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| Titel |
Sources of sediment in catchments and its eutrophication potential |
| VerfasserIn |
Josef Krása, Tomáš Dostál, Miroslav Bauer, Barbora Janotova, Pavel Rosendorf |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080034
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| Zusammenfassung |
| To help the implementation of Water Framework Directive in the Czech Republic the
four-year project was set-up to assess eutrophication factors in endangered catchments. The
assessed area covers approximately 40% of the area of the Czech Republic (almost 31 500
km2).
The erosion phosphorus loads are modeled by WATEM/SEDEM model adapted for the
purpose. For each catchment the sediment transport maps are delivered. Database
of 20Â 477 reservoirs (spatial information taken from DIBAVOD) within CR has
been built up during the project and all available information on volumes and flow
rates in the reservoirs is collected. From these, 9Â 890 reservoirs lay in the target
area and to estimate the sediment trapping efficiency their volumes and average
annual flow rates have to be assessed. The official databases offer less than 10%
data coverage so especially for smaller reservoirs the volumes and flow rates have
to be derived by analogy using pond area and catchments specific runoff. Brune
curves method readjusted by Dendy (1978) is then used for sediment trap efficiency
estimation. WATEM/SEDEM model had to be further adapted for modeling phosphorus
fluxes within catchments. The ratio of nutrient concentration in eroded sediment to
that in the original soil (the enrichment ratio, ER) commonly drops down with
raising the soil loss. We used the dependence proposed by Sharply (1995). The soil
erodibility factor of WATEM/SEDEM (K-factor) is then replaced by phosphorus
erodibility potential. Finally the erosion phosphorus transport is computed getting also
phosphorus retention in all reservoirs in target watersheds. In 2012 sediment transport
was modeled in all catchments. Assessment of silting of thousands or reservoirs
within the stream network of the target catchments is important “side output” of the
project
Balancing phosphorus sources with attempt to find the importance of erosion for
eutrophication is a complicated task. The regular monthly monitoring network in
streams and reservoirs is an important source of data for balancing phosphorus
sources but often misses the episodic erosion inputs. WATEM/SEDEM shows up
to be reasonable tool for sediment transport and particulate phosphorus transport
within large catchments, even though getting relevant high resolution input data is a
limiting factor for assessment. The topography and land-use data are good enough
for defining the spatial pattern of erosion and deposition, but for getting actual
sediment transport volumes there are not enough data on precipitation, and stream
hydrology.
Acknowledgements
Research is supported by the NAZV project No. QI102A265 “Assessment of soil erosion
and phosphorus loads causing eutrophication of stagnant water bodies” and QI91C008
“Optimization of design of technical soil erosion control measures”.
References
Dendy, F.E., and W.A. Champion. 1978. Sediment Deposition in U.S. Reservoirs.
MP-1362. U.S. Dept. Agr., Agr. Res. Serv.
Sharpley A. N.: Dependence of runoff phosphorus on extractable soil phosphorus. J.
Environ. Qual., 24, (1995), p. 920-926.
Van Rompaey A, Verstraeten G, Van Oost K, Govers G & Poesen J, 2001. Modeling mean
annual sediment yield using a distributed approach. Earth Surface Processes and Landforms
26 (11), 1221-1236. |
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