Neponset Hits New Lows

As the drought of 2016 continues, the Neponset River Watershed marks new record low flows for July and August.

By Ian Cooke, Executive Director — The extraordinary drought of 2016 has continued to take a heavy toll on the Neponset River, its tributaries, ponds and wetlands. Recent site visits and water testing by NepRWA staff and volunteers have highlighted the impacts on wildlife habitat, water quality, and recreation.

Last week I spent time visiting spots along the river in Walpole and Norwood, looking for potential habitat restoration project opportunities. It was hardly a comprehensive survey of drought impacts, but some of the highlights included:

  • A large snapping turtle trapped in an isolated pool of opaque green water in the Neponset River in South Walpole.
  • A huge area of Mill/Mine Brook in Walpole, at least half a mile long, where the streambed and a wide floodplain wetland system were completely dry.
  • Numerous shrunken ponds heavily impacted by algae as excess fertilizers in the water stagnate in the hot sun. In at least one case we spotted what may have been a toxic cyanobacteria bloom.

A Board Member who paddled the Neponset mainstem from Norwood to Dorchester this weekend reported that much of the river was impassible, turning a recreational paddling trip into a paddle/wade/drag trip.

The good news though, was that even as much of the river has shriveled, Traphole Brook, which is home to a native trout population and is un-impacted by water withdrawals, continued to flow surprisingly well.

Photos of the Drought This Summer

Click thumbnails to enlarge and see photo descriptions.

My colleague Tom Palmer spent a little time exploring the lower watershed and has posted those photos in a separate blog.

River Marks 75-Year Record Lows in July and August

How bad is the drought? We have the benefit of five continuous streamflow gauges operated by the US Geological Survey in the watershed that can help us answer that question (see our streamflow page for more on each gauge and a real time data feed from USGS).

The “Norwood” stream gauge measures flow coming from 34 square miles on the upper Neponset in Foxborough, Medfield, Dover, Walpole, Norwood and Sharon. To the east, the “Canton” stream guage measures the flow from the East Branch of the Neponset including about 27 square miles in Sharon, Stoughton and Canton.

The Norwood gauge has been flowing at about a paltry two cubic feet per second for most of the summer, while the Canton gauge has been hovering around three cubic feet per second, which is somewhat better especially in light of the smaller watershed, but still very anemic.

To place that in historical context, the Norwood gauge which has been in continuous operation for 76 years, registered the lowest average flows ever recorded for the month of July with a flow of 3.99 cubic feet per second AND the lowest average ever recorded for August as well at 2.93 cubic feet per second. The previous monthly low flow records were 5.44 cubic feet per second in July of 1997 and 4.3 cubic feet per second for August set in 1981. It is notable that not only were these new records for both months, 2016 has blown the previous records out of the water being some 26% and 31% lower than the previous lows.

One interesting observation is that while both gauges have been low, they have been extremely consistent and the daily flows have not yet sunk to the lowest daily levels ever recorded, much to my surprise.

More Than Lack of Rain Involved

While the extreme drought we currently face is driven by lack of rainfall, it is also exacerbated by man-made water withdrawals. During the years 2000-2004, these withdrawals totaled about 11 million gallons per day for the watershed which equals about 17 cubic feet per second. All but about two million gallons per day is permanently lost to evaporation, when used for lawn irrigation or discharged to sewer systems that lead somewhere outside the Neponset Watershed.

The Greenlodge Street USGS streamflow guage, located on the Canton/Dedham border near Route 128 and University Station, reflects the cumulative impact of most of these withdrawals. This gauge measures streamflow coming from an area of 84 square miles including the area measured by the Canton gauge, plus the Norwood gauge, plus an additional 22 square miles. The Greenlodge gauge has spent much of the summer at around four cubic feet per second, and has often be flowing at less than the total of the two upstream gauges, when under natural conditions we would expect it to have a significantly higher flow because of the larger watershed area.

Four cubic feet per second in the river, but 17 cubic feet per second coming out for water supply on average in August. More troubling still is the fact that water withdrawals in the Neponset Watershed have been increasing since those withdrawal figures were compiled in 2000-2004. Several communities have been upgrading their local groundwater wells to increase the amount they can pull from under the watershed, and some industrial and golf course users have also been increasing their draw as well.

Short Term Actions

In the short term, the options for blunting the impact of the drought on the River are limited, and primarily involve reducing “non-essential” water use. Lawn irrigation in particular causes water withdrawals to spike during the summer. At this point most of our communities have imposed complete outdoor water bans. We urge everyone to cooperate with local watering restrictions and encourage our communities to do more to raise awareness of the restrictions, as our volunteers have reported widespread violations of the restrictions in many communities.

We would also urge those who irrigate with private well water to voluntarily stop lawn watering. While most private wells are exempt from restrictions that apply to public water supplies, they nonetheless draw on the same shared groundwater resource and continue to contribute to impacts to the river.

Lastly, we hope that the Baker Administration’s Drought Task Force will raise the state drought level at their meeting this week and take more aggressive steps to ensure that lawn watering is scaled back in a more uniform way across hard hit areas. The Drought Task Force has been very slow to react to the drought as it has developed since last fall, and needs to be more proactive going forward.

Stronger Steps Needed in the Long Term

While our options are limited in the short term, there is much more that can and should be done at the municipal, state and even household level in the long term. These long term steps are particularly important because climate change is expected to make summer droughts much more frequent over the next several decades.

Take steps to conserve.

The most cost effective way to prepare for drought and climate change, is to increase efficiency and conservation, since doing so saves money. There is still significant potential for further savings through conservation and efficiency, but achieving those savings requires a steady, long term commitment by communities to invest in reducing leakage in their systems, and to fund outreach and incentive programs to help their customers become more efficient. This is an area that NepRWA has been working on for some time, and there is wide variation among the efforts in different communities.

Improve drought response.

The state and our municipalities need to take a more proactive stance in responding to drought conditions. The State Drought Task Force routinely waits until rivers have reached crisis levels for several months before taking action, at which point it is often too late to effectively protect ecosystems.

Utilize Water Sources with Lower Environmental Impact.

The Quabbin Reservoir is an extraordinary resource for the Commonwealth, providing the long-term water storage capacity that communities who use local groundwater sources lack. All of the communities in the Neponset Watershed have or could readily acquire supplemental water from the MWRA for use during the dry summer months. This would allow communities to reduce pumping of local wells that impact flows in the Neponset, but most communities have been moving in the opposite direction, trying to reduce their use of MWRA water in an effort to save money. Strategic use of MWRA water on a seasonal basis could substantially curb impacts on the Neponset at a surprisingly modest cost.

Regulate Private Irrigation Wells.

Private wells draw on the same public groundwater resources as their larger municipally-owned cousins, but are generally exempt from regulation by the state or local communities. This creates and unfair two-tiered system, where private well irrigators continue to draw heavily on local supplies with impunity, often engaging in the most wasteful irrigation techniques, while those on the public supply system are subject to restrictions needed to protect the environment.

The legislature should take a leadership role in addressing this unfair system by requiring those using private wells to comply with all outdoor watering rules and restrictions that apply to those using public supplies. Failing action by the legislature municipalities can and should do the same through local bylaws.

Rethink Wastewater.

One of the biggest sources of low streamflow impacts in the Neponset Watershed is that any water which gets into a sewer in our area, gets transported out of the watershed for treatment and discharge. Treating wastewater locally and recharging it to the watershed, would dramatically reduce the impacts of our water withdrawals. This summer’s streamflow data backs up this idea, with the East Branch stream gauge flowing almost twice as strong as the Norwood gauge for most of the summer when you adjust for the relative watershed size. The difference? One of the three towns upstream of the East Branch stream gauge (Sharon) recycles 100% of its wastewater back into the watershed through septic systems.

While septic systems have their challenges, they are effective recyclers, and newer technologies for decentralized “package” treatment plants could safely recycle our groundwater even in areas that are already sewered.

Leave a Reply

Your email address will not be published. Required fields are marked *