Australia Felix pcorgbgo at
Sat Jul 17 18:59:36 EDT 1999

Hello Frank,

I hope that this greets you well....

The determination of the Keypoint is often subject to a range of
explanations. To me it is quite simple: look at a primary gully and see
where the landshape changes from being more convex than concave, at this
point drive a peg in the ground. Then get your dumpy level (bunyip, a-frame
or whatever else) and mark out a contour of this contours elevation around
towards both adjacent ridges. Stop there. Do the other side. The contour
that you have marked out is the keyline. The next gully will have its own
keypoint, and its own keypoint.

The most economic landshape for dam construction is where the ground is dead
flat in some sort of drainage depression as you get the highest value water
storage capacity for every cubic metre of material pushed or excavated. This
is called the Storage Ratio. On steep gully sites (above a Keypoint for
example) the Storage ratio will be much less as the dam wall in many cases
will be larger than the water storage itself. Even in these cases we will
still construct a dam as they are cheaper storage's of water than say tanks.
We applied this principle a couple of weeks ago. The clients needed an
elevated storage to irrigate 1000 olive trees. Knowing that we needed around
1 Ml (megalitre = 1 million litres) of irrigation p.a. we surveyed a 1.5Ml
dam high on the slope opposite to grove. It was constructed as a contour or
hillside dam. The cost of the dam and diversion drain was about AUD$5K
(3days with a D6). If the dam had been constructed on a gentler slope it
would have only taken 1.5-2.0 days to build @ $140/hr) The cost of 100 000
litre (0.1Ml) tank was around $6.5K. The point is that even though the
storage ratio sucked, it was still the most cost effective storage

Anyway post us a copy of your contour plan (scan and EMAIL)and I'll be able
to help you out as an open book exercise. I've been earthmoving now for
about 16 years, with the last 7 using keyline principles on over 700
properties so I think I may be able to help.


Yours and Growing,

Darren J. Doherty

LOL!  I know what you mean. I
> 'm still a little fuzzy even after I visited the site that's why I asked
> again.
> I tend to believe in the concepts, and would like to implement such
> on my Eco-Farm ...but not clear on how to determine these points and build
> such dams at low cost.
> I'll try those sites again.  Probably been updated . I haven't been there
> a long, long time.  Frank
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