Is this all water loss?

I want to do this weight loss the healthy way, and I'm happy with a 2 pound loss a week.  I just started counting for the first time on 1/2/08 with some exercise and proper amounts of water.  My first weigh-in was in the middle of a mens. cycle, which causes water retention, and I started at 225.  It's only the morning of the 6th day, and I'm already down to 211.5!  The first 3 days I had a deficiency that I quickly learned was too high (over 1000).  I have been educated from this site to keep it between 500-100, and am sticking to this now.  I can already feel my muscles in my legs getting stronger from the moderate walking I've been doing.  My question are:

1)  Is this 13.5 lb. in 5+ days drop normal?

2)  Is all of this weight just water? 

I'm going to say yes, it's water weight.  I can easily gain upwards of 10lbs right before I start, and by the time I'm finished I've usually lost that and then some (if I stay on plan). So I would say no worries. I've really been trying to keep track of my weight before, during and after that time of month.