Groundwater Modeling in Integrated Water Resources Management—Visions for 2020     

Jens Christian Refsgaard  Anker Lajer Højberg  Ingelise Møller  Martin Hansen  Verner Søndergaard 《Ground water》2010,48(5):633-648

Groundwater modeling is undergoing a change from traditional stand-alone studies toward being an integrated part of holistic water resources management procedures. This is illustrated by the development in Denmark, where comprehensive national databases for geologic borehole data, groundwater-related geophysical data, geologic models, as well as a national groundwater-surface water model have been established and integrated to support water management. This has enhanced the benefits of using groundwater models. Based on insight gained from this Danish experience, a scientifically realistic scenario for the use of groundwater modeling in 2020 has been developed, in which groundwater models will be a part of sophisticated databases and modeling systems. The databases and numerical models will be seamlessly integrated, and the tasks of monitoring and modeling will be merged. Numerical models for atmospheric, surface water, and groundwater processes will be coupled in one integrated modeling system that can operate at a wide range of spatial scales. Furthermore, the management systems will be constructed with a focus on building credibility of model and data use among all stakeholders and on facilitating a learning process whereby data and models, as well as stakeholders' understanding of the system, are updated to currently available information. The key scientific challenges for achieving this are (1) developing new methodologies for integration of statistical and qualitative uncertainty; (2) mapping geological heterogeneity and developing scaling methodologies; (3) developing coupled model codes; and (4) developing integrated information systems, including quality assurance and uncertainty information that facilitate active stakeholder involvement and learning.  相似文献   

Modulation of longevity in Daphnia magna by food quality and simultaneous exposure to dissolved humic substances     

Rihab Bouchnak  Christian E.W. Steinberg 《Limnologica》2010,40(2):86-91

Various abiotic and biotic factors determine the natural fluctuations of Daphnia spec. populations; food quality and dissolved humic substances (HSs) being among these factors. In this contribution, we try to disentangle the relative impact of food quality and simultaneous HSs exposure on the fertility and longevity of D. magna. It is understood that HS-mediated stress leads to reduced fecundity in well-fed D. magna females; hence, it was expected that poor food, as a second stressor, would aggravate the HS-mediated effects. Three diets were tested: the green algae Pseudokirchneriella subcapitata, baker’s yeast alone, and baker’s yeast plus dissolved ascorbic acid, and exposed D. magna to a HS preparation which has been shown effective in previous bioassays. It was hypothesized that the lifespan and fertility of D. magna would be best when fed green algae, and worst when fed only baker’s yeast. However, contrary to these expectations, any addition of HSs reduced the stress caused by poor food quality and increased lifespan and fecundity. In the yeast series, asexually produced diapausing eggs occurred via a so far unknown pathway. With yeast diet, the expanded lifespans were slightly above, whereas the increased offspring numbers lay below, the corresponding data of the algae-fed individuals. The potential of HSs as an additional food source and as a means to extend the lifespan is discussed. These findings open the innovative perspective that under low quality food conditions, additional stressors at certain intensities may even be beneficial to individuals and populations.  相似文献   

博斯腾湖流域山区地表径流对近期气候变化的响应   总被引：4，自引：0，他引：4  

孙占东  Christian Opp  王润  高前兆 《山地学报》2010,28(2)

近年来,在全球和区域气候变化影响下,新疆博斯腾湖主要产流区开都河出山径流呈现异常波动,引起气候变化研究的关注.鉴于产流区复杂地形和径流补给特征以及传统观测资料的不足,借助雷达、微波及可见光等多源遥感数据从山区降水、积雪和冰川等方面与出山径流变化关系进行比较来揭示径流突变原因.结果表明,产流区平均径流深与降水量关系的转变是引起出山径流异常波动直接原因;进一步的冰川变化分析显示,径流深的波动主要由冰川融水径流变化引起:20世纪80年代中期后的温度上升加速了山顶冰川消融,导致1987～2002年的径流增加和湖泊水位升高;1984～2000年间,流域山顶冰川面积消退近40%,随着分布在较低海拔,对温度升高最敏感的中小冰川的消失,冰雪消融带来的径流增加效应开始减弱;2002年后,在流域气温、降水等变化并不显著的情况下,出山径流量却急剧降低,反映了特定冰川分布条件地区在气候变暖中融水径流先升后降的现象.  相似文献   

Modelling fluxes of water and sediment between Venice Lagoon and the sea     

Christian Ferrarin  Andrea Cucco  Georg Umgiesser  Debora Bellafiore  Carl L. Amos 《Continental Shelf Research》2010

To describe the exchange of water and sediment through the Venice Lagoon inlets a 3-D hydrodynamic and sediment transport model has been developed and applied to a domain comprising Venice Lagoon and a part of the Adriatic Sea. The model has been validated for both current velocities and suspended particle concentration against direct observations and from observations empirically derived fluxes from upward-looking acoustic Doppler current profiler probes installed inside each inlet. The model provides estimates of the suspended sediment transport in the lower 3 m of the water column that is not detected by acoustic Doppler current profiler sensors. The bedload model prediction has been validated against measured sand transport rates collected by sand traps deployed in the Lido and Chioggia inlets. Results indicate that, in the Lido inlet, 87% of the total load is in suspension, while the rest moves as bedload.  相似文献   

Climatology of ionospheric upper transition height derived from COSMIC satellites during the solar minimum of 2008     

Xinan Yue  William S. Schreiner  Jiuhou Lei  Christian Rocken  Ying-Hwa Kuo  Weixing Wan 《Journal of Atmospheric and Solar》2010,72(17):1270-1274

The electron density profiles retrieved from the Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) satellite Radio Occultation (RO) observations during 2008 are used to derive ionospheric upper transition height, where the density of O⁺ is equal to that of light ions (mainly H⁺ and He⁺). It is found that the ionosphere upper transition height is very low, with significant local time, latitude and seasonal variations, during the extremely low solar minimum of 2008. The transition height is higher in the daytime than at night, except over middle latitude region of winter hemisphere, where the transition height has minimum in the morning. There is a pronounced peak over equator for all seasons. The transition height is higher in summer than in winter hemisphere. Our results have comparability with C/NOFS satellite observations around the equatorial region during June–August of 2008. However, the IRI model gives much higher transition height than those from COSMIC and cannot reproduce its latitude and season variations well during 2008.  相似文献   

Challenges of modeling current very large lahars at Nevado del Huila Volcano,Colombia     

Raphael Worni  Christian Huggel  M. Stoffel  B. Pulgarín 《Bulletin of Volcanology》2012,74(2):309-324

Nevado del Huila, a glacier-covered volcano in the South of Colombia’s Cordillera Central, had not experienced any historical eruptions before 2007. In 2007 and 2008, the volcano erupted with phreatic and phreatomagmatic events which produced lahars with flow volumes of up to about 300 million m³ causing severe damage to infrastructure and loss of lives. The magnitude of these lahars and the prevailing potential for similar or even larger events, poses significant hazards to local people and makes appropriate modeling a real challenge. In this study, we analyze the recent lahars to better understand the main processes and then model possible scenarios for future events. We used lahar inundation depths, travel duration, and flow deposits to constrain the dimensions of the 2007 event and applied LAHARZ and FLO-2D for lahar modeling. Measured hydrographs, geophone seismic sensor data and calculated peak discharges served as input data for the reconstruction of flow hydrographs and for calibration of the models. For model validation, results were compared with field data collected along the Páez and Simbola Rivers. Based on the results of the 2007 lahar simulation, we modeled lahar scenarios with volumes between 300 million and 1 billion m³. The approach presented here represents a feasible solution for modeling high-magnitude flows like lahars and allows an assessment of potential future events and related consequences for population centers downstream of Nevado del Huila.  相似文献   

Using precipitation data ensemble for uncertainty analysis in SWAT streamflow simulation   总被引：1，自引：0，他引：1  

Michael Strauch  Christian Bernhofer  Sérgio Koide  Martin Volk  Carsten Lorz  Franz Makeschin 《Journal of Hydrology》2012

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Annual fossil organic carbon delivery due to mechanical and chemical weathering of marly badlands areas     

Yann Graz  Christian Di‐Giovanni  Yoann Copard  Nicolle Mathys  Alexandre Cras  Vincent Marc 《地球表面变化过程与地形》2012,37(12):1263-1271

A key issue in the study of the carbon cycle is constraining the stocks and fluxes in and between C‐reservoirs. Among these, the role and importance of fossil organic carbon (FOC) release by weathering of outcropping sedimentary rocks on continental surfaces is still debated and remains poorly constrained. Our work focuses on FOC fluxes due to chemical and mechanical weathering of marls in two experimental watersheds with typical badlands geomorphology (Draix watersheds, Laval and Moulin, Alpes de Haute Provence, France). Organic matter from bedrock, soil litter and riverine particles are characterized by Rock‐Eval 6 pyrolysis. FOC fluxes due to mechanical weathering are then estimated by monitoring the annual particulate solid exports at the outlets of the watersheds (1985–2005 period). FOC fluxes from chemical weathering were calculated using Ca²⁺ concentrations in dissolved loads (year 2002) to assess the amount of FOC released by the dissolution of the carbonate matrix. Results show that FOC delivery is mainly driven by mechanical weathering, with a yield ranging from 30 to 59 t km^‐2 yr^‐1 in the Moulin (0.08 km²) and Laval (0.86 km²) catchments, respectively, (1985–2005 average). The release of FOC attributed to chemical weathering was 2.2 to 4.2 t km^‐2 for the year 2002. These high FOC fluxes from badlands are similar to those observed in tectonically active mountain catchments. At a regional scale, badland outcropping within the Durance watershed does not exceed 0.25% in area of the Rhône catchment, but could annually deliver 12 000 t yr^‐1 of FOC. This flux could correspond to 27% of the total particulate organic carbon (POC) load exported by the Rhône River to the Mediterranean Sea. At a global scale, our findings suggest that erosion of badlands may contribute significantly to the transfer of FOC from continental surfaces to depositional environments. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Single- and two-phase fluid flow properties of cataclastic fault rocks in porous sandstone     

Christian Tueckmantel  Quentin J. Fisher  Carlos A. Grattoni  Andrew C. Aplin 《Marine and Petroleum Geology》2012,29(1):129-142

Understanding the impact of faults on fluid flow in the subsurface is important for the extraction of oil, gas and groundwater as well as the geological storage of waste products. We address two problems present in current industry-standard workflows for fault seal analysis that may lead to fault rocks not being represented adequately in computational fluid flow models. Firstly, fluid flow properties of fault rocks are often measured only for small-scale faults with throws not exceeding a few centimetres. Large seismic-scale faults (throws >20 m) are likely to act as baffles or conduits to flow but they are seldom recovered from subsurface cores and consequently fault rock data for them is sparse. Secondly, experimental two-phase fluid flow data is lacking for fault rocks and, consequently, uncertainties exist when modelling flow across faults in the presence of two or more immiscible phases. We present a data set encompassing both single- and two-phase fluid flow properties of fault and host rocks from the 90-Fathom fault and its damage zone at Cullercoats Bay, NE England. Measurements were made on low-throw single and zones of deformation bands as well as on slip-surface cataclasites present along the ～120 m throw main fault. Samples were analysed using SEM and X-ray tomography prior to petrophysical measurements. We show that single deformation bands, deformation band zones and slip-surface cataclasites exhibit dissimilar single- and two-phase fluid flow properties. This is due to grain-size reduction being more pronounced in slip-surface cataclasites and changes in microstructure being fault-parallel for deformation bands but mostly fault-perpendicular for slip-surface cataclasites. A trend of fault rocks with low absolute permeabilities exhibiting lower relative permeabilities than more permeable rocks at the same capillary pressure is evident.  相似文献   

Shape factors of cylindrical piezometers in uniform soil     

Silvestri V  Abou-Samra G  Bravo-Jonard C 《Ground water》2012,50(2):279-284

This article presents the analytical solution of Laplace equation for the steady flow around open-ended cylindrical piezometers located in an infinite, isotropic, and incompressible saturated soil. Shape factors are obtained for piezometers with varying length-to-diameter ratios. Comparisons are made with published factors obtained by means of approximate analytical solutions, numerical approaches, and measurements in electric analog models. It is shown that some expressions that are currently used in practice are inadequate and should be abandoned.  相似文献