Well Howdy fishneb
I like your layout plan. It shows prommise.
I do have a couple of concerns I will share with you though.
Have you worked out the grade yet? Grade = hight in inches for 100 inches of track length. So a 2% grade would raise the track 2" over 100" of track length. What is yours? Should be 2.5% to 3% to look realistic. Lots of guys go as high as 5%, but those logging nuts are dare devils. Hard core rail heads go for the real thing, 1%.
The track that comes around the outside to the left and then loops around up yhe center of the layout, in my opinion, should run around the top curve to the right directly instead of jogging into the yard through that switch. I think that will be a weak spot if you want the train to run continuously, as you may find the train derails there when it is at speed. I think the service track should come off the siding directly.
I think your turnouts are up side down. If they were the other way then you could drive the train right into or right out of the siding.
Go and check out this web page
http://www.housatonicrr.com/yard_des.html
there you will find alot of good information about planning a yard.
If you like the idea of using real water, then I wouldn't try and discurage you. Yes, it is difficult, but I feel with a good setup and carefull planning you could do it. First off, all sceanery comming in contact with water would have to be water-proof. This would be best done if you were to use fiber glass, and I don't mean the type of fiber glass that uses rezin and mat, but rather a unique stuff that is made for body work. I do not mean ordinary bondo type of fiber glass filler. I refer to the short strand fiberglass. It is much stronger than bondo type filler and is made to patch rust holes in cars. You can get it at auto suply outfits like Part Source.
It has a working time of ten to twenty minutes depending on how much hardener you mix in. Mix it on a piece of scrap tin or an old piece of glass with a 3" plaster trowle. It spreads like Cheeze Whiz and you can get quite a few different textures. Latex gloves keep your hands clean. Paint with enamils. Drop sand in the wet paint for a sandy bottom.
If you want to add a second layer to add texture or re-enforce a part, then the surface has to be sanded off to get the next layer to bond properly. Here is a tip. I use a wire brush wheel in my drill to knock off the shiney surface.
Now because your layout is on wheels and you don't want it to dump the water when moved, then here is what I would do.
I would put a resivore under the table and run the pump from there. Then I would build the pond like a bathroom sink, with a drain at the bottom of the sink and an over flow hole near the top of the sink. The drain at the bottom would have 2 or 3 little holes, not big enough to just let the water flow out, but will still drain the pond when the flow from the pump is turned off. The over flow hole on the side would be big enough to handle all the flow from the pump and would establish the level of the pond. The pond would drain back into the resevore.
By building your pond in this way it would only hold water while the pump was running and would soon drain when the pump was turned off. This way, once the pond drained, you could move the table with no fear of spilling the pond.
Another idea is to use those stainless steel bowles to build the basic pond. You could get 2 bowles that nested and drill holes in the inner one to establish the drain and the over flow and put a master drain in the outer bowle to keep it water tight. Then once mounted you could add sceanery around the pond and the stream with the short strand fiberglass.
I hope this gives you food for thought
