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  • Assignment 6 - Melcher

Relating impervious areas in eastern Massachusetts to declines in water quality as indicated by shellfish bed closings and barren eelgrass habitats.


As the urbanized area of eastern Massachusetts has expanded, ever more roadways and parking lots have been installed.  Industrial operations, land use activities, fallout of air pollutants, roadway usage and other activities contribute to the loading of particulates on urban roadways.  These materials are then carried into receiving waters by storm runoff where they constitute a substantial portion of the overall water pollution problems of cities.   Although many pollutants are contained in stormwater, many are difficult or expensive to test for in environmental concentrations.  The presence of excessive nutrients such as phosphorus and nitrogen, for example, is much more easily gauged by its effect on ecosystems.  Over-enriched waters will exhibit excess algae growth, decreasing water clarity and potentially producing dangerous neurotoxins.  The cloudiness of the water blocks light from reaching the eelgrass, eliminating habitat.  Shellfish beds must be closed when harmful algal blooms will make shellfish poisonous to humans.


  • Are watersheds with a high percentage of impervious area less likely to have approved shellfish beds?
  • Are watersheds with a high percentage of impervious area less likely to have intact eelgrass habitats?


This study will focus on the area of coastal Massachusetts between Cape Ann and the Merrimack River.  There are very small basins such Walker Creek, Saginese Creek, and Labor in Vain Creek; small river basins such as the Parker River, Rowley River, Essex River, Walker Creek; and the medium-sized Ipswich River in this area.  Watershed delineation tools that I have not learned yet will be used to draw basins.  Impervious area obtained through remote sensing will be obtained from MassGIS.  It is possible that I will want to investigate habitat impacts by land use as well as simply impervious area.  I could come up with a weighting system that assumes certain land uses that may not have large impervious areas (such as agricultural areas or golf courses), may have impacts on water quality.  I would love to show areas by census block that have a majority wastewater treatment through on-site septic systems, but I was not able to find this information in my Assignment #3.

Overlay tools will be used to highlight near-coastal areas that have potentially been impacted from anthropogenic changes to water quality.  MassGIS maps shellfish suitability areas delineating potential habitat areas for a variety of shellfish:  American Oyster
Bay Scallop, Blue Mussel, European Oyster, Ocean Quahog, Quahog, Razor Clam, Sea Scallop, Soft-shelled Clam, and Surf Clam.   Out of these potential shellfish areas I can highlight areas that have been designated as approved or prohibited by the Division of Marine Fisheries.  The most useful near-coastal area will be estuaries and bays that are served by distinct river basins.

Data Sources

Data Layer

Available from

Scale of source data

Vintage of source data

Designated shellfish growing areas



Sep. 2009

Shellfish suitability areas



Nov. 2008

DEP Eelgrass




Impervious surface


1-meter pixels


Digital Elevation Model (5K)




Land Use 2005


1-acre minimum mapping unit



The limiting factor for very small watersheds may be the DEM, in the very flat coastal plain.  Also, manmade diversions (such as storm sewers) will not be included, so all analysis should be on a somewhat large scale.   As I encountered in Assignment #5, Land Use polygons are sometimes large, but now I know that tools are available to clip them as is necessary.

Works Cited

Bowen, J. L, and I. Valiela. "The ecological effects of urbanization of coastal watersheds: historical increases in nitrogen loads and eutrophication of Waquoit Bay estuaries." Canadian Journal of Fisheries and Aquatic Science , 2001.

Historical changes in land use on coastal watersheds have increased rates of land-derived nitrogen loading to estuaries and altered their biogeochemistry and food webs. We used information on human populations and land uses within the watershed of Waquoit Bay, Cape Cod, Massachusetts, U.S.A., to model how nitrogen loads derived from atmospheric deposition, fertilizer use, and wastewater disposal have changed since the 1930s. Nitrogen loading into Waquoit Bay more than doubled between 1938 and 1990. The predominant source of nitrogen added to the bay changed from atmospheric deposition to wastewater disposal during the 1980s, reflecting the increasing urbanization of Cape Cod. Larger nitrogen loads increased nitrogen concentrations in the water, altering the assemblage of primary producers and resulting in eutrophication of the estuary. Biomass of phytoplankton and macroalgae increased, and areal cover of eelgrass (Zostera marina) decreased, with increasing nitrogen load. An increase in nitrogen load from 15 to 30 kg N.ha(-1).year(-1) virtually eliminated eelgrass meadows. Land-use changes prompted by urban sprawl can therefore be linked to marked changes in water quality and eutrophication of receiving waters.


Impact of Urban Sprawl on Water Quality in Eastern Massachusetts, USA

Jun Tu, Zong-Guo Xia, Keith C. Clarke, Allan Frei

Environ Manage (2007) 40:183–200

A study of water quality, land use, and population variations over the past three decades was conducted in eastern Massachusetts to examine the impact of urban sprawl on water quality using geographic information system and statistical analyses. Since 1970, eastern Massachusetts has experienced pronounced urban sprawl, which has a substantial impact on water quality. High spatial correlations are found between water quality indicators (especially specific conductance, dissolved ions, including Ca, Mg, Na, and Cl, and dissolved solid) and urban sprawl indicators. Urbanized watersheds with high population density, high percentage of developed land use, and low per capita developed land use tended to have high concentrations of water pollutants. The impact of urban sprawl also shows clear spatial difference between suburban areas and central cities: The central cities experienced lower increases over time in specific conductance concentration, compared to suburban and rural areas. The impact of urban sprawl on water quality is attributed to the combined effects of population and land-use change. Per capita developed land use is a very important indicator for studying the impact of urban sprawl and  improving land use and watershed management, because inclusion of this indicator can better explain the temporal and spatial variations of more water quality parameters than using individual land use or/and population density.

Jump Run Creek Shellfish Restoration Project
White, NM.   Journal of Shellfish Research .   v. 19. no. 1.   2000. p. 473 - 476.

The objective of this multi-agency project is to 1) quantify the effects of land use change on shellfish closures and 2) assess techniques that can be used mitigate those impacts. This report is based on preliminary analyses conducted over the last 18 months. The project focuses on the 320-ha watershed in Carteret County, North Carolina, that is the drainage for Jump Run Creek. Bacterial data from 1970 through 1998 indicate increased loading since 1974, which is when closure management began. Recent grab sample data from the tributaries indicate high levels of bacteria during storm events and moderate levels during dry weather. The majority of the lending is coming from the portion of the watershed draining an older, medium density neighborhood (single family houses and a trailer park. A door-to-door survey found two malfunctioning septic systems, more than 100 pets, and the presence of wildlife. Change analysis of land use/land cover shows hydrologic modifications were instituted in the 1970s. Dye studies confirm that water moves through the watershed in hours, indicating that lime for bacterial mortality is insignificant. Future analyses include ground water sampling, automated storm water monitoring, and DNA tracking of fecal sources. Planned mitigation practices will include riparian buffer restoration, stormwater wetland, bio-retention, pent filters, and education. Locations and sizing of practices will be determined through GIS-based hydrologic analysis of the watershed in conjunction with a community-design/educational approach involving neighborhood citizens.


S. R. Carpenter, N. F. Caraco, D. L. Correll, R. W. Howarth, A. N. Sharpley, V. H. Smith (1998) NONPOINT POLLUTION OF SURFACE WATERS WITH PHOSPHORUS AND NITROGEN. Ecological Applications: Vol. 8, No. 3, pp. 559-568.

doi: 10.1890/1051-0761(1998)008[0559:NPOSWW]2.0.CO;2


Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes.

Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by over-enrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems.

If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters.

From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow.