The rivers do work in Wilbur, honest. It's where the code that FT uses came from! The precipiton erosion can, amusingly enough, leave a disconnected flow system. Filling basins after precipiton erosion will reconnect the flow system, allowing rivers to run their full length.

If you have saved the river overlay channel in FT, use the Image Overlays dialog to save the overlay. Otherwise, you'll need to make a black color scheme and save the image from FT's Save As menu item. A black color scheme can be achieved in many ways, including setting the altitude color ranges to black or setting the image climate shader to a pair of black images.

FT's climate information is computed as a straight lookup into the temperature vs. rainfall table ( http://www.ridgenet.net/~jslayton/climateinfo.gif ). The impact of latitude is purely on temperature (which has some impact on rainfall as well). FT will happily place jungles at the poles if that's what you request by modifying temperature and rainfall to where jungle happens on the chart. The climate chart shows that for rainfalls less than 12.5cm/yr and temperature above -7.5C, all climates are desert; for all temperatures below -7.5C, you get tundra. If you want something other than desert, trying increasing the rainfall. Note that FT has no notion of "hot desert" or "cold desert": there is merely desert.