WATER RESOURCES

The Vineyard is blessed with an extensive and relatively high quality system of interconnected water resources: aquifers, fresh water resources, coastal ponds and surrounding shallow waters of Vineyard and Nantucket Sounds and the Atlantic Ocean. These resources are vital to the supply of safe drinking water, are a crucial, aesthetic aspect of the Vineyard's tourist industry, and are an economic support to the fishing, shellfishing and recreation industries.

Water resources are an important part of the Commission's planning program and regulatory review. Planning work is based on a systematic approach, emphasizing the intimate interaction between these systems as the basis for their protection. Planning work includes the acquisition of data on water resources and analysis based on the creation of interpretative maps and reports.

THE AQUIFER

An aquifer is an underground reservoir of water, residing in the spaces between grains of sand and gravel. The nature of the aquifer is profoundly influenced by the geology of the area. The Vineyard's main aquifer is found in the glacial outwash deposits that occupy about 60% of the Island, consisting of thick layers of sand and gravel dropped by glacial meltwater streams. The aquifer is replenished or recharged by the excess rainfall that percolates through the soil and seeps into the groundwater.
Of the 46 inches of annual precipitation, recharge is estimated to be 22.2 inches.

SOLE SOURCE AQUIFER

The entire area of Martha's Vineyard was designated a Sole Source Aquifer by the Environmental Protection Agency in 1988, emphasizing not only the importance of our aquifer but its fragility. It is the only source of drinking water for a population of about 75,000 people during the summer peak, and the only source of seepage of fresh water into our coastal great ponds that helps determine their unique nature. The water quality of public drinking water supplies are protected by zoning overlay districts as described in M.V. Source Water Protection Pro (WaterResourceQuality 34K) .

MVC AQUIFER MONITORING PROGRAM

The aquifer is in a state of dynamic equilibrium, swelling and shrinking in response to variations in the amount of precipitation and, to a lesser extent, changes in extraction of water for consumption. The Commission monitors the water table elevation in a network of 14 Well Location Map (WellLocationMap 3.0M) throughout the Vineyard. These wells have been monitored monthly for the past 10 years, and one has been measured since late 1978. The data indicate the seasonal and short-term changes in the volume of the aquifer and, as a result, changes in discharge to our fresh ponds and coastal great ponds. For example, the water table level in the well located in Edgartown in the Correllus State Forest ( Water Table Elevation in Well (WellENW52 63K) ) indicates that the aquifer at this location expands and contracts over the years by about 7 feet, from around 19 or 20 feet to about 12 or 13 feet above sea level.

The data from this monitoring program helped the MVC define the rate and path of the flow of water in the aquifer. The rate is estimated to be 1 to 2 feet per day so that rain falling in the Correllus State Forest takes decades to travel to a coastal pond and then return to the ocean. The flow paths are the basis for approximating the boundaries of the Island's watersheds, the areas above the water table that contribute groundwater to each of our coastal ponds.

POND WATERSHEDS

The 98 fresh and coastal ponds of the Vineyard are fed by seepage from the aquifer, by runoff from the surrounding uplands, and by direct precipitation. The salinity in the coastal ponds is reduced by the fresh water input creating specialized habitat and giving these ponds their unique, estuarine nature. An estuary is an enclosed body of water that has an open connection to the sea and is measurably diluted by fresh water from the surrounding land. The fresh ponds rise and fall in a pattern that is a close parallel to the water table changes indicating that they are fed by groundwater. The slope of the surrounding upland determines the area that contributes surface runoff to a pond. The shape of the water table around a pond determines the direction that water within the aquifer flows and the ultimate area that will contribute groundwater to a pond.

The area that contributes water to a pond is its Watershed Map (WatershedMap 165K) . In the western, hilly areas of the Vineyard, the soil is developed on impervious clay and till. Seepage through this kind of soil is very slow and aquifers may be confined to pockets or beds of sandy material. In these situations, the watershed of a pond like Menemsha Pond, James Pond or Daggett's Pond is defined by the topography that directs the flow of surface runoff to the pond.

The south and the north shores east of Tashmoo have very sandy soil and the watershed is not determined so much by the topography of the surrounding upland but rather by the groundwater flow paths. The Commission has prepared a MVWatersheds [document not yet available online] illustrating the approximate groundwater contribution areas to the coastal ponds.

These watersheds define areas where pollutants entering the ground may eventually affect coastal pond water quality. Nitrogen from wastewater disposal and fertilization of landscapes and farm fields is the primary nutrient of concern. The watershed map is the starting point for determining the impact on water quality of buildout within each pond's watershed.

FRESH WATER PONDS

There are 61 fresh water ponds in the six Vineyard Towns that total about 615 acres in area. The Commission has conducted water quality assessments in Crystal Lake in Oak Bluffs and in Seth's Pond in West Tisbury. These ponds are important components of our water resources but other than the two ponds mentioned they have received little attention.

Both of these ponds revealed water quality problems WaterQualityProblems [document not yet available online] during the summer months. In the case of Crystal Lake, we have a data set that shows this seasonal problem extending back 10 years. In Seth's Pond, the water quality problem was documented by short-term, intensive sampling. These studies were supported by the East Chop Association, the Oak Bluffs and West Tisbury Conservation Commissions and by the University of Washington Marine Chemistry Lab.

The Martha's Vineyard Watershed Team prepared a water inventory (PondSummary 76K) of what we know about our many ponds that emphasizes the need for more information.

Research-Assessment and Monitoring

The MV Commission collected a large amount of water quality information from our coastal ponds during 2003, 2004, 2005, 2006, and 2007. The sampling sites and the data are displayed in the 2003, 2004, 2005, 2006, and the 2007 Water Quality Survey Summary Map, respectively. If needed, view the How to Interact (HowToInteract 45K) file to help you use the map and link to the charts. For detailed information regarding these studies, please review the respective Coastal Pond Water Quality Report &mdash Coastal Pond Water Quality Report 2003 (CoastalPondWaterQualitySurvey 758K) Coastal Pond Water Quality Report 2004 (CoastalPondWaterQualitySurvey2004 638K) Coastal Pond Water Quality Report 2005 (CoastalPondWaterQualitySurvey2005 6.2M) Coastal Pond Water Quality Report- 2006 (CoastalPondWaterQualitySurvey2006 2.3M) or Coastal Pond Water Quality Survery 2007 (CoastalPondWaterQualitySurvey2007 2.8M) . These studies were funded in part by a grant from the Massachusetts Department of Environmental Protection.

WASTEWATER MANAGEMENT

The majority of residents of the Vineyard dispose of their wastewater in on-site septic systems. Only those residents and businesses in downtown Oak Bluffs, Edgartown and Tisbury are served by wastewater collection systems with central sewage treatment. Wastewater contains significant amounts of nitrogen that is very water-soluble and is not broken down in the aquifer. In the form of nitrate, the nitrogen travels with the groundwater to discharge in springs and seeps along the shore and shallow tidal areas in the ponds. In a coastal pond, nitrogen feeds the growth of microscopic plants, slime coating algae and large green algae. When these are stimulated to excess, the capability of the system to support eelgrass, shellfish and finfish is harmed.

In more intensively developed areas where there are many septic systems and private wells, the groundwater may be affected to the point where the drinking water standard for nitrate is exceeded.

Nitrogen in wastewater can be largely removed by denitrifying systems either as an individual component for a single residence or as a treatment unit for a cluster of residences. (See Wastewater and the Environment (WastewaterEnviron 105K) .)

STORMWATER MANAGEMENT

Runoff from streets carries with it all the dirt and debris that is found there. This material includes oil, metals from brake linings and tire wear, dog and bird droppings including bacteria, leaf litter and windblown debris. If not removed, this material adds silt and sediment to our ponds, contributes bacteria that may force shellfish bed closure, adds nutrients that stimulate excess phytoplankton growth and; adds undesirable metals and other chemical compounds to our waters. Most runoff flows into a settling basin before it is discharged to a water body. The town departments of public works have corrected many of the discharges that once flowed into our waters directly.

Together with the towns of Tisbury and Oak Bluffs in 2003 the Commission used our Global Positioning System to map the locations of the many storm drains in the downtown parts of these two Towns.

In previous years, the Commission assisted with grant writing for two successful grants to correct stormwater runoff from three streets into the Lagoon from the Oak Bluffs side. We also assisted with a grant to correct a stormwater discharge from Lagoon Pond Road in Tisbury. The maps prepared under this grant are MapLink7 [document not yet available online] and MapLink8 [document not yet available online] .

PARTNERSHIPS / COLLABORATION

The Commission has a close relationship with a number of agencies.

The MVC collects water table data and provides it to the US Geological Survey where it is posted on their website, and it provides water table data to the Town Water Departments in Tisbury, Oak Bluffs and Edgartown.
Eelgrass studies (see Epiphytes & Wrack Algae (Epiphytes 159K) , Wrack Algae (WrackAlgae 159K) and Sengekontacket Eelgrass,1 (EelgrassBeds 569K) ) and water quality assessments have involved working partnerships with the Shellfish Departments in Oak Bluffs, Tisbury, West Tisbury, Chilmark and Edgartown.
In 2003, our staff assisted the Edgartown Board of Health in assessing the extent and source of a nitrate contamination problem in the Edgartown Meadows area.
The Retired Senior Volunteer Program's Senior Environment Corps (SEC) has worked closely with the Commission to assess the quality of our fresh water ponds. We need more volunteers to re-establish a fresh-pond monitoring program.
The Commission works closely with the Natural Resource Department of the Wampanoag Tribe of Aquinnah in assessing coastal pond quality.
The Commission is a technical advisor to the Friends of Sengekontacket, the Tisbury Waterways, Inc., the Lagoon Pond Association, the Riparian Owners of Tisbury Great Pond, the Edgartown Ponds Advisory Committee and the Squibnocket Pond District Advisory Committee.
Commission staff sits on the Vineyard Golf Club Review Committee that oversees the environmental monitoring program.

WATER RESOURCES—RESOURCES

STAFF CONTACT

William Wilcox, Water Resources Planner, ext. 17, wilcox@mvcommission.org

MVC DOCUMENTS

MVWaterResourceContacts [document not yet available online]
Suggested Observation Well Speci (WellSpecs 77K)
Groundwater Monitoring (GWaterSampleProtocol 72K)
Native plants in Buffer Strips (BufferPlants 106K)
Water Table Data- 2008 Update (WaterTableDataUpdate 1.5M)
Crystal Lake water quality (CrystalLakeWaterQuality 427K)
SETH’S POND: Present Water Quali (SethPondWaterQuality 4.7M)