Ponds four years on

May 12th, 2016. Post by Quinta do Vale

It’s been quite a saga, this business of creating unlined ponds. I particularly wanted unlined ponds, because their principal purpose is to provide hydration for their surroundings in the course of slowing the passage of water through the quinta. But as I’ve learned, it takes a while for them to stabilise. There are six of them; two sets of two on the top and bottom terraces above and below the yurt terrace, and another pair of very small duck ponds on the bottom terrace. Small ponds – which these all are due to limitations of terrace width and slope – are much more sensitive to small perturbations.

Spillway between the ponds on the bottom terrace

Spillway between the ponds on the bottom terrace

Bottom terrace ponds

Small perturbations, in the case of the two ponds on the bottom terrace, turned out to be quite cute with fur and tails and stuff.

Vole and brown rat

Small perturbations – voles and brown rats

These ponds were dug in 2011 and are now well settled, but not before I had to resort to edging some of the banks with metre-deep lengths of corrugated metal sheeting and burying tangled balls of chicken wire in the soil around the spillway. It’s not that the rodents aren’t helpful – they’re very good at assisting in the process of hydrating the soil in the area surrounding the ponds and, along with the frogs, give the dog endless amusement. It’s just their ideas about where water should go don’t always match mine. Out through terrace walls is a definite no, as is filling the earth dam between the ponds with little perforations. Training them hasn’t been easy. A bit like herding cats.

Upper pond on the bottom terrace

Upper pond on the bottom terrace

Lower pond on the bottom terrace

Lower pond on the bottom terrace

At this stage now though, these ponds require only minimal maintenance. The plantings of marginal and aquatic plants are all well established and the two little 40cm alder saplings (Alnus glutinosa) I transplanted from the wild two years ago (before they could be removed by riparian brush cutting) are now small trees and growing vigorously. The swales which are filled by these ponds and the duck ponds in the poultry enclosure dug last year have had some small perturbation deterrent work and general maintenance and improvement as well.

Alder trees on the bottom terrace

The alder saplings in mid April 2015

Alder trees on the bottom terrace

The alder trees in early May 2016

Top terrace ponds

Small perturbations in the case of the larger two ponds on the top terrace weren’t quite so small and cute. These ponds were first dug in the spring of 2012. In the process, we uncovered the underground water channels linking the collecting tank on this terrace (behind the flat-topped rise behind the ponds in the image below) to the next one down. Having uncovered them, the challenge became covering them up again and stopping the water from finding its way back into them.

2012 was a drought year though. We built in the channel in the upper pond, but had to patiently wait for 2013’s spring rains to test it. The upper pond filled, but it was evident water was still finding its way into the channels. More work was done that summer and in 2014, for the first time, I got the upper pond full and water filling the lower pond.

Top terrace ponds filling

Top terrace ponds almost full in spring 2014

The water in the lower pond was finding its way into another branch of the channel system however, and the water never got higher than this, tantalisingly close to the pipe spillway back into the main channel. So near and yet so far.

Then later that year, my neighbours uphill decided to clean out the decades-worth of sludge in their water tanks on our mutual stream. Had they thought beyond their immediate objective – ie. what was going to happen to all that sludge they were sending down the stream bed – and phoned me, I could have diverted it down the storm drain path of the stream where it would have gone to the river. It would have taken no more than 10 minutes to do. But they didn’t. And I didn’t discover it until my main water supply tank containing our drinking water was thoroughly polluted and the collecting tank and upper pond on the top terrace were both knee-deep in sludge. The remaining two collecting tanks on the next two terraces also got their fair share.

All work on the ponds had to be put on hold until the sludge could be dug out. That didn’t happen last year as there were too many more pressing jobs needing done. Then the plan to start work this spring had to be postponed as starting work would increase the water flow to the blocked channel on the yurt terrace below. Nothing doing until the channel was cleared.

So at last we were able to get to it, largely thanks to volunteer Paul who took on the job with enthusiasm and had the collecting tank clean within a couple of days of dedicated shovelling and the water running to the ponds again.

Top terrace ponds

Top terrace collecting tank after cleaning

The lower pond had, by this time, just become a hollow in the terrace full of vegetation. We cut this and left it in situ, covering it with sludge from the upper pond so it would decompose anaerobically and gley the pond. After several applications of sludge in key areas over the channels, the pond finally filled to the spill pipe.

Top terrace ponds

Upper pond after cleaning, sealing and filling

Top terrace ponds

Water starts to fill lower pond

Top terrace ponds

Upper pond after settling out and some planting of marginal aquatic plants

Top terrace ponds

Lower pond finally full

Top terrace ponds

Lower pond with spill pipe in operation

Top terrace ponds

The ponds from the track above

After a week, the amount of water being absorbed by the surrounding soil has reduced considerably and what goes down the pipe is pretty much what’s coming into the pond. As the vegetation decomposes beneath the sludge, it should improve the seal further.

It’s so exciting to see these ponds finally full and working as they should be. Summer will bring its challenges with a reduction in the stream’s flow, but with luck they should hold water well enough by then to maintain their level. We shall see …

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2 Responses to “Ponds four years on”

  1. Mehmet Tok Says:

    Hi, don’t you have any problem with mosquitos since you have very hot summer?

  2. Quinta do Vale Says:

    They’re not too bad most years and I’ve never noticed any kind of concentration of them around the ponds. Perhaps it’s because the ponds have continual running water through them? Mosquitos need the water to be perfectly still.

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