A CITY GIRL: Passive Irrigation Plan

I wanted to help explain some of the pieces of the garden. I'm thinking this is going to be a short series of posts instead of a single, super-sonic long post.

Passive irrigation is part my master plan. The basic idea is to hold the water that comes into the garden and slow it down. Once the garden has matured, I don't plan to use any city water or quite frankly, water the garden at all. Watering the garden is defined as me standing around with a hose or sprinkler running. Some say efficient, but really I just prefer to enjoy the garden with as little input at possible. I'm planning to use swales, a banana circle, hugelkultur beds, heavy mulching, ponds and tanks to accomplish this goal.

Swales simple put are a ditch on contour with a mound on the downhill side. This is one of the most important pieces of my permaculture garden. I just have one main swale close to the house that's in green on the plan. It's also the highest point in the backyard. If it were to over fill as I'm sure it will, I have created a sill to take overflow into the pathways.

Swales collect water and slowly, but evenly saturate the land downhill. It should be on contour, but admittedly, mine swale is not. I've dug about 6" down and about 4-5 feet wide. The dirt is laid on the downhill sill of the swale for future planting. I'm going to fill the ditch with bush and tree mulch. The intention is not to keep water here like a pond, but just slow it down.

I have an erosion problem and this is part of the solution. I get rain run off from two houses down. This has caused the neighbors on the downhill side of me to flood along with my front yard. In the front yard, I've built a berm that diverts the water between my house and the uphill house. The swale captures this runoff by filling up the ditch. It will take about 5 years, but this slow moving water will saturate everything downhill from the main swale. 95% of the garden is downhill from this!

I'm capturing the runoff from my roof, the front yard drains and all the water from two houses (up). The math for that quickly adds up. The long term plan is to connect the house gutters into the swale. The mulch in the swale will eventually breakdown in 5 years if not longer. By that time, the land will be saturated. If I have to remake the swale, it will be so much easier and will be beautiful soil.

I watched and waited for my swale to fill up this last rain we had. I was disappointed it never came close or even puddled. The 50 plus bags of leaves are plugging up the water route. I definitely plan on moving the leaves and testing out the swale before I fill it up.

It really is banana trees planted in a large circle with a hole in the center filled with mulch. I would say this is a modified swale. I'm designing a half banana circle at the bottom of the concrete slab near the greenhouse.

There is a mound here that I assume the previous owner added to help stop the slab from sliding down the yard. I'm going to dig a hole at the edge of the slab and fill it will mulch. This hole should capture the rundown from the concrete slab.

Hugelkulur beds simply put are buried logs and wood that form a mound. I'm planning three Hugelkultur beds noted in the pinkish color in the plan. There is so much information on them, I don't want to go into too much detail. There are a few things that happen here to the tune of passive irrigation: After the wood starts to decay, it acts like a sponge that stores water. And since these beds are mounded, it creates a lower areas to move rain water where I want it.

I plan to dig about 4" of soil from the beds and add logs of trees I've previously cut down to the bottom. I plan on moving the soil I remove to the front of the house where I need it. I'll then add compost on top of the wood, plant out the bed and the mulch with straw.

I understand the first year of theses beds are not overwhelming abundant because the wood is taking in nitrogen instead of releasing. The second year is much more productive as the wood starts to decay more and continues to act like a sponge.

HEAVY/ SHEET MULCH

I'm going to be mulching or sheet mulching by adding lots of organic matter that continually help store water. Mulching helps mitigate water evaporation in the soil. In theory, no soil should be left exposed.

I'm sheet mulching every garden bed with a layer of leaves, then cardboard, then compost and then straw. The path ways will be covered with a layer of cardboard and tree mulch on top. I plan yearly to add tree mulch to the path ways. Then in fall, I will collect bagged leaves and add them to the top of each bed.

Over time, this will slowly raise the level of the garden. As the beds will increase in height with leaf mold, so will the pathways with tree mulch. As the pathway is filled with tree mulch, they also become a passage ways for water to travel slowly through the site and into the garden beds. The pathways are primarily designed to be a path for water to travel, and a walkway secondary. Down hill is straight up the page. Most of the pathways are oriented opposite of the slope to slow water and move it where I want it.

Ponds have to be the prettiest way to hold water. I still haven't finalized where they are going, through. I'm planning to drain to the condensate line from the AC to one of the ponds. I'm hoping I won't need to find up the pond in the summer time.

My first thought is to have one pond at the top and one at the bottom of the backyard. The one at the top will be easiest to use as everything is down hill if I wanted to empty in the main swale for irrigation. The one at the bottom would be last resort to keep last minute water in my garden.

Mosquitoes are always a concern. I plan to raise fish in the ponds that will eat the larva. The pond will also attract predator species that will help control the bad bug population. I've seen a few toads hopping around the garden, so I don't think it will be a problem.

Storage tanks are expensive and not very pretty. I plan to purchase a few of these later down the road. I really like the slim tanks that can sit on the side of the house. I plan to connect the gutters to them, and then the overflow will spill into the main swale. It seems these are a necessary evil, but they are also an important component to store rain water in long droughts and plant starts.

So everyone that is worried about how I'm going to water my plants, worry not. Right or wrong, I've thought through this. I was almost worried I wouldn't be able to have enough to say about my passive irrigation plan. With my passive irrigation plan, I hope to water the garden in the most efficient way.

If you like this sustainable gardening stuff, you can read more about the planning of the edible forest garden here.