scholarly journals Isotopic hydrograph separation in two small mountain catchments during multiple events

2018 ◽  
Vol 44 (2) ◽  
pp. 453 ◽  
Author(s):  
L. Holko ◽  
S. Bičárová ◽  
J. Hlavčo ◽  
M. Danko ◽  
Z. Kostka
Keyword(s):  
Isotopic Composition ◽  
Elevation Gradient ◽  
Rain Gauge ◽  
Windward Side ◽  
Storm Event ◽  
Hydrograph Separation ◽  
Tatra Mountains ◽  
Isotopic Signatures ◽  
Water Fractions ◽  
End Members

Two-component isotopic hydrograph separation (IHS) was developed to determine the event- and pre-event components of a single storm event. Its application for several sucessive events requires repeated determination of isotopic signatures of end-members (precipitation, pre-event component) for each event. The existence of several possible alternative signatures results in differences in calculated contributions of event-/pre- event components. This article addresses the question of how big the differences could be in small mountain catchments with different methods for detemining the end member signatures. We analyzed data on isotopic composition of daily/event precipitation at different elevations in two catchments located in the highest part of the Carpathians in July 2014.The isotopic composition of streamflow sampled every 4-6 hours was analyzed as well. Elevational gradients of δ18O and δ2H in precipitation in the study period were -0.18 ‰ 100 m-1 and -1.1 ‰ 100 m-1, respectively. An elevation gradient in deuterium excess (0.29 ‰ 100 m-1) was also found. Precipitation on the windward side of the mountains was isotopically lighter than expected for a given rain gauge elevation. Five large rainfall-runoff events occurred in the study period in the meso-scale catchment of the Jalovecký creek (Western Tatra Mountains, area 22.2 km2) and in the headwater catchment of the Škaredý creek (High Tatra Mountains, area 1.4 km2). Isotopic hydrograph separation was conducted using eight options for the isotopic signatures of event and pre-event water. The isotopic signature of the event water (rainfall) was alternatively represented by data from high or low elevations. Pre-event water was represented either by the streamflow before the event or by the value taken from the statistics of the long-term data on isotopic composition of the stream. Both isotopes (18O and 2H) were used to calculate event water fractions during peak flows of individual events. Calculated peak flow event water fractions were below 0.2-0.3 for most events. However, the differences in calculated event water fractions for alternative isotopic composition of end-members were significant even if we did not take into account changes in isotopic composition during individual rainfalls. Coefficients of variation for event water fractions calculated for various options varied during individual events from 0.14 to 0.36. It is therefore perhaps better to use a range of possible values instead of a single accurate number to interpret the IHS results. Hydrograph separations based on 18O and 2H provided similar results.

scholarly journals The importance of snowmelt spatiotemporal variability for isotope-based hydrograph separation in a high-elevation catchment

2016 ◽  
Vol 20 (12) ◽  
pp. 5015-5033 ◽  
Author(s):  
Jan Schmieder ◽  
Florian Hanzer ◽  
Thomas Marke ◽  
Jakob Garvelmann ◽  
Michael Warscher ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Elevation ◽  
Spatiotemporal Variability ◽  
Hydrograph Separation ◽  
Catchment Scale ◽  
Isotopic Signatures ◽  
The North ◽  
Stable Isotopic ◽  
Snow Model ◽  
North And South

Abstract. Seasonal snow cover is an important temporary water storage in high-elevation regions. Especially in remote areas, the available data are often insufficient to accurately quantify snowmelt contributions to streamflow. The limited knowledge about the spatiotemporal variability of the snowmelt isotopic composition, as well as pronounced spatial variation in snowmelt rates, leads to high uncertainties in applying the isotope-based hydrograph separation method. The stable isotopic signatures of snowmelt water samples collected during two spring 2014 snowmelt events at a north- and a south-facing slope were volume weighted with snowmelt rates derived from a distributed physics-based snow model in order to transfer the measured plot-scale isotopic composition of snowmelt to the catchment scale. The observed δ18O values and modeled snowmelt rates showed distinct inter- and intra-event variations, as well as marked differences between north- and south-facing slopes. Accounting for these differences, two-component isotopic hydrograph separation revealed snowmelt contributions to streamflow of 35 ± 3 and 75 ± 14 % for the early and peak melt season, respectively. These values differed from those determined by formerly used weighting methods (e.g., using observed plot-scale melt rates) or considering either the north- or south-facing slope by up to 5 and 15 %, respectively.

scholarly journals An Optimized Snowmelt Lysimeter System for Monitoring Melt Rates and Collecting Samples for Stable Water Isotope Analysis

2019 ◽  
Vol 67 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Andrea Rücker ◽  
Massimiliano Zappa ◽  
Stefan Boss ◽  
Jana von Freyberg
Keyword(s):  
Isotopic Composition ◽  
Isotope Analysis ◽  
Ground Level ◽  
Isotopic Signature ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Environmental Tracers ◽  
Hydrograph Separation ◽  
Stable Water Isotopes ◽  
Restricted Volume

Abstract The contribution of snow meltwater to catchment streamflow can be quantified through hydrograph separation analyses for which stable water isotopes (18O, 2H) are used as environmental tracers. For this, the spatial and temporal variability of the isotopic composition of meltwater needs to be captured by the sampling method. This study compares an optimized snowmelt lysimeter system and an unheated precipitation collector with focus on their ability to capture snowmelt rates and the isotopic composition of snowmelt. The snowmelt lysimeter system consists of three individual unenclosed lysimeters at ground level with a surface of 0.14 m2 each. The unheated precipitation collector consists of a 30 cm-long, extended funnel with its orifice at 2.3 m above ground. Daily snowmelt samples were collected with both systems during two snowfall-snowmelt periods in 2016. The snowmelt lysimeter system provided more accurate measurements of natural melt rates and allowed for capturing the small-scale variability of snowmelt process at the plot scale, such as lateral meltwater flow from the surrounding snowpack. Because of the restricted volume of the extended funnel, daily melt rates from the unheated precipitation collector were up to 43% smaller compared to the snowmelt lysimeter system. Overall, both snowmelt collection methods captured the general temporal evolution of the isotopic signature in snowmelt.

scholarly journals Stochastorm: A stochastic rainfall simulator for convective storms

2020 ◽  
Author(s):  
Catherine Wilcox ◽  
Claire Aly ◽  
Théo Vischel ◽  
Gérémy Panthou ◽  
Juliette Blanchet ◽  
...  
Keyword(s):  
Impact Analysis ◽  
Extreme Values ◽  
Rain Gauge ◽  
Convective Precipitation ◽  
Precipitation Event ◽  
Storm Event ◽  
Spatial And Temporal Scales ◽  
Convective Storms ◽  
Distribution Parameters ◽  
Temporal Disaggregation

AbstractStochastic rainfall generators aim to reproduce the main statistical features of rainfall at small spatial and temporal scales. The simulated synthetic rainfall series are recognized as suitable for use with impact analysis in water, agricultural, and ecological management. Convection-driven precipitation, dominant in certain regions of the world such as the intertropical belt regions, presents properties that require specific consideration when modeling: (i) strong rainfall intermittency, (ii) high variability of intensities within storms, (iii) strong spatiotemporal correlation of intensities, and (iv) marked seasonality of storm properties. In this article, improvements for an existing statistico-dynamic rainfall generator that models convective storms are presented. Notable novelties include (i) the ability to model precipitation event timing, (ii) an improved temporal disaggregation scheme representing the rainfall distribution at sub-event scales, and (iii) using covariates to reflect seasonal changes in precipitation occurrence and marginal distribution parameters. Extreme values are explicitly considered in the distribution of storm event intensities. The simulator is calibrated and validated using 28 years of five-minute precipitation data from the 30 rain gauge AMMA-CATCH network in the Sahelian region of southwest Niger. Both large propagative systems and smaller local convective precipitation are generated. Results show that simulator improvements coherently represent the local climatology. The simulator can generate scenarios for impact studies with accurate representation of convective precipitation characteristics.

scholarly journals High-resolution measurements of atmospheric molecular hydrogen and its isotopic composition at the West African coast of Mauritania

2012 ◽  
Vol 9 (12) ◽  
pp. 18799-18829
Author(s):  
S. Walter ◽  
A. Kock ◽  
T. Röckmann
Keyword(s):  
High Resolution ◽  
Isotopic Composition ◽  
Molecular Hydrogen ◽  
H2 Production ◽  
West African ◽  
Mixing Ratio ◽  
The West ◽  
Isotopic Signatures ◽  
West African Coast ◽  
African Coast

Abstract. Oceans are a net source of molecular hydrogen (N2) to the atmosphere, where nitrogen (N2) fixation is assumed to be the main biological production pathway besides photochemical production from organic material. The sources can be distinguished using isotope measurements because of clearly differing isotopic signatures of the produced hydrogen. Here we present the first ship-borne measurements of atmospheric molecular H2 mixing ratio and isotopic composition at the West African coast of Mauritania (16–25° W, 17–24° N). This area is one of the biologically most active regions of the world's oceans with seasonal upwelling events and characterized by strongly differing hydrographical/biological properties and phytoplankton community structures. The aim of this study was to identify areas of H2 production and distinguish H2 sources by isotopic signatures of atmospheric H2. Besides this a diurnal cycle of atmospheric H2 was investigated. For this more than 100 air samples were taken during two cruises in February 2007 and 2008, respectively. During both cruises a transect from the Cape Verde Island towards the Mauritanian Coast was sampled. In 2007 additionally four days were sampled with a high resolution of one sample per hour. Our results clearly indicate the influence of local sources and suggest the Banc d'Arguin as a pool for precursors for photochemical H2 production, whereas N2 fixation could not be identified as a H2 source during these two cruises. With our experimental setup we could demonstrate that variability in diurnal cycles is probably influenced and biased by released precursors for photochemical H2 production and the origin of air masses. This means for further investigations that just measuring the mixing ratio of H2 is insufficient to explain the variability of a diurnal cycle and support is needed, e.g. by isotopic measurements. However, measurements of H2 mixing ratios, which are easy to conduct online during ship cruises could be a helpful tool to easily identify production areas of biological precursors such as VOC's for further investigations.

Rainfall Anomaly over the Lee Side of Mount Carmel (Israel) and the Associated Wind Field

1997 ◽  
Vol 36 (6) ◽  
pp. 748-762 ◽  
Author(s):  
Yair Goldreich ◽  
Ariel Freundlich ◽  
Pinhas Alpert
Keyword(s):  
Wind Field ◽  
Rain Gauge ◽  
Rainfall Anomaly ◽  
Windward Side ◽  
Two Dimensional ◽  
Local Enhancement ◽  
Flow Disturbance ◽  
Model Simulations ◽  
Israel Experience ◽  
Wind Measurements

Abstract Yagur and other rain gauge stations located on the lee side of Mount Carmel in Israel experience much higher amounts of precipitation than those measured on the windward side of the mountain at a similar altitude and more rain than stations on the mountain itself. This phenomenon is consistently observed, and in the current study it is investigated primarily by means of simultaneous rain–wind observations and by using a two-dimensional simplified orographic model. Orographic model simulations suggest the existence of a flow disturbance at the lee of Mount Carmel, which might cause local rain enhancement. Results from the anemograph placed at Yagur, along with other wind measurements in the Carmel region, support the findings of this model. Observations depict the disturbed flow that occurred at the lee of Mount Carmel and was associated with rain enhancement. The channeled flow caused horizontal convergence, which is in accordance with the second hypothesis. Observations during the rainy periods indicate that the rain enhancement in Yagur is associated with the ridge-parallel flow on the lee side of the mountain. It is hypothesized that the horizontal convergence of the leeside flow with the flow over the mountain causes the local enhancement of precipitation.

scholarly journals Identifying Flow Pathways for Phosphorus Transport Using Observed Event Forensics and the CRAFT (Catchment Runoff Attenuation Flux Tool)

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1081 ◽  
Author(s):  
Russell Adams ◽  
Paul Quinn ◽  
Nick Barber ◽  
Sean Burke
Keyword(s):  
Overland Flow ◽  
Forensic Analysis ◽  
Frequency Resolution ◽  
Storm Event ◽  
Hydrograph Separation ◽  
Near Surface ◽  
Headwater Catchments ◽  
Additional Tool ◽  
Flow Pathways ◽  
Catchment Runoff

Identifying key flow pathways is critical in order to understand the transport of Phosphorus (P) from agricultural headwater catchments. High frequency/resolution datasets from two such catchments in Northwest England enabled individual events to be examined to identify the flow (Q) and Total P (TP) and Total Reactive P (TRP) dynamics (forensics). Detailed analysis of multiple flow and water quality parameters is referred to here as the event forensics. Are there more flow pathways than just surface runoff (dominated by overland flow) and baseflow (mainly groundwater) contributing at the outlet of these catchments? If so, hydrograph separation alone will not be sufficient. This forensic analysis gives a classification of four storm event response types. Three classes are based on the balance of old and new water giving enrichment and dilution of TRP pattern in the subsurface flow. A fourth type was observed where a plume of nutrient is lost to the channel when there is no observed flow. Modelling is also essential when used in combination with the event forensics as this additional tool can identify distinct flow pathways in a robust form. A case study will apply the Catchment Runoff Attenuation Flux Tool (CRAFT) to two contrasting small headwater catchments in Northwest England, which formed part of the Demonstration Test Catchments (DTC) Programme. The model will use data collected during a series of events observed in the two catchments between the period 2012 and 2014. It has the ability to simulate fast near surface (that can represent flow in the upper soil horizons and field drains) and event subsurface soil flow, plus slower groundwater discharge. The model can capture P enrichment, dilution and the role that displacement of “old” P rich water has during events by mixing these flows. CRAFT captures the dominant flow and P fluxes as seen in the forensic analysis and can create outputs including smart export coefficients (based on flow pathways) that can be conveyed to policy makers to better underpin decision making.

scholarly journals A study on WRF radar data assimilation for hydrological rainfall prediction

2013 ◽  
Vol 17 (8) ◽  
pp. 3095-3110 ◽  
Author(s):  
J. Liu ◽  
M. Bray ◽  
D. Han
Keyword(s):  
Data Assimilation ◽  
Real Time ◽  
Meteorological Data ◽  
Weather Radar ◽  
Radar Data ◽  
Rain Gauge ◽  
Radar Reflectivity ◽  
Storm Event ◽  
Hydrological Applications ◽  
Radar Data Assimilation

Abstract. Mesoscale numerical weather prediction (NWP) models are gaining more attention in providing high-resolution rainfall forecasts at the catchment scale for real-time flood forecasting. The model accuracy is however negatively affected by the "spin-up" effect and errors in the initial and lateral boundary conditions. Synoptic studies in the meteorological area have shown that the assimilation of operational observations, especially the weather radar data, can improve the reliability of the rainfall forecasts from the NWP models. This study aims at investigating the potential of radar data assimilation in improving the NWP rainfall forecasts that have direct benefits for hydrological applications. The Weather Research and Forecasting (WRF) model is adopted to generate 10 km rainfall forecasts for a 24 h storm event in the Brue catchment (135.2 km2) located in southwest England. Radar reflectivity from the lowest scan elevation of a C-band weather radar is assimilated by using the three-dimensional variational (3D-Var) data-assimilation technique. Considering the unsatisfactory quality of radar data compared to the rain gauge observations, the radar data are assimilated in both the original form and an improved form based on a real-time correction ratio developed according to the rain gauge observations. Traditional meteorological observations including the surface and upper-air measurements of pressure, temperature, humidity and wind speed are also assimilated as a bench mark to better evaluate and test the potential of radar data assimilation. Four modes of data assimilation are thus carried out on different types/combinations of observations: (1) traditional meteorological data; (2) radar reflectivity; (3) corrected radar reflectivity; (4) a combination of the original reflectivity and meteorological data; and (5) a combination of the corrected reflectivity and meteorological data. The WRF rainfall forecasts before and after different modes of data assimilation are evaluated by examining the rainfall temporal variations and total amounts which have direct impacts on rainfall–runoff transformation in hydrological applications. It is found that by solely assimilating radar data, the improvement of rainfall forecasts are not as obvious as assimilating meteorological data; whereas the positive effect of radar data can be seen when combined with the traditional meteorological data, which leads to the best rainfall forecasts among the five modes. To further improve the effect of radar data assimilation, limitations of the radar correction ratio developed in this study are discussed and suggestions are made on more efficient utilisation of radar data in NWP data assimilation.

scholarly journals Measurement report: Methane (CH<sub>4</sub>) sources in Krakow, Poland: insights from isotope analysis

2021 ◽  
Author(s):  
Malika Menoud ◽  
Carina van der Veen ◽  
Jaroslaw Necki ◽  
Jakub Bartyzel ◽  
Barbara Szénási ◽  
...  
Keyword(s):  
Time Series ◽  
Isotopic Composition ◽  
Transport Model ◽  
Isotope Analysis ◽  
Ambient Air ◽  
Coal Extraction ◽  
Night Time ◽  
Isotopic Signatures ◽  
Ch4 Emissions ◽  
Gas Leaks

Abstract. Methane (CH4) emissions from human activities are a threat to the resilience of our current climate system, and to the adherence of the Paris Agreement goals. The stable isotopic composition of methane (δ13C and δ2H) allows to distinguish between the different CH4 origins. A significant part of the European CH4 emissions, 3.6 % in 2018, comes from coal extraction in Poland; the Upper Silesian Coal Basin (USCB) being the main hotspot. Measurements of CH4 mole fraction (χ(CH4)), δ13C and δ2H in CH4 in ambient air were performed continuously during 6 months in 2018 and 2019 at Krakow, Poland, 50 km east of the USCB. In addition, air samples were collected during parallel mobile campaigns, from multiple CH4 sources in the footprint area of the continuous measurements. The resulting isotopic signatures from sampled plumes allowed us to distinguish between natural gas leaks, coal mine fugitive emissions, landfill and sewage, and ruminants. The use of δ2H in CH4 is crucial to distinguish the fossil fuel emissions in the case of Krakow, because their relatively depleted δ13C values overlap with the ones of microbial sources. The observed χ(CH4) time series showed regular daily night-time accumulations, sometimes combined with irregular pollution events during the day. The isotopic signatures of each peak were obtained using the Keeling plot method, and generally fall in the range of thermogenic CH4 formation – with δ13C between −55.3 and −39.4 ‰ V-PDB, and δ2H between −285 and −124 ‰ V-SMOW. They compare well with the signatures measured for gas leaks in Krakow and USCB mines. The CHIMERE transport model was used to compute the CH4 and isotopic composition time series in Krakow, based on two emission inventories. The χ(CH4) are generally under-estimated in the model. The simulated isotopic source signatures, obtained with Keeling plots on each simulated peak using the EDGAR v5.0 inventory, indicate that a higher contribution from fuel combustion sources in EDGAR would lead to a better agreement. The isotopic mismatches between model and observations are mainly caused by uncertainties in the assigned isotopic signatures for each source category, and the way they are classified in the inventory. These uncertainties are larger for emissions close to the study site, which are more heterogenous than the ones advected from the USCB coal mines. Our isotope approach proves to be very sensitive in this region, thus helping to evaluate emission estimates.

scholarly journals New water fractions and transit time distributions at Plynlimon, Wales, estimated from stable water isotopes in precipitation and streamflow

2019 ◽  
Author(s):  
Julia L. A. Knapp ◽  
Colin Neal ◽  
Alessandro Schlumpf ◽  
Margaret Neal ◽  
James W. Kirchner
Keyword(s):  
Time Series ◽  
Stable Isotope ◽  
Transit Time ◽  
Transport Processes ◽  
Water Isotopes ◽  
Data Sets ◽  
Hydrograph Separation ◽  
Stable Water Isotopes ◽  
Isotope Data ◽  
Water Fractions

Abstract. Long-term, high-frequency time series of passive tracers in precipitation and streamflow are essential for quantifying catchment transport and storage processes, but few such data sets are publicly available. Here we describe, present, and make available to the public two extensive data sets of stable water isotopes in streamflow and precipitation at the Plynlimon experimental catchments in mid-Wales. Stable isotope data are available at 7-hourly intervals for 17 months, and at weekly intervals for 4.25 years. Precipitation isotope values were highly variable in both data sets, and the high temporal resolution of the 7-hourly streamwater samples revealed rich isotopic dynamics that were not captured by the weekly sampling. We used ensemble hydrograph separation to calculate new water fractions and transit time distributions from both data sets. Transit time distributions estimated by ensemble hydrograph separation were broadly consistent with those estimated by spectral fitting methods, suggesting that they can reliably quantify the contributions of recent precipitation to streamflow. We found that on average, roughly 3 % of streamwater was made up of precipitation that fell within the previous 7 hours, and 13–15 % of streamwater was made up of precipitation that fell within the previous week. The contributions of recent precipitation to streamflow were highest during large events, as illustrated by comparing new water fractions for different discharges and precipitation rates. This dependence of new water fractions on water fluxes was also reflected in their seasonal variations, with lower new water fractions and more damped catchment transit time distributions in spring and summer compared to fall and winter. We also compared new water fractions obtained from stable water isotopes against those obtained from concentrations of chloride, a solute frequently used as a passive tracer of catchment transport processes. After filtering the chloride data for dry deposition effects, we found broadly similar new water fractions using chloride and stable water isotopes, indicating that these different tracers may yield similar inferences about catchment storage and transport, if potentially confounding factors are eliminated. These stable isotope time series comprise some of the longest and most detailed publicly available catchment isotope data sets. They complement extensive solute data sets that are already publicly available for Plynlimon, enabling a wide range of future analyses of catchment behavior.

scholarly journals Enzyme specific isotope effects of the Nap and Nar nitrate reductases

2020 ◽  
Author(s):  
Ciara K. Asamoto ◽  
Kaitlin R. Rempfert ◽  
Victoria H. Luu ◽  
Adam D. Younkin ◽  
Sebastian H. Kopf
Keyword(s):  
Nitrogen Isotopes ◽  
Isotope Effects ◽  
Terrestrial Ecosystems ◽  
Isotopic Signature ◽  
Main Process ◽  
Isotopic Signatures ◽  
Isotopic Pattern ◽  
Almost All ◽  
End Members ◽  
Nitrate Reductases

AbstractDissimilatory nitrate reduction (DNR) to nitrite is the first step in denitrification, the main process through which bioavailable nitrogen is removed from ecosystems. DNR fractionates the stable isotopes of nitrogen (14N, 15N) and oxygen (16O, 18O) and thus imparts an isotopic signature on residual pools of nitrate in many environments. Data on the relationship between the resulting isotopic pattern in oxygen versus nitrogen isotopes (18ε / 15ε) suggests systematic differences exist between marine and terrestrial ecosystems that are not fully understood. DNR can be catalyzed by both cytosolic (Nar) and periplasmic (Nap) nitrate reductases, and previous work has revealed differences in their 18ε / 15ε isotopic signatures. In this study, we thus examine the 18ε / 15ε of six different nitrate-reducing microorganisms that encode Nar, Nap or both enzymes, as well gene deletion mutants of the enzymes’ catalytic subunits (NarG and NapA) to test the hypothesis that enzymatic differences alone could explain the environmental observations. We find that the distribution of the 18ε / 15ε fractionation ratios of all examined nitrate reductases form two distinct, non-overlapping peaks centered around a 18ε / 15ε proportionality of 0.55 and a 18ε / 15ε proportionality of 0.91, respectively. All Nap reductases studied to date cluster around the lower proportionality (0.55) and none exceed a 18ε / 15ε proportionality of 0.68. Almost all Nar reductases, on the contrary, cluster tightly around the higher proportionality (0.91) with no values below a 18ε / 15ε proportionality of 0.84 with the notable exception of the Nar reductases from the genus Bacillus which fall around 0.62 and thus closely resemble the isotopic fingerprints of the Nap reductases. Our findings confirm the existence of two remarkably distinct isotopic end-members in the dissimilatory nitrate reductases that could indeed explain differences in coupled N and O isotope fractionation between marine and terrestrial systems, and almost but not fully match reductase phylogeny.

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