WIth only 1Gb of RAM I"ve decided to put this on hold until I get a better computer because it takes to long to do anything and sometimes it crashes and I have to get an older version from dropbox because the file is impossible to open.
What do you think?
I can't attach it (I don't know why), so here's the dropbox link.
https://www.dropbox.com/s/ywqgefk23skij ... 6.svg?dl=0

Warning - I have evidence this file is over 200 mb, in case anyone else wants to try and open it. I tried (with 4 gb RAM) and had to shut down my computer to stop the download, which was draining 100% of my memory, and brought my system to a stop!

(Note that closing Inkscape did not stop the download. And closing Firefox did not stop it either. And neither did breaking my internet connection! What the heck??)

If you only have 1 gb ram, I don't know how you manage to open it, much less do anything to it. I'd say, give it up.

You probably can't attach it because it's too big!

In fact it's a 89.7 mb file

Vacuum defs, there are about 198000 unused ones.

After that, the 89,7 MB will shrink to about 20 MB at least, based on your accuracy settings.

Still it looks much for that "relatively simple" file.
Raster image inside is not that big, but could shrink the file size by not not embedding it.

The hydro pole layer containing cad based graphics has alot of "rubbish" going on.
Circles by 257 nodes, Random lettering and random kerned texts.
Arrows could also use markers instead.

Also cloning could be used on many repeating elements.
Maybe use simpler symbols for the trees and other plants?
Colour coding for example.

Thank you. File>'Vaccume Defs' did the trick! I also appreciate the other advice. Thanks again.