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Berlin Brandenburg

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  • American Geophysical Union (CrossRef)  (11)
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  • 1
    In: Water Resources Research, April 2009, Vol.45(4), pp.n/a-n/a
    Description: Low‐cost, low‐power wireless sensor networks (mote networks) have the potential to revolutionize data collection methods in hydrology. They promise the ability to monitor catchments at very high spatial and temporal resolution with flexible sampling schemes, real time data processing and high levels of quality control. We operated an experimental network of 41 motes monitoring seven different parameters each at 15 min intervals for 10 months in a small forested catchment in southwestern British Columbia, Canada, to determine if this emerging technology is suitable for use by hydrologists in its current form. Our particular interests were ease of setup, sampling reliability, power consumption, and hardware resilience. We found that while motes gave the ability to monitor a catchment at resolution levels that were previously impossible, they still need to evolve into an easier to use, more reliable platform before they can replace traditional data collection methods.
    Keywords: Mote ; Measurement ; Network ; Wireless
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 2
    In: Geophysical Research Letters, February 2011, Vol.38(3), pp.n/a-n/a
    Description: Due to temperature differences of groundwater and streamwater, localized groundwater inflows into small streams can directly be detected with ground‐based thermographic systems in summer or winter. Infrared radiation temperatures of surface water were used to determine mixing length and to calculate the relative fraction of groundwater inflow to downstream discharge. These fractions were comparable to groundwater inflow fractions derived from electrical conductivity, kinetic water temperatures and discharge measurements. This approach advances the immediate detection and quantification of localized groundwater inflow for hydrology, geology and ecology.
    Keywords: Groundwater‐Surface Water Interaction ; Water Temperature ; Infrared Thermography
    ISSN: 0094-8276
    E-ISSN: 1944-8007
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  • 3
    Language: English
    In: Journal Of Geophysical Research-Space Physics, 2011, Vol.116
    Description: The mobilization of mercury and dissolved organic carbon (DOC) during snowmelt often accounts for a major fraction of the annual loads. We studied the role of hydrological connectivity of riparian wetlands and upland/wetland transition zones to surface waters on the mobilization of Hg and DOC in Fishing...
    Keywords: Environmental Sciences Related To Agriculture And Land-Use ; Miljö- Och Naturvårdsvetenskap
    ISSN: 0148-0227
    E-ISSN: 21562202
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  • 4
    In: Water Resources Research, March 2012, Vol.48(3), pp.n/a-n/a
    Description: We developed a method to measure in situ the isotopic composition of liquid water with minimal supervision and, most important, with a temporal resolution of less than a minute. For this purpose a microporous hydrophobic membrane contactor (Membrana) was combined with an isotope laser spectrometer (Picarro). The contactor, originally designed for degassing liquids, was used with N as a carrier gas in order to transform a small fraction of liquid water to water vapor. The generated water vapor was then analyzed continuously by the Picarro analyzer. To prove the membrane's applicability, we determined the specific isotope fractionation factor for the phase change through the contactor's membrane across an extended temperature range (8°C–21°C) and with different waters of known isotopic compositions. This fractionation factor is needed to subsequently derive the liquid water isotope ratio from the measured water vapor isotope ratios. The system was tested with a soil column experiment, where the isotope values derived with the new method corresponded well (R = 0.998 for δO and R = 0.997 for δH) with those of liquid water samples taken simultaneously and analyzed with a conventional method (cavity ring‐down spectroscopy). The new method supersedes taking liquid samples and employs only relatively cheap and readily available components. This makes it a relatively inexpensive, fast, user‐friendly, and easily reproducible method. It can be applied in both the field and laboratory wherever a water vapor isotope analyzer can be run and whenever real‐time isotope data of liquid water are required at high temporal resolution. No more trade‐off between limited temporal resolution and extensive lab work No more significant time lags between sampling and data acquisition New method is field‐deployable and utilizes readily available components only
    Keywords: Crds ; Continuous Analysis ; Equilibrium Fractionation ; Hydrophobic Membrane ; In Situ Monitoring ; Stable Water Isotopes
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 5
    In: Water Resources Research, June 2012, Vol.48(6), pp.n/a-n/a
    Description: Because of emerging vegetation and sedimentation processes, the succession of wetlands is a dynamic process. Hence, a noticeable impact on the functioning and the efficiency of constructed treatment wetlands regarding solute retention can be expected. Within 5 months a reduction of active wetland volume, a decrease of light decay, and an increase of sorption capacity were observed using four multitracer experiments in a newly established constructed wetland. Tracer breakthrough curves of conservative and nonconservative tracers were analyzed with the help of a transient storage model. The model characterized the impact of vegetation development and sediment accumulation on solute transport properties. Three different tracers allowed an assessment of wetland hydraulics, sorption processes, and light impact on photodegradable solutes. Finally, the exemplary transport prediction of a fourth, independent tracer that was both photodegradable and sorptive demonstrated a cost‐efficient technique to determine the influence of succession processes on treatment efficiency. Succession processes in wetlands alter active wetland volumes Changing wetland hydraulics directly affect non‐conservative transport processes Multitracer experiments allow untangling process interactions in wetlands
    Keywords: Conservative Transport ; Constructed Wetlands ; Multitracer ; Nonconservative Transport ; Solute Transport ; Transient Storage Model
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 6
    In: Water Resources Research, January 2012, Vol.48(1), pp.n/a-n/a
    Description: Paired watershed studies have limited researchers wishing to disentangle road and harvesting effects on peak flows or to study management schemes other than the existing scenario. The outcomes of many paired watershed studies examining peak flows have also recently been challenged since only an approach that pairs peak flows by frequency can adequately evaluate the effects of harvesting on peak flows. This study takes advantage of a model that has been developed and extensively tested at a site containing a rich set of internal catchment process observations to examine the isolated and combined effects of roads and harvesting on the peak flow regime of a snow‐dominated catchment for return periods of up to 100 years. Contrary to the prevailing perception in forest hydrology, the effects of harvesting are found to increase with return period, which is attributable to the uniqueness of peak flow runoff generation processes in snow‐dominated catchments. Planned harvesting (50% harvest area) is found to have a significant effect (9%–25% over control) on peak flows with recurrence intervals ranging 10–100 years. Peak flow frequency increases after harvesting increase with return period, with the largest events (100 year) becoming 5–6.7 times more frequent, and medium‐sized events (10 year) becoming 1.7–2 times more frequent. Such changes may have substantial ecological, hydrological, and geomorphological consequences within the watershed and farther downstream. Study findings suggest that peak flow regimes are fairly tolerant to the current level of harvesting in this particular watershed but that further harvesting may affect this element significantly. Impacts increase with flood return period, contrary to prevailing perception Magnitude of all flood sizes increases following logging Floods become more frequent following logging, especially more extreme ones
    Keywords: Dhsvm ; Forest ; Logging ; Peak Flow ; Roads ; Snow
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 7
    In: Water Resources Research, June 2012, Vol.48(6), pp.n/a-n/a
    Description: The transit time of water is an important indicator of catchment functioning and affects many biological and geochemical processes. Water entering a catchment at one point in time is composed of water molecules that will spend different amounts of time in the catchment before exiting. The next water input pulse can exhibit a totally different distribution of transit times. The distribution of water transit times is thus best characterized by a time‐variable probability density function. It is often assumed, however, that the variability of the transit time distribution is negligible and that catchments can be characterized with a unique transit time distribution. In many cases this assumption is not valid because of variations in precipitation, evapotranspiration, and catchment water storage and associated (de)activation of dominant flow paths. This paper presents a general method to estimate the time‐variable transit time distribution of catchment waters. Application of the method using several years of rainfall‐runoff and stable water isotope data yields an ensemble of transit time distributions with different moments. The combined probability density function represents the master transit time distribution and characterizes the intra‐annual and interannual variability of catchment storage and flow paths. Comparing the derived master transit time distributions of two research catchments (one humid and one semiarid) reveals differences in dominant hydrologic processes and dynamic water storage behavior, with the semiarid catchment generally reacting slower to precipitation events and containing a lower fraction of preevent water in the immediate hydrologic response. Water transit time distributions are highly irregular and variable in time Water transit time distributions differ from hydrologic response functions Differences between the two functions yield information on storage dynamics
    Keywords: Catchment Response Classification ; Event‐Preevent Water ; Hydrologic Response Functions ; Storage Dynamics ; Time Variant ; Transit Time Distributions
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 8
    In: Water Resources Research, March 2007, Vol.43(3), pp.n/a-n/a
    Description: One of the greatest challenges in the field of hillslope hydrology is conceptualizing and parameterizing the effects of lateral preferential flow. Our current physically based and conceptual models often ignore such behavior. However, for addressing issues of land use change, water quality, and other predictions where flow amount and components of flow are imperative, dominant runoff processes like preferential subsurface flow need to be accounted for in the model structure. This paper provides a new approach to formalize the qualitative yet complex explanation of preferential flow into a numerical model structure. We base our examples on field studies of the well‐studied Maimai watershed (New Zealand). We then use the model as a learning tool for improved clarity into the old water paradox and reasons for the seemingly contradictory findings of lateral preferential flow of old water where applied line sources of tracer appear very quickly in the stream following application. We evaluate the model with multiple criteria, including ability to capture flow, hydrograph composition, and tracer breakthrough. We generate output ensembles with different pipe network geometries for model calibration and validation analysis. Surprisingly, the range of runoff response among the ensembles is narrow, indicating insensitivity to specific pipe placement. Our new model structure shows that high transport velocities for artificial line source tracers can be reconciled with the dominance of preevent water during runoff events even when lateral pipe flow dominates response. The work suggests overall that preferential flow can be parameterized within a process‐based model structure via the structured dialog between experimentalist and modeler.
    Keywords: Conceptual Model ; Hillslope ; Hydrograph Separation ; Pipe Flow ; Preevent Vapor ; Tracer Breakthrough
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 9
    In: Water Resources Research, November 2003, Vol.39(11), pp.n/a-n/a
    Description: Hydrographs are an enticing focus for hydrologic research: they are readily available hydrological data that integrate the variety of terrestrial runoff generation processes and upstream routing. Notwithstanding, new techniques to glean information from the hydrograph are lacking. After early approaches of graphically separating streamflow components, hydrograph separations in the past two decades have focused on tracers as a more objective means to separate the storm hydrograph. These tracer‐based methods provide process‐based information; however, their implicit assumptions limit their applicability and explanatory power. We present a new method for isotope hydrograph separation that integrates the instantaneous unit hydrograph and embraces the temporal variability of rainfall isotopic composition (one of the largest impediments to the standard use of isotopes as tracers). Our model computes transfer functions for event water and preevent water calculated from a time‐variable event water fraction. The transfer function hydrograph separation model (TRANSEP) provides coupled but constrained representations of transport and hydraulic transfer functions, overcoming limitations of other models. We illustrate the utility of TRANSEP by applying it to two rainfall events from a 17 ha catchment at Maimai in New Zealand, where O, rainfall, and runoff data were sampled with a high temporal resolution. We explore which runoff and tracer transfer function (exponential piston flow, gamma distribution, or two parallel linear reservoirs) gave the best results for the proposed model structure and for the example data set. Uncertainty analysis was used to determine if the parameters were identifiable and if the information available for applying TRANSEP was sufficient. The results of the best performing transfer function are considered in detail to identify model performance, illustrate individual event characteristics, and interpret runoff processes in the catchment.
    Keywords: Hydrograph Separation ; Transfer Function ; Isotope ; Instantaneous Unit Hydrograph
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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  • 10
    In: Water Resources Research, November 2007, Vol.43(11), pp.n/a-n/a
    Description: Dissolved CO dynamics in stormflow and event water versus preevent water contributions to storm hydrographs were assessed in a forested headwater catchment of the Brazilian Amazon using high‐frequency data. We applied the transfer function hydrograph separation model (TRANSEP) using specific conductance as a conservative tracer, finding preevent water to average 0.79 ± 0.03 of storm discharge (mean ± 1 SE for = 14 storms). In situ, direct measurements of dissolved CO were able to capture new hydrobiogeochemical processes in real time, including CO pulses observed on the falling limb of storm hydrographs, the magnitudes of which were inversely related to preevent water fractions ( = −0.97, 〈 0.0001).
    Keywords: Dissolved Co Dynamics ; In Situ Monitoring
    ISSN: 0043-1397
    E-ISSN: 1944-7973
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