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Once again Judith demonstrated her teacher mastery.  This activity involves a great deal of preparation, some cost, and a bit of clean-up.  From what I can tell it also would need quite a bit of space for the kids to store their watersheds if the activity is to be continued the next day.  Otherwise, I can't really see the activity being done in one class period.  It would work well for block scheduling or for a 2 period lab.  I would like to able to do this kind of thing, but it is really covering middle school curriculum.  I will admit that the odds are that most of the kids I have would still benefit from the exercise, but I can't see where I can fit it into the chemistry curriculum.  The extension of this -- the testing of stream and ground water -- however, can be successfully introduced into the course.

During the activity it occured to me that there is a way that I can incorporate water testing into the chemistry course without having to take my kids outside to find a creek or stream -- considering that there isn't a stream close enough that I could (w/o administrative problems) take or send the kids to collect samples.

Central High draws kids from all over the city.  So, I can give each student a small bottle for sampling and have them go to a stream, creek, river, or pond close to their home and retrieve a water sample.  They should find the location where they took the sample on Google Maps so that we can formulate a citywide profile.  Then each student would run a series of tests on the sample.  A partner will duplicate the tests and compare results.

Yes, there are some tests that will not be valid b/c they need to be done at the time the sample is taken.  I might be able to arrange for students to run these tests on a second sample once they develop testing skills with the first sample.

This activity can't be done until 2nd semester after the kids have had enough chemistry to understand why and what they are doing and why the tests work.  After Wil's comments I can see that it might be instructive to have the students run the tests again toward the end of the year to see if there are seasonal changes . . . and to research or hypothsize why there might (or might not) be such changes.  Further extensions to this activity keep popping into my mind as I write.  For instance, if we find pollution of a certain type, we could have the kids try to determine the source of the pollutant and possibly how to prevent further pollution.