scholarly journals Variability in isotopic composition of base flow in two headwater streams of the southern Appalachians

2016 ◽  
Vol 52 (6) ◽  
pp. 4264-4279 ◽  
Author(s):  
Nitin K. Singh ◽  
Ryan E. Emanuel ◽  
Brian L. McGlynn
Keyword(s):  
Isotopic Composition ◽  
Headwater Streams ◽  
Base Flow ◽  
Southern Appalachians

Temporal Variations of Isotopic Composition of Glacier-River Water During Summer: Observations at Austre Okstindbreen, Okstindan, Norway

1988 ◽  
Vol 34 (118) ◽  
pp. 309-317 ◽  
Author(s):  
Wilfred H. Theakstone
Keyword(s):  
Isotopic Composition ◽  
River Water ◽  
Temporal Variations ◽  
Surface Melting ◽  
Base Flow ◽  
Strongly Correlated ◽  
Drainage Systems ◽  
Fine Weather ◽  
Air Temperatures ◽  
Glacier Ice

AbstractThe isotopic composition of river water discharging from the Norwegian glacier, Austre Okstindbreen, in summer varies on both daily and longer-term scales. Most δ18o values of samples from the principal river are within the range −12.5 to −14.0‰). Because new snow tends to be relatively depleted of 8180, water leaving the glacier early in the summer has low δ18O values. Subsequently, values rise as contributions of old snow, glacier ice, and their melt waters, which are isotopically heavier (median δ18O values generally above −12.0‰) dilute the δ18O depleted base-flow component of discharge, a mixture of waters with different histories of formation, storage, and transit. Accumulation-area melting contributes significantly to river discharge. Towards the end of the summer, as surface melting declines, δ18O values tend to fall. Between-year differences of within-summer trends reflect differences of development of the glacier’s drainage systems. The drainage systems are affected by outbursts from a glacier-dammed lake. During fine weather, δ18ovariations follow the diurnal cycle of surface melting: they are strongly correlated with, but lag behind, air temperatures. Perturbations during rainfall cannot be explained simply in terms of the isotopic composition of the precipitation, since low values may be associated with isotopically heavy rainfall. Displacement of water previously stored within or below the glacier may account for the anomaly. Contrasts of composition characterize different rivers leaving the glacier, because the relative contributions of various water sources differ.

Air-stream temperature correlation in forested and urban headwater streams in the Southern Appalachians

2014 ◽  
Vol 29 (6) ◽  
pp. 1110-1118 ◽  
Author(s):  
Chuanhui Gu ◽  
William P. Anderson ◽  
Jeffrey D. Colby ◽  
Christopher L. Coffey
Keyword(s):  
Headwater Streams ◽  
Stream Temperature ◽  
Southern Appalachians ◽  
Temperature Correlation ◽  
Air Stream

Long-term dynamics of organic matter and elements exported as coarse particulates from two Caribbean montane watersheds

2012 ◽  
Vol 28 (2) ◽  
pp. 127-139 ◽  
Author(s):  
T. Heartsill Scalley ◽  
F. N. Scatena ◽  
S. Moya ◽  
A. E. Lugo
Keyword(s):  
Organic Matter ◽  
Particulate Organic Matter ◽  
Headwater Streams ◽  
Structural Complexity ◽  
Base Flow ◽  
Coarse Particulate Organic Matter ◽  
North East ◽  
Storm Flow ◽  
Before And After

Abstract:In heterotrophic streams the retention and export of coarse particulate organic matter and associated elements are fundamental biogeochemical processes that influence water quality, food webs and the structural complexity of forested headwater streams. Nevertheless, few studies have documented the quantity and quality of exported organic matter over multiple years and under a range of conditions that includes both droughts and hurricanes. This study quantifies the export of coarse particulate organic matter (CPOM, > 12.7 mm), over 18 y in two headwater streams in north-east Puerto Rico. Daily exports ranged from 0 to over 170 g ha−1 d−1 and averaged 7.39 g ha−1 d−1, with similar amounts coming from leaves (3.5 g ha−1 d−1) and wood (3.2 g ha−1 d−1). Export of coarse particulate organic carbon was 3.0 g ha−1 d−1 which constitutes only 1.32% of carbon exports. Most litter falling into the streams was processed in place as only 2.3% of the leaf litter falling directly into these perennial channels was exported as CPOM. On average, 6 wk y−1 had no exports while events transporting more than 10 g ha−1 d−1 occurred every 2.8 mo. Instead of a single annual pulse as observed in deciduous systems, there were annual peaks in CPOM exports during May and September and less export during the drier period from December to February. Ratios of C:N in the exported material were highest in the driest month and lowest during rainy months, while leaf fluxes for nitrogen, phosphorus and calcium were highest in rainy months and lowest during February. Although median daily exports and exports during low- and base-flow periods were similar before and after Hugo, after 16 y exports during moderate- and high-flow periods were still less than those in the 2 y prior to the hurricane. Our observations indicate a system with high rates of internal processing that quickly returns to median daily conditions following hurricanes but requires several decades for storm-flow exports to return to pre-disturbance conditions and indicates that the long-term pattern of CPOM export is associated with the level of maturity of watershed vegetation.

scholarly journals Macropore flow of old water revisited: where does the mixing occur at the hillslope scale?

2012 ◽  
Vol 9 (4) ◽  
pp. 4333-4380 ◽  
Author(s):  
J. Klaus ◽  
E. Zehe ◽  
M. Elsner ◽  
C. Külls ◽  
J. J. McDonnell
Keyword(s):  
Stable Isotope ◽  
Isotopic Composition ◽  
Soil Water ◽  
Irrigation Water ◽  
Initial Conditions ◽  
Soil Depth ◽  
Lower Boundary ◽  
Base Flow ◽  
Macropore Flow ◽  
Hillslope Scale

Abstract. The mechanisms allowing the rapid release of stored water to streams are poorly understood. Here we use a tile drained field site to combine naturally structured soils at the hillslope scale with the advantage of at least partly controlled lower boundary conditions. We performed a series of three irrigation experiments combining hydrometric measurements with stable isotope and bromide tracers to better understand macropore-matrix interactions and stored water release processes at the hillslope scale. Stable isotope concentrations were monitored in the irrigation water, the tile drain discharge and the soil water before and after the experiment. Bromide was measured at mainly every 5–15 min in the tile drain hydrograph. Different initial conditions for each experiment were used to examine how pre-event soil moisture conditions influenced flow and transport. Different amounts of irrigation water were necessary to increase tile drain discharge above the base flow level. Hydrograph separation based on bromide data revealed that irrigation water contributions to peak tile drain discharge were on the order of 20%. Oxygen-18 and deuterium data were consistent with the bromide data and showed that pre-event soil water contributed significantly to the tile drain event flow. However, the isotopic composition of soil water converged towards the isotopic composition of irrigation water through the course of the experiment. Mixing calculations revealed that by the end of the irrigation experiments 20% of the soil water in the entire profile was irrigation water. The isotopic data showed that the pre-event water in the tile drain was mobilized in 20–40 cm soil depth were the macropore-matrix interaction leads to an initiation of macropore flow after a moisture threshold is exceeded.

scholarly journals Weertman regelation, multiple refreezing events and the isotopic evolution of the basal ice layer

1993 ◽  
Vol 39 (132) ◽  
pp. 275-291 ◽  
Author(s):  
Bryn Hubbard ◽  
Martin Sharp
Keyword(s):  
Isotopic Composition ◽  
Isotopic Fractionation ◽  
Base Flow ◽  
Isotope Enrichment ◽  
Heavy Isotope ◽  
Fractionation Process ◽  
Basal Ice ◽  
Internal Morphology ◽  
Isotopic Evolution ◽  
Simulation Results

AbstractA simple model is developed to simulate the isotopic fractionation which accompanies Weertman regelation at the bed of temperate-based glaciers. The fractionation equations of Jouzel and Souchez (1982) are applied to multiple refreezing events over measured glacier-bed profiles, and mass balance is maintained as the basal ice and meltwater produced at one bedrock hummock enter the next. Simulation results indicate that undeformed regelation ice layers are on the order of millimetres to centimetres thick, often being completely melted at the stoss face of certain hummocks and exceptionally reaching a thickness in excess of 10 cm. Neither the internal morphology nor the isotopic composition of these layers is constant, but both vary down-glacier in accordance with bedrock configuration. A glacier-wide fractionation process is identified whereby heavy isotopes are preferentially removed from the basal meltwater film and incorporated into the basal ice. This process might go some way to explaining the anomalously “light” isotopic composition measured in base-flow waters leaving some glaciers. Vertical isotope profiles through undeformed basal ice layers are reconstructed and show that significant isotopic excursions can occur at a scale of millimeteres, while the range of isotopic compositions within such multi-layered regelation ice is greater than that which would occur in ice produced by a single refreezing event. In circumstances where the regelation system is disrupted by removal of film waters into a network of linked cavities, it is found that the remaining basal ice may be significantly enriched in heavy isotopes relative to the composition of the initial mass inputs to the system. Heavy isotope enrichment of this magnitude and consideration of the thickness of the basal ice layers concerned may explain the absence of recorded basal ice samples heavy enough to have been formed in equilibrium with subglacial precipitates sampled at one of the sites (Glacier de Tsanfleuron) and reported in an earlier paper.

scholarly journals Weertman regelation, multiple refreezing events and the isotopic evolution of the basal ice layer

1993 ◽  
Vol 39 (132) ◽  
pp. 275-291 ◽  
Author(s):  
Bryn Hubbard ◽  
Martin Sharp
Keyword(s):  
Isotopic Composition ◽  
Isotopic Fractionation ◽  
Base Flow ◽  
Isotope Enrichment ◽  
Heavy Isotope ◽  
Fractionation Process ◽  
Basal Ice ◽  
Internal Morphology ◽  
Isotopic Evolution ◽  
Simulation Results

AbstractA simple model is developed to simulate the isotopic fractionation which accompanies Weertman regelation at the bed of temperate-based glaciers. The fractionation equations of Jouzel and Souchez (1982) are applied to multiple refreezing events over measured glacier-bed profiles, and mass balance is maintained as the basal ice and meltwater produced at one bedrock hummock enter the next. Simulation results indicate that undeformed regelation ice layers are on the order of millimetres to centimetres thick, often being completely melted at the stoss face of certain hummocks and exceptionally reaching a thickness in excess of 10 cm. Neither the internal morphology nor the isotopic composition of these layers is constant, but both vary down-glacier in accordance with bedrock configuration. A glacier-wide fractionation process is identified whereby heavy isotopes are preferentially removed from the basal meltwater film and incorporated into the basal ice. This process might go some way to explaining the anomalously “light” isotopic composition measured in base-flow waters leaving some glaciers. Vertical isotope profiles through undeformed basal ice layers are reconstructed and show that significant isotopic excursions can occur at a scale of millimeteres, while the range of isotopic compositions within such multi-layered regelation ice is greater than that which would occur in ice produced by a single refreezing event. In circumstances where the regelation system is disrupted by removal of film waters into a network of linked cavities, it is found that the remaining basal ice may be significantly enriched in heavy isotopes relative to the composition of the initial mass inputs to the system. Heavy isotope enrichment of this magnitude and consideration of the thickness of the basal ice layers concerned may explain the absence of recorded basal ice samples heavy enough to have been formed in equilibrium with subglacial precipitates sampled at one of the sites (Glacier de Tsanfleuron) and reported in an earlier paper.

scholarly journals Isotopic analysis of water cycle elements in different land covers in a small headwater watershed

Water Policy ◽  
2017 ◽  
Vol 19 (3) ◽  
pp. 574-585 ◽  
Author(s):  
Si-min Qu ◽  
Shuai Shan ◽  
Xi Chen ◽  
Min-min Zhou ◽  
Han Liu
Keyword(s):  
Surface Water ◽  
Isotopic Composition ◽  
Temporal Variation ◽  
Water Cycle ◽  
Isotopic Analysis ◽  
Base Flow ◽  
Land Uses ◽  
Hydrograph Separation ◽  
Isotopic Variation ◽  
Variation Range

In this study, comparisons of isotopic variation of rainfall, throughfall, surface water, and groundwater were conducted in the Meilin watershed, which represents two different land uses, chestnut wood and bamboo. Also, isotopic differences between rainfall and throughfall were identified in these sub-watersheds. The results showed that the isotopic value of incremental rainfall, incremental throughfall and surface water exhibited a marked temporal variation in the selected sub-watersheds. The throughfall isotopic variation range was smaller than that of rainfall, which may result from the different production process between rainfall and throughfall. However, the isotopic composition difference between rainfall and throughfall resulting from different land uses was insignificant. The range of isotopic composition variation of surface water was not the same as that of rainfall, indicating that surface water came from a mix of precipitation and water stored before the rainfall event. The temporal variation of the isotopic composition of groundwater was small, implying that the influence of different land uses on groundwater isotopic composition was insignificant. The total variation range of δ2H and δ18O of groundwater was smaller than that of surface water and sequential incremental rainfall, which means the δ18O of groundwater can be replaced by that of base flow before the event in the hydrograph separation.

scholarly journals Caecidotea burkensis, new species, a unique subterranean isopod from Burke’s Garden, with a synthesis of the biogeography and evolution of southwestern Virginia asellids

2021 ◽  
Vol 83 (2) ◽  
pp. 78-87
Author(s):  
Salisa Lewis ◽  
Jerry Lewis ◽  
William Orndorff
Keyword(s):  
Species Richness ◽  
New Species ◽  
River Basin ◽  
Headwater Streams ◽  
Type Locality ◽  
Southern Appalachians ◽  
Group A ◽  
Subterranean Species ◽  
A New Species

Caecidotea burkensis, a new species of subterranean asellid isopod, is described and illustrated from material collected from Lawson Cave, in Burke’s Garden, Tazewell County, Virginia. The type-locality in Burke’s Garden is located within the highest mountain basin in the southern Appalachians. Burke’s Garden is a unique, geologically isolated area encompassing one of the headwater streams of the New River basin. Phylogenetically, the isopod is a member of the forbesi Group, a clade comprised primarily of epigean species. The complex mountain valleys and coves of southwestern Virginia are an area of intense speciation among asellids that have produced a bizarre array of cavernicolous species belonging to groups of otherwise epigean isopods. In addition to a few subterranean species of the Caecidotea cannula and stygia Groups, the Lirceus hargeri Group possesses over a dozen species endemic to caves and springs in the region, mostly only now in the process of being discovered and described. With so much species richness, syntopy of two, or even three, asellid species is commonplace in caves and springs in southwestern Virginia.

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