Using reanalysis‐driven regional climate model outputs for hydrology modelling

Bias correction methods are usually applied to climate model outputs before using these outputs for hydrological climate change impact studies. However, the use of a bias correction procedure is debatable, due to the lack of physical basis and the bias nonstationarity of climate model outputs between future and historical periods. The direct use of climate model outputs for impact studies has therefore been recommended in a few studies. This study investigates the possibility of using reanalysis‐driven regional climate model (RCM) outputs directly for hydrological modelling by comparing the performance of bias‐corrected and nonbias‐corrected climate simulations in hydrological simulations over 246 watersheds in the Province of Québec, Canada. When using RCM outputs directly, the hydrological model is specifically calibrated using RCM simulations. Two evaluation metrics (Nash–Sutcliffe efficiency [NSE] and transformed root mean square error [TRMSE]) and three hydrological indicators (mean, high, and low flows) are used as criteria for this comparison. Two reanalysis‐driven RCMs with resolutions of 45 km and 15 km are used to investigate the scale effect of climate model simulations and bias correction approaches on hydrology modelling. The results show that nonbias‐corrected simulations perform better than bias‐corrected simulations for the reproduction of the observed streamflows when using NSE and TRMSE as criteria. The nonbias‐corrected simulations are also better than or comparable with the bias‐corrected simulations in terms of reproducing the three hydrological indicators. These results imply that the raw RCM outputs driven by reanalysis can be used directly for hydrological modelling with a specific calibration of hydrological models using these datasets when gauged observations are scarce or unavailable. The nonbias‐corrected simulations (at a minimum) should be provided to end users, along with the bias‐corrected ones, especially for studying the uncertainty of hydrological climate change impacts. This is especially true when using an RCM with a high resolution, since the scale effect is observed when the RCM resolution increases from a 45‐km to a 15‐km scale.     

Multi-model averaging for continuous streamflow prediction in ungauged basins

ABSTRACT

This paper assesses the possibility of using multi-model averaging techniques for continuous streamflow prediction in ungauged basins. Three hydrological models were calibrated on the Nash-Sutcliffe Efficiency metric and were used as members of four multi-model averaging schemes. Model weights were estimated through optimization on the donor catchments. The averaging methods were tested on 267 catchments in the province of Québec, Canada, in a leave-one-out cross-validation approach. It was found that the best hydrological model was practically always better than the others used individually or in a multi-model framework, thus no averaging scheme performed statistically better than the best single member. It was also found that the robustness and adaptability of the models were highly influential on the models’ performance in cross-verification. The results show that multi-model averaging techniques are not necessarily suited for regionalization applications, and that models selected in such studies must be chosen carefully to be as robust as possible on the study site.

Editor M.C. Acreman; Associate editor S. Grimaldi     

Palladium(II) chloride complexation: Spectrophotometric investigation in aqueous solutions from 5 to 125°C and theoretical insight into Pd-Cl and Pd-OH2 interactions

Monomeric palladium(II) chloro aqua complexes of the form PdCl_r(H₂O)_4-r^2-r (r = [0,4]) were studied both experimentally and theoretically to gain insight on both the stabilities and the nature of palladium-chloride interactions.The thermodynamic stabilities of these complexes were studied in aqueous solutions from 5 to 125°C with UV-vis spectrophotometry using a quartz flow-through cell. Tentative measurements up to 200°C were also carried out in pressurised titanium and gold-lined optical cells but revealed important losses in soluble palladium. The strong ligand-to-metal charge transfer bands of the palladium complexes below 350 nm were used to constrain the stepwise thermodynamic formation constants at each temperature, using results of singular value decompositions of the spectra over a broad range of palladium:chloride ratios and wavelengths. The temperature-dependent constants were used to obtain changes in enthalpy and in entropy for each reaction. The thermodynamic stabilities of PdCl(H₂O)₃⁺, PdCl₂(H₂O)₂⁰, and PdCl₃(H₂O)^- are larger at higher temperatures, whilst the one of PdCl₄^2- is smaller. All changes in entropies are positive for the former three species, but negative for the latter, presumably due to a larger solvent reorganisation around the doubly charged PdCl₄^2- species. The room temperature thermodynamic values derived from this study are also in agreement with previously published calorimetric data.Theoretical calculations on the intramolecular distributions of electrons in the different palladium(II) chloro aqua complexes, using the methods of atoms in molecules and of the electron localisation function, showed Pd-Cl and Pd-OH₂ interactions to be of largely closed-shell/ionic nature. These interactions induce an important distortion of the outer core shell electrons of Pd, as well as stable accumulations of electrons between adjacent Pd-Cl and Pd-OH₂ bonds known as ligand opposed core charge concentrations.     

Impact of permafrost development on groundwater flow patterns: a numerical study considering freezing cycles on a two-dimensional vertical cut through a generic river-plain system

The impact of glaciation cycles on groundwater flow was studied within the framework of nuclear waste storage in underground geological formations. The eastern section of the Paris Basin (a layered aquifer with impervious/pervious alternations) in France was considered for the last 120 ka. Cold periods corresponded with arid climates. The issue of talik development below water bodies was addressed. These unfrozen zones can maintain open pathways for aquifer recharge. Transient thermal evolution was simulated on a small-scale generic unit of the landscape including a “river” and “plain”. Coupled thermo-hydraulic modeling and simplified conductive heat transfer were considered for a broad range of scenarios. The results showed that when considering the current limited river dimensions and purely conductive heat transfer, taliks are expected to close within a few centuries. However, including coupled advection for flows from the river to the plain (probably pertinent for the eastern Paris Basin aquifer recharge zones) strongly delays talik closure (millennium scale). The impact on regional underground flows is expected to vary from a complete stop of recharge to a reduced recharge, corresponding to the talik zones. Consequences for future modeling approaches of the Paris Basin are discussed.     

Fault patterns by space remote sensing and the rotation of western Oregon during Cenozoic times

We used MSS-Landsat images (bands 6 and 7) as well as previous studies to interpret fault patterns in western Oregon in terms of the rotations detected by paleomagnetism. These fault zones show a great concentration between the Cascade Range and the Idaho Batholite and have several distinct trends. The north-south striking structures are attributed to the Basin and Range province, while the large NW-SE right-lateral fault zones are interpreted as resulting from an extension between the Cascades Arc and the Olympic-Wallowa lineament. The latter was a paleoplate boundary during pre-Eocene times. This extension, beginning during Late Eocene/Oligocene times and continuing through Recent times, is accompanied by a migration of the rotation pole from southeast to northwest, and by a clockwise rotation of the Coast Range—Klamath Mountains—Cascade Range block, induced by the subduction of the Farallon plate.     

Formation and ascent of granitic magmas

New results obtained by the investigation of liquidus and solidus phase relationships in the haplogranite system Qz-Ab-Or are used to discuss the evolution of magmas during their ascent in the crust. It is assumed that the magmas are formed at 720°C, 820°C, 920°C and at a depth corresponding to a pressure of 8 kbar. The starting composition of the magma is taken as 50% melt plus 50% quartz and feldspars. In case of a closed system (no heat exchange and no transfer of elements) the melt fraction of magmas, the water activity and the viscosity increase with decreasing pressure. The temperature slightly decreases. At 700°C the viscosity is approximatively 2 orders of magnitude lower than at 900°C. This is related to the higher amount of water in the (H₂O-undersaturated) melt at low T. It is also shown that dehydration melting is only realistic at high T (900°C). At lower temperatures water has to be added from outside to obtain an intrusive magma with approximatively 50% melt.

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Zusammenfassung Neue Ergebnisse, erzielt durch Untersuchungen von Liquidus und Solidus Phasenbeziehungen des Granitsystems Qz-Ab-Or, werden benutzt, um die Entwicklung eines granitoiden Magmas während seines Aufstiegs zu diskutieren. Es wird vorausgesetzt, daß die Magmen bei Temperaturen von 720°C, 820°C und 920°C gebildet werden, sowie in einer Tiefe die einem Druck von 8 kbar entspricht. Die anfängliche Zusammensetzung des Magmas wird mit einem Verhältnis von 50% Schmelze sowie 50% Quarz und Feldspäten angenommen. Im Falle eines geschlossenen Systems (kein Austausch von Wärme und Elementen) steigt die Teilschmelzbildung von Magmen, die Aktivität des Wassers und die Viskosität bei abnehmenden Druck; hierbei sinkt die Temperatur leicht. Bei 700°C ist die Viskosität um ca. 2 Größenordnungen geringer als bei 900°C. Dies wird bedingt durch den höheren Gehalt an Wasser in der (H₂O-untersättigten) Schmelze bei tieferen Temperaturen. Es wird außerdem gezeigt, daß Magmenbildung durch Dehydratation nur bei hohen Temperaturen realistisch ist (900°C). Bei tieferen Temperaturen muß Wasser von außen zugeführt werden um ein intrusives Magma zu erhalten, das ungefähr 50% Schmelze besitzt.

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Résumé L'évolution des magmas granitiques au cours de leur ascension dans la croûte est discutée à la lumière de données nouvelles relatives aux relations entre phases liquides et solides dans le système Q-Ab-Or. On suppose que les magmas se forment à des températures de 720°C, 820°C, 920°C et à une profondeur correspondant à une pression de 8 Kb. On admet pour leur composition initiale un mélange de 50% de liquide et 50% de quartz + feldspaths. Dans le cas d'un système fermé (pas d'échange de chaleur ni de matière), la fraction liquide du magma, l'activité de l'eau et la viscosité augmentent quand la pression diminue; en même temps, la température décroît légèrement. A 700°C, la viscosité est d'environ 2 ordres de grandeur plus basse qu'à 900°C. Cette propriété est en relation avec la teneur en eau plus élevée dans le liquide (sous-saturé en eau) à basse température. On peut également montrer qu'une fusion déshydratante n'est vraisemblable qu'à haute température (900°C). Aux températures plus basses, de l'eau doit être apportée de l'extérieur pour l'obtention d'un magma à 50% de liquide.

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Solubility measurements of synthetic neodymium monazite as a function of temperature at 2 kbars, and aqueous neodymium speciation in equilibrium with monazite

The solubility of synthetic NdPO₄ monazite end-member was experimentally determined from 300 up to 800 °C, at 2000 bars in pure water, and in aqueous chloride or phosphate solutions. Both the classical weight-loss method and a new method based on isotope dilution coupled with thermal ionization mass spectrometer were used. In the range of temperature studied monazite showed a prograde solubility from 10^−5.4 m at 300 °C up to 10^−2.57 m at 800 °C. Experiments in H₂O-H₃PO₄-NaCl-HCl solutions suggested Nd(OH)₃⁰ was the major species that was formed at high temperature and pressure. The equilibrium constants (log K) for the reaction:

     

Recent hydrological behavior of the East African great lakes region inferred from GRACE,satellite altimetry and rainfall observations

We have jointly analysed space gravimetry data from the GRACE space mission, satellite altimetry data and precipitation over the East African Great Lakes region, in order to study the spatiotemporal variability of hydrological parameters (total water storage, lake water volume and rainfall). We find that terrestrial water storage (TWS) from GRACE and precipitation display a common mode of variability at interannual time scale, with a minimum in late 2005, followed by a rise in 2006–2007. We argue that this event is due to forcing by the strong 2006 Indian Ocean Dipole (IOD) on East African rainfall. We also show that GRACE TWS is linked to the El Niño-Southern Oscillation cycle. Combination of the altimetry-based lake water volume with TWS from GRACE over the lakes drainage basins allows estimating soil moisture and groundwater volume variations. Comparison with the WGHM hydrological model outputs is performed and discussed.     

Morphology and magnetic survey of the Rivera-Cocos plate boundary of Colima,Mexico

The propagation of the Pacific-Cocos Segment of the East Pacific Rise (EPR-PCS) has significantly altered the plate configuration at the north end of the Middle America Trench. This ridge propagation, the collision of the EPR-PCS with the Middle America Trench, the separation of the Rivera and Cocos plates and the formation of the Rivera Transform have produced a complex arrangement of morphotectonic elements in the area of Rivera-Cocos plate boundary, atypical of an oceanic transform boundary. Existing marine magnetic and bathymetric data has proved inadequate to unravel this complexity, thus, a dense grid of total field magnetic data were collected during campaigns MARTIC-04 and MARTIC-05 of the B/O EL PUMA in 2004 and 2006. These data have greatly clarified the magnetic lineation pattern adjacent to the Middle America trench, and have revealed an interesting en echelon, NE-SW oriented magnetic high offshore of the Manzanillo Graben. We interpret these new data to indicate that the EPR-PCS ridge segment reached the latitude (~18.3°N) of the present day Rivera Transform at about Chron 2A₃ (~3.5Ma) and propagated further northward, intersecting the Middle America Trench at about 1.7 Ma (Chron 2). At 1.5 Ma spreading ceased along the EPR north of 18.3°N and the EPR-PCS has since retreated southward in association with a southward propagation of the Moctezuma Spreading Segment. North of 18.3°N the seafloor near the trench has been broken into small, uplifted blocks, perhaps due to the subduction of the young lithosphere generated by the EPR-PCS.     

Antifouling activity of commercial biocides vs. natural and natural-derived products assessed by marine bacteria adhesion bioassay

Biofilm formation is a key step during marine biofouling, the natural colonization of immersed substrata, leading to major economic and ecological consequences. Consequently, bacteria have been used for the screening of new non-toxic antifoulants: the adhesion of five strains isolated on three French locations was monitored using a fluorescence-based assay and toxicity was also evaluated. Nine biocides including commercial, natural and natural-derived products were tested. The commercial antifoulants, TBTO and Sea Nine showed low EC₅₀ but high toxicity. The non-commercial products TFA-Z showed significant anti-adhesion activities and appeared to be non-toxic, suggesting a specific anti-adhesion mechanism. In addition, the strains could be classified depending on their sensitivity to the molecules used even if strain sensitivity also depended on the molecules tested. In conclusion, TFA-Z would be a promising candidate as non-toxic antifoulant and our results strengthen the need to perform antifouling bioassays with a panel of strains showing different response profiles.