On Tuesday, May 6, 2014, the White House released a new report, the Third U.S. National Climate Assessment, as part of President Obama’s second-term objective to demand immediate action on climate change, and prepare the nation for rising temperatures and increased cataclysmic storms. According to the report, the impacts of climate change in the Northeast will culminate in “heat waves, more extreme precipitation events, and coastal flooding due to sea level rise and storm surge” (Third U.S. National Climate Assessment, 2014).
Most New Englanders over the age of 20 can tell that climate change is already happening here, even given the region’s notoriously variable weather. Compared to what was “normal” 20 years ago, spring now arrives earlier, we get less snow in winter, and average temperatures, especially at night, are warmer in all seasons. These trends stand out, even when historic variability is accounted for. Scientific models and predictions indicate that we have significantly more change ahead of us, and we will need to adapt to a different climate in the future, even if we do reduce our greenhouse gas (GHG) emissions and try to mitigate climate change impacts.
A changing climate will of course have major implications for Boston as a coastal city. For the Charles River, there are obvious impacts we will need to prepare for. Here are three of the most important:
#1: More flooding
Climate models predict – and recent records show – that our region will continue to experience larger rain storms (more total inches of rain in a given storm), as well as more intense storms (rain falling at a faster rate, measured as inches per hour). These trends will continue as the climate changes, with some models predicting an increase in mean annual rainfall of over 50%. Future storms will cause more localized flooding as drainage systems are overwhelmed, and also increase the risks of larger regional flooding as the Charles River and its tributaries are unable to handle the larger volumes of water flowing through the river system.
What CRWA is doing: CRWA’s Blue Cities Initiative focuses on redesigning urban areas so they are more “water friendly,” and less prone to flooding. By mimicking nature’s hydrology, even in dense urban neighborhoods, we can get more rainfall to soak into the ground, slow down the rate of runoff, and increase the amount of water that is taken up by plants. To prepare for more catastrophic flooding, CRWA is evaluating the potential of restored streams and wetlands in the heart of the city – along the channels of long-buried streams and on land that was once open water or marsh – to help reduce the impacts of floods.
What you can do: Homeowners can build rain gardens to capture runoff in their own backyards, install a dry well to recharge rainwater into the ground, or replace some of your grass lawn with shrubs and trees, which capture far more water than grass.
#2: Warmer water
Warmer average air temperatures, and longer growing seasons, will add up to warmer water temperatures in the Charles. The river gets warmer because of the direct effects of temperature, but also because in warm weather, the amount of water in the river is actually reduced and therefore gets warm even more easily. During the summer months, river flow naturally decreases because groundwater levels drop, reducing the amount of cool water seeping into the river from the ground. During warm weather, increased water demand for irrigation, as well as increased evaporation from plants and even from the river itself, mean there is even less water left in the river. The result is a longer “residence time” for the water, especially behind the many dams in the Charles, which create large pond-like areas all along the river where the water sits and gets warmer and warmer. Summer storms, which sluice water off of black rooftops and pavement, create sudden flushes of hot water directly into the river in many areas.
What CRWA is doing: For over two decades, CRWA has worked to to reduce non-essential water use, especially when the river is stressed in the summer months. Our work to improve water regulation and policy, to strengthen the standards for water withdrawal permits, and to support the Commonwealth’s Sustainable Water Management Initiative are all aimed at protecting the river during its critical low flow periods. Our work to increase urban vegetation, restore buried streams, and decrease runoff from urban areas will all help keep the river cooler. Our porous alley demonstration project with the City of Boston will test the viability of reducing heated runoff by using porous pavement in an ultra-urban setting.
What you can do: Reduce your water demand, especially in the summer, and eliminate or minimize outdoor watering; installing stormwater tree pits that provide shade over your driveway or parking lot and soak up stormwater. If you live along the river, allow trees and shrubs to grow along the bank to provide extra shade.
#3: More pollution
The main cause of water pollution in the Charles River today is stormwater. Rain that falls on urban areas rushes off rooftops, lawns, pavement and dirt, picking up all kinds of pollution along the way, to be collected in drains and curb-and-gutter systems and shunted directly out to the river through storm drains. Heavy rain also causes combined sewers – pipes that carry both sanitary sewage and rain runoff – to overflow into the river, and in some cases even causes direct sewer overflows. In some areas of the Charles, and along many of its tributaries, high flows from storms cause rapid erosion of the stream banks, and this sediment, along with sediments washed off of open construction sites and dirt lots, pours into the river.
More intense rainfall will mean that our already overburdened sewers and drains will overflow even more often, and our stream banks will be carved away more, resulting in increased pathogens levels and sedimentation.
What CRWA is doing: CRWA’s advocacy work focuses extensively on stormwater pollution control. We work for strong regulations, and help support cities and towns working to pay for stormwater management. We also develop pilot projects and demonstrations to test and showcase new approaches. In addition to our Blue Cities work, CRWA is developing Smart Sewering, an approach designed to reduce the impacts of large, centralized infrastructure. Our goal is to capture wastewater before it is wasted and use it as a resource, creating valuable products for resale and reducing the volume of water in sewer pipes. Smart Sewering has the potential to dramatically change urban water infrastructure, reducing sewer overflows and pollution while creating renewable energy.
What you can do: Reduce your own pollution footprint: don’t litter; pick up pet waste; don’t wash your car on pavement; minimize your use of fertilizers and pesticides; pick up and compost leaves in the fall; maintain your car to reduce oil leaks and minimize corrosion; if your town doesn’t sweep your street at least once a week, sweep out the gutter in front of your house and compost (or bag and dispose of) the sweepings. Try to keep rainfall on your property; let your downspouts drain out on vegetation, not a driveway or sidewalk. Plant more trees!
Climate change is already happening, and it will create real threats to the important progress we’ve made restoring the Charles River. CRWA is determined to keep improving the river and the watershed, even in a changing climate.
Learn more about CRWA's Climate Change Adaptation Project.