Good question, and out of curiosity, I googled (I just typed in
does water intake increase blood pressure
And found this article (and a whole bunch of others)
http://www.mc.vanderbilt.edu/reporte...x.html?ID=1022
So the answer is apparently yes. Which really makes sense when you think about it. Think of a garden hose, the more water you send through it, the more pressure.
I also know that drinking extra water does increase your blood volume. It's a fact that I've been able to use to my advantage when I have to have blood drawn.
I used to have a terrible time when having to have a blood draw, because my veins are deep and they "roll." The girls in the lab told me to drink a lot more water the day or two before the blood draw.
This has helped tremendously (just like a garden hose, the veins plump up with the increase in blood volume).