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Journal of Hydrology 270 (2003) 253-272
Cover page
Introduction
Catchment characteristics
Methods
Results
Discussion
Conclusion
Acknowledgements
& References
0022-1694/03/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0 02 2 -1 69 4 (0 2) 00 2 86 -X
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Before and after riparian management:
sediment and nutrient
exports from a small agricultural catchment, Western Australia
Lucy A. McKergowa,b,*, David M. Weaverc, Ian P. Prosserb, Rodger B. Graysona,
Adrian E.G. Reedc
aDepartment of Civil and Environmental Engineering, Cooperative Research Centre for Catchment Hydrology, University of Melbourne,
Melbourne, Vic. 3010, Australia
bCooperative Research Centre for Catchment Hydrology, CSIRO Land and Water, G.P.O. Box 1666, Canberra, ACT 2601, Australia
cDepartment of Agriculture, Western Australia, 444 Albany Highway, Albany, WA 6330, Australia
Received 15 November 2001; revised 6 September 2002; accepted 12 September 2002
Abstract
Riparian vegetation can trap sediment and nutrients sourced from hillslopes and reduce stream bank erosion. This study
presents results from a 10-year stream monitoring program (1991-2000), in a 6 km2 agricultural catchment near Albany,
Western Australia. After 6 years, a 1.7 km stream reach was fenced, planted with eucalyptus species and managed
independently from the adjacent paddocks. Streamflow, nutrient and sediment concentration data were collected at the
downstream end of the fenced riparian area, so there are data for before and after improved riparian management. Suspended
sediment (SS) concentrations fell dramatically following improved riparian management; the median event mean concentration
(EMC) dropped from 147 to 9.9 mg l-1. Maximum SS concentrations dropped by an order of magnitude. As a result, sediment
exports from the catchment decreased following improved riparian management, from over 100 to less than 10 kg ha-1 yr-1.
Observations suggest that this was the result of reduced bank erosion and increased channel stability. Riparian management had
limited impact on total phosphorus (TP) concentrations or loads, but contributed to a change in phosphorus (P) form. Before
improved riparian management, around half of the P was transported attached to sediment, but after, the median filterable
reactive P (FRP) to TP ratio increased to 0.75. In addition, the median FRP EMC increased by 60% and the raw median FRP
concentration increased from 0.18 to 0.35 mg l-1. These results suggest that there was a change in the dominant P form, from
TP to FRP. Changes in total nitrogen (TN) following improved riparian management were less clear. There were reductions in
TN concentrations at high flows, but little change in the loads or EMC. This study demonstrates the benefits of riparian
management in reducing stream bank erosion, but suggests that in catchments with sandy, low P sorption soils, there may be
limitations on the effectiveness of riparian buffers for reducing P and N exports.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Riparian buffer; Suspended sediment; Phosphorus; Nitrogen
* Corresponding author.
Address: Cooperative Research Centre for Catchment Hydrology, CSIRO Land and Water,
G.P.O. Box 1666, Canberra, ACT 2601, Australia.
Tel.: +61-2-6246-5724; fax: +61-2-6246-5845.
E-mail address: lucy.mckergow@csiro.au (L.A. McKergow).
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