July 7: Good weather means good rivers
Good weather this past weekend was also good news for local rivers. Both the Merrimack River between Manchester and Tyngsborough and the entire length of the Souhegan River had very low E. coli counts when tested by volunteers with the Souhegan Watershed Association and Lower Merrimack Local Advisory Committee.
The absence of heavy rain from Saturday through Monday allowed the rivers to flush out some of the moderately high bacteria colonies seen at the prior test two weeks ago. Unfortunately the volunteer monitors weren’t so lucky as light showers were getting them soggy during the early morning Tuesday test time.
Monitors on both rivers noted the high flow caused by the incessant heavy rains for the last month. The Souhegan was flowing at 600 cubic feet per second, ten times the expected historical flow for this date. This is a little lower than the flow rate two weeks ago but much higher percentage wise compared to its expected historic flow.
The Merrimack River was flowing at 12,000 cubic feet per second, much higher than two weeks ago. The Merrimack has been flowing at very high levels for this time of year. Last weekend the flow rate was over 20,000 CFS and caused a scheduled canoe trip sponsored by the Local Advisory Committee to move the trip to a safer river. To give a comparison of how much water that is, more water was flowing down the Merrimack every second that the average household uses in a year.
The E. coli count never reached the 88 count level that the program uses as its gold standard on either of the two rivers except for one site in Amherst that is just below the incoming flow from Beaver Brook. That site’s count was 96, still within the standards for safe swimming, boating, and fishing.
This test was a rare treat for this time of year. Very few tests in the last dozen years that SWA has been monitoring the rivers have not had any E. coli counts exceeding the 88 limit. So far the three good tests taken this year may indicate the increasing health of the rivers. The Merrimack especially has shown real improvement over the course of the last dozen years of monitoring.
SWA is still looking for a few volunteers to monitor sites along the Merrimack. Those indicating NA, not available, need monitors. Tests are done every other Tuesday early morning and take about half an hour. Prospects may contact firstname.lastname@example.org or email@example.com for information.
The next tests will be done on July 21.