So I have an email out to the water quality lab for the city of austin, but this is the silica data that was available online (in mg/l). The two values represent the silica at each of the two water treatment plants that serve different parts of the city (the first represents south austin, the second represents everything north of the river)
3Q2011 - 8.1/7.1
4Q2011 - 9.1/9.4
1Q2012 - 6.8/6.8
2Q2012 - 9.9/9.4
So it looks like there is an increase during the winter months. The question for me is how effective my RODI unit is at removing silica, and if I have passed some kind of threshold where the excess is feeding diatom growth. I also have some GHA going on, which tells me i have NO3/PO4 excess, so it's probably a combination. We just need richardL to send in a dummy sample of tap water to AWT so we can see .