Suspended sediment routing through a small on-stream reservoir based on particle properties

Purpose A novel concept of suspended sediment (SS) routing through a small reservoir is proposed that relies on the particle properties in the reservoir inflow. Methods The SS routing through the reservoir is described following the single continuous stirred tank reactor concept with only one model parameter, the SS decay coefficient. This parameter is linked to the sediment settling velocity and water flow velocity. Hence, the model does not require a direct calibration with recorded data. This model was tested on a small reservoir in Warsaw, Poland, with seven storm events. Suspended sediment samples at the reservoir inflow and outflow were taken manually during the passage of flood flows at irregular intervals. The performance of the proposed method was verified with the approach when the model parameter is estimated directly from recorded events. Results The parameter calculated based on particle properties was about 10 times higher than the corresponding parameter optimized from recorded SS events. Hence, there was a need to introduce a correction factor to accurately predict the effluent SS. This led to a high model performance for all events (Nash-Sutcliffe = 0.672 on average). Conclusions (i) The proposed SS routing model based on particle properties has been proven to accurately simulate SS in the reservoir outlet. (ii) Thus, the parameter can be estimated from the sediment settling velocity and water flow velocity, but the correction factor must be applied. (iii) Our findings acknowledge difficulties in describing SS routing through small reservoirs and indicate a lack of knowledge on the functioning of these reservoirs

Dependence of flood peaks and volumes in modeled discharge time series: effect of different uncertainty sources

Flood estimates needed for designing efficient and cost-effective flood protection structures are usually derived using observed peak discharges. This approach neglects, firstly, that floods are characterized not only by peak discharge but also by flood volume, and, secondly, that these characteristics are subject to modifications under climate and land use changes. Bivariate flood frequency analysis based on simulated discharge time series makes it possible to consider both flood peak and flood volume in design flood estimation. Further, this approach considers changes in discharge characteristics by using discharge series generated from climate time series used as an input for a hydrological model. Such series are usually not available at an hourly resolution but at a certain aggregation level (e.g. 24 h) and might not perfectly represent observed precipitation distributions. In this study, we therefore investigate how the aggregation and distribution of precipitation series and discharge distribution affect flood peaks and volumes and their dependence. We propose a framework for assessing the uncertainty in bivariate design flood estimates that is caused by different factors in the modeling chain, which consists of precipitation-discharge modeling, flood event sampling, and bivariate flood frequency analysis. The uncertainty sources addressed are precipitation aggregation and distribution, parameter and model uncertainty, and discharge resolution. Our results show that all of these uncertainty sources are relevant for design flood estimation and that the importance of the individual uncertainty sources is catchment dependent. Our results also demonstrate that substantial uncertainty is introduced already in the first step of the model chain because commonly used calibration procedures do not take into account the reproduction of flood volumes. Researchers should be aware of such deficiencies when performing bivariate flood frequency analysis on modeled discharge time series and should aim to tailor model calibration procedures to the problem at hand

Downsizing parameter ensembles for simulations of rare floods

For extreme-flood estimation, simulation-based approaches represent an interesting alternative to purely statistical approaches, particularly if hydrograph shapes are required. Such simulation-based methods are adapted within continuous simulation frameworks that rely on statistical analyses of continuous streamflow time series derived from a hydrological model fed with long precipitation time series. These frameworks are, however, affected by high computational demands, particularly if floods with return periods > 1000 years are of interest or if modelling uncertainty due to different sources (meteorological input or hydrological model) is to be quantified. Here, we propose three methods for reducing the computational requirements for the hydrological simulations for extreme-flood estimation so that long streamflow time series can be analysed at a reduced computational cost. These methods rely on simulation of annual maxima and on analysing their simulated range to downsize the hydrological parameter ensemble to a small number suitable for continuous simulation frameworks. The methods are tested in a Swiss catchment with 10 000 years of synthetic streamflow data simulated thanks to a weather generator. Our results demonstrate the reliability of the proposed downsizing methods for robust simulations of rare floods with uncertainty. The methods are readily transferable to other situations where ensemble simulations are needed

The need for legal regulation of global emissions from the aviation industry in the context of emerging aerospace vehicles

Emissions of black carbon from aerospace vehicles pose a challenge to international regulators. This mode of transport is still in its infancy, but is predicted to develop rapidly. Despite the lack of comprehensive scientific research, it has been argued that black carbon is the main contributor to climate change after greenhouse gases. These emissions, which cause transboundary pollution, cannot be effectively reduced by national laws because of differences in emissions standards. The main challenge is how to regulate them – through binding or non-binding laws – and in which form – harmonisation or unification of laws. International air and space regulations are subject to the trends of politicisation and economisation. The lack of a binding international law that regulates greenhouse gas emissions from the aviation industry is primarily caused by a lack of political will and economic calculations of certain states with respect to limits on their national interests. This article proposes soft law as a solution to stagnation in creating binding international regulations for emissions in the aviation and aerospace industry

The need for legal regulation of global emissions from the aviation industry in the context of emerging aerospace vehicles

Emissions of black carbon from aerospace vehicles pose a challenge to international regulators. This mode of transport is still in its infancy, but is predicted to develop rapidly. Despite the lack of comprehensive scientific research, it has been argued that black carbon is the main contributor to climate change after greenhouse gases. These emissions, which cause transboundary pollution, cannot be effectively reduced by national laws because of differences in emissions standards. The main challenge is how to regulate them – through binding or non-binding laws – and in which form – harmonisation or unification of laws. International air and space regulations are subject to the trends of politicisation and economisation. The lack of a binding international law that regulates greenhouse gas emissions from the aviation industry is primarily caused by a lack of political will and economic calculations of certain states with respect to limits on their national interests. This article proposes soft law as a solution to stagnation in creating binding international regulations for emissions in the aviation and aerospace industry

The mission (im)possible: towards a comprehensive legal framework regulating safety issues of point to point suborbital flights1

Space tourism is going beyond the borders of people’s actual perception on the topic of human mass transportation from one place on the Earth to another, crossing different jurisdictions. A suborbital flight from London to Sydney will last 4 hours instead of taking 23 hours as it lasts today when traveling by airplane. Point to point suborbital flights (P2P flights) offer a new mode of worldwide mass transportation. Consequently, they should be legally regulated at an international level. The article analyzes selected safety concerns which can create obstacles to the development of a global legal framework regulating the safety of P2P flights. The selected provisions of the US Commercial Space Launch Amendment Act of 2004 are reviewed in order to analyze mistakes and avoid the same mistakes at the international level. The article specifies four main threats to safety which need to be resolved internationally: the lack of a definition for the term space passenger, the lack of unified spaceport safety standards, the growing amount of space debris and weaponization of outer space. Main international space treaties are analyzed as to their suitability for P2P flights. The fictional scenario provided in the article involves a claim for damages for death as a result of vehicle crash due to pilot error, which is used as an illustration of the applicability of one of the conventions: the Montreal Convention of 1999 (air law regime) or the Liability Convention of 1972 (space law regime). Liability regime created by the Liability Convention of 1972 is entirely focused on State-to State liability, thus, the state, as opposed to passengers or their relatives and third parties, is eligible for the compensation. In the same pattern, the state of origin will pay the compensation as opposed to the manufacturer or operator of the aerospace vehicle used in the suborbital flight .It seems that it is more reasonable for the point-to-point suborbital flights to fall under the passenger-oriented Montreal Convention of 1999. It is too remote to assess whether the Liability Convention of 1972 can be amended. In the last chapter of the article, there are some suggestions regarding comprehensive legal framework regulating the safety of P2P flights.Straipsnyje analizuojamos keturios pasirinktos maršrutinių suborbitinių skrydžių saugumo grėsmės: keleivio apibrėžimo šiame kontekste nebuvimas, unifikuotų orbitinio uosto saugumo standartų nebuvimas, augantis kosmoso šiukšlių mastas bei ginklavimasis kosmose. Šios grėsmės parodo, kad oro ir kosmoso teisiniai režimai dar nėra pasirengę tinkamai reglamentuoti maršrutinius suborbitinius skrydžius

Bayesian uncertainty assessment of flood predictions in ungauged urban basins for conceptual rainfall-runoff models

Urbanization and the resulting land-use change strongly affect the water cycle and runoff-processes in watersheds. Unfortunately, small urban watersheds, which are most affected by urban sprawl, are mostly ungauged. This makes it intrinsically difficult to assess the consequences of urbanization. Most of all, it is unclear how to reliably assess the predictive uncertainty given the structural deficits of the applied models. In this study, we therefore investigate the uncertainty of flood predictions in ungauged urban basins from structurally uncertain rainfall-runoff models. To this end, we suggest a procedure to explicitly account for input uncertainty and model structure deficits using Bayesian statistics with a continuous-time autoregressive error model. In addition, we propose a concise procedure to derive prior parameter distributions from base data and successfully apply the methodology to an urban catchment in Warsaw, Poland. Based on our results, we are able to demonstrate that the autoregressive error model greatly helps to meet the statistical assumptions and to compute reliable prediction intervals. In our study, we found that predicted peak flows were up to 7 times higher than observations. This was reduced to 5 times with Bayesian updating, using only few discharge measurements. In addition, our analysis suggests that imprecise rainfall information and model structure deficits contribute mostly to the total prediction uncertainty. In the future, flood predictions in ungauged basins will become more important due to ongoing urbanization as well as anthropogenic and climatic changes. Thus, providing reliable measures of uncertainty is crucial to support decision making

Variability of the initial abstraction ratio in an urban and an agroforested catchment

The Curve Number method is one of the most commonly applied methods to describe the relationship between the direct runoff and storm rainfall depth. Due to its popularity and simplicity, it has been studied extensively. Less attention has been given to the dimensionless initial abstraction ratio, which is crucial for an accurate direct runoff estimation with the Curve Number. This ratio is most often assumed to be equal to 0.20, which was originally proposed by the method’s developers. In this work, storm events recorded in the years 2009–2017 in two small Polish catchments of different land use types (urban and agroforested) were analyzed for variability in the initial abstraction ratio across events, seasons, and land use type. Our results showed that: (i) estimated initial abstraction ratios varied between storm events and seasons, and were most often lower than the original value of 0.20; (ii) for large events, the initial abstraction ratio in the catchment approaches a constant value after the rainfall depth exceeds a certain threshold value. Thus, when using the Soil Conservation Service-Curve Number (SCS-CN) method, the initial abstraction ratio should be locally verified, and the conditions for the application of the suggested value of 0.20 should be established

Acid-Base Properties of the Adsorption of Synthetic Dyes from Solutions

The presence of synthetic dyes is often underestimated in environmental protection. However, it has been demonstrated the impact of colored compounds in ecology and human health. Green tea (GT) and peppermint (PM) tea bag wastes were used as potential adsorbents of dyes from aqueous solutions to evaluate the effect of pH on the adsorption. Basic yellow 57, basic blue 99 and crystal violet were chosen as model dyes due to their widespread use in the industry. Dye solutions at different pH values were placed in contact with the adsorbents in batch experiments at room temperature. Results indicate that crystal violet is totally removed from the solution by the adsorbents (100% removal), followed basic blue 99 and basic yellow. PM reports the highest dye removal. Our data was compared to recently published reports, indicating their potential applicability to real wastewaters, as it is optimum at neutral pH values. These results demonstrate that these materials are excellent and cost-effective candidates for the removal of dye pollutants from contaminated solutions

Long-term changes of hydrological variables in a small Lowland watershed in Central Poland

Climate-induced changes in small watersheds are still not well researched because long-term datasets are usually missing for these watersheds. Such studies can, however, improve our understanding of the watershed response to climatic changes at such a small scale being transparent. In this study, we investigate trends in temperature, precipitation and river-flow characteristics in a small watershed, typical for Central Poland, with 53 years of observations (1963–2015) using the Mann-Kendall test. Particularly, we examine whether any trends in hydro-meteorological variables can be identified, and if any associated changes in water resources in this region can already be observed. We found that this short period already allows for detecting some changes in hydro-meteorological variables. These changes could be characterized by a significant increase in the mean annual air temperature on a daily basis, and a significant decrease in the mean annual discharge on a daily basis and in the minimum annual discharge on a daily basis. Yet, no significant trend could be detected for the total annual precipitation, the maximum summer rainfall, and the maximum annual discharge on a daily basis. These findings indicate that water resources are decreasing in this region, which affects natural habitats, agriculture and local communities