Mailing Address:
P.O. Box 8068
Cumberland, RI 02864

Friends of the Blackstone River Environmental Center
100 New River Road
Lincoln, RI 02838

Preserve Elder Ballou Cemetery

Causes of Blackstone River water level fluctuations

The Blackstone river water levels naturally fluctuate based on the amount of rain that falls in a period of time. The more rain that falls in a shorter period will lead to larger fluctuations. Periods without rainfall will lead to decreases in the water levels on the river. These are natural, but there are also river management factors that lead to the fluctuations which include both water releases at key dams along the river, and outflows due to water usage by mill plants along the river.

Flow Management
An example of how man-made forces can affect the water levels on the river comes from August 11 – 14 2007. Many river stewards noticed very low levels in the river. While the rainfall accounted for natural lower levels, there were other factors at play. Looking at the USGS gauges at Northbridge and Uxbridge in Massachusetts and the Woonsocket gauge in Rhode Island these fluctutations were quite noticable. During this timeframe, the Riverdale Mills hydro facility, which usually backwaters the Northbridge gauge, held back flow in the morning on Saturday, August 11, then released it later, then started storing water again all of Sunday the 12th releasing on Monday the 13th. At each downstream gauge, the fluctuations would cascade with approximately a day’s delay before it would be noticed. For instance, looking at the Uxbridge data for the same time frame, you see that the Northbridge peaks are Uxbridge valleys and vice versa. If you look at the Woonsocket data, you see the mirror image of the Northbridge graph, but one day later.

Another example is during a period when the Blackstone gorge was running dry. Experts spoke with the Ridgewood Power facility, which runs the hydro plant there. Normally they keep a minimal flow going over their dam, but discovered that there was no flow due to a faulty transducer, which records water height on the pond was broken. They took immediate steps to fix the problem and the flow was again restored.

Man-made Outflows
there are other areas that use water directly from the river. These are considered outflows and can have a direct impact on water levels especially during dry periods. For instance, Ocean State in Burrillville, rhode Island uses 4 million gallons per day or 8-12 c.f.s.. IPA in Blackstone, formerly ANP has been trucking water from the Whitinsville Water Co. on the Mumford River to provide cooling for their plant on the Mill River. All of these possible sources, the lack of rain, more impervious surfaces reducing groundwater supply all might have significant impacts on the flow in the Blackstone River.

Special thanks to Peter Coffin and Jim Plasse for their monitoring and explanations.

If you wish to view the real-time river gauges, please check out the links below:

Leave a Reply