Modeling low-flow bedrock springs providing ecological habitats with climate change scenarios

Groundwater discharge areas, including low-flow bedrock aquifer springs, are ecologically important and can be impacted by climate change. The development of and results from a groundwater modeling study simulating fractured bedrock spring flow are presented. This was conducted to produce hydrological data for an ecohydrological study of an endangered species, Allegheny Mountain Dusky Salamanders (Desmognathus ochrophaeus), in southern Quebec, Canada. The groundwater modeling approach in terms of scale and complexity was strongly driven by the need to produce hydrological data for the related ecohydrological modeling. Flows at four springs at different elevations were simulated for recent past conditions (2006–2010) and for reference (1971–2000) and future (2041–2070) periods using precipitation and temperature data from ten climate scenarios. Statistical analyses of spring flow parameters including activity periods and duration of flow were conducted. Flow rates for the four simulated springs, located at different elevations, are predicted to increase between 2% and 46% and will be active (flowing) 1–2% longer in the future. A significant change (predominantly an increase) looking at the seasonality of the number of active days occurs in the winter (2–4.9%) and spring seasons (−0.6–6.5%). Greatest flow rates were produced from springs at elevations where sub-horizontal fractures intersect the ground surface. These results suggest an intensification of the spring activity at the study site in context of climate change by 2050, which provides a positive habitat outlook for the endangered salamanders residing in the springs for the future

Year-Round Schooling: A Catalyst for Pedagogical Change

In this article we argue that the implementation of a year-round school calendar served as a catalyst for innovations in teaching and learning and for school-level capacity-building by facilitating teachers' planning, formal and informal talk about teaching and learning, teamteaching, philosophically based programmatic changes, and a culture that supports innovation. We conclude that receptivity to change and ability to make conceptual links are keys to improving the learning environment for students and that whether the impetus is first- or second-order, structural or conceptual, is less important than is sometimes believed.Dans cet article, nous soutenons que la mise en oeuvre d'un calendrier scolaire qui s'étend sur douze mois a servi de catalyseur pour des innovations dans l'enseignement et l'apprentissage, ainsi que pour la création d'habiletés à l'échelle scolaire. En effet, une telle démarche a facilité: la planification de la part des enseignants, les conversations (formelles et informelles) au sujet de l'enseignement et de l'apprentissage, l'enseignement en équipes, l'application au programme de changements basés sur des idées philosophiques, et le développement d'une culture qui appuie l'innovation. Nous concluons d'abord que la réceptivité aux changements et l'habileté à imaginer des liens conceptuels constituent des facteurs clés pour l'amélioration de l'environnement d'apprentissage des élèves et ensuite, que la nature de l'impulsion (qu'elle soit de premier ou de second ordre, structurelle ou conceptuelle) importe moins que l'on a parfois tendance à croire

Évolution des lacs proglaciaires et déglaciation du Haut Saint-François, sud du Québec

Pendant la dernière déglaciation, un front glaciaire actif se retire vers l'amont de la haute vallée de la rivière Saint-François et vers l'aval de celle de la rivière au Saumon. Dans la vallée de la rivière Saint-François, le front glaciaire, qui recule exceptionnellement vers le nord-est, est en contact avec les eaux du lac proglaciaire Memphrémagog, alors barré dans la partie aval du bassin par la masse principale de l'indandsis. Le lobe ainsi confiné dans la vallée de la rivière Saint-François endigue, dans le bassin de la rivière au Saumon, un lac proglaciaire latéral contrôlé par des cols et des chenaux le long du front. La récession du lobe est marquée par des récurrences locales qui ont mis en place des moraines à East-Angus et à Weedon. Après le retrait du lobe, au-delà du niveau du lac proglaciaire Memphrémagog, un lac de barrage morainique persiste au contact de la glace, dans la région de Weedon.The déglaciation pattern of southern Québec, defined by previous studies, is based up on the retreat of an active ice front toward the northwest. However in the Saint-François River valley, upstream from Sherbrooke, glacial recession was toward the north and northeast. In the Saint-François River valley, the ice retreated headward while in the Saumon River valley it retreated down stream. The ice front in the upper Saint-François River was in contact with proglacial Lake Memphrémagog which was dammed by the main mass of the ice sheet in the lower part of the drainage basin. The lake in the upper Saint-François River also dammed a lateral proglacial lake in the Saumon River, which was controlled by cols to the southeast of the lake. Retreat of the ice front was punctuated by local readvances during which the East Angus and Weedon Moraines were formed. Once the margin had retreated to the northeast, above the level of proglacial Lake Memphrémagog, a moraine dammed glacial lake formed in the Weedon area.Seit der letzten Deglaziation zieht sich eine aktive Eisfront flussaufwàrts in das Hochtal des St François Flusses und flussabwârts in das des Saumon Flusses zurùck. Im TaI des St François Flusses ist die Eisfront, die sich hier Ausnahmsweise nach dem Nordosten zurùckzieht, im Kontakt mit den Gewàssern des proglazial. Sees Memphrémagog, der im flussabwârts liegenden Teil des Beckens durch die Hauptmasse des Inlandeises gesperrt ist. Der See im oberen St François Fluss sperrte auch einen seitlichen proglazial See im Saumon Fluss, welcher von Jochen im Sùdosten des Sees kontrolliert wurde. Der Rùckzug des Lappens ist durch lokale Vorschùbe gekennzeichnet, die die Moranen von East Angus und Weedon geschafft haben. Nach dem Rùckzug des Lappens ùber das Niveau des proglazialen Memphrémagog Sees hinaug, besteht noch ein Morànen Stausee, am Eiskontakt in der Region von Weedon

Développement des lacs proglaciaires et déglaciation des hauts bassins des Rivières au Saumon et Chaudière, sud du Québec

Les études antérieures sur le Quaternaire du sud du Québec mettent en évidence un modèle général de déglaciation basé sur la position des moraines principales. Notre étude, axée sur une logique des formes et des dépôts, détaille l'évolution de la récession glaciaire et le développement des lacs retenus par le front de l'inlandsis, dans une sous-région de l'Estrie. Le drainage proglaciaire a évolué en quatre systèmes principaux : le système des « étangs Frontaliers » (1), composés de petits lacs qui se sont d'abord vidés de façon diffuse vers la Nouvelle-Angleterre, avant que le drainage ne se concentre vers le fleuve Kennebec (2), puis vers le fleuve Connecticut (3), pour finalement se faire vers le lac proglaciaire Memphrémagog (4). L'évolution du retrait glaciaire commence par l'apparition de nunataks, résultant de l'amincissement de l'inlandsis. L'allure du front reflète dès lors la configuration du relief sous-jacent qui influence directement le mode de fusion de la glace. Le retrait de la glace est relativement plus rapide dans les vallées orientées dans le sens de la déglaciation et il existe une corrélation inverse entre la pente du relief et la vitesse de recul de l'inlandsis.The general pattern of de-glaciation in southern Québec in previous studies is based primarily on the location of the principal moraines. This article presents the detailed evolution of proglacial lakes and the retreat of the ice front based upon a study of the geomorphology and Quaternary deposits in a subregion of the Eastern Townships. Four main systems of proglacial drainage have been mapped: the "Étangs Frontaliers" (1) drained through various cols toward New England before the drainage concentration first in the Kennebec River (2) then in the Connecticut River (3), and finally into proglacial Lake Memphrémagog (4). The evolution of the ice front position began with the development of nunataks, resulting from the thinning of the ice-sheet and its shape reflected the underlying topography. The local retreat was faster in valleys oriented in the direction of the déglaciation and, in general, there is an inverse correlation between slope line and rate of glacier retreat.Die frùheren Forschungsarbeiten ùber das Quartâr im Sùden von Québec zeigen ein allgemeines Muster der Enteisung, das sich auf die Lage der wichtigsten Morànen stùtzt. Dieser Artikel zeigt die genaue Entwicklung proglazialer Seen und den Rùckzug der Eisfront, gestùtzt auf eine Erforschung der Géomorphologie und Quartâr Ablagerungen in einer Subregion der Cantons de l'Est. Vier Hauptsysteme fur proglaziale Entwàsserung wurden kartographiert: "Étangs Frontaliers" (1) entwâssert durch verschiedene Joche nach New England hin, bevor eine Entwàsserungskonzentration zuerst im Kennebek Fluss (2) dann in den Connecticut Fluss (3), und schliesslich in den proglazial See Memphrémagog (4) geschieht. Die Evolution der Eisfrontposition begann mit der Entwicklung von Nunataken, als Résultat von der Verdùnnung der Eisdecke, und ihre Form spiegelte die unterliegende Topographie wider. Der ôrtliche Rùckzug war in den Tàlern, die mit der Richtung der Enteisung ùbereinstimmten schneller, und im Allgemeinen gibt es eine umgekehrte Korelation zwischen Hanglinie und der Geschwindigkeit des Gletscher Rùckzuges

Nondestructive Measurement of Orbital Angular Momentum for an Electron Beam

Free electrons with a helical phase front, referred to as "twisted" electrons, possess an orbital angular momentum (OAM) and, hence, a quantized magnetic dipole moment along their propagation direction. This intrinsic magnetic moment can be used to probe material properties. Twisted electrons thus have numerous potential applications in materials science. Measuring this quantity often relies on a series of projective measurements that subsequently change the OAM carried by the electrons. In this Letter, we propose a nondestructive way of measuring an electron beam's OAM through the interaction of this associated magnetic dipole with a conductive loop. Such an interaction results in the generation of induced currents within the loop, which are found to be directly proportional to the electron's OAM value. Moreover, the electron experiences no OAM variations and only minimal energy losses upon the measurement, and, hence, the nondestructive nature of the proposed technique.Comment: 5 pages, 3 figures, and supplemental material that is comprised of text and 4 figure

Spin constrained orbital angular momentum control in high-harmonic generation

The interplay between spin and orbital angular momentum in the up-conversion process allows us to control the macroscopic wave front of high harmonics by manipulating the microscopic polarizations of the driving field. We demonstrate control of orbital angular momentum in high harmonic generation from both solid and gas phase targets using the selection rules of spin angular momentum. The gas phase harmonics extend the control of angular momentum to extreme-ultraviolet wavelength. We also propose a bi-color scheme to produce spectrally separated extreme-ultraviolet radiation carrying orbital angular momentum

Shifts in biomass and productivity for a subtropical dry forest in response to simulated elevated hurricane disturbances

Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model-based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dynamics of subtropical dry forests in Puerto Rico. Using the previously validated individual-based gap model ZELIG-TROP, we developed a new hurricane damage routine and parameterized it with site- and species-specific hurricane effects. A baseline case with the reconstructed historical hurricane regime represented the control condition. Ten treatment cases, reflecting plausible shifts in hurricane regimes, manipulated both hurricane return time (i.e. frequency) and hurricane intensity. The treatment-related change in carbon storage and fluxes were reported as changes in aboveground forest biomass (AGB), net primary productivity (NPP), and in the aboveground carbon partitioning components, or annual carbon accumulation (ACA). Increasing the frequency of hurricanes decreased aboveground biomass by between 5% and 39%, and increased NPP between 32% and 50%. Decadal-scale biomass fluctuations were damped relative to the control. In contrast, increasing hurricane intensity did not create a large shift in the long-term average forest structure, NPP, or ACA from that of historical hurricane regimes, but produced large fluctuations in biomass. Decreasing both the hurricane intensity and frequency by 50% produced the highest values of biomass and NPP. For the control scenario and with increased hurricane intensity, ACA was negative, which indicated that the aboveground forest components acted as a carbon source. However, with an increase in the frequency of storms or decreased storms, the total ACA was positive due to shifts in leaf production, annual litterfall, and coarse woody debris inputs, indicating a carbon sink into the forest over the long-term. The carbon loss from each hurricane event, in all scenarios, always recovered over sufficient time. Our results suggest that subtropical dry forests will remain resilient to hurricane disturbance. However carbon stocks will decrease if future climates increase hurricane frequency by 50% or more

A modeling study of heterogeneity and surface water-groundwater interactions in the Thomas Brook catchment, Annapolis Valley (Nova Scotia, Canada)

A modelling study of the impacts of subsurface\ud heterogeneity on the hydrologic response of a small catchment\ud is reported. The study is focused in particular on the\ud hydraulic connection and interactions between surface water\ud and groundwater. A coupled (1-D surface/3-D subsurface)\ud numerical model is used to investigate, for a range of scenarios,\ud the spatio-temporal patterns of response variables such\ud as return flow, recharge, groundwater levels, surface saturation,\ud and streamflow. Eight scenarios of increasing geological\ud complexity are simulated for an 8 km2 catchment in\ud the Annapolis Valley (eastern Canada), introducing at each\ud step more realistic representations of the geological strata\ud and corresponding hydraulic properties. In a ninth scenario\ud the effects of snow accumulation and snowmelt are also considered.\ud The results show that response variables and significant\ud features of the catchment (e.g. springs) can be adequately\ud reproduced using a representation of the geology and\ud model parameter values that are based on targeted fieldwork\ud and existing databases, and that reflect to a sufficient degree\ud the geological and hydrological complexity of the study area.\ud The hydraulic conductivity values of the thin surficial sediment\ud cover (especially till) and of the basalts in the upstream\ud reaches emerge as key elements of the basin’s heterogeneity\ud for properly capturing the overall catchment response