134 research outputs found
Studying catchment storm response using event- and pre-event-water volumes as fractions of precipitation rather than discharge
Catchment response to precipitation is often investigated using
two-component isotope-based hydrograph separation, which quantifies the
contribution of precipitation (i.e., event water Qe) or water
from storage (i.e., pre-event water Qpe) to total discharge (Q)
during storm events. In order to better understand streamflow-generating
mechanisms, two-component hydrograph separation studies often seek to relate
the event-water fraction Qe∕Q to storm characteristics or
antecedent wetness conditions. However, these relationships may be obscured
because the same factors that influence Qe also necessarily
influence total discharge Q as well. Here we propose that the fractions of
event water and pre-event water relative to total precipitation
(Qe∕P and Qpe∕P), instead of total discharge,
provide useful alternative tools for studying catchment storm responses.
These two quantities separate the well-known runoff coefficient (Q∕P, i.e.,
the ratio between total discharge and precipitation volumes over the event
timescale) into its contributions from event water and pre-event water.
Whereas the runoff coefficient Q∕P quantifies how strongly precipitation
inputs affect streamflow, the fractions Qe∕P and
Qpe∕P track the sources of this streamflow response.We use high-frequency measurements of stable water isotopes for 24 storm
events at a steep headwater catchment (Erlenbach, central Switzerland) to
compare the storm-to-storm variations in Qe∕Q, Qe∕P
and Qpe∕P. Our analysis explores how storm characteristics and
antecedent wetness conditions affect the mobilization of event water and
pre-event water at the catchment scale. Isotopic hydrograph separation shows
that catchment outflow was typically dominated by pre-event water, although
event water exceeded 50 % of discharge for several storms. No clear
relationships were found linking either storm characteristics or antecedent
wetness conditions with the volumes of event water or pre-event water
(Qe, Qpe), or with event water as a fraction of
discharge (Qe∕Q), beyond the unsurprising correlation of larger
storms with greater Qe and greater total Q. By contrast, event
water as a fraction of precipitation (Qe∕P) was strongly
correlated with storm volume and intensity but not with antecedent wetness,
implying that the volume of event water that is transmitted to streamflow
increases more than proportionally with storm size under both wet and dry
conditions. Conversely, pre-event water as a fraction of precipitation
(Qpe∕P) was strongly correlated with all measures of antecedent
wetness but not with storm characteristics, implying that wet conditions
primarily facilitate the mobilization of old (pre-event) water, rather than
the fast transmission of new (event) water to streamflow, even at a catchment
where runoff coefficients can be large.Thus, expressing event- and pre-event-water volumes as fractions of
precipitation rather than discharge was more insightful for investigating the
Erlenbach catchment's hydrological behaviour. If Qe∕P and
Qpe∕P exhibit similar relationships with storm characteristics
and antecedent wetness conditions in other catchments, we suggest that these
patterns may potentially be useful as diagnostic fingerprints of
catchment storm response.</p
A survivor population of wild colonies of European honeybees in the northeastern United States: investigating its genetic structure
Colony Collapse Disorder: A Descriptive Study
BACKGROUND: Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We initiated a descriptive epizootiological study in order to better characterize CCD and compare risk factor exposure between populations afflicted by and not afflicted by CCD. METHODS AND PRINCIPAL FINDINGS: Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels), no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor) were higher in control colonies than CCD-affected colonies. CONCLUSIONS/SIGNIFICANCE: This is the first comprehensive survey of CCD-affected bee populations that suggests CCD involves an interaction between pathogens and other stress factors. We present evidence that this condition is contagious or the result of exposure to a common risk factor. Potentially important areas for future hypothesis-driven research, including the possible legacy effect of mite parasitism and the role of honey bee resistance to pesticides, are highlighted
Using an accumulation of deficits approach to measure frailty in a population of home care users with intellectual and developmental disabilities: an analytical descriptive study
Characterisation of the British honey bee metagenome
Numerous microbial symbionts, both commensal and pathogenic, are associated with honey bees. Here, the authors genomically characterize this ‘metagenome’ of the British honey bee, identifying a diversity of commensal microbes as well as known and putative pathogen
The density of feral honey bee (Apis mellifera) colonies in South East Australia is greater in undisturbed than in disturbed habitats
Dynamic magneto-optical study of the intermediate state, current-voltage characteristics
Groundwater similarity across a watershed derived from time-warped and flow-corrected time series
Information about catchment-scale groundwater dynamics is necessary to understand how catchments store and release water and why water quantity and quality varies in streams. However, groundwater level monitoring is often restricted to a limited number of sites. Knowledge of the factors that determine similarity between monitoring sites can be used to predict catchment-scale groundwater storage and connectivity of different runoff source areas. We used distance-based and correlation-based similarity measures to quantify the spatial and temporal differences in shallow groundwater similarity for 51 monitoring sites in a Swiss prealpine catchment. The 41 months long time series were preprocessed using Dynamic Time-Warping and a Flow-corrected Time Transformation to account for small timing differences and bias toward low-flow periods. The mean distance-based groundwater similarity was correlated to topographic indices, such as upslope contributing area, topographic wetness index, and local slope.
Correlation-based similarity was less related to landscape position but instead revealed differences between seasons. Analysis of variance and partial Mantel tests showed that landscape position, represented by the topographic wetness index, explained 52% of the variability in mean distance-based groundwater similarity, while spatial distance, represented by the Euclidean distance, explained only 5%. The variability in distance-based similarity and correlation-based similarity between groundwater and streamflow time series was significantly larger for midslope locations than for other landscape positions. This suggests that groundwater dynamics at these midslope sites, which are important to understand runoff source areas and hydrological connectivity at the catchment scale, are most difficult to predict
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