Sources and Yield of Dissolved Inorganic and Organic Constituents in Headwater Streams of the Upper Gulf Coastal Plain, Mississippi

Author(s): Mangum, C.; Hatten, J.; Dewey, J.; Choi, B.

Mississippi has more than 8 million hectares of land in active forest management, much of which is in headwater watersheds. Headwater systems contribute water and initiate dissolved material export to downstream fluvial environments. Nutrients, such as nitrogen and dissolved organic carbon (DOC), are constituents that frequently lead to impaired rivers in Mississippi. This study analyzes event data from 4 ephemeral (1.8-3.8 ha) and 1 perennial (32 ha) forested headwater system in Upper Gulf Coastal Plain, Mississippi over a 15 month period. We measured dissolved inorganic and organic constituents in samples collected during storm and baseflow conditions. We calculated the flux of nitrate, dissolved organic nitrogen (DON) and phosphorus with average kilograms per hectares per year yields of 0.48, 7.83 and 0.25 respectively. We also used an end member mixing model to determine the source of water and compared those results with nutrient fluxes during both storm and baseflow conditions. The data show that dissolved constituents are primarily mobilized during the rising limb of storm events. The source of these materials appears to be shallow mineral soil horizons (A horizons). In our presentation we will discuss how the source of water interacts with flux of nitrogen and implications for forest management and downstream environments.
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Technical Sessions

1 Best Management Practices #1
2 Delta Water Assessment
3 Flood Assessment & Mgmt.
4 Wetlands
5 Watershed Mgmt. #1
6 Non-Point Source Assessment
7 Modeling
8 Water Quality
9 Best Mgt. Practices #2
10 Delta Water Conservation
11 Sedimentation
12 Storm Water
13 Watershed Mgt. #2
14 Public Water Systems
15 Surface Water Assessment & Evaluation

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