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| Titel |
Regionalization of patterns of flow intermittence from gauging station records |
| VerfasserIn |
T. H. Snelder, T. Datry, N. Lamouroux, S. T. Larned, E. Sauquet, H. Pella, C. Catalogne |
| 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 ; 17, no. 7 ; Nr. 17, no. 7 (2013-07-11), S.2685-2699 |
| Datensatznummer |
250018931
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| Publikation (Nr.) |
 copernicus.org/hess-17-2685-2013.pdf |
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| Zusammenfassung |
| Understanding large-scale patterns in flow intermittence is important for
effective river management. The duration and frequency of zero-flow periods
are associated with the ecological characteristics of rivers and have
important implications for water resources management. We used daily flow
records from 628 gauging stations on rivers with minimally modified flows
distributed throughout France to predict regional patterns of flow
intermittence. For each station we calculated two annual
times series describing flow intermittence; the frequency of zero-flow
periods (consecutive days of zero flow) in each year of record (FREQ; yr−1),
and the total number of zero-flow days in each year of record (DUR; days).
These time series were used to calculate two indices for each station, the
mean annual frequency of zero-flow periods (mFREQ; yr−1), and the mean
duration of zero-flow periods (mDUR; days). Approximately 20% of stations had
recorded at least one zero-flow period in their record. Dissimilarities
between pairs of gauges calculated from the annual times series (FREQ and DUR) and
geographic distances were weakly correlated, indicating that there was
little spatial synchronization of zero flow. A flow-regime classification
for the gauging stations discriminated intermittent and perennial stations,
and an intermittence classification grouped intermittent stations into three
classes based on the values of mFREQ and mDUR. We used random forest (RF) models to
relate the flow-regime and intermittence classifications to several
environmental characteristics of the gauging station catchments. The RF
model of the flow-regime classification had a cross-validated Cohen's kappa
of 0.47, indicating fair performance and the intermittence classification
had poor performance (cross-validated Cohen's kappa of 0.35). Both
classification models identified significant environment-intermittence
associations, in particular with regional-scale climate patterns and also
catchment area, shape and slope. However, we suggest that the fair-to-poor
performance of the classification models is because intermittence is also
controlled by processes operating at scales smaller than catchments,
such as groundwater-table fluctuations and seepage through permeable
channels. We suggest that high spatial heterogeneity in these small-scale
processes partly explains the low spatial synchronization of zero flows.
While 20% of gauges were classified as intermittent, the flow-regime
model predicted 39% of all river segments to be intermittent, indicating
that the gauging station network under-represents intermittent river
segments in France. Predictions of regional patterns in flow intermittence
provide useful information for applications including environmental
flow setting, estimating assimilative capacity for contaminants, designing
bio-monitoring programs and making preliminary predictions of the effects of
climate change on flow intermittence. |
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