LRHO Completed Projects

• Surface Water Quality vs. Landscape Characteristics
• Instream Nutrient Dynamics in Five First Order Streams
• Suburbanization, Water Quality and Property Values

Surface Water Quality vs. Landscape Characteristics

We examined the relationships between dissolved inorganic nitrogen (DIN), orthophosphate (PO₄-P), dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) flux and landscape characteristics known to control inorganic N export (human population density, urban land use and agriculture) and organic C export (soil C:N ratios, soil C (or N) storage and wetland cover) among 12 sub-basins of a suburbanizing basin, the Lamprey River basin (479 km²) in southeastern New Hampshire. Total nitrogen flux from the Lamprey was dominated by DON (1.27 kg ha^-1 yr^-1), with nitrate and ammonium flux of 0.50 and 0.13 kg ha^-1 yr^-1, respectively. Human population density was the strongest predictor of nitrate flux (r²=0.77, p<0.001) among the landscape characteristics that we measured, and together with riparian agriculture, explained 88% (p<0.001) of the variance. Orthophosphate-P flux from the Lamprey was 0.05 kg ha^-1 yr^-1 and was not related to any of the landscape characteristics that we measured. Dissolved organic nitrogen flux was not related to factors that control inorganic nitrogen and was closely tied to dissolved organic carbon (DOC) flux (r²=0.83, p<0.001). Basin wetland cover was the strongest predictor of both DON (r²=0.74, p<0.001) and DOC (r²=0.81, p<0.001) flux. In addition to basin wetland cover, soil nitrogen storage provided additional explanatory power in DON flux and together these variables explained 85% (p<0.001) of the variance. Despite the similarities between annual DON and DOC flux, DON and DOC concentrations behaved quite differently. DON concentration was negatively related to discharge (r²=0.41; p<0.001), but DOC concentration was not related at all. This implies that although the sources of DON and DOC are similar, their transport along hydrologic flow paths is somewhat different.

Daley, M.L. Export of Dissolved Organic Carbon, Dissolved Organic Nitrogen and Nitrate from the Lamprey River Watershed, New Hampshire: Examining Relationships with Watershed Characteristics. Thesis, University of New Hampshire, Durham, NH. May 2002.

Daley, M.L., McDowell, W.H. and Aitkenhead-Peterson, J.A. Landscape controls on nitrogen, phosphorus and carbon flux in a suburbanizing basin. Resubmitting to Biogeochemistry.

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Instream Nutrient Dynamics in Five First Order Streams

Excess nutrient loading associated with increased human population density is an increasing problem for suburban watersheds. Previous research has focused on either basin scale nutrient dynamics or small scale additions to understand instream processes. The impact of human population density on first order streams has largely been overlooked. In this study, 5 first order tributaries of the Lamprey River that have varying watershed population densities were sampled along a longitudinal profile. Each stream was divided into 6-12 sampling stations depending on length and flow conditions. Samples were analyzed for NO₃-N, NH₄-N, dissolved organic nitrogen (DON), total dissolved nitrogen (TDN) and dissolved organic carbon (DOC). The stream with the highest population density, which was completely dependent on onsite sewage disposal (L1) had the highest concentration of NO₃-N, which increased significantly (p<0.05; r=0.5-.96) from the headwaters to the mouth. As NO₃-N increased, NH₄-N decreased downstream with concentrations an order of magnitude smaller at the end of the longitudinal profile. Groundwater investigations were coupled with stream sampling for stream with the highest watershed septic system density and combined with a dilution gauging experiment. The results indicate that the increased N was entering the stream through groundwater as NO₃ and not being retained or transformed. Concentrations of DOC in the stream were relatively constant throughout each of the tributaries. High concentrations of NO₃-N in the developed sub-catchments are not seen in the main stem of the Lamprey, indicating that the mechanisms for retention and processing are scale dependant.

Blumberg, J.E. Instream Nutrient Dynamics in Five First Order Tributaries in the Lamprey River Watershed, New Hampshire. Thesis, University of New Hampshire, Durham, NH. December 2002.

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Suburbanization, Water Quality and Property Values

Population density has been shown to predict water quality, specifically NO₃-N flux (kg ha^-1 yr^-1), both in New Hampshire and globally. Property value may also be related to water quality. We examined whether average property values per hectare can be used to predict water quality or if property value can explain the residual variation seen when population density is used to predict NO₃-N flux. Thirty streams were sampled over a one year period, 14 in the Lamprey River watershed, 8 in the Oyster River watershed, and 8 in the Ossippee River watershed. Samples were analyzed for nitrate, phosphate, ammonium, dissolved organic nitrogen (DON), and dissolved organic carbon (DOC). The 30 sub-basins were characterized by land use data (NH GRANIT), population density (Census 2000) and property value. Property value was found to predict NO₃-N fluxes across the thirty sub-basins and within sub-basins of the Lamprey River watershed and the Oyster River watershed. Property value was also found to explain the residual variation seen when population density was used to predict NO₃-N fluxes in the Lamprey River sub-basins and the 22 sub-basins of the Lamprey and Oyster River watersheds that fall within the Boston metropolitan area.

O'Donnell, T.E., 2004. Suburbanization, Water Quality and Property Values in Three Northern Forest Watersheds. Thesis, University of New Hampshire, Durham, NH.

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