Modélisation régionale des débits de crue du bassin hydrographique du Cris : approche régionale classique et par modèles de référence

Une régionalisation débit-durée-fréquence des débits de crue est réalisée sur les sous bassins du Cris qui draine une superficie d'environ 14 300 km2 à l'ouest de la Roumanie. Cette régionalisation concerne 78 sous bassins dont les chroniques de débit quotidien et de pointe observées sont de trente ans en moyenne et pour lesquels nous disposons des pluies maximales de bassin de 1 jour à 10 jours calculées à partir de 92 postes pluviométriques. La régionalisation est menée selon deux approches : une approche régionale classique et une approche à partir de trois modèles adimensionnels de référence établis sur trois sites observés de France. La différence fondamentale entre les deux approches réside en ce que l'une prend en compte l'information spatiale pluie-débit inventoriée du Cris et que l'autre considère essentiellement l'information pluie-débit de chaque site de référence français. L'approche modèles de référence a pour base conceptuelle une typologie des crues qui pour un site cible est prédéfinie par un critère de choix, tandis que l'approche classique nécessite que soient définis des régions hydrologiques homogènes. Cette démarche est menée sur les trois sous bassins hydrographiques du Cris et permet d'étendre la région hydrologique homogène à l'ensemble du bassin du Cris. L'approche régionale comme l'approche modèles de référence privilégie la loi exponentielle adaptée aux valeurs supérieures à un seuil pour ce qui concerne les quantiles de crue de faible période de retour et pour des durées de 1j à 10j selon la dynamique de crue des sous bassins. Pour les quantiles de crue de grande période de retour les deux approches sous tendent le modèle du GRADEX, forme d'extrapolation des distributions observées par le gradex des pluies maximales. Quelle que soit l'approche de régionalisation, en tout site cible doivent être disponibles deux descripteurs de régime : le débit de pointe décennal Q10 et une durée caractéristique de crue D. Afin de comparer essentiellement l'incertitude des modélisations sur les quantiles de crue, D et Q10 sont connus et déduits des observations. Les résultats présentés montrent une bonne validité du modèle régional ajusté sur l'ensemble du Cris. Ceci indique que la zone étudiée est relativement bien homogène. Concernant les modèles de référence, leur critère de choix n'apparaît pas pertinent lorsqu'on s'intéresse aux faibles périodes de retour, mais se révèle significatif pour les fortes périodes de retour. Ce résultat est en grande partie dû à la méthode d'extrapolation appliquée. Celle ci est liée à la méthode du GRADEX et utilise l'information locale sur les gradex de pluie, comme cela est souvent le cas en France. Il est à noter que ces modèles de référence établis sur des chroniques de débit et pluie d'avant 1992 n'ont pas été réactualisés. L'exemple du bassin du Cris montre qu'ils n'en gardent pas moins un caractère opérationnel pour l'estimation des quantiles de crue de durée d (0 < d(j) < 10) et de période moyenne de retour T (5 < T(an) < 1000).When local information on streamflows is insufficient for estimating flood quantiles, a Regional Flood Frequency Analysis (RFFA) is usually carried out. Once homogeneous hydrological regions are defined, methods such as the "Index-Flood" method can be applied. In most cases, the variable understudy is the maximum peak flood (instantaneous or mean daily value, depending available data). However, the severity of a flood is not only defined by its peak, but also by its volume and duration.For this reason, Cemagref has developed for several years an approach which, in addition to the classic flood/frequency relationship, takes into account the notion of duration: the flood-duration-frequency approach (QdF). In a similar manner to the rainfall intensity-duration-frequency analysis, averaged discharges are computed over different fixed durations d. For each duration, a frequency distribution of maximum averaged discharges is studied. Finally, a continuous formulation is fitted, as a function of the return period (T) and the duration (d) over which discharges have been averaged. Rare quantiles are determined using rainfall frequency information, according the so-called "GRADEX" method ("aesthetic" version). The regionalization of the QdF approach leaded to define three sets of dimensionless QdF curves. The originality of the method is that each set was fitted to one unique basin, located in France, and corresponding to a distinct hydrological regime. A choice criterion, involving maximal rainfall distributions, determines which reference basin has to be considered. In this way, the QdF regionalization differs from the classic concepts mentioned in the first paragraph. The classic approach takes into account the whole streamflow-rainfall information available on a homogeneous hydrological region, while the QdF regionalization developed at Cemagref considers the streamflow-rainfall information available on the three French reference basins. The aim of this research is to apply classical regional concepts (homogeneous regions) to the QdF approach and to compare results with thus obtained using the three French reference basins. One interest of the study is that it has been conducted in Romania, ie, outside the area where the three reference basins are located.The case study is carried out on the Cris river sub-catchments which cover an area of about 14 300 km2, in the west of Romania. This regionalization concerns 78 sub-catchments having about thirty years of streamflow measurements (daily flow and instantaneous flood peaks). For validation purpose, two basin sets are constituted: a calibration set (54 basins) and a validation set (24 basins). Furthermore, maximal rainfalls over 1 day to 10 days are available for these basins, from 92 rain-gauge stations. First, regional QdF curves are deduced according the definition of homogeneous regions. Three regions are defined, corresponding to the three main sub-catchments of the Cris basins. After different tests, it is shown that the whole Cris basin can be considered as a unique homogeneous region. Then, the regionalization involving the three French reference basins is carried out. In both cases, methods are applied with the exponential law adjusted on peak over threshold values, for small return periods. Durations are ranging from 1 day to 10 days, according to the flood dynamic of the studied basins. For long return periods, both approaches use the GRADEX method, which extrapolates discharge distributions according to the rainfall distributions. Whatever the regional approach used, two descriptors have to be estimated for each target site, in order to unscale the dimensionless regional QdF curves. Theses two descriptors are the 10-year-return-period peak flood Q10 and a flood characteristic duration D. In order to compare the uncertainty of the two approaches, D and Q10 are local values, deduced from observations.The results presented shows a good validity of the regional model fitted to the whole Cris basin. This indicates that this region is quite homogeneous. Concerning the reference models, their choice criterion does not appear to be pertinent for small return periods, but becomes relevant for high return periods. In this case, estimations are comparable to thus provided using the whole regional information available on the Cris basin. This result is mainly due to the extrapolation method used. It is related to the GRADEX method and takes into account the local information about rainfall gradex, as it is often done in France. One point to be noticed is that these reference models have not been updated since they have been established in 1992. Despite that, the Cris basin example shows their operational ability for estimating flood quantiles of duration d (0 < d(day) < 10) and return period T (5 < T(year) < 1000). From an operational point of view, the three reference basins can be a valuable option. Indeed, a regional analysis is sometime difficult to carry out: data not available or too costly, time available for the study to short, etc. On the other hand, the three reference basins method is easier to apply and requires less data. However, uncertainties and hypothesis of the method should be kept in mind. In particular, we should be aware that high return period quantiles are given according the GRADEX method, ie using the frequency rainfall information. Consequently, the hypothesis of this method should be respected

Change of Soil Biomass Carbon Microorganism in Ultisols Soil Due to Application of Humic Acid and TSP Fertilization

Soil biomass carbon microorganism (C-mic) is one indicator of soil fertility. The application of humic acid, vermicompost aqueous extract, and TSP fertilization applied to the soil will affect the activity of soil microorganisms. This research aimed to study the effect of humic acid, vermicompost extract, and TSP fertilization on C-mic. The first factor was the application of humic acid (h), namely, without humic acid, commercial origin, and humic acid-like from watery extract vermicompost. The second factor is TSP fertilization (p) divided into four dose levels: without TSP fertilizer, TSP fertilizer 100 kg ha-1, TSP fertilizer 200 kg ha-1, and TSP fertilizer 300 kg ha-1. Data were analyzed by analysis of variance and continued with the Least Significant Difference (LSD) test at the 5% significance level. The correlation between C-organic, soil pH, soil temperature, soil moisture content, stalk dry weight, and weight of corn kernels with C-mic was tested by correlation test. The results showed that the application of humic acid and TSP fertilization had no significant effect on C-mic, and there was no interaction between the two at seven days after planting (DAP), 56 DAP, and 104 DAP. There was a correlation between soil organic carbon 7 DAP (r: 0.34*), 56 DAP (r: 0.59*), and 104 DAP (r: 0.53*), soil moisture content at 7 DAP (r: 0.36*), soil pH at 56 DAP (r: 0.42*) and 104 DAP (r: 0.43*), soil temperature at 104 DAP (r: -0.52*), stalk dry weight at 56 DAP (r: 0.34*), corn kernels weight at 113 DAP (r: 0.65*) with C-mic

Pharmacokinetic/Pharmacodynamic Correlation of Cefquinome Against Experimental Catheter-Associated Biofilm Infection Due to Staphylococcus aureus.

Biofilm formations play an important role in Staphylococcus aureus pathogenesis and contribute to antibiotic treatment failures in biofilm-associated infections. The aim of this study was to evaluate the pharmacokinetic/pharmacodynamic (PK/PD) profiles of cefquinome against an experimental catheter-related biofilm model due to S. aureus, including three clinical isolates and one non-clinical isolate. The minimal inhibitory concentration (MIC), minimal biofilm inhibitory concentration (MBIC), biofilm bactericidal concentration (BBC), minimal biofilm eradication concentration (MBEC) and biofilm prevention concentration (BPC) and in vitro time-kill curves of cefquinome were studied in both planktonic and biofilm cells of study S. aureus strains. The in vivo post-antibiotic effects (PAEs), PK profiles and efficacy of cefquinome were performed in the catheter-related biofilm infection model in murine. A sigmoid E max model was utilized to determine the PK/PD index that best described the dose-response profiles in the model. The MICs and MBICs of cefquinome for the four S. aureus strains were 0.5 and 16 μg/mL, respectively. The BBCs (32-64 μg/mL) and MBECs (64-256 μg/mL) of these study strains were much higher than their corresponding BPC values (1-2 μg/mL). Cefquinome showed time-dependent killing both on planktonic and biofilm cells, but produced much shorter PAEs in biofilm infections. The best-correlated PK/PD parameters of cefquinome for planktonic and biofilm cells were the duration of time that the free drug level exceeded the MIC (fT &gt; MIC, R (2) = 96.2%) and the MBIC (fT &gt; MBIC, R (2) = 94.7%), respectively. In addition, the AUC24h/MBIC of cefquinome also significantly correlated with the anti-biofilm outcome in this model (R (2) = 93.1%). The values of AUC24h/MBIC for biofilm-static and 1-log10-unit biofilm-cidal activity were 22.8 and 35.6 h; respectively. These results indicate that the PK/PD profiles of cefquinome could be used as valuable guidance for effective dosing regimens treating S. aureus biofilm-related infections

AGN Dusty Tori: II. Observational Implications of Clumpiness

From extensive radiative transfer calculations we find that clumpy torus models with \No \about 5--15 dusty clouds along radial equatorial rays successfully explain AGN infrared observations. The dust has standard Galactic composition, with individual cloud optical depth \tV \about 30--100 at visual. The models naturally explain the observed behavior of the 10\mic silicate feature, in particular the lack of deep absorption features in AGN of any type. The weak 10\mic emission feature tentatively detected in type 2 QSO can be reproduced if in these sources \No drops to \about 2 or \tV exceeds \about 100. The clouds angular distribution must have a soft-edge, e.g., Gaussian profile, the radial distribution should decrease as $1/r$ or $1/r^2$. Compact tori can explain all observations, in agreement with the recent interferometric evidence that the ratio of the torus outer to inner radius is perhaps as small as \about 5--10. Clumpy torus models can produce nearly isotropic IR emission together with highly anisotropic obscuration, as required by observations. In contrast with strict variants of unification schemes where the viewing-angle uniquely determines the classification of an AGN into type 1 or 2, clumpiness implies that it is only a probabilistic effect; a source can display type 1 properties even from directions close to the equatorial plane. The fraction of obscured sources depends not only on the torus angular thickness but also on the cloud number \No. The observed decrease of this fraction at increasing luminosity can be explained with a decrease of either torus angular thickness or cloud number, but only the latter option explains also the possible emergence of a 10\mic emission feature in QSO2.Comment: To appear in ApJ September 20, 200

Evaluating observed versus predicted forest biomass: R-squared, index of agreement or maximal information coefficient?

The accurate prediction of forest above-ground biomass is nowadays key to implementing climate change mitigation policies, such as reducing emissions from deforestation and forest degradation. In this context, the coefficient of determination ($${R^2}$$) is widely used as a means of evaluating the proportion of variance in the dependent variable explained by a model. However, the validity of $${R^2}$$ for comparing observed versus predicted values has been challenged in the presence of bias, for instance in remote sensing predictions of forest biomass. We tested suitable alternatives, e.g. the index of agreement ($$d$$) and the maximal information coefficient ($$MIC$$). Our results show that $$d$$ renders systematically higher values than $${R^2}$$, and may easily lead to regarding as reliable models which included an unrealistic amount of predictors. Results seemed better for $$MIC$$, although $$MIC$$ favoured local clustering of predictions, whether or not they corresponded to the observations. Moreover, $${R^2}$$ was more sensitive to the use of cross-validation than $$d$$ or $$MIC$$, and more robust against overfitted models. Therefore, we discourage the use of statistical measures alternative to $${R^2}$$ for evaluating model predictions versus observed values, at least in the context of assessing the reliability of modelled biomass predictions using remote sensing. For those who consider $$d$$ to be conceptually superior to $${R^2}$$, we suggest using its square $${d^2}$$, in order to be more analogous to $${R^2}$$ and hence facilitate comparison across studies

Modélisation statistique des modules annuels et des étiages du bassin roumain du Timis-Bega, similitudes régionales avec la Moselle française

Le bassin hydrographique du Timis-Bega, d’une superficie d’environ 13 000 km2, est situé à l’ouest de la Roumanie. Le contexte orographique, l’influence climatique méditerranéenne, la nature et l’occupation du sol font que cette zone géographique relativement restreinte présente une assez grande diversité des écoulements. Cette dernière est considérée à travers le choix de 19 sous-bassins, de quelque km2 à plusieurs centaines de km2. La régionalisation des modules et des débits d’étiage du Timis-Bega a été entreprise à la suite de travaux analogues réalisés sur le bassin hydrographique de la Moselle française (GALÉA et CANALI, 2005). Ces travaux avaient montré l’adéquation de la loi de Weibull à deux paramètres pour décrire la variabilité temporelle et spatiale des modules annuels et des étiages des sous-bassins observés. Deux principaux résultats avaient été soulignés, l’un concernait la faible différenciation des lois régionales établies pour les modules et les étiages des années moyennes à « sèches »  (F ≤ 0,5), l’autre mettait l’accent sur l’usage de jaugeages épisodiques d’étiage pour améliorer la performance des modèles régionaux. Notre propos est de vérifier ces considérations, établies pour le bassin de la Moselle, dans le contexte hydro-climatique du Timis-Bega. Les résultats obtenus permettent de confirmer tant l’aspect peu différencié des lois régionales que l’aspect amélioration de la performance des modèles régionaux. Plus précisément, cette amélioration résulte d’une meilleure précision, que celle obtenue par régression multiple classique, de l’estimation du descripteur de régime local, le module annuel médian ou le débit journalier médian d’étiage qui représente une source d’incertitude importante du modèle régional respectif. L’usage d’une information épisodique sur les débits d’étiage, concomitante à un site étudié et à un sous-bassin de référence, permet l’estimation du débit journalier médian et, par extension, celle du module annuel médian. Une explication à cette extension pourrait être trouvée dans la faible différenciation des lois régionales pour les fréquences moyennes à « sèches ». L’intérêt des jaugeages épisodiques d’étiage nous semble assez porteur pour être pris en considération lors d’une démarche ultérieure de régionalisation à bases géostatistiques des descripteurs de régime. Enfin, un résultat inattendu concerne la quasi similitude des lois régionales de la Moselle et du Timis-Bega tant en ce qui concerne les modules annuels que les étiages. Ce résultat, à considérer avec prudence, abonderait dans le sens de la théorie des régions hydrologiques homogènes.The catchment area of Timis-Bega (13,000 km2) is located in the western part of Romania. The orographical context, the Mediterranean climatic influence, the nature of the ground and the vegetation contribute to this relatively restricted geographical area’s great diversity of flows. This latter characteristic is based on a study of 19 sub-basins, ranging in size from a few km2 to several hundred km2. The regionalization of annual mean discharge and low flow in the Timis-Bega catchment was undertaken following similar work realized on the French Moselle catchment. This earlier work showed that the two-parameter Weibull distribution adequately described the spatial and temporal variability of annual mean discharge and low flow for the studied sub-catchments. The two principal results of the preceding study were the weak differentiation among the regional models established for annual mean discharge and low flow, and the recommended use of episodic gauging of low flows for the improvement of the regional models. Our intention was to verify these preceding considerations, established for the French Moselle basin, in the hydro-climatic context of Timis-Bega. The results obtained allowed us to confirm the weak differentiation among the regional models as well as the improvement of the regional models. More specifically, this improvement resulted from the better precision, compared to that obtained by traditional multiple regression methods, of the estimation of the local discharge descriptor, the median annual mean discharge or the median minimal daily low flow discharge. The use of low flow episodic discharge measurements, that are concomitant between the studied and reference sub-catchments, allows the estimation of the median minimal daily low flow discharge and the median annual mean discharge. This fortuitous result is explained by the weak differentiation observed between the regional annual mean discharge model and the regional average low flow discharge model for average to dry years. We believe episodic measurements of low flow should be considered when collecting data that will be used for the generation of regionalization flow descriptors by geostatistical methods. Lastly, the similarities between the regional distributions of annual mean discharge and low flow for both the Moselle and Timis-Bega regions were unexpected. This result should, however, be considered with caution, as it implies the existence of homogeneous hydrological regions

Evaluating extracts of spondias mombin for antimicrobial activitie

The plant Spondias mombin Linn. also called yellow mombin in English, Igongo/Ichankla in Idoma, and Uchakuru in Igbo, is common in the forest and savanna regions of Nigeria. It is used in several countries of the world to treat various ailments including infectious diseases. Water, chloroform, methanol, and petroleum ether extracts of leaf, root, and bark of the mature plant were screened for antimicrobial activity using an indicator-based microdilution technique. Inhibition was measured as minimal inhibitory concentration (MIC). The growth of Streptococcus pyogenes (mean MIC = 0.139 mg), Candida albicans (mean MIC = 0.148 mg), Salmonella typhi (mean MIC = 0.226 mg), Escherichia coli (mean MIC = 0.265 mg), and Staphylococcus aureus (mean MIC = 0.289 mg) in broth cultures were inhibited. Inhibition was significantly correlated with plant parts (r = -0.435; p < 0.05), leaf extracts having the greatest inhibitory effect (mean MIC = 0.060 mg), and the bark extracts the least (mean MIC = 0.389 mg). Statistical tests show that the mean MICs of leaf and bark extracts differ significantly (