Development causes profound changes to streamflow patterns in a river—increasing water levels during rainstorms and flooding events, and reducing water levels during the dry summer months. While streamflow problems are less intuitive than water pollution issues, they are just as important, if the river is to be a recreational amenity, drinking water source, and valued wildlife habitat.
Our Water Conservation Program is designed to help address the summer low-flow problem. Almost 160,000 people get some or all of their drinking water from underground aquifers connected to the river. However, because of the way we handle wastewater, very little water ever is returned. The result is a 60-80% reduction in August streamflow in much of the watershed, according to research by the US Geological Survey.
By partnering with towns and water districts to help encourage residents to take advantage of opportunities to use water more efficiently, we reduce the impact on the river while also lowering water bills and saving energy for years to come.
The second prong in our streamflow strategy is to address polluted runoff. Without a doubt, polluted runoff is our most serious water quality problem, but it also is a key part of our streamflow problem.
When we turn a forest or a meadow into a parking lot, three things happen: 1) We prevent rain from soaking into the ground to recharge the aquifers that feed the river and our drinking water supplies; 2) We increase the amount of water that runs to the river by reducing both recharge and evapotranspiration; and 3) We accelerate the speed at which that runoff reaches the river.
Whereas forested land sends zero gallons of surface runoff to the river during an average year (all the rain soaks into the ground or is evapotranspired by plants), an acre of unmanaged pavement sends about one million gallons of surface runoff to the river. That runoff arrives at the river within minutes of rainfall, causing water levels to rise much higher than normal for a few hours and then drop suddenly below natural levels—scouring out stream-bottom habitats with a flood of hot, dirty water, and sometimes damaging nearby property.
For the river, the difference between forest and parking lot is not unlike the difference between the slow, steady energy our bodies get from a healthy, whole-grain snack versus the spike and crash in our blood sugar from a candy bar.
Our polluted runoff program aims to reduce this spike and crash streamflow pattern by working with communities to ensure that development projects intercept the rush of water, clean it, and allow it to soak into the ground. We also work with communities to retrofit runoff controls on town-owned pavement.
We are excited to work with the six communities on both parts of the streamflow problem, and we hope to see more watershed towns take a comprehensive approach in the coming months.
Although general policies tend to be set at the state or federal level, implementation occurs at the local level, and so strong leadership in our cities and towns is critical.
Questions? Contact Executive Director Ian Cooke at 781-575-0354 or cooke@neponset.org.