Excellent Oxygen Levels Shows Signs of Good River Health

The final testing date for this season saw generally acceptable E. coli levels and excellent dissolved oxygen levels in both the Souhegan and Merrimack Rivers. 

Dissolved oxygen levels are an important general indicator of river health. The higher the levels the better for fish and all of the other river organisms. This summer has seen good dissolved oxygen (DO) levels almost all season. The frequent heavy rains splashed lots of oxygen into the water and increased whitewater flows over rocks in the rivers. Both of these rivers have rocky rapids in the upper reaches. This week the Souhegan saw DO levels around 9, which is excellent. The Merrimack was in the 8 range, also excellent. Both rivers seemed to indicate good health all summer long – and this is the period when DO levels drop to their lowest levels. 

The water testing program also measures the E. coli levels in both rivers – the Merrimack between Manchester and Tyngsborough and the Souhegan throughout its entire length. E. coli levels indicate the levels of pollution in the rivers and indicates the quality of water for human contact. Counts less than 88 are the gold standard for public swimming beaches. Counts higher than this may cause eye and ear infections or gastrointestinal problems for humans bathing in the water. Generally counts higher than 126 should be avoided and over 400 is dangerous. E. coli levels often rise after heavy rains.

This week the monitors found very acceptable levels of E. coli in the Merrimack. This has generally been true all summer long. The Merrimack is fairly clear of E. coli except after heavy rains. The Merrimack E. coli counts were mostly in the teens between the Amoskeag Dam in Manchester and the Tyngsborough Bridge. The highest level found was at the Thorntons Ferry access in Merrimack where the level was only 32. This is a site that has seen some abuse on a regular basis. Trash, shotgun shells, and an oily slick were reported here. The Greeley Park boat ramp was 25.

The Souhegan E. coli levels followed the usual pattern of being clean from Ashburnham to Wilton; having unacceptable levels as the river slows down and meanders through Milford and Amherst; and cleaning up again through the rural parts of Merrimack and out to the mouth of the river. The highest reading on the river was seen in Downtown Wilton where the level was 365. Downstream of the Oval in Milford the level was 249. Downstream of the center of Greenville the level was 72. 

All of the usual swimming holes on the Souhegan were at an acceptable level except for the Amherst Canoeport at Boston Post Road. Here the level was 179. Watson Park in Merrimack was very clean at 22. 

All of the results, as well as results for the entire summer, can be seen on a map on the Nashuatelegraph.com.

This season also saw the expansion of the program to include the placing of two electronic water monitors in each of the rivers that will continue to provide data as long as they are in the rivers. The program also continued monitoring three brooks in New Ipswich that flow into the Souhegan. And additional testing was done twice a week at Greeley Park in Nashua  and Watson Park in Merrimack. Signs were also posted here to notify swimmers of the bacteria levels and safety of the river water.

This all volunteer program is sponsored by the Souhegan Watershed Association and the Lower Merrimack Local Advisory Committee. It has been collecting data for 17 years and plans are being made to continue beginning in June next year. There is always a need for volunteers to monitor one site. More information can be gotten by contactingswawatertesting@gmail.com.

All of the biological and chemical tests are done in certified labs in the Manchester, Nashua,Merrimack, and Milford wastewater treatment facilities.

Here are the results for all of the sites tested:

E-COLI MONITORING RESULTS FOR TESTS TAKEN ON SEPTEMBER 10, 2013

SOUHEGAN RIVER SITES:

1. Billy Ward Pond, Ashburnham  #1 -1, #2 - NA
2. SoR  333  Water Loom Pond, New Ipswich  3
3. SoR  320  Highbridge, New Ipswich  48.8
4. SoR  309  Above Greenville Mill Pond, Greenville  91.0
5. SoR  296  Downtown Greenville upstream of WWTP 71.7
6. SoR  291  Green Bridge off Rte 31 below Greenville WWTP   131.4
7. SoR  218  Below the Horseshoe, Wilton   58.6
8. SoR  210  Downtown Wilton  365.4
9. SoR  201  Pine Valley Mill, West Milford   95.9
10. SoR  170  Behind Hayward Field, West Milford   NA
11. SoR  155  Souhegan Valley Boys and Girls Club, Milford   129.6
12. SoR  146  Swing Bridge, Milford  248.9
13. SoR  133  Riverside Cemetery, Milford  161.6 (172.2 DUP)  
14. SoR  130  Behind Lorden Plaza, Milford  148.3
15. SoR  122  Amherst Country Club  209.8
16. SoR  116  Amherst Conservation land Fairway Road, Amherst   149.7
17. SoR  095  Boston Post Road Canoeport, Amherst  178.5
18. Sor   070   Seaverns Bridge, Merrimack  261.3
19. SoR  057  Indian Ledges, Merrimack  59.1
20. SoR  034  Turkey Hill Bridge, Merrimack  31.5   
21. SoR  001   Watson Park, DW Hwy, Merrimack  22.1

MERRIMACK RIVER SITES:

1.      Mer  600  Above Amoskeag Dam, Manchester  8.6

2.      Mer  590  Arms Park, Manchester  14.2

3.      Mer  570  Goffs Falls, Litchfield  15.6

4.      Mer  560  Depot Street, Merrimack   NA

5.      Mer  550  Upstream of Souhegan River, Merrimack   NA

6.      Mer  540  Thorntons Ferry, Merrimack  32.3

7.      Mer  530  Greeley Park, Nashua  24.6

8.      Mer  520  Taylors Falls Bridge, Nashua   31.3

9.      Mer  510  Sagamore Bridge, Hudson  20.1

10.  Mer  500  Pheasant Lane Mall, Hudson   NA

11.  Mer  490  Upstream of Tyngsboro Bridge  17.3

Flow on Upper Souhegan was 18 CFS and expected flow for that date is 21

Flow on Lower Souhegan was 45 CFS and historic flow for that date is 39

Flow on Merrimack was 2570 CFS and historic flow for that date is 1390

RAINFALL -  No rain for three days

Temperatures: Souhegan 16C;  Merrimack 18C