July 27th, 2011

     I went to my site on the Wapsipinicon to do my water testing and wow! The water was really high again! Last week it was down to shallows on my side of the river with the main channel by the far bank. This week the river was bank full. My phosphate reading was quite high (a 1 this week up from a .2 last week). I also set up a lab bacteria test and an IOWATER bacteria test. The lab bacteria test had a reading of 21,000 E.Coli ber 100 ml of water. By comparison, last week I had a reading of 10 E.Coli per 100 ml. The IOWATER bacteria test is not ready to read for another 24 hours and already has numerous colonies growing where last week I had one colony. I did not dilute the water as much since I had such a low reading last week and I wanted to get a more accurate reading this time. But with the reising river, the E. Coli readings also typically rise, so I guess I should have known I needed to dilute it more. (It's harder to count bacteria colonies when there are too many of them- they start to blend together.)
     Higher phospahte could mean more runoff from ferilized lawns and croplands or more human and animal waste. Since the chloride level did not increase, and chloride is evidence of human and animal waste in the water, I believe the runoff from fertilized lawns and crops caused the increase in phosphate. The higher levels of  E. Coli must be from stirred up sediment, not human and animal waste since the chloride level did not increase. (E. Coli gets trapped in sediment.) The river was really brown and turbid (not clear), so there was a high level of sediment in it.
     In the classroom, my students prefer one right answer. I like the ambiguity in a multiple data situation. I like to figure out what my particular set of data indicates. I like having to weed out what the reason probably is not, until only one possibility is left. I feel more confident that my conclusion is the correct one this way. I hope my students can learn to enjoy a question with many possible solutions and enjoy the hunt for the correct solution by eliminating possibilities as they continue to collect data.