Identifying riparian buffer effects on stream nitrogen in southeastern coastal plain watersheds

Area of Science:

• Environmental Science
• Water Quality Management
• Agricultural Hydrology

Background:

• Southeastern U.S. freshwaters and estuaries face eutrophication from agricultural non-point sources (NPS).
• Riparian buffers are a common strategy to reduce NPS, but their watershed-level effectiveness is challenging to quantify.

Purpose of the Study:

• To compare the efficacy of riparian buffer models versus land use/land cover (LULC) models in predicting stream total nitrogen concentrations (TNC).
• To assess the nitrogen reduction capacity of riparian buffers in Southeastern Coastal Plain watersheds.
• To evaluate the influence of headwaters and artificial drainage on buffer performance.

Main Methods:

• Utilized corrected Akaike information criterion (AICc) and model averaging for model comparison.
• Compared flow-path riparian buffer models with LULC models across 24 Southeastern Coastal Plain watersheds.
• Incorporated factors like cropland, non-buffered cropland, headwaters, and artificial drainage into models.

Main Results:

• A buffer model including cropland and non-buffered cropland best explained stream TNC (R² = 0.75), outperforming LULC models.
• Predicted current buffers remove 52% of edge-of-field nitrogen and 45% of potential watershed nitrogen.
• An average of 26% of stream nitrogen leaked through buffered cropland, with non-headwater buffers showing minimal impact.

Conclusions:

• Adequate restoration of riparian buffers on all cropland could potentially reduce stream TNC by 34%.
• Findings offer realistic nitrogen removal expectations for watershed managers aiming to meet water quality goals.
• Artificial drainage must be considered when assessing buffer effectiveness and stream nitrogen dynamics.