Souhegan​, Merrimack Rivers: Generally Normal​ As Season Winds Down

MERRIMACK, NH — The final Souhegan Watershed Association (SWA) water quality monitoring testing for this season took place on a clear, sunny day for a welcome change by the monitors, according to a press statement. This summer it seems most of the test dates were on or just after rainstorms. While the rainstorms provide the most beneficial data, the clear weather was appreciated by the volunteers. Several appreciated not having to negotiate slippery rocks and muddy trails.

The Merrimack River returned to excellently low E. coli counts with one exception. A water sample taken near the Taylors Falls Bridge in Nashua had a count of 866.4, almost 10 times greater than what would be allowed for public swimming beaches. The rest of the river between Manchester and Tyngsborough tested well below the 88 threshold for a public beach. The prior two tests taken this summer had unusually high counts - probably attributed to runoff from work being done at the Amoskeag Dam in Manchester.

Typically the Merrimack River has low E. coli counts, like what was seen on most of the sites tested this week.

Work on the Pawtuckett Dam in Lowell, which backs up water as far as Merrimack, has been completed and the river level is slowly returning to normal levels. Eventually the planned replacement of the plywood "boards" with a modern inflatable bladder like the one recently built at the Jackson Falls Dam near Margarita’s in Nashua will correct the long overdue problem of raising and lowering the river and messing up summer recreation, the habitat, and erosion.

SWA tests the entire length of the Souhegan River from Ashburnham, MA, to the mouth of the river in Merrimack. This river flashes up and down like a small river is expected to do. Typically the upstream section from Ashburnham downstream as far as Wilton has very acceptable E. coli counts. And that’s what the tests found this week. The test at Water Loom Pond in New Ipswich was only 5.2, excellent. Further downstream at The Horseshoe in Wilton, a popular swimming hole, the count was 24.6, still excellent.

As the river runs into population centers in Wilton and Milford, counts typically go up, usually to unacceptable levels. The levels were not as high as usual this week, but they were once again unacceptable. The E. coli level at the Swing Bridge in Milford was 290.9, well into the unacceptable range.

Typically the counts remain high as the river slows down and becomes more shallow and sandy through Amherst. Another spot where kids hang out at the Boston Post Road Canoeport near Souhegan High School in Amherst was a bit better than usual but still a barely acceptable 121.1.

The river cleaned up in the more rural parts of Merrimack, but the count at the popular swimming spot at Watson Park in Merrimack was 129.6, slightly higher than acceptable and is posted with a red flag to indicate that swimmers there are exposing themselves to ear and eye infections and gastrointestinal problems. This site will be tested for the last time this season on Aug.& 31.

Besides the usual reports of ducks, herons, and animal tracks, monitors reported lots of colorful flowers and especially Cardinal Flowers all along the Souhegan shoreline. An osprey was even spotted flying over the river near downtown Milford.

This summer both rivers returned to a more normal life. Last year at this time we were in a drought condition that severely impacted the Souhegan that required a couple of interventions to prevent loss of habitat. The Souhegan now has requirements to protect the river flow during severe conditions. This year no watering restrictions have been needed.

This is the final test for this season. Thirty volunteers collect samples from their specific site along and transport the samples to one of the wastewater treatment plants in the area where certified technicians prepare and read the results. E. coli samples require an incubation period of 24 hours before the results are available. The labs at the wastewater treatment facilities in Manchester, Nashua, Merrimack, Milford, and Greenville all are critical partners in this program.

Volunteers are always welcome to replace retiring volunteers; they can contact George May at georgemay@comcast.net for more information. Some of our present volunteers have been with the program since its inception more than 20 years ago. The plan is to continue monitoring beginning again next June.

Here are the results for E. coli tests this week:

E-COLI MONITORING RESULTS FOR TESTS TAKEN ON AUGUST 22, 2017

SOUHEGAN RIVER SITES:

1. Billy Ward Pond, Ashburnham #1 NA; #2 NA
2. SoR 333 Water Loom Pond, New Ipswich 5.2
3. SoR 320 Highbridge, New Ipswich 61.3
4. SoR 309 Above Greenville Mill Pond, Greenville 172.2
5. SoR 296 Downtown Greenville upstream of WWTP 157.6
6. SoR 291 Green Bridge off Rte 31 below Greenville WWTP 96.0
7. SoR 218 Below the Horseshoe, Wilton 24.6
8. SoR 210 Downtown Wilton NA
9. SoR 201 Pine Valley Mill, West Milford 90.6
10. SoR 170 Behind Hayward Field, West Milford 224.7
11. SoR 155 Souhegan Valley Boys and Girls Club, Milford NA
12. SoR 146 Swing Bridge, Milford 290.9
13. SoR 133 Riverside Cemetery, Milford 248.1
14. SoR 130 Behind Lorden Plaza, Milford 106.7
15. SoR 122 Amherst Country Club 201.4
16. SoR 116 Amherst Conservation land Fairway Road, Amherst NA
17. SoR 095 Boston Post Road Canoeport, Amherst 121.1
18. SoR 057 Indian Ledges, Merrimack 55.6
19. SoR 034 Turkey Hill Bridge, Merrimack 96.0
20. SoR 001 Watson Park, Merrimack 129.6

MERRIMACK RIVER SITES:

1. Mer 600 Above Amoskeag Dam, Manchester NA
2. Mer 590 Arms Park, Manchester NA
3. Mer 580 Upstream of Piscataquog River, Manchester NA
4. Mer 570 Goffs Falls, Litchfield 66.3
5. Mer 560 Depot Street, Merrimack 65.7
6. Mer 550 Upstream of Souhegan River, Merrimack 24.1
7. Mer 540 Thorntons Ferry, Merrimack NA
8. Mer 530 Greeley Park, Nashua 83.6
9. Mer 520 Taylors Falls Bridge, Nashua 866.4
10. Mer 510 Sagamore Bridge, Hudson 35.9
11. Mer 500 Pheasant Lane Mall, Hudson NA
12. Mer 490 Upstream of Tyngsboro Bridge 30.9

Flow on Upper Souhegan was 18 CFS. Expected flow for that date is 25
Flow on Lower Souhegan was 46 CFS. Historic flow for that date is 41
Flow on Merrimack was 2350 CFS. Historic flow for that date is 1429
RAINFALL: Clear, warm, no rain
Temperature: Souhegan 21c; Merrimack 22c

Submitted by George May.