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| Titel |
Applying SWAT to predict ortho-phosphate loads and trophic status in four reservoirs in the upper Olifants catchment, South Africa |
| VerfasserIn |
J. M. Dabrowski |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 18, no. 7 ; Nr. 18, no. 7 (2014-07-16), S.2629-2643 |
| Datensatznummer |
250120411
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| Publikation (Nr.) |
 copernicus.org/hess-18-2629-2014.pdf |
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| Zusammenfassung |
| Excessive phosphate loading in the upper Olifants River, South Africa has
resulted in widespread eutrophication and associated ecosystem health
impacts. The majority of sewage treatment works (STWs) are operating poorly
and are likely an important source of bioavailable ortho-phosphate (OP) in
the catchment. The Soil Water Assessment Tool (SWAT) was used to identify
important sources of OP loading in the catchment and to predict changes in
the trophic status of four reservoirs associated with three STW effluent OP
standards (the current average of 4 mg L−1 and standards of 1 and
0.1 mg L−1). Nash–Sutcliffe and PBIAS statistics showed good model
performance for simulations of flow and OP loading using a multi-site
calibration and validation approach. Key sub-catchments responsible for high
OP loading were identified. Three of the four reservoirs are heavily impacted
by OP loading originating from STWs. Two reservoirs show mean annual OP
concentrations indicative of eutrophic conditions and a 1 mg L−1
effluent standard would reduce concentrations to well within the mesotrophic
range. There was little difference in OP loads and concentrations associated
with the 1 and 0.1 mg L−1 effluent standards, indicating that
attention to nonpoint sources would be required to realise any benefit
associated with the strictest effluent standard. Regression analyses and
associated 95% prediction limits between simulated OP loads and
concentrations for all effluent treatment scenarios from 2002 to 2010 allowed
for the quantification of OP loading that would ensure a specific trophic
status in each reservoir. This study is one of the first to apply SWAT in
simulating OP loading and concentrations in large reservoirs, and its
application in South Africa provides further support for its utility
throughout a wide geographical area. |
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