The method of creating lakes and streams in TRS19 has not changed since the earliest versions of Trainz. Make a depression in the terrain, use the water tool to fill the area with a "floating" water "texture", then raise or lower the water height to the required level. All of this is in the Topology Tool.
"Moving water", such as in a fast flowing stream or a waterfall, is an animated scenery object. Water surface effects, such as ripples, etc, is set in the Environment Tools as stated in the post above.