Water Sampling Techniques and Parameters

Why should lake water be tested?

This question can be answered with another question: why should I have a medical exam if I’m healthy? Lake water quality sampling is a way to prevent or identify many issues. It can also help us direct our actions to maintain or improve the health of our lakes. How can we know if the lower layer of cold water (hypolimnion) at the bottom of the lake is well oxygenated or if it is lacking oxygen (anoxia)?  Are the levels of phosphorus in the lake elevated and if so, what does that imply? Here is a checklist summarizing each the sampling  parameters along with the appropriate sampling technique, the source, the effects on water quality and how to interpret sampling
results for each.


What is phosphorus? 

Phosphorus is an essential nutrient for all plant and algae growth. Phosphorus plays a major role in the eutrophication (i.e. premature aging) of a lake (see Figure 1, page 2). According to certain studies (Carignan et al., 2003), three (3) major factors will contribute to increased loads of phosphorus in lake waters, namely wetlands, turnover times for the lake waters and  humankind’s impact (in particular, disruption of features in the riparian strips). According to Richard Carignan, problems stemming  from premature eutrophication (plant and algae growth) start to become serious when phosphorus levels reach 10 μg/ litre.



Why should we sample phosphorus levels and when?

Phosphorus sampling could be done every month from spring to fall, since it is directly related to aquatic plant growth. However the volunteer lake monitoring network program created by Québec’s Ministry of the Environment, the MDDELCC (ministère du développement durable, de l’Environnement et Lutte contre les changements climatiques) called Réseau de surveillance volontaire des lacs (RSVL) recommends testing three times during summer: in mid-June, mid‑July and mid-August. The compilation 0f phosphorus‑sampling results obtained over the three summer season months gives a representative snapshot of the lake’s  phosphorus levels. Sampling can also be done in the spring and fall, when seasonal water mixing occurs (immediately after the ice melts and prior to freeze‑up). With this sampling, we can determine the levels of phosphorus released into the lake waters. It can also serve as an indicator that there is a depletion of oxygen in the lake’s deep waters; this could be a precursor to a cyanobacterial bloom (blue-green algae). Sampling Technique: A lake’s total phosphorus levels are determined from a water sample collected from the pelagic zone—the deepest part of the lake, or from a sample taken at the lake’s centre at a depth of approximately two (2) metres below its surface for summer readings, or samples taken over the entire depth of the water column in the photic zone for seasonal water mixing sampling. Samples are then sent quickly to the lab for testing and results are usually given in μg/litre or mg/litre. To get complete details on the
sampling technique, please refer to the water quality sampling protocol:  (French only)
or watch the video here:

Interpretation of results:
The quantity of phosphorus present in a lake’s waters is a determinant of that lake’s trophic state, or in other words, its biological ageing state


Classes trophiques

Phosphore total


Chlorophylle a





0 - 4

0 - 1

12 et +


4 - 10

1 - 3

12 - 5


7 - 13

2,5 - 3,5

6 - 4


10 - 30

3 - 8

5 - 2,5


20 - 35

6,5 - 10

3 - 2


30 - 100

8 - 25

2,5 - 1


100 et +

25 et +

1 - 0

Carbone organique dissous (mg/L)


Incidence sur la transparence

< 3

Peu coloré

Très faible incidence

≥ 3 > 4

Légèrement coloré

Faible incidence

≥ 4 > 6



≥ 6

Très coloré

Forte incidence


Natural sources of phosphorus entering a lake's watershed come mainly from rain and debris carried by winds and deposited in the water, from rivers and streams, wetlands and beaver bonds. The main sources of phosphorus of human origin imported into lakes include noncompliant and below-standard septic systems, lawn and garden fertilizers, the excessive deforestation of riparian strips,
industrial waste, riparian strip erosion and unsustainable agriculture.


Effects on water quality:
Excess amounts of phosphorus in the water can lead to excessive growth of aquatic plants and algae (cyanobacteria). It can alter the taste and smell of water, create anoxic conditions (lack of oxygen) in deeper waters and contribute to the replacement of members of the salmonid
species of fish (trout) with species tolerant of more polluted conditions.
In short, an increase in phosphorus is directly related to a lake's eutrophication (aging).


What is chlorophyll A and why should we sample it?
Chlorophyll A is a pigment, which gives plants, algae and cyanobacteria their green colour. It serves as an indicator that an abundance of microscopic algae (phytoplankton) exists in the lake. These algae determine the production rate of organic matter in the lake and increase
in relation to the concentration of phosphorus present in the lake. Eutrophic lakes have thick algae growth. 

Sampling Technique: 

To determine the amount of chlorophyll A in a lake, water is sampled three (3) times during the summer (in June, July
and August), with the sample taken close to the surface of the lake (at a depth of about one [1] metre). The water is poured into an opaque bottle intended for this analysis. The sample is then sent quickly to the testing lab where the algae will be analyzed. The chlorophyll A
concentration is measured in micrograms of pigment per litre of water (g/l) or milligrams of pigment per cubic meter of water (mg/m3). Less than 1μg/l is deemed a very low concentration of this pigment, and over 25μg/l, extremely high (see Table 1, page 4). Comparing the data
collected over the years will show if a lake’s productivity is stable.


What is dissolved organic carbon and why should we sample it? 

Dissolved organic carbon (DOC) results from the decomposition of organic matter (plants, micro-organisms, animal carcasses and man-made contaminants and is the reason for amber-coloured or
brownish water. It can help determine the extent of organic pollution, which, in high concentrations, will have an impact on the levels of dissolved oxygen reserves in the water.

Sampling Technique: 

The sampling technique used to determine the levels of dissolved organic carbon is basically the same as used to measure chlorophyll A. Results are expressed in milligrams per litre (mg/l) where levels of less than 3 mg/l represents water with a slight colouration and 6 mg/l and above, water with a pronounced colouration (see Table 1, page 4). Consequently, the concentration of dissolved organic carbon has a direct impact on water transparency.



What is water transparency and how do we sample it ?
Water transparency is how easily (or how deep) sunlight can penetrate through the water. Water transparency is measured with a Secchi disk (see Figure 2) and is an indicator of the amount of organic matter suspended in the water. The more transparent the water, the better the quality. Transparency diminishes with the increase of microscopic algae present in the waters of the lake.

Sampling Technique:
Simply stated, water transparency is measured using a Secchi disk; it is a circular disc measuring 20 cm across with white and black quadrants and is attached to a cord with graduated depth markings. A Secchi disk measurement should always be taken from the shady side of a boat; it is plunged into the water and the depth at which we can no longer see the disk is noted. Ideally, transparency should be measured every two weeks from June to October since the data obtained is very qualitative and will vary according to changing weather conditions. This way, we know the average value obtained will better reflect reality. Transparency is measured in metres and is an indicator of the lake’s trophic state. To get complete details on the sampling technique, please refer to the following document: .

Figure 2. Disque de Secchi. Source :



What are fecal coliforms and why should we sample?
Fecal coliforms are bacteria that come from the feces of human and warm-blooded animals. Their presence in the water indicates a certain contamination from fecal matter and associated microbes has occurred. Sampling to determine the presence and levels of fecal coliforms will determine if the water is safe for recreational use (especially swimming).

Sampling Technique:
Fecal coliform sampling is relatively simple. Position yourself in shallow waters—about knee high, and collect a sample of water from just below the surface. The sample is then quickly sent to the laboratory for testing. The results are expressed in units per 100 millilitres of water (see Table 2, page 4). It is recommended to repeat sampling in all the areas used for swimming and to do so on different occasions, since factors such as wind, temperature and contamination can have an impact on the results. Protecting the health of users is the main incentive for conducting these tests.

Water sampling method. MDDELCC


Tableau II. Classification of the water quality used for recreational use

Water Quality

Fecal Coliforms / 100 millilitres



0 - 20

All recreational  used allowed


21 – 100

All recreational  used allowed


101 – 200

All recreational  used allowed


More than 200

Swimming and other direct contact with water are compromised   

Very poor

Plus de 1000

All recreational uses are compromised



What are cyanobacteria and why should we sample?
Cyanobacteria (also know as blue-green algae) are aquatic microorganisms able to produce natural toxins, called cyanotoxins. Naturally present in the water, cyanobacteria only become a problem when they proliferate. If conditions are favourable, for example when large quantities of phosphorus can be found in the water, cyanobacteria can reproduce quickly. When this occurs, they form what are referred to as algal blooms, which are visible to the naked eye, and can generally be found floating on the surface of the water. These blooms are generally green or turquoise in colour and can look like spilled paint floating on the surface, or like froth or scum lining the shores or again, like floating pea or broccoli soup. Alternatively, certain rarer species of cyanobacteria have red pigments and will look like masses of varying shades of red spread or diffused on the water (even from underneath sheets of ice). For examples of cyanobacterial blooms, please consult the MDDELCC identification guide (French only) Guide d’identification des fleurs d’eau de cyanobactéries available in their offices or online at (French only).

Health risks for bathers and other recreational users:
When cyanobacteria produce toxins, they can be harmful to human health. It is strongly recommended to avoid contact with this contaminated water and to avoid ingestion as well. Symptoms generally include diarrhea, nausea, vomiting and abdominal pain when ingested and irritation of the skin, eyes or throat after contact has occurred. If large quantities have been ingested, cyanotoxins can affect the digestive system, the liver and the nervous system.

What to do:
If you suspect the presence of algal blooms in a lake, you must contact the MDDELCC without delay at 819‑772‑call their environmental emergency line ‘Urgence-Environnement’ at 1‑866‑694-5454. You can also go online and fill out the visual sighting of cyanobacterial bloom report:

Recommendations and best practices:
As you can see, all the components of water are linked together. What seems like simple deforestation of the shores of a lake can increase the levels of phosphorus in the water, which can start a chain reaction with ripple effects working their way along and affecting all the elements and the living organisms that make up the lake’s ecosystem. This is why respecting the delicate balance of these ecosystems is so important and why each and every one of us should strive to adhere to environmental best practices, which start with the following:

  • Test the waters of your lake annually, either through your lake association, the Federation of Lakes of Val‑des-Monts or the Volunteer Lake

  • Monitoring Network (RSVL). Š

  •  Respect the integrity of the riparian strip by not mowing the lawn and by replanting trees and shrubs when

  • necessary.

  •  ŠŠDo not place fill or other materials that may leach or wash away and pollute the riparian strip area. ŠŠ

  • Become a member and play an active role in your lake association.

  •  ŠŠProperly maintain your septic system and have it inspected.  Ensure all plumbing fixtures (sinks, washing machines, etc.) drain into the septic system and not into the French drain (weeping tile) or directly onto the land.

  • ŠŠUse non-motorized pleasure crafts or reduce motorboat speeds to reduce the impact of waves on shorelines.

  • ŠŠLimit the use of pesticides, herbicides and phosphorus‑based household products.

  • ŠŠReduce contamination by aquatic invasive species by cleaning your pleasure craft before and after each time you use it in a different body of water. 

  • ŠŠOn private roads, ensure culverts are stable to avoid sand and other materials leaching or washing away and ending up in surrounding lakes

  • and streams.


To find out more, to register with the MDDELCC (ministère du Développement durable, de l’Environnement et Lutte contre les
changements climatiques) volunteer lake monitoring network program (RSVL), to consult articles on water and lake water quality sampling:  (Mostly French)

‘La trousse des lacs’, a toolkit for anyone interested in the health of lakes (French only): 

Conseil Régional de l’Environnement (CRE) Laurentides (French only):

For further information, please contact the Federation Coordinator, Mélanie Renaud: