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| Titel |
Regional analysis of groundwater droughts using hydrograph classification |
| VerfasserIn |
J. P. Bloomfield, B. P. Marchant, S. H. Bricker, R. B. Morgan |
| 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 ; 19, no. 10 ; Nr. 19, no. 10 (2015-10-28), S.4327-4344 |
| Datensatznummer |
250120836
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| Publikation (Nr.) |
 copernicus.org/hess-19-4327-2015.pdf |
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| Zusammenfassung |
| Groundwater drought is a spatially and temporally variable phenomenon. Here
we describe the development of a method to regionally analyse and quantify
groundwater drought. The method uses a cluster analysis technique
(non-hierarchical k-means) to classify standardised groundwater level
hydrographs (the standardised groundwater level index, SGI) prior to
analysis of their groundwater drought characteristics, and has been tested
using 74 groundwater level time series from Lincolnshire, UK. Using the test
data set, six clusters of hydrographs have been identified. For each cluster
a correlation can be established between the mean SGI and a mean
standardised precipitation index (SPI), where each cluster is associated
with a different SPI accumulation period. Based on a comparison of SPI time
series for each cluster and for the study area as a whole, it is inferred
that the clusters are independent of the driving meteorology and are
primarily a function of catchment and hydrogeological factors. This
inference is supported by the observation that the majority of sites in each
cluster are associated with one of the principal aquifers in the study
region. The groundwater drought characteristics of the three largest
clusters, which constitute ~ 80 % of the sites, have been
analysed. There are differences in the distributions of drought duration,
magnitude and intensity of groundwater drought events between the three
clusters as a function of autocorrelation of the mean SGI time series for
each cluster. In addition, there are differences between the clusters in
their response to three major multi-annual droughts that occurred during the
analysis period. For example, sites in the cluster with the longest SGI
autocorrelation experience the greatest-magnitude droughts and are the
slowest to recover from major droughts, with groundwater drought conditions
typically persisting at least 6 months longer than at sites in the other
clusters. Membership of the clusters is shown to be related to unsaturated
zone thickness at individual boreholes. This last observation emphasises the
importance of catchment and aquifer characteristics as (non-trivial)
controls on groundwater drought hydrographs. The method of analysis is
flexible and can be adapted to a wide range of hydrogeological settings
while enabling a consistent approach to the quantification of regional
differences in response of groundwater to meteorological drought. |
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