scholarly journals Identifying residence times and streamflow generation processes using δ<sup>18</sup>O and δ<sup>2</sup>H in meso-scale catchments in the Abay/Upper Blue Nile, Ethiopia

2013 ◽  
Vol 10 (8) ◽  
pp. 10333-10377 ◽  
Author(s):  
S. Tekleab ◽  
J. Wenninger ◽  
S. Uhlenbrook
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Spring Water ◽  
Residence Times ◽  
Nile Basin ◽  
Source Areas ◽  
Mean Residence Times ◽  
Seasonal Time Scale ◽  
Meso Scale

Abstract. Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin. Stable isotope composition in precipitation, spring water and streamflow were analyzed (i) to characterize the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time of water using a sine wave regression approach; and (iii) to identify runoff components using classical two component hydrograph separations at a seasonal time scale. The results show that the isotopic composition of precipitation exhibit marked seasonal variations, which suggests different sources of moisture generation for the rainfall in the study area. The Atlantic–Indian ocean, Congo basin, and the Sud swamps are the likely the potential moisture source areas during the main rainy (summer) season. While, the Indian–Arabian, and Mediterranean Sea moisture source areas during little rain (spring), and dry (winter) seasons. The spatial variation of the isotopic composition is affected by the amount effect and to less extent by altitude and temperature effects. A mean altitude effect of −0.12‰ (100 m)−1 for 18O and −0.58‰ (100 m)−1 for 2H were discernable in precipitation isotope composition. The seasonal variations of the isotopic signature of the spring water exhibit a damped response as compared to the river waters, which shows that the spring water has longer residence times than the river water. Results from the hydrograph separation at a seasonal time scale indicate the dominance of event water with an average of 71% and 64% of the total runoff during the wet season in the Chemoga and Jedeb catchment, respectively. The stable isotope compositions of streamflow samples were damped compared to the input function of precipitation for both catchments and this damping was used to estimate mean residence times of stream water of 4.1 and 6.0 months at the Chemoga and Jedeb catchment outlet, respectively. Short mean residence times and high proportions of event water components suggest catchment management measure aiming at reduction of overland flow/soil erosion and increasing of soil water retention and recharge to enable sustainable development in these agricultural dominated catchments.

scholarly journals Characterisation of stable isotopes to identify residence times and runoff components in two meso-scale catchments in the Abay/Upper Blue Nile basin, Ethiopia

2014 ◽  
Vol 18 (6) ◽  
pp. 2415-2431 ◽  
Author(s):  
S. Tekleab ◽  
J. Wenninger ◽  
S. Uhlenbrook
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Isotopic Composition ◽  
Residence Times ◽  
Nile Basin ◽  
Blue Nile ◽  
Source Areas ◽  
Blue Nile Basin ◽  
Mean Residence Times ◽  
Meso Scale

Abstract. Measurements of the stable isotopes oxygen-18 (18O) and deuterium (2H) were carried out in two meso-scale catchments, Chemoga (358 km2) and Jedeb (296 km2) south of Lake Tana, Abay/Upper Blue Nile basin, Ethiopia. The region is of paramount importance for the water resources in the Nile basin, as more than 70% of total Nile water flow originates from the Ethiopian highlands. Stable isotope compositions in precipitation, spring water and streamflow were analysed (i) to characterise the spatial and temporal variations of water fluxes; (ii) to estimate the mean residence time of water using a sine wave regression approach; and (iii) to identify runoff components using classical two-component hydrograph separations on a seasonal timescale. The results show that the isotopic composition of precipitation exhibits marked seasonal variations, which suggests different sources of moisture generation for the rainfall in the study area. The Atlantic–Indian Ocean, Congo basin, Upper White Nile and the Sudd swamps are the potential moisture source areas during the main rainy (summer) season, while the Indian–Arabian and Mediterranean Sea moisture source areas during little rain (spring) and dry (winter) seasons. The spatial variation in the isotopic composition is influenced by the amount effect as depicted by moderate coefficients of determination on a monthly timescale (R2 varies from 0.38 to 0.68) and weak regression coefficients (R2 varies from 0.18 to 0.58) for the altitude and temperature effects. A mean altitude effect accounting for −0.12‰/100 m for 18O and −0.58‰/100 m for 2H was discernible in precipitation isotope composition. Results from the hydrograph separation on a seasonal timescale indicate the dominance of event water, with an average of 71 and 64% of the total runoff during the wet season in the Chemoga and Jedeb catchments, respectively. Moreover, the stable isotope compositions of streamflow samples were damped compared to the input function of precipitation for both catchments. This damping was used to estimate mean residence times of stream water of 4.1 and 6.0 months at the Chemoga and Jedeb catchment outlets, respectively. Short mean residence times and high fractions of event water components recommend catchment management measures aiming at reduction of overland flow/soil erosion and increasing of soil water retention and recharge to enable sustainable development in these agriculturally dominated catchments.

scholarly journals Measurement report: Spatial variability of northern Iberian rainfall stable isotope values – investigating atmospheric controls on daily and monthly timescales

2021 ◽  
Vol 21 (13) ◽  
pp. 10159-10177
Author(s):  
Ana Moreno ◽  
Miguel Iglesias ◽  
Cesar Azorin-Molina ◽  
Carlos Pérez-Mejías ◽  
Miguel Bartolomé ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Air Temperature ◽  
Isotope Composition ◽  
Significant Negative Correlation ◽  
Relative Role ◽  
Northern Spain ◽  
Mass Source ◽  
Highly Correlated

Abstract. For the first time, this article presents a large dataset of precipitation isotopic measurements (δ18Op and δ2Hp) sampled every day or 2 d from seven sites on a west-to-east transect across northern Spain for 2010–2017. The main aim of this study is to (1) characterize the rainfall isotopic variability in northern Spain at daily and monthly timescales and (2) assess the principal factors influencing rainfall isotopic variability. The relative role of air temperature and rainfall in determining the stable isotope composition of precipitation changes along the west-to-east transect, with air temperature being highly correlated with δ18Op at daily and monthly timescales, while a few sites along the transect show a significant negative correlation with precipitation. The highest air temperature–δ18Op dependency is found for a station located in the Pyrenees. Frontal systems associated with North Atlantic cyclones are the dominant mechanism inducing precipitation in this region, particularly in winter. This study allows an exploration of the role of air mass source and trajectory in determining the isotopic composition of rainfall in northern Iberia by characterizing the moisture uptake for three of the seven stations. The importance of continental versus marine moisture sources is evident, with clear seasonal and spatial variations. In addition, the type of precipitation (convective versus frontal rainfall) plays a key role, with convective rainfall associated with higher δ18Op values. This comprehensive spatiotemporal approach to analyzing the rainfall isotopic composition represents another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a paleoclimate and hydrological tracer.

Isotope-age-dating of alpine spring water and global change : Evidence from temperature, chemistry and tritium data

2020 ◽  
Author(s):  
Martin Kralik ◽  
Erika Papp
Keyword(s):  
Land Use ◽  
Global Change ◽  
Water Temperature ◽  
Air Temperature ◽  
Land Use Changes ◽  
Spring Water ◽  
Residence Times ◽  
Temperature Changes ◽  
On Line ◽  
Mean Residence Times

&lt;p&gt;Global air-temperature changes over the last 150 years and in particular during the last 30 &amp;#8211; 40 years are well documented world-wide. In alpine areas in Europe the increase in air-temperature is even higher in the range of 2&amp;#176; C. Very few studies exist about groundwater temperature changes due to global warming. The increase or decrease in temperature at the point of discharge depends besides the air temperature at the time of infiltration on the amount of precipitation, the local meteorological conditions, the mean residence time, the land use, and the natural and anthropogenic heat flow during the passage underground.&lt;/p&gt;&lt;p&gt;Nearly no papers exist about the water quality changes due to global change impacts and Mean Residence Times (MRT). This is very difficult to evaluate due to missing long-term quality measurements and strong impacts by anthropogenic activities and land use changes. To avoid the complication by anthropogenic land use changes and activities the authors investigated the on-line discharge, temperature, and electric conductivity measurements as well as quarterly hydro-chemical and isotope analyses of 40 Alpine springs from a monitoring network all over the Austrian Alps (approx. 60,000 km&lt;sup&gt;2&lt;/sup&gt;). All the selected springs have a recharge area with no or minimal anthropogenic impacts during the last 30 &amp;#8211; 40 years. About 235,000 on-line measurements and 11,000 chemical analyses were evaluated for trends and compared to daily measurements at meteorological and surface water stations close to the recharge areas of the springs. To show the connection to the paleoclimatology changes of existing &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O measurements on precipitation and spring water was evaluated as well indicating altitudes of recharge areas in range of 500 &amp;#8211; 2400m.&lt;/p&gt;&lt;p&gt;Forty springs with a minimum record of 16 years have been selected for trend analysis over a period of 20 years (1993 &amp;#8211; 2013). 28 (74%) of the selected spring show a significant mean increase in water temperature of 0.34 &amp;#176;C in the range of 0.06 to 1.03 &amp;#176;C. This increase is half of the air- and water temperature increase in meteorological stations and surface waters close to the recharge areas of the investigated springs. The electric conductivity linearly increased in 21 (55%) of the investigated springs at about 4%. The discharge stayed the same in most springs. In 23 (72%) springs the content of dissolved oxygen decreased over these 20 years at about 9% percent.&lt;/p&gt;&lt;p&gt;The reasons of the changes in water-temperature, dissolved load and the oxygen content as well as the impact of different Mean Residence Times (MRT) will be discussed and interpreted.&lt;/p&gt;

Stable isotope composition of walleye: 15N accumulation with age and area-specific differences in δ13C

2001 ◽  
Vol 58 (6) ◽  
pp. 1253-1260 ◽  
Author(s):  
Nathanael C Overman ◽  
Donna L Parrish
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Carbon Isotope ◽  
Trophic Position ◽  
Isotope Composition ◽  
Isotope Analysis ◽  
Isotopic Fractionation ◽  
Stomach Content Analysis ◽  
Metabolic Effects ◽  
N Accumulation

Stable nitrogen and carbon isotope ratios were measured for walleye (Stizostedion vitreum) collected across Lake Champlain, Vermont, to determine relationships between isotopic composition and diet, location of capture, length, weight, and age. Variation in δ13C values reflected area-specific differences in isotopic composition of organisms collected across the lake. A critical assumption in the application of isotope techniques is that a predictable relationship exists between the diet and isotopic composition of an organism. Our results indicate that isotopic fractionation factors may not be independent of age as has largely been assumed. By combining stable nitrogen and carbon isotope analysis with conventional stomach content analysis, we documented significant age effects in the δ15N composition of adult walleye that were not attributable to observed changes in diet. Age accounted for 81% of the variation in δ15N values of walleye (ages 2–27, N = 65, δ15N range = 15.3–19.2‰), providing evidence supporting 15N accumulation over the life span of walleye. Therefore, the risk of making faulty inferences of trophic position and food web interactions based on δ15N values may be increased when age is unknown. Our results indicate that metabolic effects associated with age require greater consideration in applications of stable isotope analysis.

scholarly journals The O and H stable isotope composition of freshwaters in the British Isles. 2. Surface waters and groundwater

2003 ◽  
Vol 7 (2) ◽  
pp. 183-195 ◽  
Author(s):  
W. G. Darling ◽  
A. H. Bath ◽  
J. C. Talbot
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Isotopic Composition ◽  
Surface Waters ◽  
Isotope Composition ◽  
Weighted Average ◽  
Ice Age ◽  
Annual Rainfall ◽  
British Isles ◽  
Contour Maps

Abstract. The utility of stable isotopes as tracers of the water molecule has a long pedigree. The study reported here is part of an attempt to establish a comprehensive isotopic "baseline" for the British Isles as background data for a range of applications. Part 1 of this study (Darling and Talbot, 2003) considered the isotopic composition of rainfall in Britain and Ireland. The present paper is concerned with the composition of surface waters and groundwater. In isotopic terms, surface waters (other than some upland streams) are poorly characterised in the British Isles; their potential variability has yet to be widely used as an aid in hydrological research. In what may be the first study of a major British river, a monthly isotopic record of the upper River Thames during 1998 was obtained. This shows high damping of the isotopic variation compared to that in rainfall over most of the year, though significant fluctuations were seen for the autumn months. Smaller rivers such as the Stour and Darent show a more subdued response to the balance between runoff and baseflow. The relationship between the isotopic composition of rainfall and groundwater is also considered. From a limited database, it appears that whereas Chalk groundwater is a representative mixture of weighted average annual rainfall, for Triassic sandstone groundwater there is a seasonal selection of rainfall biased towards isotopically-depleted winter recharge. This may be primarily the result of physical differences between the infiltration characteristics of rock types, though other factors (vegetation, glacial history) could be involved. In the main, however, groundwaters appear to be representative of bulk rainfall within an error band of 0.5‰ δ18O. Contour maps of the δ18O and δ2H content of recent groundwaters in the British Isles show a fundamental SW-NE depletion effect modified by topography. The range of measured values, while much smaller than those for rainfall, still covers some ‰ for δ18O and 30‰ for δ2H. Over lowland areas the "altitude effect" is of little significance, but in upland areas is consistent with a range of –0.2 to –0.3‰ per 100 m increase in altitude. Groundwaters dating from the late Pleistocene are usually modified in δ18O and δ2H owing to the effects of climate change on the isotopic composition of rainfall and thus of recharge. Contour maps of isotopic variability prior to 10 ka BP, based on the relatively limited information available from the British Isles, allow a first comparison between groundwaters now and at the end of the last Ice Age. The position of the British Isles in the context of the stable isotope systematics of NW Europe is reviewed briefly. Keywords: Stable isotopes, surfacewaters, groundwater, British Isles

scholarly journals The Analysis of Short-Term Dataset of Water Stable Isotopes Provides Information on Hydrological Processes Occurring in Large Catchments from the Northern Italian Apennines

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1360 ◽  
Author(s):  
Cervi ◽  
Dadomo ◽  
Martinelli
Keyword(s):  
Stable Isotopes ◽  
Isotopic Composition ◽  
Sine Wave ◽  
Hydrological Processes ◽  
Water Molecules ◽  
Residence Times ◽  
Catchment Characteristics ◽  
Mean Residence Times ◽  
Italian Apennines ◽  
Short Time

This study discusses a dataset of water stable isotopes from precipitation (4 rain gauges) and surficial water (9 rivers) from the northern Italian Apennines, an area in which clay-rich bedrocks widely outcrop and the runoff response to precipitation events is very rapid. The dataset has been compiled starting from existing data that had previously been published in the literature and consists of monthly values of stable isotopes oxygen-18 (18O) and deuterium (2H) lasting over the period from January 2003 to December 2006 (precipitation) and from January 2006 to December 2007 (surficial water). For this period, mean residence times estimated by means of a sine-wave fitting technique make evident the significant differences over time spent by water molecules within the 9 catchments. Moreover, isotopic compositions of rivers deviated from those of precipitations revealing the influence of some catchment characteristics in differentiating the isotopic composition in rivers. Further correlations between mean residence times of river water and selected catchment characteristics reveal the role of orography and bedrocks in delaying the water molecules during their flow-paths. In addition, time series and cross–correlation analyses indicate a certain control by the main watershed divide on the isotopic composition of river waters, which is reflected in a progressive isotopic variation with longitude. The study shows that, despite using a short-time dataset (2-years for surficial water) of sparse stable isotopes can provide remarkable indications for depicting hydrological processes in large catchments made up of clay-rich bedrocks.

scholarly journals Isotopic composition of precipitation in Poland: a 44-year record

2019 ◽  
Vol 67 (6) ◽  
pp. 1637-1648 ◽  
Author(s):  
Marek Duliński ◽  
Kazimierz Różański ◽  
Anna Pierchała ◽  
Zbigniew Gorczyca ◽  
Michał Marzec
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Environmental Isotopes ◽  
Monthly Precipitation ◽  
Stable Isotope Composition ◽  
Tritium Content ◽  
European Continent ◽  
The North ◽  
The North Atlantic Oscillation

Abstract Isotopic composition of precipitation (2H/1H and 18O/16O isotope ratios, tritium content) is nowadays widely used in numerous applications of environmental isotopes—most notably in hydrology, climatology and biogeochemistry. Here we present a long record (44 years) of stable isotope composition and tritium content in monthly precipitation available for the Krakow station (southern Poland). Krakow is the only site in Poland for which long-term record of the isotopic composition of monthly precipitation is available. The tritium data are discussed here in the context of generally declining levels of bomb tritium in the global atmosphere and growing influence of technogenic emissions of this isotope. Two aspects of temporal variability of stable isotope composition of precipitation collected in Krakow are discussed here: (i) seasonality and (ii) interannual changes of δ18O and δ2H signal. Whereas the seasonality of stable isotope signal is generated mainly by seasonally varying the degree of rainout of air masses bringing moisture from the source regions (subtropical Atlantic Ocean) to the centre of the European continent, the North Atlantic Oscillation seems to govern interannual changes of δ18O and δ2H on the decadal timescale. Progressing warming of the local atmosphere, in the order of 1.8 °C in the past four decades, leaves its imprint in stable isotope signal measured in Krakow precipitation; the slope of isotope–temperature relationship is in the order of 0.50‰/°C for δ18O and 3.5‰/°C for δ2H.

Chromium Stable Isotope Panorama of Chondrites and Implications for Earth Early Accretion

2021 ◽  
Vol 923 (1) ◽  
pp. 94
Author(s):  
Ke Zhu ◽  
Frédéric Moynier ◽  
Conel M. O’D. Alexander ◽  
Jemma Davidson ◽  
Devin L. Schrader ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Isotope Composition ◽  
Acid Leaching ◽  
Building Blocks ◽  
Silicon Isotope ◽  
Stable Isotope Fractionation ◽  
Two Samples ◽  
Enstatite Chondrite ◽  
Enstatite Chondrites

Abstract We investigated the stable isotope fractionation of chromium (Cr) for a panorama of chondrites, including EH and EL enstatite chondrites and their chondrules and different phases (by acid leaching). We observed that chondrites have heterogeneous δ 53Cr values (per mil deviation of the 53Cr/52Cr from the NIST SRM 979 standard), which we suggest reflect different physical conditions in the different chondrite accretion regions. Chondrules from a primitive EH3 chondrite (SAH 97096) possess isotopically heavier Cr relative to their host bulk chondrite, which may be caused by Cr evaporation in a reduced chondrule-forming region of the protoplanetary disk. Enstatite chondrites show a range of bulk δ 53Cr values that likely result from variable mixing of isotopically different sulfide-silicate-metal phases. The bulk silicate Earth (δ 53Cr = –0.12 ± 0.02‰, 2SE) has a lighter Cr stable isotope composition compared to the average δ 53Cr value of enstatite chondrites (–0.05 ± 0.02‰, 2SE, when two samples out of 19 are excluded). If the bulk Earth originally had a Cr isotopic composition that was similar to the average enstatite chondrites, this Cr isotope difference may be caused by evaporation under equilibrium conditions from magma oceans on Earth or its planetesimal building blocks, as previously suggested to explain the magnesium and silicon isotope differences between Earth and enstatite chondrites. Alternatively, chemical differences between Earth and enstatite chondrite can result from thermal processes in the solar nebula and the enstatite chondrite-Earth, which would also have changed the Cr isotopic composition of Earth and enstatite chondrite parent body precursors.

scholarly journals Spatial variability of northern Iberian rainfall stable isotope values: Investigating climatic controls on daily and monthly timescales

2020 ◽  
Author(s):  
Ana Moreno ◽  
Miguel Iglesias ◽  
Cesar Azorin-Molina ◽  
Carlos Pérez-Mejías ◽  
Miguel Bartolomé ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Time Scales ◽  
Air Temperature ◽  
Isotope Composition ◽  
Source Region ◽  
Precipitation Amount ◽  
Relative Role ◽  
Northern Spain

Abstract. This article presents for the first time a large dataset of rainfall isotopic measurements (d18Op and d2Hp) sampled every day or every two days from seven sites in a west-to-east transect across northern Spain for 2010–2017. The main aim of this study is to: (1) characterize rainfall isotopic variability in northern Spain at daily and monthly time scales, and (2) assess the principal influencing factors determining rainfall isotopic variability. This comprehensive spatio-temporal approach allows exploring the role of air mass source in determining the isotopic composition of rainfall in northern Iberia by using back-trajectories; Atlantic fronts are found to be the dominant source of northern Iberia rain events studied. The relative role of air temperature and rainfall amount in determining the stable isotope composition of precipitation changes along the west-to-east transect. Air temperature appears to be the most significant influence on d18Op at daily and monthly time scales with the highest air temperature-d18Op dependency found for the Pyrenean station while a few sites in the transect show a significant negative correlation with precipitation amount. Distance from the coast, site elevation, and moisture source region (Atlantic versus Mediterranean) also significantly modulate the d18Op values and ranges but the type of precipitation (convective vs frontal rainfall) plays a key control, with convective rainfall associated with higher d18Op values. This dataset of the rainfall isotopic composition represents another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a palaeoclimate and hydrological tracer.

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