Evaluation of Factors Influencing Stream Water Quality in the Coastal Region of New Hampshire:
A Third Year of Monitoring and Study Report
US Geological Survey
New Hampshire-Vermont District
in cooperation with the
New Hampshire Office of State Planning
The coastal region of New Hampshire is experiencing significant population growth and development. State and local planners need water-resource information to make informed decisions related to the potential environmental effects of urban sprawl, while also understanding the current water-quality of streams in the coastal region. There is also a need to establish baseline information on the current levels of nutrients, bacteria, and other constituents of concern, and the health of stream biota to determine how increasing population and development impacts the water quality of coastal streams. Specific concerns are: 1) What are the effects of various intensities of urban land-use on stream-water quality? 2) How do selected constituent concentrations vary with hydrologic conditions? 3) What are the current conditions of macroinvertebrate communities and algal biomass and how do these relate to nutrient concentrations and stream site characteristics?
In 2000 a study was implemented by the New Hampshire Office of State Planning (OSP) Coastal Program (NHCP) to assess the impacts of varying amounts of impervious surfaces on water quality in three small basins of the coastal region (Ted Diers and Joanne McLaughlin, oral commun., 2001). This initial study had been followed by a joint USGS/OSP project to assess the effects of urban development on water quality; and follows to a limited degree, the approach taken by the United States Geological Survey (USGS) assessing urbanization effects on water-quality in the Boston metropolitan area; a number of the streams studied were in the New Hampshire coastal region (McMahon and Cuffney, 2000; Robinson, K.W., written commun., 2000). The proposed study would build upon both the NHCP sampling program and the USGS urban land-use gradient study to better define the water quality effects from increasing urbanization.
The cooperative USGS/OSP project has been operating for two years. This document is a revised statement of work, which reflects the completed work in years one and two, and the proposed work for years three and four. Water samples were collected on a monthly basis, between June and November during the first year of monitoring, primarily in the Exeter River basin, in Rockingham County, NH. The impervious surface cover within the selected watersheds during the first year was not at a desirable range. Therefore, five new sites were selected to replace five existing sites to incorporate a more desirable range of impervious surface cover among the sampling sites during year two (Figure 1). Water samples were collected between March and September during the second year of monitoring at ten sites in small coastal watersheds of New Hampshire (table1). The NHCP will benefit from the results of the expanded program by having the scientific data needed to support the management of future growth in the region.
Table 1. Sampling sites in the Coastal Region.
|USGS station number||Site name||Percent Impervious Cover||Years/year sampled||Number of samples to date|
|01073554||Exeter River at Wells Road, near Chester||1.8||2001 and 2002||12|
|01073572||Fordway Brook at Lane Road, near Raymond||2.2||2001 and 2002||12|
|01073562||Towle Brook at Towle Road, near Chester||2.7||2001 and 2002||12|
|01073720||Parting Brook at Route 85, near Newfields||3.4||2001 and 2002||12|
|01073690||Parkman Brook at Route 106, near Stratham||6.3||2001 and 2002||12|
|01073050||Reservoir Brook at Madbury Road, at Durham||15.30||2002||5|
|01073040||College Brook at Mill Pond Road, at Durham||23.4||2002||5|
|010728802||Berry Brook at 6th Street, at Dover||29.9||2002||5|
|01073800||Hodgsons Brook at Cate Road, near Portsmouth||32.0||2002||5|
|01073798||Paul Brook at Woodbury Avenue, near Newington||38.0||2002||5|
Nitrite plus nitrate, total phosphorus, Escherichia coli (E. coli), and field measurements including specific conductance, pH, dissolved oxygen, turbidity, and discharge have been conducted monthly during the sampling season. Results indicate that the larger the percentage of impervious surface within a basin, the larger the potential for negative impacts on water quality. Based on these initial results, there is a need to further define the effects of increasing urban land-use on water quality. From the existing water-quality data at all sites, specific conductance ranged from about 90 to 3000 microsiemens per centimeter (ms/cm) (figure 2). Turbidity, used as a surrogate for suspended particles in the water, ranged from about 1 to 45 Nephelometric Turbidity Units (NTUs) (Figure 2). The ranges of specific conductance, a general measure of the dissolved ionic constituents in water, are much higher at sites with larger percentages of impervious surface. Turbidity generally follows a similar pattern as specific conductance. Higher values for turbidity at sites with larger percentages of impervious surface may relate to increased surface runoff at these sites.
Yields (kilograms per day per square mile (kg/day/sq. mi)) for selected water-quality constituents are shown on Figure 3. Yields account for the stream discharge at the time of sample collection as well as for basin size. Yields normalize the comparison of data among sites with differing stream discharge and basin sizes, thus making them more comparable than using concentrations alone. Nitrite plus nitrate yields ranged from < 0.1 to 8.2 kg/day/sq. mi (figure 3). Total phosphorus yields ranged from < 0.1 to 1.8 kg/day/sq. mi (figure 4). E. coli yields ranged from about 1.0 E8 to 1.0 E14 counts per day per square mile (cts/day/sq. mi.) (figure 3). Ranges of nitrogen yields, as measured by nitrite plus nitrate, is higher at sites with larger percentages of impervious surface. The increased particulate matter, as measured by turbidity, may also influence the slightly higher ranges of total phosphorus yields at sites with larger percentages of impervious surface. E. coli yields generally follow similar patterns as the chemical constituents, whereas the ranges of E. coli are larger at sites with larger percentages of increased impervious surface.
Future data analysis will include correlations of chemical constituents to other watershed variables such as percentages of land use, population density, percent of wetlands, percent of sewer and septic, as well as other variables. Although patterns are observed in the data, seven samples (the amount of samples collected at the end of the current field season) at the five new selected sites is minimal for data analysis techniques. Also, the first two sampling seasons were considered to be less than normal water conditions. A third year of sampling is needed to incorporate a more appropriate amount of data for data analysis techniques as well as trying to incorporate information from more typical water conditions.
The overall objectives of the study are to assess how the water-quality of selected streams in the coastal region of New Hampshire varies as a result of increasing urbanization and to determine if there is a threshold level of urbanization that corresponds to significant degradation of water-quality conditions. Preliminary results indicate that increased concentrations of nutrients and bacteria are observed with increasing urbanization. An additional year of monitoring would be used to further refine and confirm these initial results. Specific tasks will include:
- Design a water-quality sampling program to address water-quality and water-resource management concerns – completed;
- Establish baseline or reference water-quality conditions at both undeveloped/headwater streams and streams in watersheds that are expected to experience significant urban growth in the near future –completed;
- Provide an assessment of water-quality, through both chemical and biological sampling, and the measurement of flow characteristics at selected stream sites over a three year period;
- Attempt to determine the extent of urban land use at which impacts on water quality become significant and document these results.
The proposed study will provide an analysis of water quality as measured by total phosphorus, nitrite plus nitrate, E. coli, and macroinvertebrates at selected stream sites in the coastal region. The USGS personnel from the Water Resources Division in the New Hampshire/Vermont District and OSP personnel would be involved in performing this study. Methods of study can be categorized into three major components.
- Monthly water-quality sampling (total phosphorus, nitrite plus nitrate, E. coli) was conducted from June through November in the field season of 2001. Monthly water-quality sampling was conducted from March through September in the field season of 2002. Samples for pesticides and metals have also been collected in 2002. Sites sampled in 2002 incorporate a more desirable range of percent impervious surface cover than sampling sites in 2001. A third year of sampling would be conducted from March through September in 2003.
- Collect samples for total phosphorus, nitrite plus nitrate, and E. coli at the selected sites approximately 7 times during each year. The equal-width-increment method (Shelton, 1994), the multiple vertical method or a single vertical method has been used for collection of the water samples where appropriate. Results from the water samples will be statistically analyzed, where appropriate, to determine the occurrence and distribution of the chemical data among sites and will be correlated to land-use settings. The data will also be analyzed for ranges, exceedance of water-quality standards (where applicable), and seasonal characteristics. Quality-control samples consist of about 15 percent of the total sample size and will include field replicates and field blanks (if applicable). The quality-control samples will be used to estimate the bias and variability in the environmental data. Dissolved oxygen, specific conductance, temperature, and pH will be determined at the time of sampling. All data will be quality assured and verified.
- Macroinvertebrate community samples have been collected during periods of low-flow during both field seasons. A quantitative approach has been utilized for the collection of the biological data (Cuffney and others, 1993; Porter and others, 1993). A third year of sampling would be conducted during low flow in 2003. The biological data will be related to the water-chemistry and land-use data using richness (total number of taxa and species) and composition (percentage of mayflies, stoneflies and caddisflies and diversity indices) measures to determine the degree that water chemistry and/or land use effects stream biota.
Water samples are analyzed by the New Hampshire Department of Environmental Services in Concord, NH. Macroinvertebrate samples are analyzed by Eco Analysts in Moscow, ID.
- Instantaneous streamflow measurements are made at the time of sample collection at all sites. The streamflow data will be used to calculate instantaneous loads for total phosphorus, nitrite plus nitrate, and E. coli. The assessment of constituent loads will provide a quantitative method for comparison of data among sites and to relate land-use to water quality.
- Publication of results will occur in year four. The project will include preparation and publication of a Water-Resources Investigations Report by USGS and OSP. The report will summarize results from data collection activities during the three year monitoring program.
Relevance and Benefits
As a priority issue of the Survey, the information from this study will contribute to understanding the effects of urban sprawl in coastal regions. Collection and dissemination of the information will: (1) meet the broad USGS goal of furnishing tools and critical results needed by other agencies for management of water quality in coastal regions; and (2) provide valuable information for assessing the impact of urban sprawl on water resources. This information will be helpful in making decisions and taking actions necessary to understand urban sprawl impacts. The study will also provide information towards developing a longer-term monitoring program to assess the changes in water-quality over time. Study results can be used to determine effects of land use on water quality and provide water managers with the needed information to protect and manage the State's water resources. The information provided by this study will assist the OSP in assessing the water resources in the area and provide tools for evaluating urban sprawl in the coastal region.
Reports and Products
The study will result in a published USGS Water-Resources Investigations Report co-authored by the Office of State Planning. The report will provide sampling results on concentrations and loads of total phosphorus, nitrite plus nitrate and E. coli as well as semi-quantitative measures on the macroinvertebrate community. The report will provide relations between these parameters and water-chemistry and basin characteristics/urban intensity. The water chemistry and biological data will be related to various basin characteristics to identify thresholds of urbanization that affect water quality. The report will also identify environmental indicators (population density; percent impervious cover; etc.) that may be appropriate to assess effects of urban growth. Quarterly reviews of the study's progress will be provided to the OSP.
Cuffney, T.F., Gurtz, M.E., and Meador, M.R., 1993, Methods for collecting benthic invertebrate samples as part of the National Water-Quality Assessment Program: US Geological Survey Open-File Report 93-406, 66 p.
McMahon, G., and Cuffney, T.F., 2000, Quantifying urban intensity in drainage basins for assessing stream ecological conditions: Journal of the American Water Resources Association, v. 36, n.6, p. 1247-1261.
Porter, S.D., Cuffney, T.F., Gurtz, M.E., and Meador, M.R., Methods for collecting algal samples as part of the National Water-Quality Assessment Program: US Geological Survey Open File Report 93-409, 39 p.
Shelton, L.R., 1994, Field guide for collecting and processing stream-water samples for the National Water-Quality Assessment program: US Geological Survey Open-File Report 94-455, 42 p.