Streamflow and water-quality measurements were made on the Ottawa River and selected tributaries between 1999 to 2002. Ten sets of streamflow measurements were made at an index station on the Auglaize River at Fort Jennings (station 04186500) and at 19 other sites along the Ottawa River and selected tributaries. These data were collected to relate daily mean streamflow at the Auglaize River at Fort Jennings and the instantaneous streamflow at each of the other 19 sites.
Two sets of water-quality samples were collected and 4 or 5 dissolved-oxygen measurements were made at the 19 sites. Water samples were collected during periods of potential stress on the aquatic communities, once during low flow and once during a runoff event that occurred after recent land application of pesticides. The first set of water-quality samples was analyzed for groups of nutrients, major ions and trace elements, and physical properties, whereas the second set was analyzed for nutrients, pesticides, and physical properties.
With regard to nutrients and physical properties, median values of specific conductance, pH, dissolved oxygen, alkalinity, and orthophosphate were higher during low flow than during the runoff event. In contrast, the median concentrations of total phosphorus, ammonia nitrogen, nitrite plus nitrate nitrogen, and ammonia plus organic nitrogen were higher during the runoff event than during low flow. Orthophosphate, total phosphorus, and dissolved-oxygen concentrations all had wider ranges during the low-flow sampling than the runoff-event sampling.
Of the 25 major ions and trace elements analyzed for, 15 were detected in all 18 samples, and 10 were detected infrequently or not detected at all. The runoff samples were analyzed for 48 pesticides, 18 of which were detected in one or more samples and 30 of which were not detected. Of the 18 pesticides detected, 13 were detected in 5 or more samples. Five pesticides acetochlor, atrazine, deethylatrazine, metolachlor, and simazine were detected in all the samples.
