About this river
Merrimack River is an 18.4 mile river near Nashoba Paddler, LLC in Massachusetts. Streamflow is measured at the USGS gauge Merrimack River below Concord River at Lowell, MA (site 01100000). The National Hydrography Dataset places it at stream order 8. Reach geometry comes from the USGS National Hydrography Dataset.
Typical flow by month
1923 to 2026
Merrimack River typically runs highest in April, at a median 17,550 cfs, and lowest in September, at 2,095 cfs. The highest flow on record for any single day is 161,000 cfs, in 1936.
| Month | Typical (cfs) | Usual range (cfs) | Relative level |
|---|---|---|---|
| January | 6,280 | 4,350 to 9,350 | |
| February | 6,230 | 4,370 to 9,320 | |
| March | 10,000 | 6,960 to 15,300 | |
| April | 17,550 | 12,200 to 25,100 | |
| May | 9,080 | 7,010 to 14,200 | |
| June | 4,860 | 3,220 to 8,080 | |
| July | 2,730 | 1,780 to 4,340 | |
| August | 2,140 | 1,440 to 3,590 | |
| September | 2,095 | 1,420 to 3,400 | |
| October | 3,030 | 1,970 to 4,810 | |
| November | 5,300 | 3,315 to 9,045 | |
| December | 6,440 | 4,070 to 10,700 |
Typical is the median of each month’s daily median values, and the usual range runs from the median 25th to the median 75th percentile, across about 103 years of record. Statistics published by the US Geological Survey for Merrimack River below Concord River at Lowell, MA (site 01100000). Conditions on any given day can fall well outside the usual range. Check the current reading before you go.
Boat access nearby
8 mapped launches sit in the mapped area of Merrimack River, all of them public access. Ramp data comes from the USGS national boat-ramp inventory.
- Merrimack River (Southwell)Merrimack RiverPublic
- Flint PondFlint PondPublic
- Mascuppic LakeMascuppic LakePublic
- Musquash Pond Conservation AreaMusquash PondPublic
- Forest LakeForest LakePublic
- Claveau LandingOttarnic PondPublic
- Robinson PondRobinson PondPublic
- WindhamCanobie LakePublic
Embed this gauge on your site
Paste this snippet anywhere, an outfitter page, a club site, a trip report, to show Merrimack River's live streamflow, water level and 7-day trend. It reads the USGS gauge directly, updates itself, and links back here.
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