High level phosphates (colour study)

A study to help us make colour tests more accurate!

This study is now closed to new participants.

We are looking for participants across Canada to help us create reference photos to better read inexpensive colour-based water tests. This first step creates references for two types of test strips (high-level phosphates and alkalinity, pH, and hardness).

We sent you our ‘testers’ package, which includes test strips, reference card, field sheets, and reference materials. Each test should take less than 5 minutes to conduct. Participants already include NGOs (like SwimDrinkFish), Conservation Authorities and scientists from across Canada. But, we need more places and people to participate to give us the best results. Results from this study will be published widely with our academic partners (and, we hope, you!), and you’ll be the first to hear about new tools, grants for new equipment and more.

Why this project?

Many inexpensive water tests are analyzed through colour comparison, but eyes interpret hues differently (for example, pH strips can have wildly different results based on their readings from orange to pink, which is affected by common types of colour blindness). Color-sensing technology is often inaccurate because lighting affects sampling.

We are looking at how machine learning applies an algorithms that ‘read’ colours, and, through integrating different datasets, helps create meaning for citizen science water testers.

By participating in this project you are helping us verify an artificial intelligence model designed to adjust the image and detect the true color and value of the test strip. This will allow us to eliminate human error and become more accurate: the model could interpret a finer scale not detectable by the human eye.

We are also exploring how to legitimize crowd-sourced data so it can be used by academics and policymakers in decision-making and consulting academic partners to understand rigorous protocols. This project will help us have these conversations!

This method and machine learning model can be extended to read more tests (we are hoping to soon ‘read’ the liquid test for dissolved oxygen, for example). If you know any other tests that you think might be useful for our testkits, please email kat@waterrangers.ca.

What kinds of water to test?

We are looking to use these phosphate strips as an ‘early detection’ for high levels of phosphates in water.

This means the best tests should be taken in water suspected to be contaminated by a sewage overflow, agricultural run-off, or faulty septic systems at the source, where you expect phosphate readings of 0.1ppm (100ppb) or more.

Older lakes and ponds might also be suitable candidates for this study. It is not suitable for monitoring healthy, young lakes, though. For example, regular lake testing in Ontario would be around 0.031ppm (10ppb of phosphorus) and so wouldn’t be suitable for these tests (NOTE: To convert phosphates to phosphorous, multiply the ppb value for phosphorus by 3.066 then divide by 1000 to equal ppm phosphate).

How to test

Green container: Phosphates (ppm)

  1. With dry hands, remove 1 strip from the container. Close container.
  2. Dip strip into water for 5 seconds and remove.
  3. Hold the strip level, with pad side up, for 45 seconds (do not shake excess water from strip)
  4. Lay strip on reference card and take a photo.
  5. Compare the test pads to the colour chart on the back of the green container and record your interpreted value on your field sheet.
  6. (optional) If you take a sample to the lab, record value on field sheet.
  7. Follow instructions below for sharing your results with us.

Navy container: Alkalinity, pH, Hardness

  1. With dry hands, remove 1 strip from the navy container. Close container.
  2. Dip strip into water for 2 seconds and remove.
  3. Shake once to remove excess water. Read immediately.
  4. Lay strip on reference card and take a photo.
  5. Compare the test pads to the colour chart on the back of the navy container (holding strip vertically) and record your interpreted values on your field sheet.
  6. (optional) If you take a sample to the lab, record value on field sheet.
  7. Follow instructions below for sharing your results with us.

How to share your tests

Simplest: Just with your phone camera

So long as you have geo-tagging enabled on your phone, you can take photos of your test strip(s) on our reference card, and send them to us. Fill out the field sheet and take a photo of that, too. Email your photos to kat@waterrangers.ca

More helpful: Through the Water Rangers App

Use the Water Rangers site to fill out our specially designed data form. That way we have sample locations on the map, and observations are attributed to you. You’d take photos of the reference card and attach it to the observation in.

  1. Register online at app.waterrangers.ca/register
  2. Once you’re registered, you can also download our app for iPhone and Android.
  3. Join the group, Water Rangers Testers app.waterrangers.ca/groups/water-rangers-testers (click ‘Join group’ top right while logged in)
  4. Conduct your tests, choosing your test site on the map, and filling out the observation form with your interpretation of the colours. Add photos of your reference card with test strip. If you’re testing for other parameters, you can include them here too.

Taking a lab sample?

We are conducting our own samples in the lab, but the more validation we get, the better. If you are also analysing pH with a probe, or phosphate levels in the lab, please record the ‘true’ value for us to use too. This will help us build our model so much faster!

Join the study

This project was funded by CIRA’s Community Investment Program,who are supporting us to build a stronger Canada online. Thank you for supporting us!

About Water Rangers

Water Rangers is a Canadian non-profit organization who support citizen science for water by building tools that are easy and fun to use but also innovative and scalable. Our team are designers and developers supported by scientists as we build new multi-sector tools that we hope will empower more Canadians to contribute meaningful water quality data. We’ve been honoured to win awards for Aquahacking (2015), Great Lakes Observing System Data Challenge (2016), Friends of the Tay Watersheds Environmental Award (2017), Friends of the South Nation Conservation Recognition (2018) and WatersNext Early Adopter Award (2018). We are growing quickly, and have participated in, and are planning research projects with several universities on accuracy, effectiveness and human responses.

Open data platform

We have an open-data online platform at app.waterrangers.ca where groups can define their testing protocol using your own testing equipment and form and organize volunteers. Groups can get support uploading existing datasets, and embed activity feeds and results on their own site too. You can learn more about our online platform at app.waterrangers.ca//help/faq


We also aim to lower barriers for anyone to get involved in water testing through our water testing kits, where we include tools that match our criterias (easy-to-use, affordable, and immediate results). This project supports making inexpensive testing equipment better by using technology (machine learning) to interpret colour-based tests. Our testkits are being used across Canada, but mostly in Eastern Ontario right now. Learn more at store.waterrangers.ca.


Here are some answers to some of the questions we’ve had so far!

For those using the kit already, are the 4-in-1 test strips meant to replace the current strips?

The 4-in-1 are the same strips as the current ones found in our test kits, but for this project, we cut the top 2 pads off (it was a great opportunity to have less ‘noise’ for these people helping us with the study). We are also talking to the manufacturer of the same strips to see if we can make this the standard experience. We are sticking with the hth strips (or the same manufacturer) to maintain continuity, though!

Is there a temperature range for the phosphates test (ie. x degrees C)?

Yes. We have found that tests done at low temperatures have given much higher readings. Optimal air and water temperatures should be around 20 degrees. We will be testing the range (to see if accuracy is affected at 15 or lower, or 25 or higher), so please record air and water temperature in your measurement if possible. You can also bring the sample back indoors to warm up to room temperature.

The same sample indoors and outdoors give very different readings when the air and water temperature are winter conditions.

When do you expect high levels of phosphates?

We are looking to start the phosphates during spring run-off (potential for high levels near agriculture, sewers, etc). Naturally high levels associated with algae start in the Fall, but we’re hoping we’ll have a better idea how all this works so you can get some results.

Is there any value in doing a baseline test before the spring/summer agricultural runoff starts in warmer weather?

This test isn’t sensitive enough to warrant baseline data. While it would be nice to be able to detect very low levels, we do not expect any precision at this time.

Are additional phosphate strips available, and if so, what is the cost ? (… just planning for the future)

Yes, you can get more! They are Hach Aquachek Phosphate strips, since these were the safest and most relevant for our project (results of our comparison of available tests will be published soon). For the duration of this study this year, though, you can get more from us, since we have funding. If you are comfortable handling chemicals, the Hanna Checker is also excellent, and can potentially read lower levels.

The colours seem a bit darker on the colour comparison on the backs of the containers…

We are looking for tonal matches for the backs of the container, so consider the colour, not the darkness. This is a supplementary analysis we’re asking you to do, to compare human eyes to computer analysis. The algorithm we want to build will only use the photos with the reference card (the one with the many circles).