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A LANDSCAPE MODEL TO PREDICT TOTAL NITROGEN LEVELS IN SURFACE WATERS OF THE WILLAMETTE AND CENTRAL VALLEYS ECOREGION OF THE WESTERN UNITED STATES
Citation:
Heggem, D T., A C. Neale, R. K. Hall, AND K B. Jones. A LANDSCAPE MODEL TO PREDICT TOTAL NITROGEN LEVELS IN SURFACE WATERS OF THE WILLAMETTE AND CENTRAL VALLEYS ECOREGION OF THE WESTERN UNITED STATES. Presented at Environmental Monitoring and Assessment Program (EMAP) Symposium 2004, Newport, RI, May 3-7, 2004.
Impact/Purpose:
There are four basic objectives of the project:
Demonstrate the application of a comparative landscape assessment in analyzing the vulnerability of surface and coastal water conditions to declines based on landscape conditions (as estimated by landscape indicators as demonstrated in the mid-Atlantic landscape atlas) in western environments;
Develop and apply landscape assessment approaches relative to specific issues, including an ability to prioritize the vulnerability of areas relative to the Clean Water Act 303(d) designations; Quantify relationships between landscape conditions (as measured by landscape indicators) and surface and coastal waters in the west to reduce the uncertainty in comparative landscape assessments, and issue-specific, landscape assessments (e.g., Total Maximum Daily Load (TMDLs);
Complete a west-wide, comparative landscape assessment relative to surface and coastal water vulnerability;
Transfer landscape assessment technologies to Regional Offices so that they can conduct landscape assessments at many scales.
Description:
Excess nutrients are a leading cause of impairment to streams, rivers, lakes and the coastal ecosystems. Excessive nutrient loadings result in increased primary productivity of plant and algal communities leading to eutrophication and other impacts to aquatic resources. Nitrogen is an essential macronutrient for primary production of plant communities and, when out of balance, is a direct contributor to water body impairment. As a part of the Western Environmental Monitoring and Assessment Program (EMAP), we are developing a landscape indicator to predict nitrogen loading to western aquatic systems. The key to this work is to establish a quantitative relationship between landscape pattern metrics and nitrogen loading in streams. A number of recent studies have shown strong relationships between surface water quality and landscape characteristics. In this study, a simple nutrient export simulation model based on land-cover composition is used to estimate total loads of nitrogen to the stream using EMAP surface water nitrogen data collected in Oregon in 1997 and 1998. A regression model is developed using the landscape metric of nitrogen loading and relating that metric to the surface water nitrogen data.. This paper describes this model and then applies it to the Willamette and Central Valley nutrient ecoregions. This model will be a valuable tool for land use managers in determining nutrient conditions in surface waters and for identifying and reporting impaired water bodies.