TRIBUTARIES
OF THE SOUTH SHORE ESTUARY RESERVE |
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| I. What is a tributary? |
A tributary is a stream that flows into a larger stream or other body of water. Surface runoff and groundwater in the South Shore Estuary Reserve drains to over 100 tributaries, which then flow into the estuary’s bays and marshes. The streamside land area is called the riparian zone. This area performs many important functions for maintaining tributary health, such as providing habitat and filtering toxins before they enter the stream. Many undeveloped riparian areas of South Shore tributaries are tidal wetlands. |
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The area of land that drains into a particular body of water, such as a tributary, is a watershed. The tributary map shows the locations of tributaries and watersheds in the Reserve. The rain that falls within the watershed boundaries displayed eventually makes its way to the bays of the South Shore Estuary Reserve, some of it via the rivers and streams shown. Rain replenishes aquifers that store water underground through a process known as groundwater recharge. Many of the tributaries along the South Shore are above-ground expressions of these deposits.
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| II. Why are tributaries important? |
| Habitat: Tributaries provide freshwater which mixes with saltwater from the ocean, creating a biologically productive ecosystem in the estuary. Tributaries and streamside areas are important habitat for a variety of estuarine species, including ducks and muskrats. Anadromous fishes, such as alewives and trout, spawn in freshwater tributaries and live as adults in saltwater. These fish are an important food source for other estuarine species. |
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Recreation: Tributaries provide many opportunities for recreation, including fishing, kayaking and canoeing, swimming, birding, and observing nature. Tributaries act as natural connectors for boaters to maritime centers and the bay. |
Drainage: Tributaries function to naturally drain upland surface runoff, and groundwater from underground aquifers. When heavy rains occur, water moves over the land. As water moves, it can pick up pollutants and carry them via storm drains to tributaries, which act as natural drainage channels.
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| III. How do humans impact tributaries? |
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Pollution: Non-point source pollution, or pollution that cannot be attributed to a specific location, is the primary water quality concern in the Reserve. Storm water runoff from roads, septic systems, parking lots and construction activity can carry pollutants into tributaries and the estuary. Pollution from point sources, such as wastewater treatment plants and industrial plants, also compromises tributary health. |
| Invasive Species: Introduction of non-native and invasive species, such as Japanese knotweed and Cabomba, affects habitat quality, natural wetland functions, and prevents growth of native species. Alien wildlife species can also upset the ecological balance of a tributary ecosystem by out competing native species. |
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Barriers: Dams, culverts and other structures can alter the natural flow of water in tributaries. This can lead to impaired habitat by disruptingnatural sediment transport, a necessary process for sustaining marshlands around river mouths that provide nursery habitat, biofiltration, and storm buffers. Water quality is impaired by still water in ponds formed by dams, raising water temperatures and decreasing oxygen levels. Barriers can prevent fish and other wildlife from accessing upstream areas because of low flow depth, high velocity, small openings, high and steep embankments, or “perched” openings above the stream bottom. Similarly, barriers prevent kayakers and canoers from traveling upstream. |
| Shoreline hardening: Bulkheads, rock riprap, and other structures built along the banks of tributaries eliminate habitat and natural stream buffers, which mitigate flooding and protect water quality. |
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Groundwater depletion: Tributaries in the Reserve are fed by groundwater as well as by surface water. Over pumping water from underground aquifers lowers the water table, and can reduce water flow in tributaries. Impervious surfaces, such as roads and parking lots, reduce groundwater recharge.
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| IV. What can you do to help protect and restore tributaries? |
| Prevent Polluted Runoff: It is easy to reduce non-point source pollution by using best management practices. These include cleaning up pet wastes, limiting the use of pesticides and fertilizers, using non-toxic biodegradable household cleaners, properly disposing of toxic materials, and maintaining home septic systems. (See Simple Ways Homeowners can Protect the South Shore Estuary Reserve brochure for more information) |
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Maintain and Restore Vegetation Buffers: Adequate vegetation buffers of native woody plants along tributaries filter toxins from runoff, absorb excess nutrients, provide habitat for many wildlife species, and protect against erosion by trapping sediments. Removal of non-native and invasive species allows growth of natural buffers. Native plants are already adapted to the region’s climate, and require the least amount of care. Backyard buffers can enhance aesthetic quality, provide shade, and attract wildlife such as birds and butterflies. |
| Adopt a Tributary: Learn about the watershed you live in and the tributary closest to you. Organize clean-ups and promote citizen monitoring of a tributary in your area. Share this information with friends and neighbors. |
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Watershed Action Plans: Participate in the development and implementation of watershed action plans for tributaries in your area. For more information about watersheds and watershed action plans, visit the water quality page (coming soon!).
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