MyGardenPal Blog

The site for the second dam on the property is on the hill just above the horse arena area.  On the ridge above the horse arena is an access

Dam site for higher dam

road that traverses across the property from the main driveway and connects with the new lower dam wall to make a continuous driveway from the new entry all the way to just above our house where it merges with our existing driveway.

Above this road, just above the horse arena (which I will  call the community garden area henceforth) is where the new dam has been created.  This area was chosen as it will capture the spill from the swales higher up the hill, and can gravity feed water down to the community garden area for irrigation.

This dam has a short swale on either side to feed into the dam, and one of them also acts as the spillway once the dam is full.  Water from the spillway then flows down to the lower dam.

Another dam site view

This dam is a long football shape so it fits nicely across the hill.

Scratching out the new dam

The final product was actually quite bigger than I had imagined.  It is about two meters deep to water line with about 750cm of freeboard (the wall above water height) which is hard to tell from the photos as their is no perspective.  I’d estimate this dam will hold about 70,000+ litres of water when full.  The bottom dam is a little smaller so probably about 60,000 litres in that one.  The point is that this is over 130,000 litres of water that is captured for irrigation (not counting what is captured by the swales) that would have just flowed away taking top soil and nutrients with it.

We have scatter sown a bunch of ground cover plants over the outer wall of the dam (same as we put onto the swale – a full species list of all the plants we used will be the subject of another post).  These will hopefully take root before we have a major storm to stabilise the wall and prevent erosion.  We will be planting lemon grass seedlings along here as well within the next week or two which will slow down water flowing off of the dam wall.

Finished dam

We have not had a rain event since this higher dam went in so it is still empty.  I’ll post photos of it when it is full.

Dam wall above driveway

One further point about these two new dams.  There was a lot of rock to dig through to create them (thank goodness we had a 20 ton excavator!) but more importantly there was plenty of clay so they should be sealed quite well.  As the dam was dug, about ever 30cm of wall height the excavator operator would change the bucket for a big round compression tool and use this to get almost 100% compression.  So these dam walls are very solid made from a mix of rock and clay.  I can’t wait for this one to fill up.

Later today we are transplanting some lilies from our existing dam into the already full new lower dam.  The lilies help to slow down evaporation, attract wild life, and of course also look pretty.