sustainable gardening question: rain barrels for irrigation and bioswale runoff solution? - Ask Extension
Greetings,
I am new to the area and am starting to plan my garden in my new home.
I live on top of a largely forested hill, but I have a large ...
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sustainable gardening question: rain barrels for irrigation and bioswale runoff solution? #875896
Asked July 04, 2024, 2:14 AM EDT
Greetings,
I am new to the area and am starting to plan my garden in my new home.
I live on top of a largely forested hill, but I have a large backyard with three terraces. I want to turn these terraces into gardening space rather than monoculture grass. Right now, I am planning a small berry patch on one section of one of the terraces. I would like to use a drip irrigation system that is connected to a rain barrel(s).
I have a few questions about rain barrel collection.
1. I have seen two different descriptions of rain water collection requirements in Oregon. One description says that Oregon law only allows for rainwater collection from a roof gutter. The other description states that you must catch rainwater off of an artificial, impervious surface such as a roof or a paved parking lot. The terrace I am cultivating is away from the house and elevated from the ground level. I was hoping to make a passive drip irrigation that relies on gravity. Would it be legal to make a free-standing rain barrel with a catchment made of something like an upside down umbrella? We are only looking at storing 50-100 gallons at a time.
If this is an acceptable method, I was hoping to put one or two 50 gallon rain barrel near the edge of my retaining wall, as it is slightly elevated and would allow for a passive flow for an irrigation drip system. But, if it is feasible, I have a more perplexing question.
2. I am reading about planning for an overflow system with rain barrels. One solution I have read about involves placing the rain barrel within a natively planted bioswale and using that as a runoff solution. Is this a feasible/effective solution for rain barrel overflow? If yes, I know very little about bioswales, and I'm wondering if it would be advisable/possible to create a bioswale along the wall of the terrace or is that a recipe for eroding the wall? I have included a terribly labeled picture to try and describe what I am talking about.
Thank you for y
Linn County Oregon
Expert Response
Hi, Jennifer,
I can't advise you on the legalities of rain barrels. You will need to check with your municipality for local regulations, if any.
What I can say, though, is that rain barrels have very limited usefulness in our summer-dry climate. There is generally no rain at all, or virtually none, during the 3-4 hottest months of the year, just when people are needing to water their gardens the most. A rain barrel doesn't hold much water. You should calculate the water needs of the area you want to water, and see how far 50 gallons will go. Once the 50 gallons is gone, you are unlikely to get any more until fall. (As an aside, a rain barrel hooked up to a roof gutter can get some water during the summer. Even a very small rain event can generate quite a lot of water over the area of a roof).
To be genuinely useful, people usually need to install a much bigger holding tank - several thousand gallons - that can fill up during the spring and hold enough water to last through the summer with careful use. The elevation drop you have could make this very effective for gravity feed.
A bioswale to collect the runoff sounds like a good idea, but putting it behind a brick wall is not. Yes, it could well erode the soil behind the wall, but more importantly, water-laden soil weighs a lot, and is always trying to move downhill. If you add more water than the soil would naturally hold, it could be more weight than the wall can bear. The weight-bearing ability of the wall depends on how it was constructed - does it lean in at the top? doesn't look like it in the photo - and if good drainage is installed behind it.
It looks like you have a very promising site there. I suggest you spend this summer sitting with it, studying where sun and shade are, what if any moist areas there are, what the soil is like, and what grows naturally there. You can also study what other people are growing in your area, and solutions for summer-dry climates. Fall is an excellent time to plant, and you might be able to have more solid plans by then.
I can't advise you on the legalities of rain barrels. You will need to check with your municipality for local regulations, if any.
What I can say, though, is that rain barrels have very limited usefulness in our summer-dry climate. There is generally no rain at all, or virtually none, during the 3-4 hottest months of the year, just when people are needing to water their gardens the most. A rain barrel doesn't hold much water. You should calculate the water needs of the area you want to water, and see how far 50 gallons will go. Once the 50 gallons is gone, you are unlikely to get any more until fall. (As an aside, a rain barrel hooked up to a roof gutter can get some water during the summer. Even a very small rain event can generate quite a lot of water over the area of a roof).
To be genuinely useful, people usually need to install a much bigger holding tank - several thousand gallons - that can fill up during the spring and hold enough water to last through the summer with careful use. The elevation drop you have could make this very effective for gravity feed.
A bioswale to collect the runoff sounds like a good idea, but putting it behind a brick wall is not. Yes, it could well erode the soil behind the wall, but more importantly, water-laden soil weighs a lot, and is always trying to move downhill. If you add more water than the soil would naturally hold, it could be more weight than the wall can bear. The weight-bearing ability of the wall depends on how it was constructed - does it lean in at the top? doesn't look like it in the photo - and if good drainage is installed behind it.
It looks like you have a very promising site there. I suggest you spend this summer sitting with it, studying where sun and shade are, what if any moist areas there are, what the soil is like, and what grows naturally there. You can also study what other people are growing in your area, and solutions for summer-dry climates. Fall is an excellent time to plant, and you might be able to have more solid plans by then.
