The role of irrigation runoff and winter rainfall on dissolved organic carbon loads in an agricultural watershed

Agriculture, Ecosystems and Environment
By: , and 

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Abstract

We investigated the role of land use/land cover and agriculture practices on stream dissolved organic carbon (DOC) dynamics in the Willow Slough watershed (WSW) from 2006 to 2008. The 415 km2watershed in the northern Central Valley, California is covered by 31% of native vegetation and the remaining 69% of agricultural fields (primarily alfalfa, tomatoes, and rice). Stream discharge and weekly DOC concentrations were measured at eight nested subwatersheds to estimate the DOC loads and yields (loads/area) using the USGS developed stream load estimation model, LOADEST. Stream DOC concentrations peaked at 18.9 mg L−1 during summer irrigation in the subwatershed with the highest percentage of agricultural land use, demonstrating the strong influence of agricultural activities on summer DOC dynamics. These high concentrations contributed to DOC yields increasing up to 1.29 g m−2 during the 6 month period of intensive agricultural activity. The high DOC yields from the most agricultural subwatershed during the summer irrigation period was similar throughout the study, suggesting that summer DOC loads from irrigation runoff would not change significantly in the absence of major changes in crops or irrigation practices. In contrast, annual DOC yields varied from 0.89 to 1.68 g m−2 yr−1 for the most agricultural watershed due to differences in winter precipitation. This suggests that variability in the annual DOC yields will be largely determined by the winter precipitation, which can vary significantly from year to year. Changes in precipitation patterns and intensities as well as agricultural practices have potential to considerably alter the DOC dynamics.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title The role of irrigation runoff and winter rainfall on dissolved organic carbon loads in an agricultural watershed
Series title Agriculture, Ecosystems and Environment
DOI 10.1016/j.agee.2013.07.004
Issue 179
Year Published 2013
Language English
Publisher Elsevier
Contributing office(s) California Water Science Center
Description 10 p
First page 1
Last page 10
Country United States
State California
Other Geospatial Central Valley
Online Only (Y/N) N
Additional Online Files (Y/N) N
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