OK John, let me pace you through it.  I have been over this only about 3,000
times so you need to bear with me.

I assure you that the effluence from the moat is accounted for.

It flows from the outlet of the moat at the east and flows via a trench
(downhill naturally) past Bush Barrow and on down hill to Stonehenge (oops,
Rockhenge) Bottom eventually flowing into the Avon at the Village of Lake
about 6 miles down stream from West Amesbury.

Now let's see if we can find the text and maybe a picture.

You may like to print these steps so you will have them to follow.

Step #1 First go here:

Step #2  Scroll down to where you see this heading:

The surrounding moat of Stonehenge comprises three distinct parts:

You're doing well.

Step# 3

Now drop down a little till you see (underlined) northwest reservoir

Step #4

Left click on northwest reservoir

Now you should see some numbered text, but no picture.


To see a picture, you need to click on some of those black vertical lines at
the top of the screen.

Are you getting the picture?

If so, take a look at the area at the top of the picture and try to find a
dark line marked 5 -6-7.

That dark line is a trench that carries the effluence away from the moat of
ROCKHENGE and as a result the entire monument is not flooded.

See how easy it is?  

At 11:16 AM 10/23/2015 +0100, you wrote:
>This is all good and fine having a spring supplying the moat, but the
>level of the moat needs regulating otherwise the continual supply of
>water would flood the entire site.
>Perhaps what would be needed is some form of drainage channel, running
>downhill from the site to a safe outflow such as a river, lets say.
>The channel would need some form of containment, perhaps a dug channel
>or just manmade levees either side.
>So we need to consider looking for a structure that fulfills these
>requirements, leading away from the site. A fluvial channel, like a
>stream, with the characteristic erosional features along its bed that
>we would expect from similar natural features.
>One wonders of anyone has identified any structures that might satisfy
>this notion?