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THE ASSOCIATION OF LAND USE/LAND COVER AND NUTRIENT LEVELS IN MARYLAND STREAMS
Citation:
Senay, G., A. Liu, S M. Cormier, B Subramanian, AND S.T Y. Tong. THE ASSOCIATION OF LAND USE/LAND COVER AND NUTRIENT LEVELS IN MARYLAND STREAMS. Presented at International Congress on Ecosystem Health: Managing for Ecosystem Health, Sacramento, CA, August 15-20, 1999.
Description:
Anthropogenic nonpoint sources of nutrients are known to cause accelerated eutrophication of estuaries. The Chesapeake Bay is one of the world's largest estuaries exhibiting the eutrophication problem caused by pollution from various land use activities. The sources contributing to this include streams, areal deposition and direct loading to the bay. This study focused on the sources to the stream. Spatial and statistical analyses were conducted to investigate the relationships between field measurements of stream chemistry (nitrate, sulfate, dissolved organic carbon, etc.) habitat and satellite-derived land use maps for the state of Maryland. Hydrologic Unit Code (HUC) watershed boundaries (8-digit) were used as the basis for grouping stream chemistry data. Arc/Info, a leading GIS software, was used to compute percent land cover area (forest land, crop land, pastureland, etc.) within a HUC. The percent agricultural lands (crop, pasture, etc.) were positively correlated (significant) with nitrate (NO3) and dissolved organic carbon (DOC) while percent forest cover was negatively correlated (significant) with NO3 and DOC. These resutls were in agreement with other reports and with the fundamental understanding of the role of the land cover types in chemical loadings to streams. The percent forest and percent agriculture land use displayed opposite signs in the correlation matrix with stream chemistry data including sulfate and pH variables. Although there was a negative correlation between percent forest and NO3 in the streams, this was likely due to a reduction in the area occupied by agricultural lands, a predominant source of NO3, not the amount of forest area per se. This was further supported by the presence of a negative correlation between percent forest area and percent agricultural area. These analyses indicated that agriculture was the main source of NO3 pollution in Maryland streams. The next step in this study is investigation of the point sources leading to the chemical loadings to the streams.