@article{KernHellebrandGoemmeletal.2012, author = {Kern, J{\"u}rgen and Hellebrand, Hans J{\"u}rgen and G{\"o}mmel, Michael and Ammon, Christian and Berg, Werner}, title = {Effects of climatic factors and soil management on the methane flux in soils from annual and perennial energy crops}, series = {Biology and fertility of soils}, volume = {48}, journal = {Biology and fertility of soils}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0178-2762}, doi = {10.1007/s00374-011-0603-z}, pages = {1 -- 8}, year = {2012}, abstract = {Methane flux rates were measured on a loamy sand soil within perennial and annual energy crops in northeast Germany. The study was performed in closed chambers between 2003 and 2005 with four measurements per week. A mixed linear model including the fixed effects of year, rotation period, crop and fertilisation was applied to determine the influence of climatic factors and soil management on the CH4 flux. Soil water content and air temperature were added as co-variables. With the exception of air temperature, all fixed effects and the co-variable soil water content influenced the CH4 flux. The soil of annual crops consumed 6.1 mu g CH4 m(-2) h(-1), significantly more than the soil of perennial crops with 4.3 mu g CH4 m(-2) h(-1). It is suggested that soil water content plays the key role in CH4 flux between pedosphere and atmosphere. In the range of water contents between 5\% and 15\%, our model describes that a soil water content increase of 1\% induces a net emission of 0.375 mu g CH4 m(-2) h(-1). As the soil of the experimental field was well-drained and aerobic, it represented a net sink for CH4 throughout the study period.}, language = {en} } @article{AmourMuttiChristetal.2012, author = {Amour, Frederic and Mutti, Maria and Christ, Nicolas and Immenhauser, Adrian and Agar, Susan M. and Benson, Gregory S. and Tomas, Sara and Alway, Robert and Kabiri, Lachen}, title = {Capturing and modelling metre-scale spatial facies heterogeneity in a Jurassic ramp setting (Central High Atlas, Morocco)}, series = {Sedimentology : the journal of the International Association of Sedimentologists}, volume = {59}, journal = {Sedimentology : the journal of the International Association of Sedimentologists}, number = {4}, publisher = {Wiley-Blackwell}, address = {Malden}, issn = {0037-0746}, doi = {10.1111/j.1365-3091.2011.01299.x}, pages = {1158 -- 1189}, year = {2012}, abstract = {Each simulation algorithm, including Truncated Gaussian Simulation, Sequential Indicator Simulation and Indicator Kriging is characterized by different operating modes, which variably influence the facies proportion, distribution and association of digital outcrop models, as shown in clastic sediments. A detailed study of carbonate heterogeneity is then crucial to understanding these differences and providing rules for carbonate modelling. Through a continuous exposure of Bajocian carbonate strata, a study window (320 m long, 190 m wide and 30 m thick) was investigated and metre-scale lithofacies heterogeneity was captured and modelled using closely-spaced sections. Ten lithofacies, deposited in a shallow-water carbonate-dominated ramp, were recognized and their dimensions and associations were documented. Field data, including height sections, were georeferenced and input into the model. Four models were built in the present study. Model A used all sections and Truncated Gaussian Simulation during the stochastic simulation. For the three other models, Model B was generated using Truncated Gaussian Simulation as for Model A, Model C was generated using Sequential Indicator Simulation and Model D was generated using Indicator Kriging. These three additional models were built by removing two out of eight sections from data input. The removal of sections allows direct insights on geological uncertainties at inter-well spacings by comparing modelled and described sections. Other quantitative and qualitative comparisons were carried out between models to understand the advantages/disadvantages of each algorithm. Model A is used as the base case. Indicator Kriging (Model D) simplifies the facies distribution by assigning continuous geological bodies of the most abundant lithofacies to each zone. Sequential Indicator Simulation (Model C) is confident to conserve facies proportion when geological heterogeneity is complex. The use of trend with Truncated Gaussian Simulation is a powerful tool for modelling well-defined spatial facies relationships. However, in shallow-water carbonate, facies can coexist and their association can change through time and space. The present study shows that the scale of modelling (depositional environment or lithofacies) involves specific simulation constraints on shallow-water carbonate modelling methods.}, language = {en} } @article{NoackScheckWenderothCacace2012, author = {Noack, Vera and Scheck-Wenderoth, Magdalena and Cacace, Mauro}, title = {Sensitivity of 3D thermal models to the choice of boundary conditions and thermal properties: a case study for the area of Brandenburg (NE German Basin)}, series = {Environmental earth sciences}, volume = {67}, journal = {Environmental earth sciences}, number = {6}, publisher = {Springer}, address = {New York}, issn = {1866-6280}, doi = {10.1007/s12665-012-1614-2}, pages = {1695 -- 1711}, year = {2012}, abstract = {Based on newly available data of both, the structural setting and thermal properties, we compare 3D thermal models for the area of Brandenburg, located in the Northeast German Basin, to assess the sensitivity of our model results. The structural complexity of the basin fill is given by the configuration of the Zechstein salt with salt diapirs and salt pillows. This special configuration is very relevant for the thermal calculations because salt has a distinctly higher thermal conductivity than other sediments. We calculate the temperature using a FEMethod to solve the steady state heat conduction equation in 3D. Based on this approach, we evaluate the sensitivity of the steady-state conductive thermal field with respect to different lithospheric configurations and to the assigned thermal properties. We compare three different thermal models: (a) a crustal-scale model including a homogeneous crust, (b) a new lithosphere-scale model including a differentiated crust and (c) a crustal-scale model with a stepwise variation of measured thermal properties. The comparison with measured temperatures from different structural locations of the basin shows a good fit to the temperature predictions for the first two models, whereas the third model is distinctly colder. This indicates that effective thermal conductivities may be different from values determined by measurements on rock samples. The results suggest that conduction is the main heat transport mechanism in the Brandenburg area.}, language = {en} } @article{CostaBronstertdeAraujo2012, author = {Costa, A. C. and Bronstert, Axel and de Araujo, Jose Carlos}, title = {A channel transmission losses model for different dryland rivers}, series = {Hydrology and earth system sciences : HESS}, volume = {16}, journal = {Hydrology and earth system sciences : HESS}, number = {4}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-16-1111-2012}, pages = {1111 -- 1135}, year = {2012}, abstract = {Channel transmission losses in drylands take place normally in extensive alluvial channels or streambeds underlain by fractured rocks. They can play an important role in streamflow rates, groundwater recharge, freshwater supply and channel-associated ecosystems. We aim to develop a process-oriented, semi-distributed channel transmission losses model, using process formulations which are suitable for data-scarce dryland environments and applicable to both hydraulically disconnected losing streams and hydraulically connected losing(/gaining) streams. This approach should be able to cover a large variation in climate and hydro-geologic controls, which are typically found in dryland regions of the Earth. Our model was first evaluated for a losing/gaining, hydraulically connected 30 km reach of the Middle Jaguaribe River (MJR), Ceara, Brazil, which drains a catchment area of 20 000 km(2). Secondly, we applied it to a small losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch Experimental Watershed (WGEW), Arizona, USA. The model was able to predict reliably the streamflow volume and peak for both case studies without using any parameter calibration procedure. We have shown that the evaluation of the hypotheses on the dominant hydrological processes was fundamental for reducing structural model uncertainties and improving the streamflow prediction. For instance, in the case of the large river reach (MJR), it was shown that both lateral stream-aquifer water fluxes and groundwater flow in the underlying alluvium parallel to the river course are necessary to predict streamflow volume and channel transmission losses, the former process being more relevant than the latter. Regarding model uncertainty, it was shown that the approaches, which were applied for the unsaturated zone processes (highly nonlinear with elaborate numerical solutions), are much more sensitive to parameter variability than those approaches which were used for the saturated zone (mathematically simple water budgeting in aquifer columns, including backwater effects). In case of the MJR-application, we have seen that structural uncertainties due to the limited knowledge of the subsurface saturated system interactions (i.e. groundwater coupling with channel water; possible groundwater flow parallel to the river) were more relevant than those related to the subsurface parameter variability. In case of the WEGW application we have seen that the non-linearity involved in the unsaturated flow processes in disconnected dryland river systems (controlled by the unsaturated zone) generally contain far more model uncertainties than do connected systems controlled by the saturated flow. Therefore, the degree of aridity of a dryland river may be an indicator of potential model uncertainty and subsequent attainable predictability of the system.}, language = {en} } @article{KneisBuergerBronstert2012, author = {Kneis, David and Buerger, Gerd and Bronstert, Axel}, title = {Evaluation of medium-range runoff forecasts for a 50 km(2) watershed}, series = {Journal of hydrology}, volume = {414}, journal = {Journal of hydrology}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2011.11.005}, pages = {341 -- 353}, year = {2012}, abstract = {We generated medium-range forecasts of runoff for a 50 km(2) headwater catchment upstream of a reservoir using numerical weather predictions (NWPs) of the past as input to an operational hydrological model. NWP data originating from different sources were tested. For a period of 8.5 years, we computed daily forecasts with a lead time of +120 h based on an empirically downscaled version of the ECMWF's ensemble prediction system. For the last 3.5 years of the test period, we also tried the deterministic COSMO-EU forecast disseminated by the German Weather Service for lead times of up to +72 h. Common measures of skill indicate superiority of the ensemble runoff forecast over single-value forecasts for longer lead times. However, regardless of which NWP data were being used, the probability of event detection (POD) was found to be generally lower than 50\%. In many cases, values in the range of 20-30\% were obtained. At the same time, the false alarms ratio (FAR) was often found to be considerably high. The observed uncertainties in the hydrological forecasts were shown to originate from both the insufficient quality of precipitation forecasts as well as deficiencies in hydrological modeling and quantitative precipitation estimation. With respect to the anticipatory control of reservoirs in the studied catchment, the value of the tested runoff forecasts appears to be limited. This is due to the unfavorably low POD/FAR ratio in conjunction with a high cost-loss ratio. However, our results indicate that, in many cases, major runoff events related to snow melt can be successfully predicted as early as 4-5 days in advance.}, language = {en} }