Stream Monitoring

All summer I volunteered to monitor water quality on the Rum River in Anoka. The Pleasant Street bridge is my station. I had to buy some equipment to do this job. I needed a bucket, a rope, a long tape measure, a plumb bob, and a thermometer. Once a week I would park my car on the bridge and subjectively measure the river quality. I'd rate the appearance from 1 (clear) to 5 (muddy and green). I'd rate the recreational suitability from 1 (very good) to 5 (would not even swim in it). I would throw the bucket over the bridge and bring up a sample from the middle of the stream. Once I threw it over and did not notice some anglers in a boat. They told me they were tempted to pull back on the rope and I'm glad they didn't because that would have scared me half to death. I pull the bucket up trying not to rub the rope against the bridge. I pour some into a transparency tube. This tube is 60 cm tall. You can see in the graph above that most of the time the Rum River was very transparent. Things started out clear in the beginning of May. By the end of May, the water was cloudier. Things got a little clearer for a while until June 29 when I got my lowest reading ever of 34.4 cm. I remember that day. I even had a big green glob in the tube. By the middle of July the water cleared up and stayed clear the rest of the season. After transparency, I would measure the water temperature which varied from 58 to 80 degrees Fahrenheit. Finally I would measure the depth of the stream. I used the same place on the bridge railing to measure how far down the surface of the water was from the railing. This figure never varied more than a foot. The Anoka dam is just downriver from Pleasant Avenue so that keeps the depth of the river from changing very much. I also measured the rainfall from my home every day. My work is done for the season and I turned my figures in to the MN Pollution Control Agency. In reviewing my data, what I don't understand is why river water is less transparent in May and June. Lakes, from my experience, start out clear, worsen as the temperature increases, are at their worst transparency during the dog days of August and clear up again in the fall. Why aren't rivers the same? This week I'm starting another Master Naturalist course and I'll try to get an answer to that question. In the meantime, I'm taking a break until Project Feederwatch starts in November.