Your "lake" seems to have a lot of corner points, far too many (As Kris said), and that adds toward your waypoint number, which in turn increases lag, depending on how good your machine is, you will have a waypoint cap which will dictate the number of waypoints Zero Hour, and thus your computer can handle. The average number you dont want to exceed is about 1000 if you are creating multiplayer or community maps, because you have to take into account everyone else's computers too. It may seem like a massive number, but it's easy to achieve without even realising it, because after setting all the water points there you will have to outline areas, set AI waypoints, add roads if needed, and you may have more than one body of water too. By the looks of things that river and lake combo casts about 100 waypoints, possibly more, you can reduce that by placing points and corners sparingly to about 25-50.
Your tutorial is easy to follow, aye, but does not well explain how rivers work, or how to stretch or shrink the water texture on rivers. You have stated that people should not use the river tool unless they have mastered the tool but the tutorial says it will explain how to create a river, surely the river tool is key to this? And furthermore, if anyone has mastered the river tool why would they be using this tutorial?
I dont mean to belittle you here, or bash your tutorial, but you must take these things into account next time when you create a tutorial like this.
Other than the things I have pointed out though, good job, you seem to be helping others out, as the poster above me states. We need some more tutorials around here too, the place was getting a little dusty.
Edited by Nidmeister, 25 May 2010 - 10:35.