looks like the ideal place to let your dog run and play, but is deadly

If you live in Northern California, the Toxic algae is also found in streams and rivers, and not always marked. This isn’t just a NorCal thing either, while on our road trip we found warning signs in Wisconsin and South Dakota at a couple small public lakes. I just don’t allow Chico in anything but the Ocean if it is clear from health risks, or when we were in Michigan he went in Lake Erie.

http://www.pressdemocrat.com/news/4530224-181/mendocino-county-issues-algae-alert