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permaculture design: deciding what to do with seasonal water source  RSS feed

 
Mariah Wallener
Posts: 167
Location: Cowichan Valley, Vancouver Island, Canada
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I'm placing this in this forum because my question is more about design, I think. Feel free to move it if necessary.

We have a small acreage on a gentle south facing slope with a couple small hilly bits in between. During the wet season (basically October-ish to May-ish) we get heavy rains frequently and when we do a small river forms on our property. It comes in near the highest point of the property and currently flows down a path/roadway to a low spot between two little hills where it forms a small seasonal pond that dries up in late spring/early summer. So by the time the dry season comes around there is nothing left of it.

It kills me to see so much water disappearing when we get so dry in the summer. I would also love to have a pond on the property to increase diversity and allow us to have some ducks and maybe even grow some fish.

I'm trying to decide on which of these options would be best for us:

1) build swales on contour along the hillside to capture the water and distribute it to hugel beds or swale-side plantings. thing is, it will be wet during the wet season when we really don't need to add extra irrigation. in summer when we need it these swales will be dry. hugel beds anywhere here will do great at providing irrigation since they can get a nice soaking from the rains. swales seem redundant in this scenario.

2) build a proper ditch for the incoming water, place stones periodically to make little waterfalls (because they make a pretty sound), dig the current pond much deeper. try to seal it so the water stays there until the dry season. don't know if I could use it to irrigate (would have to pump, as this site is below where gardens and house are).

3) try to capture it somewhere higher on the property by building a pond from scratch on the hillside (this would require some heavy excavating) to allow for gravity feeding of water to drip irrigation systems in place further down the hill


What would you do?

 
Tyler Ludens
pollinator
Posts: 9742
Location: Central Texas USA Latitude 30 Zone 8
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The theory behind swales is that they soak excess water into the landscape so that it is available in the soil for the dry periods. So I don't think they're redundant in your situation.

Short video explaining how a swale works: http://www.youtube.com/watch?v=UFeylOa_S4c


So I would probably want to put in a series of swales. Eventually enough water may be stored in the soil to keep the pond filled, or you may be able to design the swales to both fill themselves and the pond.

Darren Doherty is answering questions in the earthworks forum and he might be able to offer specific advice on how to design swales or keyline to save the water on the property and fill the pond.

 
Paul Cereghino
gardener
Posts: 856
Location: South Puget Sound, Salish Sea, Cascadia, North America
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If you have surface runoff (which it sounds like you do) swales may be useful. Using keyline principles, you'd run your swales slightly downhill (1%) towards the ridges, so that the water that would normally congregate in the valley, is sent out to the ridges, distributing rainfall more evenly over the land. The volume of your swales would be designed to store your rainfall event... while we are wet, we don't have the deluges of the south... maybe an inch over 24 hours is really heavy rain for us. Your soil texture may determine the economy of ponds. I expect that unless you have running water in summer that storing some water for summer is the key to productivity in our climate. Good luck... definitely look into Keyline, Yeomans, and modern practitioners like Doherty.
 
Andrew Millison
Instructor
Posts: 112
Location: Corvallis, Oregon
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It sounds like the most desirable option is to excavate a new pond as high up in the watershed that you are able. Swales will keep the overall landscape hydrated more, but a pond will give you a volume of water that you are able to direct for irrigation. If you are able to site the pond above your growing areas, then you can use gravity for irrigation, either through a pressurized system like drip, or as rapid flood flow irrigation as the Keyline system suggests.

Ponds are costly, but you'll be putting in permanent long term water storage for directed summer usage

Good luck,

Andrew
 
Mariah Wallener
Posts: 167
Location: Cowichan Valley, Vancouver Island, Canada
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Thanks for the replies, everyone.

Tyler, perhaps I've been watching too many "Greening the Desert" videos, lol. I will go check out that video you provided. I didn't think the water soaking in during the wet season would last through the dry season, although with hugel beds I could see that happening.

Paul, thanks for the references. I do think storing water for summer is our main issue, as we do get a long dry stretch here (about 8 weeks or more with no rain). Harvesting rainwater via roof runoff etc is in the plans, but I still want a pond even if for nothing else than the aesthetic appeal and habitat it provides.

Off to research more, thanks folks!
 
Matt Saager
Posts: 48
Location: Oregon - Willamette Valley
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While you're thinking it through... what about combining the different options.
- new pond high on the property, to hold water
- swales at 1% slope out to the ridges, to move water across the landscape
- hugel beds in the swale berms, to provide grows area with minimal irrigation required
- existing lower pond, expand/rework to include swales for water harvesting

Sounds like it might be alot of work all at once, but it might be a good long term plan.
 
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