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Rain brings E. coli levels up once again

The Souhegan Watershed Association conducts volunteer water quality tests on the Souhegan and Merrimack Rivers every two weeks during the summer. The luck of the draw means that many of the tests this summer have come during or after heavy rainstorms. That happened again for this week’s testing. Almost an inch of rain fell on Friday and Saturday, Aug. 4 and 5, before the test on Tuesday, Aug. 8. The bacteria that were swept into the rivers by the rain then were still alive when tests were conducted on Aug. 8 and that means that E. coli levels were often in an unhealthy level on both rivers.

The Merrimack River between Manchester and Tyngsborough typically tests at a very acceptable E. coli level. Not so at the tests two weeks ago, and again, not so last week. Only three of the sites tested at acceptable levels; four were unacceptable for public swimming. There isn’t evidence of much swimming on this stretch of the Merrimack, but the most popular spot where people do gather tested at almost 550 colonies of bacteria – and anything over 406 is dangerous to humans. Downstream, the stretch through Nashua tested below the 88 level that indicates an acceptable level.

Some of the high readings may be attributed to work being done on the Amoskeag Dam in Manchester and the resulting disturbance may be a contributing factor.

The Souhegan River is a much smaller river and so sees the effects of the rains more quickly and more severely. The upper headwaters of the Souhegan in Ashburnham, Mass., and New Ipswich were at acceptable E. coli bacteria levels. From Greenville to Milford the levels were unacceptable, but less than the dangerous 406 level. Through Milford and Amherst levels exceeded 406 by a factor of two. One site tested over 1,000.

Once the river reached the more rural areas of Merrimack, the E. coli levels were reduced but never reached an acceptable level. At Watson Park in Merrimack, just before the river empties into the Merrimack, the level was 90.8, slightly higher than the acceptable 88 level. SWA posts a flag at Watson Park to show the water quality; this week the flag is yellow, indicating a level that may be OK, but not completely acceptable for small children or those with impaired immune systems. Swimmers ear and eye and gastrointestinal trouble may result for some people.

Besides E. coli testing, SWA monitors the dissolved oxygen levels in both rivers. This test is the best test for the general health of the river itself, for the fish, insects, habitat. This test showed both rivers to be in good health. And this has been true all summer.

It was also noted that the rivers are flowing exactly as much as they should be at this time of year. Last year rivers were in danger of losing their ability to sustain their habitat because of the very low flows. That’s all turned around.

Volunteers mentioned seeing the usual great blue herons, beavers and assorted wildlife along the rivers. They also noted that the cardinal flowers were in full bloom. Fewer people, hikers and fishermen, however, were out in the early morning along the rivers this week.

The next test will be done on Aug. 22 and will be the final test this year. We hope to continue testing beginning in June next year and are always looking for volunteers willing to adopt a site. More information is available at www.souheganriver.org.

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