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41.
Gunnar Lischeid Dagmar Balla Ralf Dannowski Ottfried Dietrich Thomas Kalettka Christoph Merz Uwe Schindler Jörg Steidl 《Environmental Earth Sciences》2017,76(1):40
Facing the challenges of the European Water Framework Directive and competing demands requires a sound knowledge of the hydrological system. This is a major challenge in regions like Northeast Germany. The landscape has been massively reshaped during repeated advances and retreats of glaciation during the Pleistocene. This resulted in a complex setting of unconsolidated sediments with high textural heterogeneity and with layered aquifer systems, partly confined, but usually of unknown number and extent of single aquifers. The Institute of Landscape Hydrology aims both at a better understanding of hydrological processes and at providing a basis for sustainable water resources management in this region. That would require sound information about the respective regions of interest that are rarely available at sufficient degree of detail. Thus, there is urgent need for alternative approaches. For example, time series of groundwater head, lake water level and stream runoff do not only depend on (unknown) geological structures, but in turn can reveal information about major geological features. To that end, different approaches have been developed and successfully applied at different scales, based both on advanced time series analysis and dimension reduction approaches and on well-known and rather simple methods. This approach has been coined “forensic hydrology”: Like in a crime story, numerous pieces of evidence are combined in a systematic way to end up with a consistent conceptual model about the prevailing cause–effect relationships. An example is given for the Quillow catchment in Northeast Germany in a rather complex geological setting. 相似文献
42.
A Probabilistic Modelling System for Assessing Flood Risks 总被引：4，自引：2，他引：4
In order to be economically viable, flood disaster mitigation should be based on a comprehensive assessment of the flood risk.
This requires the estimation of the flood hazard (i.e. runoff and associated probability) and the consequences of flooding
(i.e. property damage, damage to persons, etc.). Within the “German Research Network Natural Disasters” project, the working
group on “Flood Risk Analysis” investigated the complete flood disaster chain from the triggering event down to its various
consequences. The working group developed complex, spatially distributed models representing the relevant meteorological,
hydrological, hydraulic, geo-technical, and socio-economic processes. In order to assess flood risk these complex deterministic
models were complemented by a simple probabilistic model. The latter model consists of modules each representing one process
of the flood disaster chain. Each module is a simple parameterisation of the corresponding more complex model. This ensures
that the two approaches (simple probabilistic and complex deterministic) are compatible at all steps of the flood disaster
chain. The simple stochastic approach allows a large number of simulation runs in a Monte Carlo framework thus providing the
basis for a probabilistic risk assessment. Using the proposed model, the flood risk including an estimation of the flood damage
was quantified for an example area at the river Rhine. Additionally, the important influence of upstream levee breaches on
the flood risk at the lower reaches was assessed. The proposed model concept is useful for the integrated assessment of flood
risks in flood prone areas, for cost-benefit assessment and risk-based design of flood protection measures and as a decision
support tool for flood management. 相似文献
43.
E. M. Alessi F. Deleflie A. J. Rosengren A. Rossi G. B. Valsecchi J. Daquin K. Merz 《Celestial Mechanics and Dynamical Astronomy》2016,125(1):71-90
We present the results of an extensive numerical exploration performed on the eccentricity growth in MEO associated with two possible end-of-life disposal strategies for GNSS satellites. The study calls attention to the existence of values of initial inclination, longitude of ascending node, and argument of perigee that are more advantageous in terms of long-term stability of the orbit. The important role of the initial epoch and a corresponding periodicity are also shown. The present investigation is influential in view of recent analytical and numerical developments on the chaotic nature of the region due to lunisolar perturbations, but also for the upcoming Galileo and BeiDou constellations. 相似文献
44.
Estimating groundwater recharge for an arid karst system using a combined approach of time‐lapse camera monitoring and water balance modelling 
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下载免费PDF全文 Stephan Schulz Gerrit H. de Rooij Nils Michelsen Randolf Rausch Christian Siebert Christoph Schüth Mohammed Al‐Saud Ralf Merz 《水文研究》2016,30(5):771-782
Groundwater is the principal water resource in semi‐arid and arid environments. Therefore, quantitative estimates of its replenishment rate are important for managing groundwater systems. In dry regions, karst outcrops often show enhanced recharge rates compared with other surface and sub‐surface conditions. Areas with exposed karst features like sinkholes or open shafts allow point recharge, even from single rainfall events. Using the example of the As Sulb plateau in Saudi Arabia, this study introduces a cost‐effective and robust method for recharge monitoring and modelling in karst outcrops. The measurement of discharge of a representative small catchment (4.0 · 104 m2) into a sinkhole, and hence the direct recharge into the aquifer, was carried out with a time‐lapse camera. During the monitoring period of two rainy seasons (autumn 2012 to spring 2014), four recharge events were recorded. Afterwards, recharge data as well as proxy data about the drying of the sediment cover are used to set up a conceptual water balance model. The model was run for 17 years (1971 to 1986 and 2012 to 2014). Simulation results show highly variable seasonal recharge–precipitation ratios between 0 and 0.27. In addition to the amount of seasonal precipitation, this ratio is influenced by the interannual distribution of rainfall events. Overall, an average annual groundwater recharge for the doline (sinkhole) catchment on As Sulb plateau of 5.1 mm has estimated for the simulation period. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
45.
The Tracking and Imaging RAdar (TIRA) at the Research Establishment for Applied Science (FGAN) was used in the L-band (1.33 GHz) to observe the Leonid shower in 1999. The radar beam was pointed directly into the radiant in the constellation Leo to receive “head echoes” from meteoroids when they ablate in the atmosphere at altitudes around 100 km. Two hundred and eighty-seven meteors were observed during 21 h in the early hours of November 17 and 18, 1999. The individual velocities, radiants and rough heliocentric orbits are calculated. Criteria are derived from optically observed Leonids which are then applied to decide whether an echo was created by a Leonid or a background meteoroid. However, in most cases the accuracy in the observational data is not good enough to allow for a clear distinction. Only for 100 meteors the velocity errors were less than 10 km/s. Out of those, 71 could be excluded on a 3σ level to be a Leonid (95 are excluded on a 1σ level). This confirms the theory that the Leonids have dominantly sizes of optical meteoroids with no significant extension in the lower mass range. Therefore, the risk of meteoroid impacts on spacecraft does not increase considerably during a Leonid storm. Background measurements 9 days after the Leonids maximum were taken in 2001 which corroborated the overall results obtained in 1999. 相似文献
46.
Shallow groundwater in a middle mountain catchment of Nepal: quantity and quality issues 总被引：1，自引：0，他引：1
Bhawani S. Dongol Juerg Merz Monika Schaffner Gopal Nakarmi Pravakar B. Shah Smita K. Shrestha Pradeep M. Dangol Madhav P. Dhakal 《Environmental Geology》2005,49(2):219-229
The use of shallow groundwater in middle mountain catchments of Nepal is a recent development. It was only in early 1998 that a number of dug wells had been constructed in the Jhikhu Khola catchment. But their numbers are rapidly increasing. While it seems to be a good way of accessing additional water resources both for domestic (current) and agricultural purposes (future), it is very important that the groundwater resources are not overexploited. Current dug wells are used to abstract groundwater, which is seasonally being recharged by the abundant monsoon rainfall. The water levels responded rapidly to the rainfall and differed according to the location of the well. The water quality parameters indicated that the water of most of the wells was not suitable for drinking purposes without prior treatment. Microbiological contamination is of particular concern, in addition to the high nitrate and phosphate levels. Some wells show elevated turbidity levels, indicating that there is an interaction between the muddy surface water and the water in the well. 相似文献
47.
Uncertainty and multiple objective calibration in regional water balance modelling: case study in 320 Austrian catchments 总被引：2，自引：0，他引：2
We examine the value of additional information in multiple objective calibration in terms of model performance and parameter uncertainty. We calibrate and validate a semi‐distributed conceptual catchment model for two 11‐year periods in 320 Austrian catchments and test three approaches of parameter calibration: (a) traditional single objective calibration (SINGLE) on daily runoff; (b) multiple objective calibration (MULTI) using daily runoff and snow cover data; (c) multiple objective calibration (APRIORI) that incorporates an a priori expert guess about the parameter distribution as additional information to runoff and snow cover data. Results indicate that the MULTI approach performs slightly poorer than the SINGLE approach in terms of runoff simulations, but significantly better in terms of snow cover simulations. The APRIORI approach is essentially as good as the SINGLE approach in terms of runoff simulations but is slightly poorer than the MULTI approach in terms of snow cover simulations. An analysis of the parameter uncertainty indicates that the MULTI approach significantly decreases the uncertainty of the model parameters related to snow processes but does not decrease the uncertainty of other model parameters as compared to the SINGLE case. The APRIORI approach tends to decrease the uncertainty of all model parameters as compared to the SINGLE case. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
48.
Gunnar Lischeid Marco Natkhin Jörg Steidl Ottfried Dietrich Ralf Dannowski Christoph Merz 《Advances in water resources》2010
The biosphere reserve Schorfheide-Chorin is a scenic region with many lakes. Hydraulic coupling between lakes and groundwater is difficult to assess due to the very heterogeneous Pleistocene deposits with a complex layering of different aquifers, part of them being confined. Thus, a principal component analysis of time series of groundwater and lake water levels was performed. The first two principal components provided a quantitative measure of damping of the input signal, i.e., the extent to which time series of groundwater pressure heads or lake water levels are smoothed and delayed with respect to the input signal, i.e., groundwater recharge or precipitation minus evapotranspiration, respectively. The lakes differed substantially with respect to damping behaviour, indicating different impacts of deep groundwater contribution. For most of the groundwater wells, damping increased linearly with mean depth to water table. In contrast, some wells exhibited nearly identical behaviour independent of depth. High-pass filtered data of water table level from these wells were strongly and inversely correlated with those of barometric pressure fluctuations, pointing to a confined aquifer which was evidently not connected to the adjacent lake. 相似文献
49.
Stephan Schulz Rike Becker Juan Carlos Richard-Cerda Muhammad Usman Tim aus der Beek Ralf Merz Christoph Schüth 《水文研究》2021,35(3):e14077
Information on water balance components such as evapotranspiration and groundwater recharge are crucial for water management. Due to differences in physical conditions, but also due to limited budgets, there is not one universal best practice, but a wide range of different methods with specific advantages and disadvantages. In this study, we propose an approach to quantify actual evapotranspiration, groundwater recharge and water inflow, i.e. precipitation and irrigation, that considers the specific conditions of irrigated agriculture in warm, arid environments. This approach does not require direct measurements of precipitation or irrigation quantities and is therefore suitable for sites with an uncertain data basis. For this purpose, we combine soil moisture and energy balance monitoring, remote sensing data analysis and numerical modelling using Hydrus. Energy balance data and routine weather data serve to estimate ET0. Surface reflectance data from satellite images (Sentinel-2) are used to derive leaf area indices, which help to partition ET0 into energy limited evaporation and transpiration. Subsequently, first approximations of water inflow are derived based on observed soil moisture changes. These inflow estimates are used in a series of forward simulations that produce initial estimates of drainage and ETact, which in turn help improve the estimate of water inflow. Finally, the improved inflow estimates are incorporated into the model and then a parameter optimization is performed using the observed soil moisture as the reference figure. Forward simulations with calibrated soil parameters result in final estimates for ETact and groundwater recharge. The presented method is applied to an agricultural test site with a crop rotation of cotton and wheat in Punjab, Pakistan. The final model results, with an RMSE of 2.2% in volumetric water content, suggest a cumulative ETact and groundwater recharge of 769 and 297 mm over a period of 281 days, respectively. The total estimated water inflow accounts for 946 mm, of which 77% originates from irrigation. 相似文献
50.
An integrated indicator framework for spatial assessment of industrial and social vulnerability to indirect disaster losses 总被引：2，自引：0，他引：2
The focus of this study is on multi-dimensional vulnerability of regions to indirect disaster losses. An integrated indicator framework has been developed which captures the multi-layered vulnerability drivers in industrial production systems and also accounts for the social fragilities and coping capacities in communities. By combining industrial vulnerability and social vulnerability spatially, and proposing a methodology to account between their interactions, the total vulnerability to indirect risks of regions is revealed. The outcome of the framework is a ranking of industrial sectors and geographic areas according to their vulnerability against indirect losses. It answers the question which of the two affected regions is in a better position to cope with indirect consequences in a disaster. Indicators provide a flexible framework for the comparison and integration of different data types and allow the combination of social as well as economic aspects. Decision-Making Trial and Evaluation Laboratory (DEMATEL) methodology was applied to analyze direct and indirect dependencies within the selected social and industrial vulnerability indicators. The hierarchical indicator system has been implemented in a software system based on multi-criteria decision theory (MCDA) with an interactive interface to take into account a broader range of expert judgement. The methodology was applied in a case study in the state of Baden-Wuerttemberg in Germany for 16 different industrial sectors. The approach helps to identify particular vulnerable processes and points out where mitigation measures could be implemented most effectively. 相似文献