elevated substantially by human activities

Basic measures of water quality

Temperature

• Required because it affects processes within the water body, such as biological respiration, chemical reactions, etc.

Dissolved oxygen

• Fundamental for life in the aquatic ecosystem, including decomposition processes

pH

• May be influenced by chemical inputs but can also affect chemical and biological processes in the water

Major ions

• Depend on biogeochemical conditions; very variable in natural waters

Suspended solids

• Affects the transparency of the water, which in turn in can affect primary productivity and the aquatic ecosytem

Other physical/chemical measures of water quality

Conductivity

• Sensitive to dissolved solids, mainly mineral salts

• Indicates changes in water quality but does not identify cause

Total Organic Carbon (TOC)

• Convenient, non-specific measure of general water quality,

particularly organic contamination

Biochemical Oxygen Demand (BOD)

• Measure of the biochemically degradable organic matter

present in the water

Chemical Oxygen Demand (COD)

• Widely used as an indicator of the presence of sewage or

industrial effluents

Ecosystem-related parameters

Nutrients

Principally nitrogen and phosphorus compounds

• Essential for living organisms but excess can cause major changes

in aquatic ecosystems (eutrophication)

• Run-off/discharge from land sources: fertiliser use, manure and

sewage

Chlorophyll concentrations

• Photosynthetic pigment in plants and algae

• Provides an indirect measure of algal biomass and productivity

Ecological characteristics

• Presence or absence of specific species or combinations of species

that have preferred environmental characteristics, such as high

oxygen concentrations

Biological characteristics: Macro- to Micro Scale

• Ecosystem monitoring – e.g. remote sensing

• Community monitoring – e.g. species diversity

and abundance

• Species monitoring – bioindicators, biomonitors

http://www7333.nrlssc.navy.mil/images/projects/Ruhul_Lake_Erie.png

Biological community structure monitoring

Based on species numbers (diversity) and abundance

• Generates a numerical value (index)

• Can measure stress in the environment, e.g. Simpsons

Index, Shannon Weaver index

• Unstressed environments: Large numbers of species

and no single species highly dominant

• Maximum diversity: large number of species in relatively low

numbers

• Stressed environments: sensitive species disappear

and more tolerant species thrive

• Minimum diversity: community richness reduced, few

species but in large numbers

Bioindicator species

Presence or absence of indicator species

within the environment

Organisms, populations or assemblages

• Used for qualitative (non-specific) indication

of anthropogenic impacts

• Developed and used extensively in the

aquatic environment, especially rivers

Indicator organisms: Example for temperate rivers

• Chironomus sp.

• Asellus sp.

• Gammarus sp.

• Baetis rhodani

• Ephemera danica

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Status and trends using ecological data only

National rivers survey – Northern Ireland

• Based on benthic invertebrates

• Presents clear information to non-experts

http://www.doeni.gov.uk/niea/water-home/quality/rivers/rivers_historical_monitoring_results/gqabiolexpln.htm

Complex biological indicators

Index of Biological Integrity (IBI)

A synthesis of diverse biological information which numerically depicts associations between human influence and biological attributes

Requires extensive knowledge of aquatic communities and their responses to human impacts Reference wetlands Impaired wetlands

Invertebrate groups

http://water.epa.gov/type/wetlands/assessment/fact2.cfm

Species and community monitoring: Points to be considered

• What exactly are the organisms

responding to?

• Can the species integrate all impacts on the water body?

• Are they sensitive enough to changes in the water body?

• Geographical applicability: local, regional, global

• Need for trained biologists/taxonomists

• Relative cost compared with chemical measurements

Microbiological monitoring

• Microbiological indicators used where people will

come into contact with the water (e.g. drinking, personal hygiene, food preparation, recreational use)

• Can indicate faecal contamination of a water body by animals and/or humans

• The faecal coliform bacterium Escherichia coli is one of several used as indicators of the presence of potentially pathogenic micro-organisms

• Thermotolerant coliforms (faecal coliforms including E. coli) can also be used

Contaminants - Trace elements and organic compounds

• Usually of interest where human impacts are

suspected

• Require specific analytical facilities

• Can be expensive and difficult to measure at

low concentrations

• The range of new compounds with potential

impacts on aquatic ecosystems and/or human

health is growing rapidly – which ones should

be included?

Monitoring for contaminants: selecting a chemical or biological approach

• Is the toxic substance known?

• Expected concentration range and type of toxic substance

governs methods available

• Are effects on the environment important?

• Is there a risk that the toxic substance may bioaccumulate?

• Is there a risk to human health?

• Would sediment or biota samples be more appropriate?

Sediment Monitoring: Total mercury in surface sediments

Total mercury concentrations (ppm) in surficial sediments of the Great lakes (1997–2000). Reprinted from Environmental Pollution, Vol. 129,

Marvin et al. Spatial and temporal trends in surface water and sediment contamination in the Laurentian Great Lakes, 131–144,

Choosing what to monitor

Selecting what to include in a water quality monitoring programme depends on the

objectives of the monitoring programme, i.e. what do you need to know?

• Wastewater dilution and assimilation

• e.g. chemical measurements, oxygen depletion

• Inorganic pollutants and possible risk to human health

• e.g. filter feeding organisms, fish

• Pollutant impacts on aquatic ecosystem and recovery over time

• e.g. communities of aquatic species

• Accumulation of contaminants in a water body over time

• e.g. sedimented particles

Choosing the best approach for ambient

water quality

What do you want to know and how will

the information be used?

Should the needs of the ecosystem be

considered?

Classifying water quality: guidelines, standards and targets

Targets can be:

• precise values/standards

• a range of values, or

• a water quality classification

Water quality classifications can be used for biological and chemical

characteristics

• High, Good, Moderate, Poor, Bad

• Excellent, Good, Fair, Marginal, Poor

Classifications can be used to indicate whether water is suitable for

particular uses

Key Question: What gives the best indication of impacts on ambient water quality?

• Baseline or background conditions are needed

for reference (pristine conditions hardly likely to

occur anywhere in present day)

• Basic parameters indicate natural influences

• Physical and chemical parameters may indicate

human influence

• Biological indicators integrate all possible

influences on water quality but are usually non-

specific

• Select according to the monitoring programme

objectives

Water quality indicators

Biological and chemical parameters can be compiled to produce water

quality indicators

Indicators can be used to:

• Provide information to decision makers and the public on the state of

the environment

• Support policy development and priority setting, by identifying the

key factors causing pressure on the aquatic environment

• Monitor the extent and effects of these policies

• Provide a means of linking environmental impacts to socio-economic

activities and give an early warning of environmental problems

Water quality indicators: advantages and disadvantages

Composite indicators enable:

• Simplification

• Quantification

• Communication

Limitations of composite indicators:

• Require high quality data

• Data must be updated regularly

P.J.T.M. van Puijenbroeka et al., 2014

Netherlands

Ireland EPA

Status and trends combining ecological and basic chemical analysis

• Chemical status is assessed against Environmental Quality Standards (target values)

• Combined with status according to biological monitoring classes

Generating large amounts of data - getting citizens involved

Large amounts of data, but limited accuracy

Example - The Great Secchi Dip-in

Since July, 1994, more that 10,000 volunteers have

provided more than 41,000 transparency records on

more than 7,000 waterbodies in North America

The volunteers belong to 394 programmes, both

volunteer and professional, in:

50 USA states,

9 Canadian provinces, and

6 other countries

http://dipin.kent.edu/

Summary

Water quality can be monitored in different

ways using physical, chemical and

biological approaches

The most suitable approach depends on:

• What you need to know

• Resources available

• The target audience of the data

generated

Thank you for listening

We are interested in your opinions

Please feel free to ask questions