Terrain was generated with the ANT Landscapes add-on. Generated 4 different ones and moved them to their spots in the scene.
Trees were created with the sapling add-on and the leaves were textures from Textures.com
Material for the landscape was from cc0texures.com
The ‘water’ is just a regular plane with low roughness and a bit of metallic to get that reflectivity.
The clouds were an image texture from kaiserbold.
For the lighting I used Nishita Sky lighting.
Here’s it all together in blender: