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What’s Upstream? GIS’s critical role in developing nutrient reference conditions for estuaries
Citation:
Clinton, P., C. Brown, AND Walt Nelson. What’s Upstream? GIS’s critical role in developing nutrient reference conditions for estuaries. Presented at 2014 SCGIS Conference, Pacific Grove, CA, July 11 - 13, 2014.
Impact/Purpose:
The abstract introduces Geographic Information Systems (GIS) tools and processes employed for research conducted under the Safe and Sustainable Water Resources (SSWR) Task 2.3A, entitled “Nutrient Management for Sustainability of Aquatic Ecosystems.” One of the goals of the EPA Office of Water is to assist States Territories and Tribes “ in the development of numeric nitrogen and phosphorus criteria, which will help states, territories, and tribes move toward adopting water quality standards for nitrogen and phosphorus.” To that end the EPA publishes technical resources that describe the techniques for developing numeric criteria for nitrogen and phosphorus pollution. The GIS tools and processes we will present demonstrate a useful approach for developing nutrient reference conditions for freshwater input to estuaries in the Pacific Northwest.
Description:
Eutrophication due to excess levels of nitrogen and phosphorus can seriously impair ecological function in estuaries. Protective criteria for nutrients are difficult to establish because the source can vary spatially and seasonally, originate either from the watershed or the ocean, and be natural or anthropogenic. GIS tools and processes can help in developing nutrient criteria by establishing reference conditions representative of natural background nutrient levels. Along the Oregon Coast in the Pacific Northwest, the primary source of nutrients in the wet season (November-April) is generally riverine. We delineated and extracted explicit spatial data from watersheds upstream of riverine water quality monitoring stations for parametric comparison to recorded nutrient levels. The SPARROW model (Wise and Johnson, 2011) was used to estimate relative contributions of nutrient sources at each station. Both raster and vector spatial data were used and include land use / land cover, demography, geology, terrain, precipitation and forest type. The relationships of nutrients to spatial data were then explored as an approach to establishing the reference expectation.