Approximately what percentage of water absorption takes place in the small intestine vs. the colon (and a followup question)?

High school biology classes always taught me that the colon does the majority of the water absorption, but I read recently that as much as 90% of water absorption occurs in the small intestine. Anyone know what the correct figures are on this?

And if so much water absorption occurs in the small intestine, why do diseases that only affect the colon, such as ulcerative colitis, often have as a symptom very watery diarrhea?