Application Of Numerical Modelling For Conceptualizing Abstraction Rate Control In A Well Field Under Complex Boundary Conditions

This paper aims at presenting a concept for regulating water abstraction from a well field which ensures an efficient exploration of river filtrate while complying with defined minimum residence time of inflowing water. Being located on an island between a river and an attendant channel, the investigated well field consists of eight radial collector wells aligned parallel to the river flow direction. The water-level in the river is kept comparatively constant due to a downstream hydropower plant. In the channel, the water level is controlled by two weirs. Following a defined hydrograph with an amplitude of about one meter, the channel water level is on average four meters below the water level of the river. Therefore, the boundary conditions for the well field are subject to strong seasonal fluctuations. For legal reasons, water originating from the channel must remain in the underground for at least 60 days. To analyse on-site flow conditions, a three dimensional finite difference model was developed, calibrated and validated. The water balances of 23 observed steady state conditions with different abstractions from the wells and varying basic conditions were computed with the model. The computed inflow rates from the channel were analysed by comparing them with observed hydraulic heads and it was possible to show a high correlation with the ratio of certain hydraulic head gradients. A linear correlation (R² \u3e0.9) of the quantity and the flow time of inflowing water from the channel could be formulated by analysing the modelling results. By combining these findings, it was possible to develop a criterion for restricting the abstraction from each well according to a minimum water-flow time without the requirement of a parallel operated numerical model. The underlying parameters are computed from hydraulic head values enabling automatically real time control of a non-measurable value through measurable parameters

Hydrology needed to manage droughts: the 2015 European case

Hydrology needed to manage droughts: the 2015 European cas

Trends in flow intermittence for European rivers

Intermittent rivers are prevalent in many countries across Europe, but little is known about the temporal evolution of intermittence and its relationship with climate variability. Trend analysis of the annual and seasonal number of zero-flow days, the maximum duration of dry spells and the mean date of the zero-flow events is performed on a database of 452 rivers with varying degrees of intermittence between 1970 and 2010. The relationships between flow intermittence and climate are investigated using the standardized precipitation evapotranspiration index (SPEI) and climate indices describing large-scale atmospheric circulation. The results indicate a strong spatial variability of the seasonal patterns of intermittence and the annual and seasonal number of zero-flow days, highlighting the controls exerted by local catchment properties. Most of the detected trends indicate an increasing number of zero-flow days, which also tend to occur earlier in the year, particularly in southern Europe. The SPEI is found to be strongly related to the annual and seasonal zero-flow day occurrence in more than half of the stations for different accumulation times between 12 and 24 months. Conversely, there is a weaker dependence of river intermittence with large-scale circulation indices. Overall, these results suggest increased water stress in intermittent rivers that may affect their biota and biochemistry and also reduce available water resources

Feasibility of ultrasound measurement in a human model of acute compartment syndrome

Abstract Background Early diagnosis of acute compartment syndrome (ACS) of the leg is essential to improve the outcome. Direct invasive measurement is currently recommended to measure intracompartmental pressure. A non-invasive and reproducible means of making the diagnosis would be a step forward. The purpose of this exploratory study was to investigate the feasibility of non-invasive ultrasound-guided angle measurement as a surrogate of increased pressure in a model of ACS. Methods A model of ACS was generated by infusion of saline into the anterior compartment of the leg of human cadavers to incrementally increase the intracompartmental pressure from 10 to 100 mmHg. In 40 legs (20 cadavers), the angle (TFA, tibia-fascia angle) between the anterolateral cortex of the tibia and the fascia of the anterior compartment was measured at each 10 mmHg pressure increase using ultrasound in a standardized transversal plane. A multilevel linear regression model was used to estimate intracompartmental pressure from delta TFA (ΔTFA). Results TFA (mean [± SD]) increased from 61.0° (± 12.0°) at 10 mmHg up to 81.1° (± 11.1°) at 100 mmHg compartment pressure. Each increase ΔTFA by one degree was associated with an increase in pressure by 3.9 mmHg (95% CI, 3.8–4.0, p < 0.001). Conclusions We found that intracompartmental pressure of the anterior compartment of the calf can be well estimated by ultrasound-based ΔTFA in this post mortem experiment. Our findings indicate that non-invasive TFA measurement is feasible and it is reasonable that this will hold true in real life, but the findings are too preliminary to be used in clinical practice now

Analysing 21st century meteorological and hydrological drought events in Slovakia

Several quite severe droughts occurred in Europe in the 21st century; three of them (2003, 2012 and 2015) hit also Slovakia. The Standardized Precipitation Index (SPI) and Standardized Precipitation and Evapotranspiration Index (SPEI) were used for assessment of meteorological drought occurrence. The research was established on discharge time series representing twelve river basins in Slovakia within the period 1981–2015. Sequent Peak Algorithm method based on fixed threshold, three parametric Weibull and generalized extreme values distribution GEV, factor and multiple regression analyses were employed to evaluate occurrence and parameters of hydrological drought in 2003, 2011–2012 and 2015, and the relationship among the water balance components. Results showed that drought parameters in evaluated river basins of Slovakia differed in respective years, most of the basins suffered more by 2003 and 2012 drought than by the 2015 one. Water balance components analysis for the entire period 1931–2016 showed that because of continuously increasing air temperature and balance evapotranspiration there is a decrease of runoff in the Slovak territory

A catalogue of European intermittent rivers and ephemeral streams. Science and Management of Intermittent Rivers and Ephemeral Streams

SMIRES is a COST Action addressing the Science and Management of Intermittent Rivers & Ephemeral Streams (coord. T. Datry, INRAE, and G. Singer, University of Innsbruck; http://www.smires.eu). This COST Action had brought together scientists from various research field and stakeholders to develop a European multidisciplinary network for synthesising the fragmented and recent knowledge on temporary water courses, improving our understanding of Intermittent Rivers and Ephemeral Streams (IRES) and translating this into a science-based, sustainable management of river networks. The working group “Prevalence, distribution and trends of IRES” (WG1) has the central role to provide the physical basis of the SMIRES Action. One of the tasks of WG1 was to compile flow gauging data at the European scale. As part of this work, examples of intermittent rivers and ephemeral streams were collected across Europe, including gauged catchments with both natural and highly influenced river flow regimes. A total of 40 examples have been put together in this catalogue to provide an overview of the variety of IRES in Europe. The selected IRES are not meant to be representative of all intermittent water courses in Europe but rather highlight the variety in these water courses. Introductory pages describe the procedures used to create the catalogue including definitions of the statistical measures reported for the individual intermittent rivers and ephemeral streams, and provide an overview of the catalogued water courses. Information on the selected gauged intermittent rivers and ephemeral streams is summarised in a two-page document: The first standardized page describes the main characteristics of the catchments (land-use, geology, climate, etc.) and the river flow regime. Two panels display the hydrographs and flow durations curves, and a table gives metrics specific to river flow intermittence relevant for ecology. The second page is dedicated to the description and reasons for intermittence. A short description about the spatio-temporal pattern of zero-flow events. This section may describe the seasonal behaviour of the stream, observed long-term trends, locations with frequently observed zero-flow events along the river network, etc. The monitoring network, including gauging stations and other types of observations (e.g. visual inspection of the flow states at different locations along the river) in the catchment, are also described

The European 2015 drought from a hydrological perspective

In 2015 large parts of Europe were affected by drought. In this paper, we analyze the hydrological footprint (dynamic development over space and time) of the drought of 2015 in terms of both severity (magnitude) and spatial extent and compare it to the extreme drought of 2003. Analyses are based on a range of low flow and hydrological drought indices derived for about 800 streamflow records across Europe, collected in a community effort based on a common protocol. We compare the hydrological footprints of both events with the meteorological footprints, in order to learn from similarities and differences of both perspectives and to draw conclusions for drought management. The region affected by hydrological drought in 2015 differed somewhat from the drought of 2003, with its center located more towards eastern Europe. In terms of low flow magnitude, a region surrounding the Czech Republic was the most affected, with summer low flows that exhibited return intervals of 100 years and more. In terms of deficit volumes, the geographical center of the event was in southern Germany, where the drought lasted a particularly long time. A detailed spatial and temporal assessment of the 2015 event showed that the particular behavior in these regions was partly a result of diverging wetness preconditions in the studied catchments. Extreme droughts emerged where preconditions were particularly dry. In regions with wet preconditions, low flow events developed later and tended to be less severe. For both the 2003 and 2015 events, the onset of the hydrological drought was well correlated with the lowest flow recorded during the event (low flow magnitude), pointing towards a potential for early warning of the severity of streamflow drought. Time series of monthly drought indices (both streamflow- and climate-based indices) showed that meteorological and hydrological events developed differently in space and time, both in terms of extent and severity (magnitude). These results emphasize that drought is a hazard which leaves different footprints on the various components of the water cycle at different spatial and temporal scales. The difference in the dynamic development of meteorological and hydrological drought also implies that impacts on various water-use sectors and river ecology cannot be informed by climate indices alone. Thus, an assessment of drought impacts on water resources requires hydrological data in addition to drought indices based solely on climate data. The transboundary scale of the event also suggests that additional efforts need to be undertaken to make timely pan-European hydrological assessments more operational in the future.</p

The European 2015 drought from a hydrological perspective

In 2015 large parts of Europe were affected by drought. In this paper, we analyze the hydrological footprint (dynamic development over space and time) of the drought of 2015 in terms of both severity (magnitude) and spatial extent and compare it to the extreme drought of 2003. Analyses are based on a range of low flow and hydrological drought indices derived for about 800 streamflow records across Europe, collected in a community effort based on a common protocol. We compare the hydrological footprints of both events with the meteorological footprints, in order to learn from similarities and differences of both perspectives and to draw conclusions for drought management. The region affected by hydrological drought in 2015 differed somewhat from the drought of 2003, with its center located more towards eastern Europe. In terms of low flow magnitude, a region surrounding the Czech Republic was the most affected, with summer low flows that exhibited return intervals of 100 years and more. In terms of deficit volumes, the geographical center of the event was in southern Germany, where the drought lasted a particularly long time. A detailed spatial and temporal assessment of the 2015 event showed that the particular behavior in these regions was partly a result of diverging wetness preconditions in the studied catchments. Extreme droughts emerged where preconditions were particularly dry. In regions with wet preconditions, low flow events developed later and tended to be less severe. For both the 2003 and 2015 events, the onset of the hydrological drought was well correlated with the lowest flow recorded during the event (low flow magnitude), pointing towards a potential for early warning of the severity of streamflow drought. Time series of monthly drought indices (both streamflow- and climate-based indices) showed that meteorological and hydrological events developed differently in space and time, both in terms of extent and severity (magnitude). These results emphasize that drought is a hazard which leaves different footprints on the various components of the water cycle at different spatial and temporal scales. The difference in the dynamic development of meteorological and hydrological drought also implies that impacts on various water-use sectors and river ecology cannot be informed by climate indices alone. Thus, an assessment of drought impacts on water resources requires hydrological data in addition to drought indices based solely on climate data. The transboundary scale of the event also suggests that additional efforts need to be undertaken to make timely pan-European hydrological assessments more operational in the future.</p