EnviroTex Lite

Ret, I work exclusively with EnviroTex Lite when it comes to modeling liquid. Here is pics of my one and only tank (that I am too embarrassed to show very much otherwise), just for reference sake on the product's propensity for creeping. 

Product can be seen creeping up artifacts in the river. The concave would be more pronounced in pourings that are smaller in coverage; the "pull" from the capillary action of the product climbing up the surrounding structures would more pronounced. 

One way to deal with the meniscus problem is by undercutting the bank right at the desired waterline, pouring the resin to a depth just below the cut-back bank, allow to harden, then carefully add a final layer of groundwork to cover this interface. Depending on scene type, bushes, grass, tree limbs, etc., can be used to hide the meniscus. This technique can be found on page 82 of Osprey's; Terrain Modelling, by Richard Windrow. Good luck!

The other way listed in the above book involves a hair drier / heat gun and risks setting your diorama on fire...and your house.

We'll just skip that one for now.