Rainwater harvest – the glut

There is a paradox in harvesting rainwater. It all happens at the time you least need or want any water. And when you do need it, there isn’t much to work with. The ideal would be a nice big shower to refill the butts, followed by a week of sunshine. Right now, there is water everywhere – and to be honest I could do with a lot less of it. Mike came round the other day and told me that Kings Hill is really, really muddy, and I said “Good”. But it wasn’t that I was glad he’s living in mud, I was simply relieved that I probably haven’t caused the water problems in my own garden. 

You will remember in previous posts and in Permaculture Magazine 74 I explained how the water comes down from a small roof section and up to the top of the garden where it is collected in two water butts. These are now properly connected so that when one is full the second starts to fill from it. It isn’t overly quick, but even in dry spells I nearly managed with the ducks’ original butt so three times the amount should be ample. But when I’m not using any, it becomes full and stays full – except that it doesn’t, it overflows. I couldn’t see exactly where the water went, but I presume some of it flowed down the concrete path to the drain, and some just increased the surface water in the garden.

So I finally got round to digging the swale along the top of the garden. This has three intended functions: 1) to act as a soakaway for the above; 2) to stem the flow of rainwater coming down to the house from above the property (largely run-off from the garages, which are not provided with any drainage); 3) to irrigate the garden.

For the first function, the soakaway, it is evident that the swale doesn’t need to be very deep. As much as anything it is acting as a guide for the water – a bit like when you hang a chain from a gutter or run your finger down the inside of a tent. It really needs an overflow that works the instant the water gets too high – but that means drilling a hole, and I want to be certain this is the best way to do it. At the moment I just leave the tap trickling into the swale when it’s raining. The plan is for the overflow to run into the ducks’ bowl, which will in turn overflow into the swale, because that way they get cleaner or replenished water without me having to do anything – and it’s grey water flowing away rather than nice clean rain. The problem with a lot of this is that you have to experiment gradually with cause and effect; keep observing, change things slowly and incrementally.

The second function, to deal with run-off, is working nicely. I covered the swale ditch with a heavy metal grille, as the run-off comes down the path where it normally soaks in and makes the path splodgy and waterlogged. Right now the water is gathering in the swale – where it presumably has two choices. It can either soak in where it is, or it can flow along the swale and be distributed more evenly. At the moment it isn’t doing either. This must be a combination of compaction under the path, and insufficient quantity to spread. Either way, it’s not on the surface of the path. And it feels good to have a bridge!
As for function 3, right now the garden doesn’t need any irrigation, and I’m not going to know until the next drought whether it is functioning as intended. However, I have taken hoses off the taps, which gives me a second source of water for the duck bath and, in some future time when the garden needs watering, I can use it for that too. My goal is not to use the mains hosepipe at all, for the whole summer.
Right now, though, there is just too much water. Yesterday we found it had collected in the corner or the front path, an unintended consequence of the breeze block steps joining the doorstep. It was a good plan from the point of view of stabilising the structure and aesthetically integrating it, but now there’s no way for the water to drain. The chances are some extra water at this end is attributable to the duck water ‘acequia‘ – I’ve noticed how much further and faster it flows when the ground is already saturated. For a few hours I berated myself for being a bad permaculturist, and then I remembered that the real problem is the impermeable concrete as applied by South Hams District Council. It’s great in the summer having the irrigation, and it does seem to drain away – and it won’t get any higher than the first breeze block, which is below the damp course. So I think I’m alright, but it’s a salutary reminder to think things through really well, always to ask the question: ‘And if I do [this], what is likely to happen?’

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