Find out how much water you could capture in a year. Draw a box over your roof. You might be surprised!

On July 11, 2012, Ottawa City Council passed the new 2012 Green Building Promotion Program. Green buildings constitute high levels of environmental performance in design, construction and operation. Energy, water and resource efficiency are a key components of a Green Building. Harvesting rainwater or recycling greywater to irrigate lawns and flush toilets is a significant green building technique. The Save the Rain app facilitates the rainwater harvesting process by calculating annually how much rain can be captured from a rooftop.

OpenData sources used

Drinking Water Summary data (communal wells) -
Ontario Well Record data - Records

The value it provides to residents

For centuries, people have collected rainwater for drinking, washing and irrigation purposes. With the advent of municipal water treatment, rainwater collection became less popular in urbanized centres, though water storage cisterns can still be found in old farmhouses across Canada. But recently, rainwater harvesting has experienced an increase in popularity in countries around the globe as a result of droughts, water shortages and the rising costs of drinking water and stormwater infrastructure. Canada, too, is experiencing an increase in rainwater harvesting for lawn and garden irrigation, and many municipalities have begun to offer rebates for rain barrels. But larger, more sophisticated systems that capture, store, treat and redirect greater quantities of rainwater for other uses are still relatively new. (src:

The Save the Rain app facilitates the rainwater harvesting design process by calculating annually how much rain can be captured from any rooftop. The Save the Rain app also displays the Ottawa communal well locations and associated water quality reports.


  1. Kathy Laudon

    Great idea! I can't believe how much water we could be harvesting. Would love to implement this at our house.

  2. Martin Barrett

    Thx Mark, this is an idea everyone can use to help out the local water supply. If its another hot one like last yr this will be gold.....

  3. Priscilla Laudon

    Well, Mr. Mark - there lots of rain out our way - I am sure it could be used much more efficiently! Thank you for your genius!!

  4. Annette Gramm

    Great Idea Mark! Interesting to think about how much it rains and we could bottle up to water our garden and grass.

  5. Malcolm Clark

    Great idea Mark,let's stop paying so much for water and collect it ourselves.

  6. Ken Nentwig

    Love the idea - seems it extends well past Ottawa's boundaries according to the video, so someone even in Kemptville could use it!

  7. kristine morgan

    Smart thinking!

  8. JJ Restrepo

    Amazing App... Save the Rain teaches that not only water starved communities can use The Rain. Yes, I can too in the same way.
    I live in an apartment that has a small terrace portion uncovered. I can save there!!! because I want to do my part to use the rain as a sustainable water supply.

  9. Herb Lainchbury

    Nice work Mark!

  10. Garry Gramm

    Great App Mark. Considering how much rain we get in Vancouver Area it makes a lot of sense to try and capture as much as we can. Using water in this way will help sustain our supply for the future by deceasing the dependency on the water supply for such things as watering the lawn and the garden, particularly in a hot dry summer.

  11. Ken Nentwig

    Mark - nice work: I tried it again, this time outside of Kemptville.... Actually on Vancouver Island, and find it very interesting. Hope you get some really good sponsorships or something from this!

  12. Barbara Davey

    Love it! My husband grew up in the mountains in Jamaica and they collect every drop of water from the roof and put it to good use... Drinking, cooking, cleaning, laundry, watering garden and livestock, And yes, even flushing the toilet! It goes off the roof into a large holding tank and even gets them through the dry season. The "first" world could take some lessons.

  13. Brad Madu

    Wow your app seems a lot more significant to me now that I am living in Zambia than it would have a couple months ago. That 318 kg of corn would sure come in handy.

  14. Ghassan Herzallah

    Brilliant stuff

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