This article was originally published in the Narragansett Bay Watershed Counts 2016 Report
Many residents of Rhode Island and Massachusetts are familiar with the Blackstone, Taunton, and Pawtuxet rivers, and other rivers that flow into Narragansett Bay. But these sizable rivers begin as numerous small, nameless “headwater” streams many miles from the bay, bubbling up from groundwater or trickling out of wetlands, bogs, ponds, and lakes. Even the Mighty Mississippi begins with a barely noticeable stream. The connection of headwaters to the recognizable larger rivers and the estuary they empty into is an important chapter in the story of the Narragansett Bay watershed, both for the environment and people.
What are headwaters?
Headwaters are often tiny streams that mark the origin of a watershed and are many miles inland from the ocean or bay into which rivers empty. Headwater streams are often called “first-order streams.” When two first-order streams meet, they form a second-order stream; then two second-order streams meet and form a third-order stream, and so on. Fourth-order and higher streams typically constitute a river. Headwater streams make up over 80 percent of the total length of earth’s waterways, and Narragansett Bay’s headwater streams are in keeping with this pattern.
What are the headwaters of the Narragansett Bay watershed?
The Blackstone River and the Taunton River contribute over 70 percent of the freshwater that flows into Narragansett Bay. The headwaters of the Blackstone River originate in and around Worcester, Massachusetts. Because they are situated in an urban environment, many of these waterways are now buried underground as part of the city’s stormwater management system. Other headwater streams in the watershed originate in well-protected parks and natural areas. The Taunton River’s headwaters originate in the wetlands and bogs of Southeast Massachusetts. This flat, wet, swampy environment contrasts with the Blackstone River’s origin in steep, rocky, forested terrain. In Rhode Island, the Pawtuxet and Pawcatuck Rivers start as headwater streams in the central and western parts of the state before flowing into Narragansett Bay and Little Narragansett Bay. These streams, similar to many of the Blackstone River’s headwaters in Massachusetts, are often in forests.
What makes headwater stream ecosystems unique?
Because many of the tiny streams that make up the bay’s headwaters are in dense forests, they are covered by a canopy of leaves and branches that shade and cool the water during hot summer months. In the fall, these same trees create a drift of red and yellow leaves into the stream, which provides food for a variety of invertebrates, salamanders, and fish.
Headwater streams are also often fast-moving compared to the rivers into which they flow. These streams tend to be in hilly areas at a higher elevation than the higher-order rivers downstream. Many headwater areas are close to the drainage divide—the point at which water begins to move downhill, separating two watersheds. The elevation drop from the drainage divide creates fast-moving water and step pools, resulting in high levels of dissolved oxygen that are ideal for cold-water fish such as trout. The largest U.S. drainage divide is the Continental Divide in the Rocky Mountains, which separates water flowing to the Pacific Ocean from water flowing to the Mississippi River and into the Gulf of Mexico. Drainage divides occur between large watersheds as well as between smaller ones such as the Narragansett Bay watershed and the Buzzards Bay watershed.
Why are headwaters important?
Individual headwater streams are small, but they collectively make up over 80 percent of the stream length in most watersheds. They also tend to be sensitive environments that can be susceptible to land-use impacts, such as development and agriculture. Development along a headwater stream results in runoff from parking lots and other impervious surfaces entering directly into the waterbody, while agriculture along a waterway can increase the amount of fertilizer and nutrients that enters the stream. When rainwater and runoff are allowed to soak into natural areas, the soil and plant root systems provide two major benefits: 1) many contaminants such as excess nitrogen, phosphorous, and sediments are filtered out, and 2) the water flow slows down before it enters the stream. Without natural areas to filter water before it enters these headwater streams and other waterways, the waters are inundated with pollution and unnaturally high flows, destroying these unique headwaters habitats.
In addition, first-order headwater streams also contribute more than half of the volume of water to major rivers. Consequently, whatever is in the first-order stream flows to the major rivers and then into Narragansett Bay and the ocean. So, if a headwater stream is contaminated with oil from a neighboring urban area or has a high level of nitrogen from manure (referred to as nutrients) used on an adjacent farm, then not only is the headwater stream impacted, but the problem flows downstream to other communities as well.
“Rivers are a reflection of whatever happens upstream,” said Dr. Arthur Gold, a watershed hydrology expert at the University of Rhode Island. “Whatever’s going on in the headwater streams—the extent of flooding that occurs, pollutants that they’re carrying, the temperature of those particular streams—that gets transmitted, merges with these other headwater streams, and begins to influence downstream sites.”
Headwater wetlands and bogs can also serve as nutrient sinks, absorbing nitrogen and other nutrients that would otherwise flow downstream into the bay and cause problems at high levels, such as algae blooms and low oxygen zones in the bay’s estuaries that can cause fish kills and negatively impact other marine life. Headwater ponds and lakes can serve as ideal habitat and spawning grounds for migratory species such as river herring and American eels. These fish spend part of their lives in the ocean before entering Narragansett Bay and then swimming upriver to the headwaters. These fish rely on a healthy habitat be it the ocean, the bay, or the headwaters and they require an unobstructed path that connects all three.
Humans also benefit from healthy headwater streams. These streams collect and channel rainwater to downstream ponds, lakes, reservoirs, and rivers, which often supply drinking water and are used for recreational activities such as swimming, fishing, and boating. Clean headwaters make it easier to keep downstream waters clean with attention to appropriate human use, preventing beach closures and warnings for consumption of harvested fish and seafood.
Does this mean that we should not use the land around headwaters?
The best-case scenario for streams, rivers, and Narragansett Bay would be for areas around headwaters to be free from any type of human activity. However, this is far from realistic. Many cities were built along rivers so fast-flowing waters could power mills during the Industrial Revolution. Now, being near waterways allows ships to easily transport cargo and people. Towns are often located close to headwaters so water can be drawn from natural aquifers and people can enjoy swimming and fishing as well as beautiful views. Crops are grown near streams to intercept the water that is flowing through the soil and make irrigation easier.
Along with the environmental roles described above, these community uses are also important roles of headwaters and rivers. Communities, states, and the federal government need to carefully consider the impact of development activities and take intentional, well-planned steps to protect headwaters and rivers so that we can use and enjoy headwaters without destroying their role in a healthy ecosystem.
How can we protect headwaters?
One of the best ways to protect watersheds is to preserve or re-establish riparian buffers—the vegetated land along the banks of streams and rivers. In addition to providing habitat for aquatic and land animals, the plants and microscopic organisms in the soil of the riparian zones filter rainfall and runoff before they enter the stream by using and storing nutrients and other contaminants.
Reducing impervious surfaces in neighboring cities and towns and leaving some land undeveloped allows rainwater and runoff to filter into the soil before flowing into the streams and rivers. The creation of greenways and rain gardens in these areas can help divert rainwater into the ground for natural filtering instead of funneling it directly into streams and rivers through storm drains. The organic matter that makes its way into the stream bed from trees and other plants in riparian zones also serves as an important food source for aquatic animals.
Upgrading wastewater treatment plants to reduce the volume of effluent discharged into headwater streams helps maintain the natural flow and temperature of the water, and helps keep nutrient and bacteria levels low. This benefits both headwater streams and areas downstream.
Limiting fertilizer use on farms, golf courses, and lawns also reduces runoff of excess nutrients to nearby waterways. Testing soils to see if your lawn needs fertilizer is important—and required in Massachusetts for phosphorus—before application, and closely following directions can help to reduce nutrient levels while still promoting optimal plant growth and health.
Limiting water use, especially during dry periods, can also help preserve headwater streams. Overuse of drinking water supplies, in particular excessive residential lawn irrigation, can dry up the natural wells and aquifers that feed headwater streams. One simple way to retain water for dry days is by installing a rain barrel or cistern. This allows homeowners to collect water during the wet season and save it for another time when streams need the most help, turning runoff into a resource. Even small things like turning off the water while you brush your teeth matters.
Significant populations live in and rely on the Narragansett Bay watershed for food, recreation, and tourism. The watershed stretches from the south shore of Rhode Island on the edge of the vast Atlantic Ocean to the narrow headwater streams in central Massachusetts. It is critical for communities and watershed residents to recognize that tiny streams are connected to larger rivers and Narragansett Bay. These headwaters are part of the same watershed and deserve the same respect and care as larger bodies of water.
How is climate change affecting headwaters?
Climate change impacts in the Narragansett Bay watershed include changing precipitation patterns and increasing air temperatures. In the last half century, New England has seen a 71% increase in very heavy precipitation events, which leads to higher water flows and flooding of headwater streams, increasing nutrient transfer to downstream waters and the bay, as well as erosion of stream and river banks.
Although it may seem counterintuitive, changing precipitation patterns are also expected to make droughts longer and more intense. This could dry up tiny headwater streams and vernal pools (temporary springtime pools), resulting in loss of habitat, decreased water flow to downstream rivers, and decreased drinking water supplies.
Increasing air temperatures also warms the water in the streams and rivers, which can impact the plants and animals that live there. Plants and animals may not be as healthy in warmer waters; they may not grow as big or may not successfully reproduce. If water temperatures get too high, they may not survive at all.
Communities can help mitigate the impacts of climate change on streams by making well-informed decisions about water use and land development.