[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU | International audience | PIETE: Un projet pour étudier la partition entre l'évaporation et la transpiration à l'aide d'isotopes de l'eau: expérimentation de terrain et de laboratoire, et modélisation

Tesis (M. Sc) -- CATIE, Turrialba (Costa Rica), 2010 | GA 17 indicator of both human and animal contamination from and HB 13, a strain found only in human origin samples. The concentration for each strain was evaluated and compared with fecal bacterial indicators, (e.g.) fecal coliforMON, Clostridium perfringens and somatic phages, all these in order to determine which of the two bacterial groups is better in terMON of their ability to discriminate the source of fecal contamination. It was finally concluded in this study that the use of traditional indicators of fecal contamination as fecal coliforMON, Clostridium perfringens and somatic phages, are still useful in order to evaluate water quality samples, however, those are not able to establish differences in their concentration in each of the sampling stations with different pollution source, so its use remains only as indicators but not fecal contamination discriminators, this suggests the need for more studies with new strains of Bacteroides, known to discrimine source of pollution, but these have to be isolated from the site where we want to make the discrimination analysis, as this would give a better recovery rate, together with the particular nutritional and environmental requirements inherent to the area of the study. Se hizo una evaluación de los fagos de Bacteroides de las cepas RYC 2056, propias de muestras con contaminación de origen animal, GA 17 propias de contaminación de origen humana y en menores concentraciones de origen animal y HB 13 que se encuentran en muestras de origen humano. Se evaluó su concentración y se comparó con bacterias indicadoras de contaminación fecal, como lo son coliformes fecales, Clostridium perfringes y fagos somáticos, esto con el fin de determinar cual de estos dos grupos bacterianos es mejor en cuanto a su capacidad de discriminar la fuente de la contaminación de origen fecal. Se pudo concluir finalmente con este estudio que el uso de indicadores tradicionales de contaminación fecal como colíformes fecales, Clostridium perfringes y fagos somáticos, siguen siendo de gran utilidad para la evaluación de diferentes muestras de aguas, sin embargo, no se lograron establecer diferencias en cuanto a su concentración en cada una de las estaciones de muestreo con diferente origen de contaminación, por lo que su uso sigue siendo sólo como indicadores y no discriminadores de contaminación fecal, permitiendo sugerir la necesidad de hacer estudios nuevos con cepas de Bacteroides, que son conocidas como bacterias discriminadoras de la fuente de contaminación, pero que sean aisladas del sitio donde se desee hacer el análisis de discriminación, ya que así se daría una mejor recuperación de estos, al evaluarse con los requerimientos nutricionales y ambientales propios de la zona a estudiar. An assessment was developed with bacteriophage strains RYC 2056, typical of contaminated samples of animal origin

The 1,750-km²endorheic Honey Lake basin (California–Nevada, USA) was part of the 22,000-km²Pleistocene Lake Lahontan pluvial lake system which existed between 5,000 and 40,000 years BP. The basin consists of two subbasins separated by a low elevation divide. Groundwater in the western subbasin has a maximum total dissolved solids (TDS) content of only ∼1,300 mg/L; however eastern subbasin groundwater has a maximum TDS of ∼46,000 mg/L. This TDS distribution is unexpected because 94% of surface water TDS loading is to the western subbasin. In situ reactions and upwelling thermal groundwater contributing to groundwater chemistry were modeled using NETPATH. The TDS difference between the subbasins is attributed to post-Lake Lahontan isostatic rebound about 13,000 years ago. Prior to rebound the subbasins did not exist and the low point of the basin was in the eastern area where hydraulic isolation from the larger Lake Lahontan and frequent desiccation of the basin surface water resulted in evaporite mineral deposition in accumulating sediments. After rebound, the terminal sink for most surface water shifted to the western subbasin. Although most closed basins have not been impacted by isostatic rebound, results of this investigation demonstrate how tectonic evolution can impact the distribution of soluble minerals accumulating in shallow basins.

Water resources have been overexploited for agricultural irrigation and industrial production in the upper and middle reaches of the Heihe River, northwestern China. Due to inadequate water resources management, the runoff entering into the lower reaches has been continuously reduced in recent years. The Heihe River is the primary recharge source for the groundwater of the lower reaches, so the decrease in runoff has caused the groundwater level to decline. As a result, a series of ecological and environmental problems has now appeared in the lower reaches, including river-flow interruptions, drying up of associated lakes, degeneration of vegetative cover and so on. In view of these issues, the National Water Diversion Project was put into practice in July 2000. It has significantly increased the quantity and frequency of flows entering into the lower reaches of the Heihe River, and has recharged the groundwater and improved the water quality to some degree along the length of the river. The water deliveries have had obvious influences on the groundwater in the lower reaches. The groundwater level increase and groundwater quality improvement have been of great benefit in restoring the ecological environment that was destroyed in past years.

The two-dimensional variably-saturated numerical model HYDRUS-2D, previously calibrated to recharge events from an infiltration basin, was used to predict water-table mounding under hypothetical basin design scenarios, and the primary factors that affect water-table mounding were evaluated. Infiltration basins are often utilized in urban environments to recharge stormwater to the aquifer. As a result of localized recharge beneath these basins, mound formation may reduce the thickness of the unsaturated zone available to filter pollutants and may reduce the infiltration rate of the basin. Understanding the effects of various physical factors on water-table mound formation is important for infiltration basin siting. For sandy loam and loamy sand subsurface materials, mound heights increased as the thickness of both the unsaturated and saturated zones decreased. Mound heights increased as the initial soil moisture, basin size and ponding depth increased. A thin sedimentation layer on the basin floor delayed mound formation, but only slightly decreased the maximum mound height. This analysis could be used in future selection of infiltration basin locations; however, the analysis is limited to conditions that represent only a select range of basin design conditions and parameters typical of a glacial till environment in Wisconsin, USA.

Based on the regional hydrogeology and the stratigraphy beneath the Los Alamos National Laboratory (LANL) site, New Mexico (USA), a site-scale groundwater model has been built with more than 20 stratified hydrofacies. A stepwise inverse method was developed to estimate permeabilities for these hydrofacies by coupling observation data from different sources and at various spatial scales including single-well test, multiple-well pumping test and regional aquifer monitoring data. Statistical analyses of outcrop permeability measurements and single-well test results were used to define the prior distributions of the parameters. These distributions were used to define the parameter initial values and the lower and upper bounds for inverse modeling. A number of inverse modeling steps were performed including the use of drawdown data from the pump tests at two wells (PM-2 and PM-4) separately, and a joint inversion coupling PM-2 and PM-4 pump test data and head data from regional aquifer monitoring. Parameter sensitivity coefficients for different data sets were computed to analyze if the model parameters can be estimated accurately with the data provided at different steps. The joint inversion offers a reasonable fit to all data sets. The uncertainty of estimated parameters for the hydrofacies is addressed with the parameter confidence intervals.

The 1996 reauthorization of the Safe Drinking Water Act required that each state in the US addresses the protection of public drinking water sources, including the development and implementation of a source-water assessment program. Such a program includes delineating source-water assessment areas, inventorying potential contaminant sources within this area, and determining the water system's susceptibility to contamination. The public was also involved in various phases of the program. Hawaii’s groundwater source assessment program is presented, along with an approach for implementation, which is consistent with federal requirements. The approach integrates groundwater models, aquifer databases, and a geographic information system. Source assessment areas were delineated by using numerical groundwater-flow models that used site-specific data to their fullest availability. The proposed approach is flexible enough to allow easy future updates as more sources are identified or as new information becomes available. The final product includes numerical scores that quantify the relative source susceptibility to contamination. Aquifer models developed in this study are potentially useful for future site-specific protection efforts or for other modeling purposes.

The southeast area of the Argentine Pampas is characterized by the presence of an unconfined aquifer in a wide plain. A methodology is proposed that deals with the aquifer vulnerability where the homogeneity of the hydrogeological variables used by traditional methods (in this case, DRASTIC-P) causes vulnerability maps to show more than 80% of the territory under the same class. This absence of discrimination renders vulnerability maps of little use to decision-makers. In addition, the proposed methodology avoids the traditional vague classification (high, low, and moderate vulnerability) which is highly dependent on subjectivity in its association of each class with hydrogeological considerations. That traditional vulnerability assessment methodology was adapted using a geographic information system to reclassify classes, based on the Natural Breaks (Jenks) method. The pixel-to-pixel comparison between the result obtained by the DRASTIC-P and the reclassified classes generates the so-called operational vulnerability index (OVI), which shows four classes, associating each with different hydrogeological requirements to make decisions.