Stress test modelling to assess catchment drought resistance and recovery

2020 ◽  
Author(s):  
Michael Stoelzle ◽  
Jost Hellwig ◽  
Kerstin Stahl ◽  
Markus Weiler ◽  
Erik Tijdeman ◽  
...  
Keyword(s):  
Heat Waves ◽  
Stress Test ◽  
Balance Model ◽  
Drought Event ◽  
Model Structure ◽  
Stress Tests ◽  
Groundwater Storage ◽  
Worst Case ◽  
Hydrogeological Characteristics

<p>Dry spells and heat waves control the frequency and duration of streamflow drought events. Groundwater storage and release in catchments can modulate their timing and severities in terms of deficit volume and persistence. To better understand the role of recharge and groundwater storage for catchment sensitivity to droughts we investigate the effect of recharge scenarios on streamflow drought characteristics and baseflow for 50 mesoscale catchments with different hydrogeological characteristics in southwestern Germany. In model experiments, we simulate daily recharge on a 1 km resolution with the water balance model TRAIN reflecting the most dominant soil-vegetation processes. Then we calibrate long-term reference simulations, fitting the outflow of different conceptual groundwater box models with varying model structure to hydrograph-separated baseflow. After calibration, we define probabilistic stress tests as scenarios of reduced pre-drought recharge. The tolerance of catchments to different drought intensities is analyzed based on the concepts of resistance, resilience, and recovery to drought situations. Results suggest that catchments with higher resistance and resilience are less sensitive to recharge stress, but recovery is often much slower. However, by comparing the events of e.g. 2003 and 2018 specifically, we show that the sensitivity is also a function of the intensity and duration of the stress test simulation, the drought event characteristics, and the storage memory of catchments. Additionally, the performance ranking of all groundwater models in each catchment allows to link the variability in model structure to catchment properties (e.g. geology). The analysis shows that catchments with short-term or long-term storage memory react differently under different stress tests. Stress test simulations may help to answer planning-relevant questions such as which preconditions make a drought intensification or prolongation more likely and how long does it take for the system to recover to the reference condition. Catchment-specific stress tests with historical worst-case pre-conditions before extreme drought events may thus be a way forward to constrain relevant timescales of drought management and drought early warning.</p>

scholarly journals Stress testing as complement to climate scenarios: recharge scenarios to quantify streamflow drought sensitivity

2020 ◽  
Vol 383 ◽  
pp. 43-50
Author(s):  
Michael Stoelzle ◽  
Maria Staudinger ◽  
Kerstin Stahl ◽  
Markus Weiler
Keyword(s):  
Stress Testing ◽  
Stress Test ◽  
Ecological Integrity ◽  
Climate Scenarios ◽  
Stress Tests ◽  
Worst Case ◽  
Drought Sensitivity ◽  
Dry Spells ◽  
Reference Simulation ◽  
Recovery Times

Abstract. Precipitation deficits and temperature anomalies are often the main cause for low flows and summer streamflow droughts. However, where groundwater is the main contribution to sustain water availability and ecological integrity during dry spells, the role of recharge and catchment storage is crucial to understand streamflow drought sensitivity. Here we introduce recharge stress tests as complement to climate scenarios to characterize and quantify the streamflow drought sensitivities of catchments. The stress tests are presented by applying them to six headwater catchments in Switzerland with various catchment and streamflow characteristics. The stress tests drive the bucket-type hydrological model HBV in a framework, in which pre-drought recharge conditions can be decreased to test how catchments respond to and recover from drought. We identified an upper limit of stress test durations around 12 months as indicator of maximum recharge- and storage-memory for the study catchments. Varying response on stress testing across the catchments suggests different storage properties and thus different recovery times from drought. From the stress test simulations, we found up to 200 d longer summer streamflow droughts with additional streamflow deficits which account for up to 40 d of median flow. Using a worst-case pre-drought recharge in stress test simulation leads to minimum flow reductions of 50 %–80 % compared with the reference simulation. Based on the results we conclude with recommendations for further stress test research in drought hydrology.

scholarly journals Optimal portfolios in the presence of stress scenarios A worst-case approach

2021 ◽  
Author(s):  
Ralf Korn ◽  
Lukas Müller
Keyword(s):  
Investment Decision ◽  
Stress Test ◽  
Insurance Companies ◽  
Stress Tests ◽  
Optimal Portfolios ◽  
Worst Case ◽  
Verification Theorem ◽  
Portfolio Strategies ◽  
Portfolio Approach ◽  
Worst Case Approach

AbstractInsurance companies and banks regularly have to face stress tests performed by regulatory instances. To model their investment decision problems that includes stress scenarios, we propose the worst-case portfolio approach. Thus, the resulting optimal portfolios are already stress test prone by construction. A central issue of the worst-case portfolio approach is that neither the time nor the order of occurrence of the stress scenarios are known. Even more, there are no probabilistic assumptions regarding the occurrence of the stresses. By defining the relative worst-case loss and introducing the concept of minimum constant portfolio processes, we generalize the traditional concepts of the indifference frontier and the indifference-optimality principle. We prove the existence of a minimum constant portfolio process that is optimal for the multi-stress worst-case problem. As a main result we derive a verification theorem that provides conditions on Lagrange multipliers and nonlinear ordinary differential equations that support the construction of optimal worst-case portfolio strategies. The practical applicability of the verification theorem is demonstrated via numerical solution of various worst-case problems with stresses. There, it is in particular shown that an investor who chooses the worst-case optimal portfolio process may have a preference regarding the order of stresses, but there may also be stress scenarios where he/she is indifferent regarding the order and time of occurrence.

scholarly journals Analýza zátěžových testů u skialpinistů

2012 ◽  
Vol 6 (1) ◽  
pp. 29-34
Author(s):  
Matouš Jindra ◽  
Ladislav Vomáčko ◽  
Dita Formánková ◽  
Klára Coufalová
Keyword(s):  
Maximum Stress ◽  
Stress Test ◽  
Maximum Load ◽  
Bicycle Ergometer ◽  
Load Test ◽  
Previous Experience ◽  
Stress Tests ◽  
Professional Information

We analyze 3 types of maximum stress tests on the basis of the lack of professional information about competitive ski mountaineering. Th e obtained data was compared with the maximum stress test on the treadmill; bicycle ergometer and treadmill using a roller ski modifi ed for ski mountaineering. Th e values which were measured shows great technical demands on the test using roller skis. Based on this information, we recommend long-term training on the treadmill using roller skis, before the maximum load test. Th e results show the smallest deviation of the maximum values among respondents who had previous experience with modifi ed roller skis for ski mountaineering.

Characterization of CMOS Structures (0.6 µm process) Submitted to HBM and COM ESD Stress Tests

1997 ◽  
Author(s):  
G. Meneghesso ◽  
E. Zanoni ◽  
P. Colombo ◽  
M. Brambilla ◽  
R. Annunziata ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrostatic Discharge ◽  
Stress Test ◽  
Complete Characterization ◽  
Stress Tests ◽  
Test Procedures ◽  
Emission Microscopy ◽  
Fast Rise ◽  
Scanning Electron

Abstract In this work, we present new results concerning electrostatic discharge (ESD) robustness of 0.6 μm CMOS structures. Devices have been tested according to both HBM and socketed CDM (sCDM) ESD test procedures. Test structures have been submitted to a complete characterization consisting in: 1) measurement of the tum-on time of the protection structures submitted to pulses with very fast rise times; 2) ESD stress test with the HBM and sCDM models; 3) failure analysis based on emission microscopy (EMMI) and Scanning Electron Microscopy (SEM).

Efficient Analysis of a Catenary Riser

2006 ◽  
Author(s):  
Elizabeth Passano ◽  
Carl M. Larsen
Keyword(s):  
Operating Conditions ◽  
Stochastic Simulations ◽  
Worst Case ◽  
Nonlinear Structure ◽  
Tension Response ◽  
Extreme Response ◽  
Analysis Strategies ◽  
Low Tension ◽  
Term Response

The paper deals with the challenge of predicting the extreme response of catenary risers, a topic of both industry and academic interest. Large heave motions introduced at the upper end of a catenary riser can lead to compression and large bending moments in the region immediately above the touch down area. In the worst case, dynamic beam buckling may occur. The focus of the paper will be on understanding the riser behaviour in extreme, low-tension response and in establishing suitable analysis strategies to predict the extreme response. Results from long nonlinear stochastic simulations of many sea states with varying environmental and operating conditions may be combined to describe the long-term response of a nonlinear structure such as a catenary riser. However, this theoretically straight-forward approach is very demanding computationally and ways to limit the extent of nonlinear stochastic simulations are therefore sought. The usefulness of simpler methods such as regular wave analysis to improve understanding of the physical behaviour and to aid in concentrating the nonlinear simulations to where they are most useful, will be demonstrated.

Pleistocene–Holocene environmental change in the Canary Archipelago as inferred from the stable isotope composition of land snail shells

2011 ◽  
Vol 75 (3) ◽  
pp. 658-669 ◽  
Author(s):  
Yurena Yanes ◽  
Crayton J. Yapp ◽  
Miguel Ibáñez ◽  
María R. Alonso ◽  
Julio De-la-Nuez ◽  
...  
Keyword(s):  
Environmental Change ◽  
Canary Islands ◽  
Environmental Changes ◽  
Isotope Composition ◽  
Moving Average ◽  
Land Snail ◽  
Balance Model ◽  
Low Latitude ◽  
The Times

AbstractThe isotopic composition of land snail shells was analyzed to investigate environmental changes in the eastern Canary Islands (28–29°N) over the last ~ 50 ka. Shell δ13C values range from −8.9‰ to 3.8‰. At various times during the glacial interval (~ 15 to ~ 50 ka), moving average shell δ13C values were 3‰ higher than today, suggesting a larger proportion of C4 plants at those periods. Shell δ18O values range from −1.9‰ to 4.5‰, with moving average δ18O values exhibiting a noisy but long-term increase from 0.1‰ at ~ 50 ka to 1.6–1.8‰ during the LGM (~ 15–22 ka). Subsequently, the moving average δ18O values range from 0.0‰ at ~ 12 ka to 0.9‰ at present. Calculations using a published snail flux balance model for δ18O, constrained by regional temperatures and ocean δ18O values, suggest that relative humidity at the times of snail activity fluctuated but exhibited a long-term decline over the last ~ 50 ka, eventually resulting in the current semiarid conditions of the eastern Canary Islands (consistent with the aridification process in the nearby Sahara). Thus, low-latitude oceanic island land snail shells may be isotopic archives of glacial to interglacial and tropical/subtropical environmental change.

Heat waves in Berlin and Potsdam, Germany – Long‐term trends and comparison of heat wave definitions from 1893 to 2017

2018 ◽  
Vol 39 (4) ◽  
pp. 2422-2437 ◽  
Author(s):  
Daniel Fenner ◽  
Achim Holtmann ◽  
Alexander Krug ◽  
Dieter Scherer
Keyword(s):  
Heat Wave ◽  
Heat Waves ◽  
Long Term Trends
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