Tuesday, September 17, 2013

On being a bit silly about potential water-catchment

In the last 24 hours we've had just over 80mm of rain. Not exactly flood material (though the river is up, Pearl happily reported when she arrived home), but as anyone who's depended on tank and/or dam water will tell you, it's pretty great. Ducks are happy, snails are happy (grrr), garden's happy, newly-planted 800 shelter-belt trees are happy. And pretty much every conversation I've had in the last day or so has involved at least a little bit of "how good's the rain!?", and/or excited comparisons of mm's fallen into different friends' rain gauges around the traps. The excitement (and relief) around town is palpable, and kind of nice.

Olive and I took advantage of the situation by designating today a 'reading day', which comprised much lolling in the loft finishing various novels, eating scrambled duck eggs, drinking tea, and peeking out the window intermittently to admire the rain. 
loft-view of rainy rain over the valley
It also involved a couple of mad dashes outside in raincoats and gumboots to check on the situation with our overflowing duck dam.

One problem with living in a climate where it doesn't rain that often, is that sometimes when it rains quite a bit, you're not prepared. This of course, is very silly: the less rain you get, the more prepared you should be to catch the rain when it does fall. In some ways, we do OK with this. Our tank is slightly larger than the tank recommended by the quite handy tankulator site, for our tiny roof catchment. When I was researching tank size, I figured it'd be better to have a tank that's never completely full than a tank that ever overflows. So far, we've been lucky in that our tank is big enough to catch all the heavy rain that falls, so we can take advantage of it in dry spells.

The little duck dam (OK, OK... It's kind of more of a pond..) on the other hand, is way way way too small for the catchment it has. The duck dam receives water off the road, which is caught by our driveway and an under-the-road-culvert and delivered into the swale that runs through the orchard, which in turn runs into the dam. This is great, and it means we catch a lot of water when it rains even a little bit. But the dam isn't big enough to hold it all. After rain like we've had today, I suspect it's maybe only a third as big as it needs to be to take advantage of rainfall like this, let alone anything more substantial.
poor little overflowing duck dam (with rivulets of road-water and happy snail-foraging ducks) as seen from the loft
Part of the reason for this kind of significant and stupid oversight was the fact that the main purpose for the dam was to get the earth for our floor, and so that's what I was mostly thinking about when it was dug. I (foolishly) wasn't concentrating properly on the road, the culvert, the swale, and the amount of water all these things would deliver into our poor little dam. Not that I have a one track mind or anything...

I can't even tell you how frustrating it is to see a dam overflowing water that I know we'll desperately need in 2, 4 or 6 months time. Not to mention kind of stressful when the rain is rushing into the dam at such a rate that the spillway can't cope and water starts flowing over the dam wall. The obvious answer is, of course, to extend the dam, but that's easier said than done, mostly because it will involve a fair chunk of money and getting an excavator out to do it. But it will be done, sooner rather than later, especially given that people are saying it'll be a wet Spring... Though people also said that about Winter and it didn't really happen.

So I hope you, dear reader will learn from our mistake: carefully consider your catchment  before you build a dam or pond even  if you're simultaneously thinking about something exciting like an earth floor. Especially if there's a road involved. Those buggers catch a hell of a lot of water.

1 comment:

  1. YEs! How beautiful has this rain been?? I'm in absolute bliss when it's raining heavily outside. I go into a trance of wonderful ... until the sun comes out. Then I'm back to whinging!!