Upland and in-stream controls on baseflow nutrient dynamics in tile-drained agroecosystem watersheds

JOURNAL OF HYDROLOGY

卷:556

Article

Ford, William I.¹  King, Kevin²  Williams, Mark R.³ 

[1] Univ Kentucky, Biosyst & Agr Engn, Lexington, KY 40546 USA

[2] USDA ARS, Soil Drainage Res Unit, Columbus, OH USA

[3] USDA ARS, Natl Soil Eros Res Lab, W Lafayette, IN USA

关键词: Water quality;    Nutrients;    Drainage;    Agriculture;    Time-series;    CEAP;   

DOI  :  10.1016/j.jhydrol.2017.12.009

来源: Elsevier

【 摘 要 】

In landscapes with low residence times (e.g., rivers and reservoirs), baseflow nutrient concentration dynamics during sensitive timeframes can contribute to deleterious environmental conditions downstream. This study assessed upland and in-stream controls on baseflow nutrient concentrations in a low-gradient, tile-drained agroecosystem watershed. We conducted time-series analysis using Empirical mode decomposition of seven decade-long nutrient concentration time-series in the agricultural Upper Big Walnut Creek watershed (Ohio, USA). Four tributaries of varying drainage areas and three main-stem sites were monitored, and nutrient grab samples were collected weekly from 2006 to 2016 and analyzed for dissolved reactive phosphorus (DRP), nitrate-nitrogen (NO3-N), total nitrogen (TN), and total phosphorus (TP). Statistically significant seasonal fluctuations were compared with seasonality of baseflow, watershed characteristics (e.g., tile-drain density), and in-stream water quality parameters (pH, DO, temperature). Findings point to statistically significant seasonality of all parameters with peak P concentrations in summer and peak N in late winter-early spring. Results suggest that upland processes exert strong control on DRP concentrations in the winter and spring months, while coupled upland and in-stream conditions control watershed baseflow DRP concentrations during summer and early fall. Conversely, upland flow sources driving streamflow exert strong control on baseflow NO3-N, and in stream attenuation through transient and permanent pathways impacts the magnitude of removal. Regarding TN and TP, we found that TN was governed by NO3-N, while TP was governed by DRP in summer and fluvial erosion of P-rich benthic sediments during higher baseflow conditions. Findings of the study highlight the importance of coupled in-stream and upland management for mitigating eutrophic conditions during environmentally sensitive timeframes. (C) 2017 Elsevier B.V. All rights reserved.

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