Rainwater harvesting in the RDN

Normally, I’d lead with a pithy comment about how much it rains here in Nanaimo and the Central Island, because it’s a lot. Annually around 1200 mm (nearly 4 ft), according to Environment Canada.

And while the summer of 2014 has been inordinately dry and hot, it’s not the sort of thing that affects how much water we have at our disposal.

Water management isn’t really about how wet it is (or isn’t), it’s about our ability to store what we get effectively. If we consider that approximately 4 feet of water falls over the entirety of Nanaimo every year, that means there’s (give or take) about 111 billion litres of water up for grabs (closer to 70 billion, since you can’t reasonably catch every drop). Balance against that, our annual consumption is around 17 billion (based on volumes of 530 litres per day, per person, in Nanaimo).

That means, if we could effectively capture, I dunno, 30% of the total, available water (not counting water that falls on other water) that falls annually over the entirety of the city, we’d never have to draw from the aquifer, or deplete the water table.

Now, let’s consider that in most cases, capturing rainwater on a grand scale is a huge pain in the butt, and is probably not going to happen.

So it comes down to individual action, which, thankfully, is pretty easy. You can put a cistern on your property, for example. The RDN even has a program in place that can provide you with a bit of relief in the form of their Rainwater Harvesting Incentive Program.

In essence, you can get up to $750 back from the RDN if you implement a rainwater harvesting system on your property. The full details are available here on the RDN website, including rebate information and links for places to buy barrels. I reached out to the RDN to ask about the program. It’s been very successful thus far, in 2013, the RDN Rainwater Harvesting Incentive program contributed to the installation of approximately 574,700 L of rainwater collection in our region.

So, primarily, the initiative is intended for dwellings who draw on private wells, those who rely on groundwater. Deanna McGillivray, Special Projects Assistant for the Drinking Water & Watershed Protection Program, explains who benefits most from a rainwater collection program.

Obviously, this applies most directly to residents on their own private wells, who rely on groundwater for domestic water. It is especially applicable in cases where residents are on wells that seasonally have low productivity (i.e. water table retreats in the summer and less water is available for pumping), are drawing from groundwater that is directly interacting with surface water (i.e. direct impact on stream base flows), or have naturally occurring contaminants in their groundwater (i.e. iron, manganese, boron) and require an alternate source of clean water. However, there are also benefits for residents with water serviced properties. These include: exemption from municipal watering restrictions when using harvested rainwater, resilience in the event of failure of piped system (though failures are extremely rare and unlikely), management of roof run-off during storm events if a property is prone to flooding, and less energy used to deliver water to the residence.

Makes sense. Deanna continues, explaining how using harvested rainwater reduces stress on local aquifers, leaving more for communities and environmental needs. She cites the example of ensuring that there’s sufficient water to maintain critical base flow in local streams, enough to protect fish and aquatic health.

It’s easy to see how important that is, the dry summer this year left our local streams and rivers dangerously low. The Cowichan River has been struggling with low levels for years, this summer, they’ve hit all time lows with the river flowing at only seven cubic metres per second. It’s dangerous for salmon, and other fish fry, as talked about in this article in the Cowichan News Leader.

So, rainwater collection is a good idea, and it seems like the RDN is doing its part to make it happen. The downside is that you only qualify for the rebate if you’re collecting 1,000 gallons (approximately 4,500 litres) or more. That’s pretty significant, more than I could manage on our small property in the OCQ.

The good news is that you can, with a little bit of cash and ingenuity (also, Google), build a simple rainwater collection system in your backyard.

What you’ll need

I like this project, because it satisfies my build it and buy it used requirements (remember the three B’s of Sustainability? Yeah. I still use those.)

So, you probably need about $100 to make it happen. You can start by figuring out exactly how much you need. I found this set of equations to figure out exactly how much rainwater is available. You can also just multiply the average annual rainfall by the square footage of the catchment area, and account for about 40% loss.

I found these fine folks in Victoria selling food-grade 55 gallon (that’s about 250 litres) barrels for $25 each. You can also find deals on Craigslist, and DEMXX.

The parts are available at any hardware store. I won’t get into the details of how to build it, suffice it to say, there are lots of awesome tutorials out there on building rainwater collection systems, my favourite being this one on The Self-Sufficient.

Also, it’s important to note that the water we’d be collecting wouldn’t be any good for drinking. Filtration and purification are complicated, and more than we’d want to take on initially. I’m also mildly concerned about freezing, though we don’t really have the temperatures here. I’d like to be able to collect over the winter to save for the summer.

However we do it, it makes a lot of sense to minimize our reliance on the city water systems, to decrease our usage, and to take advantage of the plentiful resources that might otherwise give cause to complain.

How about you? Are you excited by the prospect of catching your own water? Have a system in your back yard? Let us know!

1 Comment

  1. One caution to cieits and counties when they consider ordinances or other means of encouraging adoption of this technology is that some system manufacturers/distributors promote the use of devices to supplement the storage with potable water as a means of having a reliable irrigation water supply 100% of the time. Such supplementation side-steps the purpose for encouraging adoption of the harvesting technology (saving potable water). To encourage efficient landscape water use, local governments considering an exemption from watering restrictions should focus on how the water is being used (for example, allow handwatering and microirrigation of non-lawn plant materials on an as-needed basis instead of following normal watering days and hours) instead of providing a blanket exemption for any landscape use of the system.

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