Génèse des débits dans les petits bassins versants ruraux en milieu tempéré : 2 - Modélisation systémique et dynamique

La deuxième partie de cette synthèse bibliographique sur la genèse des débits montre comment les connaissances acquises sur le fonctionnement des petits bassins ruraux (cf. Partie 1) peuvent être utilisées pour les modéliser. Elle présente les différents types de modèles hydrologiques (empiriques globaux de type "boîte noire", conceptuels globaux ou semi-spatialisés, physiques spatialisés, physico-conceptuels semi-spatialisés) disponibles pour générer des chroniques événementielles ou continues, et déduit de l'analyse de leurs avantages et limites respectifs certaines recommandations pour leur choix et leur usage. Elle indique ensuite différents problèmes rencontrés dans toute modélisation, et quelques pistes possibles pour les résoudre: incorporation des flux couplés à l'eau dans les modèles hydrologiques, erreurs liées à la structure du modèle (limites et simplifications théoriques, approximations numériques, discrétisations temporelle et spatiale), problèmes métrologiques et méthodologiques limitant la disponibilité des données, hétérogénéités à toutes les échelles limitant l'adéquation des données pour paramétrer les modèles, calage du modèle limitant son aptitude à simuler des scénarios de changement. Elle souligne la nécessité d'une validation multicritère des modèles et d'une estimation de l'incertitude sur les simulations générée par ces diverses sources d'erreurs, ainsi que le besoin d'une meilleure interaction entre expérimentation de terrain et modélisation.The second part of this review on streamflow generation analyses how the knowledge available from field studies (see Part 1) has been used since the 1960s or could be used to improve catchment modelling. After a presentation of the main model types, the various problems encountered during the modelling process are discussed.The large variety of hydrologic models available for event or continuous simulation can be reduced to a few main types according to the ways the functional, spatial and temporal aspects of the catchment behaviour are represented. Lumped "blackbox" models are useful for many engineering problems but can not be used in "extrapolation" and give no information on the internal catchment dynamics. Lumped conceptual models, which consider a catchment as a system of interconnected reservoirs and simulate the main global fluxes, use empirical lumped relationships and parameters that often have no great physical meaning and are not measurable. Semi-distributed conceptual models use the same reservoir description, but at the scale of "homogeneous" units derived from a space discretisation, which allows one to take catchment structure explicitly into account. Physically-based distributed models, which use theoretical equations and measurable parameters, provide a dynamic explanation of catchment behaviour but require too much information and are too complex to be easily used at the catchment scale. Physico-conceptual semi-distributed models try to overcome the limits of the previous types, while keeping their advantages, by simplifying the dynamic approach and discretization using new concepts.Physically-based or conceptual models, which describe or explain the water cycle at the catchment scale, are very useful for research, but their use in practical applications comes up against several problems. It is still difficult to incorporate into catchment models the water-coupled fluxes (energy, sediments, solutes, biomass) because of the poorly-known complexity of their interactions. Even sophisticated models are based on many approximations of the reality: lack of suitable theory for some processes, simplification of the theories available, numerical approximation, space and time discretisation all generate simulation errors related to the chosen model structure. Data availability is limited by measurement problems (differences in measurement scale, lack of appropriate measurement techniques), and methodological problems (sampling and interpolation procedures, ...), even though remote sensing is expected to help solve some of them. Data suitability is limited by space and time heterogeneity at all scales, which reduces the representativity of any measurement and complicates the parameterization and upscaling needed. Model calibration (either manual, automatic, or stochastic), which leads to the numerical equifinality of both model parameterization and structure, limits the validity domain of the model, its transposability to other conditions and catchments, and its ability to simulate change scenarios. The effects of these limitations on model quality could be reduced by using multivariable and multiscale validation procedures and should be quantified using stochastic estimation of the simulation uncertainties associated with model and data uncertainties. In order to further progress in catchment modelling, as needed by a large range of environmental issues, field hydrologists and modelers should reinforce their co-operation, especially through interdisciplinary studies on long-term research catchments and carefully designed field experiments

Génèse des débits dans les petits bassins versants ruraux en milieu tempéré: 1 - Processus et facteurs

La première des deux parties de cette synthèse bibliographique sur la genèse des débits montre que la complexité et la diversité des organisations et fonctionnements hydrologiques constatées dans les petits bassins versants ruraux peuvent s'analyser et s'interpréter à l'aide de "clés de lecture" simples, issues d'une approche systémique et dynamique, et utiles aussi pour les modéliser (cf. Partie 2). Elle présente les différents processus tant superficiels que souterrains pouvant contribuer à cette genèse, ainsi que les facteurs du milieu qui les contrôlent: forçages atmosphériques aux limites, conditions hydriques et hydrologiques initiales, propriétés hydrodynamiques des milieux et interfaces traversés, topographie et morphométrie en 3-D du bassin. Elle rappelle ou introduit plusieurs concepts utiles pour caractériser dans chaque cas les combinaisons de processus et facteurs en jeu et leurs effets hydrologiques: seuils fonctionnels et grandeurs caractéristiques contrôlant la forme et la non-linéarité de la réponse du bassin, concepts de "zone ou période active variable" pour un processus donné et de "zone ou période contributive variable" pour un flux aux limites donné décrivant son organisation interne. Elle discute les avantages et limites des différentes méthodes (graphiques, isotopiques, géochimiques) de décomposition des hydrogrammes de crue ainsi que leur complémentarité dans l'étude du système bassin versant.This 2-part review on streamflow generation presents the state of the art in both field studies and modelling of the hydrologic behavior of rural catchments. It focuses mainly on temperate environments and water flows within small catchments, but many points have a more general significance.The first part presents the main results of hillslope hydrology since the 1960s, mainly obtained on small research catchments. It appears that floods can be generated by a large range of both surface and subsurface processes, and not only by infiltration-excess surface runoff, as is still assumed by some hydrologists and modellers. In each case, the processes involved and their combinations are very variable in time and space, depending on the variable combinations of several environmental factors: precipitation and energy inputs imposed by atmosphere forcings at the upper boundary, variations in initial hydric (soil) and hydrologic (catchment) conditions which cause nonlinearities in catchment responses, water storage and resistance-to-transfer properties of the various compartments (vegetation, surface, soil, subsoil) and their interfaces, catchment 3-D topography and morphometry controlling compartment geometry and gravity forces.The non uniform and non random distributions of these processes and factors determine the catchment functional, spatial and temporal organization: (1) at each point, process activation or deactivation results from a balance between water supply from above and local water storage or transfer capacities depending on functional thresholds related to these water properties; (2) spatio-temporal variations of factors lead to some recurrence of conditions favorable or unfavorable to each process in some areas of variable extent and some periods of variable duration: this leads to the concepts of "variable active area and/or period" (for a given process); (3) these active areas and periods contribute to outfluxes only if they are hydraulically connected to the catchment boundaries: this leads to the complementary concepts of "variable contributing area and/or period" (for a given global outflux). Several hydrograph separation methods are used to estimate various contributions to streamflowwhich are difficult to measure in situ. They all have severe limitations: graphical methods are rather arbitrary, tracer methods are based on simplifying assumptions (end-member homogeneity, conservative tracer behaviour,...) that are not very realistic. Moreover, considering the same streamflow from different points of view, they give results that are not comparable but rather complementary: velocity criterion (rapid, delayed, slow flows) for graphical methods, time origin criterion ("pre-event"/"event" water) for water-related isotope tracers, space origin criterion ("source" reservoirs) for other physico-chemical tracers. Lastly, none of them identifies directly the processes involved. Nevertheless, they are very useful in showing that streamflow is a complex mixing of various water types, with high proportions of subsurface and pre-event water in many cases - contrary to classical hydrologic interpretations. Thus, the complexity and diversity of hydrologic patterns and behaviors observed in small rural catchments, and especially the continuum of streamflow generation situations (from pure surface to pure subsurface contributions), can be analysed and characterized using these simple concepts and methods provided by a dynamic systems approach. They are therefore useful for catchment modelling also (see Part 2)

Congenital Midline Upper Lip Sinuses: 3 Rare Cases

Congenital sinuses of the upper lip are rare congenital malformations. There have been only 40 cases described in the literature. We report 3 cases of congenital midline upper lip sinus in Caucasian children. Two of those lesions were associated with other anomalies (complete cleft palate and hemifacial macrosomia or submucous cleft palate with bifid uvula). The pathophysiology remains unexplained yet. Congenital upper lip sinuses can be considered as possible microforms of cleft-lips. Associated anomalies are frequent and must be sought. The treatment is a full excision of the sinus tract and of the skin around the punctum in order to avoid risks of recurrence

Multiplication rate variation in the human malaria parasite Plasmodium falciparum.

It is important to understand intrinsic variation in asexual blood stage multiplication rates of the most virulent human malaria parasite, Plasmodium falciparum. Here, multiplication rates of long-term laboratory adapted parasite clones and new clinical isolates were measured, using a newly standardised assay of growth from low starting density in replicate parallel cultures with erythrocytes from multiple different donors, across multiple cycles. Multiplication rates of long-term established clones were between 7.6 and 10.5 fold per 48 hours, with clone Dd2 having a higher rate than others (clones 3D7, HB3 and D10). Parasite clone-specific growth was then analysed in co-culture assays with all possible heterologous pairwise combinations. This showed that co-culture of different parasites did not affect their replication rates, indicating that there were no suppressive interactions operating between parasites. Multiplication rates of eleven new clinical isolates were measured after a few weeks of culture, and showed a spectrum of replication rates between 2.3 and 6.0 fold per 48 hours, the entire range being lower than for the long-term laboratory adapted clones. Multiplication rate estimates remained stable over time for several isolates tested repeatedly up to three months after culture initiation, indicating considerable persistence of this important trait variation

Évolution actuelle (1960-2021) de l’enneigement dans les Vosges à l’aide du modèle régional du climat MAR

peer reviewedL’évolution actuelle de l’enneigement dans les Vosges (N-E de la France) a été simulée à une résolution de 4 km avec le modèle régional du climat MAR (version 3.13) forcé par les réanalyses ERA5. Moyennant un petit ajustement de seulement 3 paramètres (dont 1 °C d’augmentation du seuil de température neige/pluie), MAR a été optimisé et validé sur 5 et 8 hivers (DJF) par rapport à des observations quotidiennes (température, précipitation, hauteur de neige). Sur les 62 hivers (DJF) 1960-2021, MAR suggère une diminution significative statistiquement d’environ un facteur deux de la hauteur moyenne de neige, due à l’augmentation significative des températures (~+2 °C/62 ans). Bien que les précipitations aient légèrement augmenté (+10-20 %/62 ans) à cause d’un renforcement (non significatif) de la circulation d’ouest, elles tombent de plus en plus sous forme de pluie, en particulier en dessous de 1000 m. Au-dessus de 1000 m, il ne neige pas moins qu’avant mais il y a plus de fonte réduisant le manteau neigeux entre deux événements neigeux. En extrapolant les tendances actuelles, une anomalie de +2.5 °C (resp. +3.8 °C) par rapport aux hivers 1960-90 serait suffisante pour ne plus avoir de neige en moyenne en-dessous de 750 m (resp. 1000 m)

Frequency and clinical genetics of familial dilated cardiomyopathy in Cape Town: Implications for the evaluation of patients with unexplained cardiomyopathy

Background. Studies from Europe and North America suggest that 20 - 50% of patients with dilated cardiomyopathy (DCM) may have familial disease. There is little information on the frequency and clinical genetics of familial DCM in Africa. Purpose. To determine the frequency and probable mode of inheritance of familial DCM in patients referred for investigation of the cause of DCM at a tertiary centre in Cape Town. Methods. We conducted a retrospective analysis of consecutive patients diagnosed with DCM between 1 February 1996 and 31 December 2009 to determine the frequency of familial disease. Results. Of 109 unrelated patients with DCM, 29 (26.6%) had familial disease. Their mean age of onset of cardiomyopathy (28.01 (standard deviation (SD) 15.33) years) was significantly younger than that for non-familial cases (39.1 (SD 12.6) years) (p=0.001). Male predominance (N=21, 72.4%) and racial distribution (15 (48.3%) coloured patients, 10 (34.5%) black Africans, 4 (13.8%) white individuals, and 1 (3.4%) of Indian descent) of familial DCM probands were similar to the non-familial cases. Of the 29 patients with familial DCM, 2 (7%) had at least one relative diagnosed with peripartum cardiomyopathy. Pedigree analysis of the 29 families was consistent with autosomal dominant inheritance in 72.4%, autosomal recessive inheritance in 17.2% and X-linked recessive inheritance in 10.4%. Conclusions. Familial DCM affects at least a quarter of African patients with DCM, presents at a young age, is associated with peripartum cardiomyopathy, and follows an autosomal dominant pattern of inheritance in the majority of families. Family screening for familial DCM is indicated in all cases of unexplained DCM, including patients with peripartum cardiomyopathy

Clinical epidemiology of laboratory-confirmed Buruli ulcer in Benin: a cohort study

Background Buruli ulcer, caused by Mycobacterium ulcerans, was identifi ed as a neglected emerging infectious disease by WHO in 1998. Although Buruli ulcer is the third most common mycobacterial disease worldwide, understanding of the disease is incomplete. We analysed a large cohort of laboratory-confi rmed cases of Buruli ulcer from Pobè, Benin, to provide a comprehensive description of the clinical presentation of the disease, its variation with age and sex, and its eff ect on the occurrence of permanent functional sequelae. Methods Between Jan 1, 2005, and Dec 31, 2011, we prospectively collected clinical and laboratory data from all patients with Buruli ulcer diagnosed at the Centre de Dépistage et de Traitement de l’Ulcère de Buruli in Pobè, Benin. We followed up patients to assess the frequency of permanent functional sequelae. All analyses were done on cases that were laboratory confi rmed. Findings 1227 cases of laboratory-confi rmed Buruli ulcer were included in the analysis. Typically, patients with Buruli ulcer were children (median age at diagnosis 12 years) presenting with a unique (1172 [96%]) large (≥15 cm, 444 [36%]) ulcerative (805 [66%]) lesion of the lower limb (733 [60%]). Atypical clinical presentation of Buruli ulcer included Buruli ulcer osteomyelitis with no identifi able present or past Buruli ulcer skin lesions, which was recorded in at least 14 patients. The sex ratio of Buruli ulcer widely varied with age, with male patients accounting for 57% (n=427) of patients aged 15 years and younger, but only 33% (n=158) of those older than 15 years (odds ratio [OR] 2·59, 95% CI 2·04–3·30). Clinical presentation of Buruli ulcer was signifi cantly dependent on age and sex. 54 (9%) male patients had Buruli ulcer osteomyelitis, whereas only 28 (4%) of female patients did (OR 2·21, 95% CI 1·39–3·59). 1 year after treatment, 229 (22% of 1043 with follow-up information) patients presented with permanent functional sequelae. Presentation with oedema, osteomyelitis, or large (≥15 cm in diameter), or multifocal lesions was signifi cantly associated with occurrence of permanent functional sequelae (OR 7·64, 95% CI 5·29–11·31) and operationally defi nes severe Buruli ulcer. Interpretation Our fi ndings have important clinical implications for daily practice, including enhanced surveillance for early detection of osteomyelitis in boys; systematic search for M ulcerans in osteomyelitis cases of non-specifi c aspect in areas endemic for Buruli ulcer; and specifi c disability prevention for patients presenting with osteomyelitis, oedema, or multifocal or large lesions. Our fi ndings also suggest a crucial underestimation of the burden of Buruli ulcer in Africa and raise key questions about the contribution of environmental and physiopathological factors to the recorded heterogeneity of the clinical presentation of Buruli ulcer