Yes, it is due to the hardness of the water here in Canada. If you can buy a water softener filtration system to soften the water coming from your shower, it could possibly lessen your severity of your hair loss during shower time. But these water softener can be quite expensive to buy and if you can't afford it, don't worry because there are other cheaper and more affordable ways.
Another reason would be the presence of Chlorine in the shower water. In Canada, the water treatment plant people uses Chlorine to kill bacteria and other viruses present in our tap water. They needed to put in a certain amount of Chlorine to prevent outbreak of disease from consumption of tap water and other uses. These Chlorine are very similar to the commercial bleach liquid you get from the supermarket, only difference is the tap water chlorine are much more diluted and slightly modified and added with other elements.
One piece of advice would be to use the Chlorine shower filter widely available in home hardware stores such as HomeDepot.ca, Lowes.ca, Canadiantire.ca, Rona.ca, amazon.ca, eBay.ca and Walmart.ca. This shower filter will trap most of the Chlorine contained in the shower water. Chlorine is partly responsible for making people loose hair during shower. By removing these Chlorine, you will notice that your hair loss during shower is less severe.
One type of shower filter by Sprite company is shown below and can be bought at Lowes Home Improvement Store at Lowes.ca.