تحلیل عدم قطعیت و ارزیابی ریسک روگذری سد مارون با استفاده از روش مونتکارلو و روش مربع لاتین

The relationship between vegetation and seasonal changes in water level was examined in a system of terrestrializing floating peat mat and pond in a warm temperate zone. The duration of flooding, or drawdown period, is related to vegetation in the mat. The first process of terrestrialization would be the attenuation of floating‐sinking movement of the mat and the consequent stabilization of water level. Water level at the time when the movement of the mat was attenuated determined the subsequent vegetation change at the site. Two series of succession according to terrestrialization were recognized, and started from initial conditions of low and high water levels respectively. Habitats in low initial water levels experienced short flooding and long drawdown periods. Species changes in the successional series were:Menyanthes trifoliata‐Rhynchospora fauriei‐Eriocaulon sikokianum‐Sphagnum cuspidatum. Submerged peat was experimentally emerged, and the crowded community of Rhynchospora fauriei and Eriocaulon sikokianum established within one or two years. Appearance of these species was controlled by the water level of the habitats in winter. Another series of species changes in terrestrialization process was:Menyanthes trifoliata‐Phragmites australis‐Carex thunbergii or Isachne globosa. Habitats of these types of vegetation were in the area with relatively high initial water level (long flooding and short drawdown) when the floating‐sinking movement of the mat attenuated. After the temporal paludification, the water level was lowered by the accumulation of peat in the process of terrestrialization.

Joint analysis of input and parametric uncertainties in watershed water quality modeling: A formal Bayesian approach

Extreme all-direction wave conditions and joint probabilities of high waves and high water levels are derived at selected locations in the southern Arabian Gulf. The wave conditions are obtained using the spectral wave model SWAN with wind and offshore wave information procured from ocean weather, supplemented with local water level records. Wave transformations from offshore to nearshore and waves generated by local wind conditions are derived using wind speed and direction, offshore wave height, peak period and direction and water level inputs to the SWAN model. The model predicted extreme 3-hourly wind speeds for return periods ranging from 0.06 – 200 years and the wave conditions for each storm. The study indicates that future sea level rise to 2058 gives 1:50, 1:100 and 1:250 return period water levels of 2.64, 2.71 and 2.79 mCD respectively at Jebel Ali.   Key words: Joint probability, extreme water levels, extreme waves, return period, wave modelling.

This research examines the consistency of the value of tidal datum obtained for Nwaniba River in Akwa Ibom State of the Niger Delta (Nigeria). Two sets of tidal data from 10/05/2007-10/06/2007 and 10/05/2017-10/06/2017 observed three times a day (Morning: 7: 30-9: 30; afternoon: 12: 00-14: 00 and evening: 16: 00-18: 00) at every 2 minutes interval were considered in order to evaluate a trend. Mean Highest Water Level (MHWL), Mean Lowest Water Level (MLWL) and Mean Water Level (MWL) for the three times per day were computed. The weekly MHWL and MLWL for each of the 5 week; average MHWL and MLWL for the 5 weeks were also computed. The water level measured within (10/05/2017-10/06/2017) is higher than that of (10/05/2007-10/06/2007) except in few cases. The highest (149.000 cm) and lowest (1.80 cm) water levels for 2007 observation were recorded on 08/06/2007 at (08: 40) and on 10/05/2007 at (7: 46) and 23/05/2007 at (8: 28) respectively; while the highest (152.300 cm) and lowest (1.801 cm) water levels for 2017 observation were recorded on 15/05/2017 at (07: 53) and on 27/05/2017 at (9: 08) and on 08/06/2017 at (08: 32) respectively. The observed Lowest Water Level (LWL) of 1.800 cm was adopted as the tidal datum for Nwaniba River in 2007. The observed LWL for 2017 is 1.801 cm; and the difference between the 2017 LWL and 2007 LWL which is (δLWL) is 0.001 cm. The value of (δLWL) = 0.001 cm shows that the value of LWL of 1.800 cm adopted in 2007 as the tidal datum still remains consistent when compared to the observed LWL of 1.801 cm for 2017 observations. Based on the LWL obtained for 2007 and 2017, it can be concluded that the tidal datum for Nwaniba River is consistent from 2007 to 2017. Also, based on the difference between average MWL for 2007 and 2017 = (δMWL) = 1.247 cm, it can be concluded that the water level at Nwaniba River has increased with 1.247 cm for the period of observation. In addition, the range of values of R2 obtained is 0.000-0.046 i.e. 5 %, which shows that only 5 % of the variation in MHWL and MLWL can only be attributed to the variation in time.

The effects of extreme water levels on water quality were examined for shallow nearshore vs. deeper offshore regions of Lake Okeechobee, a large subtropical lake in Florida USA. Water quality attributes were compared using mid-summer (June-August) observations for the highest and lowest five years of water levels since 1988. Differences in chlorophyll-a (Chl-a), chloride (Cl), color, nutrients, total nitrogen to total phosphorus ratio (TN: TP), Secchi Disk depth, transparency ratio (defined as the ratio of Secchi Disk depth to total depth), and total suspended solids (TSS) were examined to test hypotheses of interactions within and between the two regions under high and low water levels. The offshore region had consistently higher nutrient and TSS concentrations and lower Secchi Disk depth and transparency ratio. At high water levels within the offshore region, Cl, color, TSS, TP and TN were lower and Secchi Disk depth and color were higher. In contrast, at high water levels within the nearshore region, Chl-a, TP, TN, dissolved inorganic N and TSS concentrations were higher, and Cl, color, and transparency ratio were lower. Submerged aquatic vegetation, epiphyton, and benthic algae grow and compete for nutrients with phytoplankton in the nearshore region, but are absent from the deeper offshore region. The contrasting responses of the two lake regions indicate that water-level management actions taken to reduce eutrophication symptoms (e. g., algal blooms) in one region may not work in the other. In the case of Lake Okeechobee, the nearshore region supports most of the lake's ecological and societal values, so low water levels have a net benefit to ecosystem functions. In other lakes this may not be the case, highlighting the importance of understanding spatial variation of phytoplankton responses to water level in large shallow lakes.

Based on the geological and hydrogeological conditions, and in situ hydrogeological tests of the emergency groundwater source in Nantong City, China, a 3D numerical model of the heterogeneous anisotropy in the study area was established and calibrated using data from pumping and recovery tests. The calibrated model was used to simulate and predict the water level of the depression cone during the emergency pumping and water level recovery. The results showed that after seven days of pumping, the water level in the center of the depression cone ranged from −51 m to −55 m, and compared with the initial water level, the water level dropped by 29 m to 32 m. The calculated water level has a small deviation compared with that of the analytical solution, which indicates the reliability and rationality of the numerical solution. Furthermore, during water level recovery, the water level of pumping wells and its surroundings rose rapidly, which was a difference of about 0.28 m from the initial water level after 30 days, indicating that the groundwater level had recovered to the state before pumping. Due to the emergency pumping time is not long, the water levels of Tonglu Canal, surrounding residential wells, and other aquifers will not be affected. After stopping pumping, the water level recovers quickly, so the change of water level in a short time will not lead to large land subsidence and has little impact on the surrounding environment.

Hydrological conditions drive the distribution of plant communities in wetlands to form vegetation zones where the material cycling varies with plant species. This mediation effect caused by the distribution of vegetation under hydrological conditions will affect the emission of N2O during the nitrogen migration in wetlands. In this study, five vegetation zones in the second largest wetland of China were investigated in situ during high and low water levels to elucidate the effect mediated by vegetation. With the increase in the rate of change of water levels, the zones of the mud flat, nymphoides, phalaris, carex, and reeds were distributed in sequence in the wetland, and the densities of carbon and nitrogen sequestrated by plants also increased. The carbon and nitrogen densities in each zone during low water level was significantly higher than that during high water level, while the organic carbon and the total nitrogen of sediments during high water level was higher. Sediments converted between source and sink for both carbon and nitrogen, during the annual fluctuation in water level. The flux in N2O emissions showed significant differences between the vegetation zones during each water level period. The emission flux decreased with the increasing C : N ratio in sediments, approximating the threshold at 0.23 μg m−2 h−1 when the C : N ratio > 25. The phylum abundance of Firmicutes, Proteobacteria, and Chloroflexi in sediments increased with flooding. The denitrifying nirS and nirK genes and anammox hzsB gene were significantly affected by water level fluctuation, with the maximal variations of these genes occurring in the mud flat and nymphoides zone. The results indicate that the distribution of plants under hydrological conditions modified the stoichiometric ratio of sediments, resulting in the variations of N2O emission fluxes and microbial communities in vegetation zones. Therefore, hydraulic regulation rather than direct planting would be an effective strategy to reduce greenhouse gas emissions in freshwater wetlands.

In recent years, the constructions of pile-supported ballastless track-bed have been developed rapidly in China. It appears important to assess the accumulative settlement of this kind of track-bed after years of operation, especially under unfavorable conditions, such as the rising of water level. In this study, a full-scale physical model simulating the pile-supported ballastless track-bed was established. The soil arching effect was previously developed in this model by draining out water in the water bags among the pile caps. The effects of water level and loading cycle on the accumulative settlement of this model were investigated following four testing procedures: water level rising, cyclic loading at high water level, water level lowering, and cyclic loading at low water level. The results indicated that the total accumulative settlement of the track-bed increased rapidly in the beginning of loading and tended to stabilize as the loading cycle increased at high water level, whereas the value varied slightly when loading at low water level. The distribution of the accumulative settlement inside the subgrade at the end of loading with high water level and at the end of this test both presented parabolic shaped variation trends, with the peak point occurring above the water bag and lower values developing above the pile cap. At the high water level, a modified model was applied to estimate the accumulative settlement of the unsaturated zone above the water level (height of soil arch), and the fitting parameters in this model were precalibrated using the testing data. The estimated results revealed that the deformation of the unsaturated zone above the water level accounted for a minor portion of that of the whole tack-bed. By contrast, the zone below the water level is the dominant factor to influence the accumulative settlement of the whole track-bed. From a practical point of view, a well-performing drainage system should be set up to avoid the rising of water level.

The sampling-based uncertainty analysis method is a stochastic approach to estimate response uncertainties caused by the uncertainty in the input parameters. Conventionally, to minimize the effects caused by the Monte Carlo stochastic uncertainty, lots of particle histories have been used for the uncertainty analysis. However, this can cause inefficiencies in the uncertainty analysis. To optimize the calculation efficiency, how the Monte Carlo stochastic uncertainty influences the response uncertainty should be clearly verified. In this study, a method to estimate the accuracy of the response uncertainty is proposed by introducing a standard error and an error propagation theory. Using the proposed method, response uncertainties and standard errors of the multiplication factors for three benchmark problems are evaluated by the Monte Carlo method. Our results show that the proposed method can accurately estimate the accuracy of the response uncertainty caused by the input uncertainty in using the Monte Carlo simulation method. The proposed method can be directly utilized to estimate the accuracy of the sampling-based uncertainty analysis using the Monte Carlo simulation method. Also, it is expected that the proposed method will contribute to an increase in the calculation efficiency in the sampling-based sensitivity and uncertainty analysis.

Organotins (OTs) pollution in the aquatic environment of the Three Gorges Reservoir (TGR) was assessed during the reservoir's operating cycle. Butyltins (BTs) and phenyltins (PhTs) in the water phase and suspended particulate matter (SPM) at different water levels were analysed. It was found that the distribution of OTs in the surface and bottom water phases were similar, with the dominant OTs being BTs at the low water level and PhTs at the high water level. The detection rates and concentrations of OTs in the water phase at the high water level were both higher than those at the low water level, with most OTs being monobutyltin (MBT) at the low water level and monophenyltin (MPhT) at the high water level. The concentrations of OTs in SPM at the low water level were higher than those at the high water level, and BTs, especially dibutyltin (DBT) and tributyltin (TBT), were the predominant OTs whether surface or bottom layer at each water level. The BTs and SPM concentrations had a significant positive relationship in all samples, indicating that the SPM concentration would determine the distribution of BTs in the aquatic environment of the TGR region (TGRR). The difference in the distribution of OTs at the different water levels indicated that the hydrological and hydraulic behaviour of the TGR influences OTs transport in the aquatic environment of the TGRR.

Tides exert a major control on the coastal zone by influencing high sea levels and coastal flooding, navigation, sediment dynamics, and ecology. Therefore, any changes to tides have wide ranging and important implications. In this paper, we uniquely assess secular changes in 15 regularly used tidal levels (five high water, five low water and five tidal ranges), which have direct practical applications. Using sea level data from 220 tide gauge sites, we found changes have occured in all analyzed tidal levels in many parts of the world. For the tidal levels assessed, between 36% and 63% of sites had trends significantly different (at 95% confidence level) from zero. At certain locations, the magnitude of the trends in tidal levels were similar to trends in mean sea level over the last century, with observed changes in tidal range and high water levels of over 5 mm yr−1 and 2 mm yr−1, respectively. More positive than negative trends were observed in tidal ranges and high water levels, and vice versa for low water levels. However we found no significant correlation between trends in mean sea level (MSL) and any tidal levels. Spatially coherent trends were observed in some regions, including the north‐east Pacific, German Bight and Australasia, and we also found that differences in trends occur between different tidal levels. This implies that analyzing different tidal levels is important. Because changes in the tide are widespread and of similar magnitude to MSL rise at a number sites, changes in tides should be considered in coastal risk assessments.

This study applied Log-Pearson Type III probability distribution to model time series annual peak flow records of River Niger recorded at Lokoja gauging station. This was necessitated by the need to provide reliable data for safe and economic hydrologic design for security of lives and property at downstream of river Niger basin. Though several methods have been adopted in the study area for flood mitigation, however, it has become apparent that these measures are inadequate and no attempt has been made to apply statistical approach for provision of sustainable solution. Though flood cannot be prevented but the impact can be reduced by applying adequate counter measures. Therefore, this study shows the result of flood frequency analysis based on annual peak flow measurement covering a period of 18 years (1995-2012) carried by National Inland Water Ways (NIWA) at Lokoja gauge station. The probability distribution function was applied to return periods (T) of 2, 5, 10, 25, 50, 100 and 200 years. The predicted discharges corresponding to these return periods are 18886.065, 22425.127, 24889.683, 28145.456, 30670.104, 33281.363 and 35997.757 m3/s, respectively. This study also revealed that the return period of 2012 flood is over 50 years. The predictive model which relates the expected discharge to return period is given by X = 3679.7 In(R) + 16381 where X is the expected discharge and R is the return period. Key words: Flood, return periods, discharge, prediction, hydrologic design.

A series of airborne topographic LiDAR data were obtained from May 2008 to January 2014 over two coastal sites of northern France (Bay of Wissant and east of Dunkirk). These data were used with wind and tide gauge measurements to assess the impacts of storms on beaches and coastal dunes, and particularly of the series of major storms that hit western Europe during the fall and early winter of 2013. Our results show a high variability in shoreline response from one site to the other, but also within each coastal site. Coastal dune erosion and shoreline retreat occurred at both sites, particularly on the coast of the Bay of Wissant where shoreline retreat up to about 40 m was measured. However, stability or even shoreline advance were also observed despite the occurrence of an extreme water level with a return period >100 years during the storm Xaver in early December 2013. Comparison of shoreline change with variations of coastal dune and upper beach volumes revealed only weak relationships. Our results nevertheless showed that shoreline behavior seems to strongly depend on the initial sediment volume on the upper beach before the occurrence of the storms. According to our measurements, an upper beach volume of about 30 m3 m−1 between the dune toe and the mean high water level is sufficient at these sites to protect the coastal dunes from storm waves associated with high water levels with return periods >10 years. The identification of such thresholds in terms of upper beach width or sediment volume may represent valuable information for improving the management of shoreline change by providing an estimate of the minimum quantity of sand on the upper beach necessary to ensure shoreline stability in this region. Copyright © 2016 John Wiley & Sons, Ltd.

Uncertainty analysis is a key element of sound techno-economic analysis (TEA) of CO2 Capture and Storage (CCS) technologies and systems, and in the communication of TEA results. Many CCS technologies are relatively novel, with only few large-scale projects constructed and in operation to date. Therefore, uncertainties in technology performance and costs are often substantial, making it imperative that they be characterized and reported. Although uncertainty analysis itself is not novel, with some methods already frequently used by the CCS TEA community, a document that provides a comprehensive overview of methods and approaches, as well as guidance on their selection and use, is still lacking. Given its importance, we seek to fill this gap by providing a critical review of uncertainty analysis methods along with guidance on the selection and use of these methods for CCS TEAs, highlighting good practice and examples from the CCS literature. The paper starts by identifying the different audiences for CCS TEAs, the different modelling approaches available for CCS technology performance and cost analysis, and the different roles that uncertainty analysis may play. It then continues to discuss established, as well as emerging, uncertainty analysis methods and addresses how and when each method is best used, as well as common pitfalls. We argue that the most commonly used method of one-parameter-at-a-time ‘local’ sensitivity analysis may often be a suboptimal choice, and that other approaches may be more suitable or lead to more insight, especially since uncertainty analysis software is becoming more widespread and easier to use. Finally, the paper discusses the benefits of advanced uses of uncertainty analysis in, for instance, the design of CCS experiments or in the design and planning of CCS infrastructure. Sound uncertainty analysis has an important role to play in TEAs of CCS technologies and systems, and there are many opportunities to bring the use of uncertainty analysis to a higher level than currently practiced. This review of and guidance on available methods is intended to help accelerate continued methods development and their application to more robust and meaningful CCS performance and costing studies.

Assessing the local effects of climate change on coastal areas, and in particular on coastal cities and settlements, is one of the greatest challenges facing our society, aimed at finding innovative and sustainable solutions to increase the resilience of coastal communities to adverse climatic actions. In particular, the use of climate data is crucial for defining a downscaling strategy that starts with climate services on a global scale and goes on to define impacts on a local scale. A comprehensive 'global to local' approach is fundamental to envisage coastal flooding problems. Estimating the effects of CC in coastal cities  requires increasing the resolution of urban-scale models to unprecedented levels, to simulate land and coastal flooding conditions for various scenarios and with different return periods, also allowing for the evaluation of financial resilience strategies or ecosystem solutions for adaptation, following a true multidisciplinary approach and fostering, through participatory approaches, the public engagement of citizens, scientists and policy-makers, to identify solutions technically and socially acceptable. We present the results of a full “global to local” study, to estimate the effects of coastal and riverine floods associated with extreme events at three coastal cities located in the Mediterranean Sea (Massa - Italy and Villanova - Spain) and the Bay of Biscay (Oarsoaldea - Spain), for different climate projections. The present work is part of the H2020-SCORE project and the analyzed cities are organized in a network of Coastal City Living Labs (CCLLs). We implemented a relocatable modeling chain which uses the data from a Regional Circulation Model (RCM) provided by EuroCordex as atmospheric forcing to three different models: i) a WaveWatchIII model for the simulation of wave forcing, ii) a SHYFEM model for the simulation of storm surges and sea-level dynamics iii) a LISFLOOD model for river discharge. The wave and sea-level models are implemented on unstructured grids with increasing resolution at the target cities, whereas the river discharge is determined considering the basin located upstream of the city. The simulations are performed for the evaluation, historical, RCP45 and RCP85 datasets associated with the CMIP5 experiment. Time series of wave height and water level close to the coast, and river discharge are employed in an extreme value analysis procedure to obtain values associated to specific return periods (namely 25, 100, 200 years). These values are employed to simulate floods due to the effect of storm surge and peak river discharge, by means of a hydraulic model built on a high-resolution digital elevation model of the coastal city, including information on buildings, coastal bathymetry and river cross sections. Preliminary results from the calculated hazard maps (water depth associated with a return period event) show interesting differences in the three analyzed coastal cities based on different exposure to coastal or riverine floods.