I said I would so.....
I've just posted a 'how I did' rivers on my blog. These rivers are not the best you'll see, not by a long distance, but they are simple and quick to make, robust, utilitarian and easy to store wargame terrain pieces. The post might be useful to beginners and anyone needing lots of half decent, tidy river sections quickly and cheaply.
I've also discovered, by complete happen chance, a trick for dulling down 'over-blue' paint jobs on water which you might find useful sometime.
https://olicanalad.blogspot.co.uk/2018/04/going-with-flow-making-rivers-fast-and.htmlHope you find it worth a look,
James