Plasma Effects Off-Screen

I'm using a slow moving plasma effect to create waterfalls, but they only start 'flowing' when they are on-screen. Is there any way to tell the plasma to start doing its thing even when it's off-screen?

As it stands, you have to wait a few seconds before the waterfall is fully flowing as the plasma slowly works it's way down. Speeding it up isn't an option, since making it fast enough to almost instantly be in full flow completely breaks the illusion of flowing water.

Unfortunately Plasma effects don't work well with scrolling layouts. A possible solution might be to have the plasma effect on a static layer (scroll rates set to 0%) and hide the layer when a waterfall isn't on screen.

Then you just have the static waterfall "background" part scrolling, and position the water objects to the position they should be at when the waterfall is on-screen, and show the layer.