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Rainfall and reservoir water level fluctuations are the main external factors of landslides in the Three Gorges Reservoir area. To improve the analysis of slope stability under the combined effect of reservoir water level fluctuations and rainfall, a simplified method for phreatic line calculation of slopes is proposed in this study. Based on the obtained phreatic line, the expression of normal stress on the sliding surface of the slope under the hydrodynamic forces is deduced, and a global analysis method to solve the slope safety factor under hydrodynamic force is proposed. Finally, the safety evolution of a slope in the Three Gorges Reservoir area is studied under the combined effect of reservoir water level fluctuations and rainfall. Key words: slope, landslide, phreatic line, reservoir water level fluctuations, rainfall. Les fluctuations du niveau des eaux pluviales et des reservoirs sont les principaux facteurs externes des glissements de terrain dans la zone du reservoir des Trois Gorges. Afin d'ameliorer l'analyse de stabilite des talus sous l'effet des fluctuations combines de niveau d'eau de reservoir et de la pluie, une methode simplifiee pour le calcul de la ligne de la nappe phreatique des pentes est proposee dans cette etude. Base sur la ligne phreatique obtenue, l'expression de la contrainte normale sur la surface de glissement de la pente sous les forces hydrodynamiques est deduite, et on propose une methode d'analyse globale pour resoudre les coefficients de securite de la pente sous une force hydrodynamique. Enfin, l'evolution de la securite d'une pente dans la region du reservoir des Trois Gorges est etudiee sous l'effet combine des fluctuations de niveau d'eau de reservoir et de la pluie. [Traduit par la Redaction] Mots-cles : pente, glissement de terrain, ligne de nappe phreatique, fluctuations de niveau d'eau de reservoir, pluie., Introduction From the previous literature on landslides, rainfall is a main triggering factor to induce landslides in the Three Gorges Reservoir area (Yin et al. 2012; Sun et al. 2016a). [...]

Artificial neural networks (ANNs) are promising alternatives for the estimation of suspended sediment concentration (SSC), but they are dependent on the availability data. This study investigates the use of an ANN model for forecasting SSC using turbidity and water level. It is used an original method, idealized to investigate the minimum complexity of the ANN that does not present, in relation to more complex networks, loss of efficiency when applied to other samples, and to perform its training avoiding the overfitting even when data availability is insufficient to use the cross-validation technique. The use of a validation procedure by resampling, the control of overfitting through a previously researched condition of training completion, as well as training repetitions to provide robustness are important aspects of the method. Turbidity and water level data, related to 59 SSC values, collected between June 2013 and October 2015, were used. The development of the proposed ANN was preceded by the training of an ANN, without the use of the new resources, which clearly showed the overfitting occurrence when resources were not used to avoid it, with Nash-Sutcliffe efficiency (NS) equals to 0.995 in the training and NS = 0.788 in the verification. The proposed method generated efficient models (NS = 0.953 for verification), with well distributed errors and with great capacity of generalization for future applications. The final obtained model enabled the SSC calculation, from water level and turbidity data, even when few samples were available for the training and verification procedures. [ABSTRACT FROM AUTHOR]

With the completion of the Danjiangkou Dam, the impoundment and drainage of dams can significantly alter shorelines, hydrological regime, and sediment and can result in the loss of soil and original riparian vegetation. Revegetation may affect soil properties and have broad important implications both for ecological services and soil recovery. In this work, we investigated the soil properties under different restoration approaches, and before and after submergence in the water level fluctuation zone (WLFZ) of the Danjiangkou Reservoir. Soil physical (bulk density and soil moisture), chemical (pH, soil organic carbon, nitrogen, phosphorus and potassium contents), and heavy metals were determined. This study reported that restoration approaches have impacts on soil moisture, pH, N, soil organic carbon, P, K and heavy metals in the WLFZ of the Danjiangkou Reservoir. Our results indicated that different restoration approaches could increase the soil moisture while decrease soil pH. Higher soil organic carbon in propagule banks transplantation (PBT) and shrubs restoration (SR) indicate that PBT and SR may provide soil organic matter more quickly than trees restoration (TR). SR and TR could significantly improve the soil total P and available P. PBT and SR could improve the soil total K and available K. SR and TR could significantly promote Cu and Zn adsorption, and Pb and Fe release by plant. Submergence could significantly affect the soil pH, NO 3 － -N, NH 4 ＋ -N, total P and available P. Submergence could promote NO 3 － -N and available P adsorption, and NH 4 ＋ -N and total P release by soil. The soil quality index (SQI) values implied that TR and PBT greatly improved soil quality. The present study suggests that PBT and TR could be effective for soil restoration in WLFZ of the Danjiangkou Reservoir. [ABSTRACT FROM AUTHOR]

Nam-Co Lake is the largest saltwater lake in Tibet and less influenced by human activity. In order to study the change of water level of Nam-Co Lake over the past decades and the impacts of climate change on the region, this paper combined height measurements of ERS-1, ERS-2, ENVISAT, ICESat-2 and CryoSat-2. We found that the water level of Nam Co Lake experienced three periods of change, namely, slightly decreasing period (1992-1993), significantly increasing period (1995-2005), and stable period (2006-2015). The change is consistent with the change of meteorological factors in the Nam-Co Basin. The increase of glacier melt water and precipitation in the basin is considered to be the cause of the overall trend of water level. [ABSTRACT FROM AUTHOR]

Shallow lakes in semiarid regions experience frequent water level fluctuations. Each long-lasting episode of water-level lowering leaves behind abandoned littoral forms and deposits whose identification and mapping is hampered by their smooth relief. Given the difficulty of recognising these possible relict forms using traditional geomorphological techniques, two sources of information were employed in the present work: high resolution (1:15,000) aerial photographs and a digital terrain model (DTM) generated from LiDAR data. The improved definition of surface elevation enhanced the quality of geomorphological mapping as well as the accurate delineation of subtle geoforms. The method was applied to Gallocanta Lake, a highly fluctuating shallow lake 14 km in area and less than 3 m deep located in a mountainous semiarid area of NE Spain. As a result, a sequence of relict coastal features (RCF) with high lateral continuity has been identified around the lakebed. These include well-preserved spits with recurved hooks, counter-spits, bays closed by barrier islands, beach ridges, deltas and cliffs. The highly precise LiDAR-derived topographic maps suggest a much greater extension of the lacustrine environment during the Late Pleistocene, reaching at least 51 km of water surface and about 13 m of depth above the present lake bottom. The method presented in this paper generates very detailed palaeogeographical maps that are particularly useful for reconstructing lake changes in semiarid environments as a function of climate change. [ABSTRACT FROM AUTHOR]

Large Amazonian rivers are characteristically subject to seasonal floods. We examine how inundation extent affects the partial pressure of carbon dioxide (pCO2) and CO2 outgassing in the Madeira River, a large tributary to the Amazon River. We show data from nine field campaigns performed between 2009 and 2011, complemented with data from one additional campaign in April 2014 that is representative of the largest flood on record. Both the pCO2 (range, 835-9694 μatm) and CO2 outgassing (range, 641-12,253 mg C m−2 d−1) had large seasonal variability (with peaks during high water), and fit exponential relationships with water level. CO2 outgassing per unit area in 2014 was 50% higher than the other highest rate in our dataset. Reconstruction of CO2 fluxes since 1968 indicates that extreme-flood years outgas 20% more CO2 per unit area than years without reported occurrence of extreme floods. Our findings indicate a positive feedback between climate change, extreme flooding, and CO2 outgassing from river water. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Combined sewer overflow (CSO) structures are constructed to effectively discharge excess water during heavy rainfall, to protect the urban drainage system from hydraulic overload. Consequently, most CSO structures are not constructed according to basic hydraulic principles for ideal measurement weirs. It can, therefore, be a challenge to quantify the discharges from CSOs. Quantification of CSO discharges are important in relation to the increased environmental awareness of the receiving water bodies. Furthermore, CSO discharge quantification is essential for closing the rainfall-runoff mass-balance in combined sewer catchments. A closed mass-balance is an advantage for calibration of all urban drainage models based on mass-balance principles. This study presents three different software sensor concepts based on local water level sensors, which can be used to estimate CSO discharge volumes from hydraulic complex CSO structures. The three concepts were tested and verified under real practical conditions. All three concepts were accurate when compared to electromagnetic flow measurements. [ABSTRACT FROM AUTHOR]

Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-desiccation cycles) on carbon turnover. 13C-labelled particulate organic carbon was used to trace and estimate carbon uptake into bacterial biomass (via phospholipid fatty acids) and respiration. Microbial community changes were monitored by combining DNA- and RNA-based real-time PCR quantification and terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA. The shifting hydrological regimes in the sediment primarily caused two linked microbial effects: changes in the use of available organic carbon and community composition changes. Drying sediments yielded the highest CO2 emission rates, whereas hydrological shifts increased the uptake of allochthonous organic carbon for respiration. T-RFLP patterns demonstrated that only the most extreme hydrological changes induced a significant shift in the active and total bacterial communities. As current scenarios of climate change predict an increase of drought events, frequent variations of the hydrological regimes of many lake littoral zones in central Europe are anticipated. Based on the results of our study, this phenomenon may increase the intensity and amplitude in rates of allochthonous organic carbon uptake and CO2 emissions. [ABSTRACT FROM AUTHOR]

Evapotranspiration (ET) is an important component of the wetland water budget. Water level declines in Poyang Lake, the largest freshwater lake in China, have caused concerns, especially during low water levels. However, how wetland ET and its partitioning respond to abnormally low water levels is unclear. In this study, wetland ET was estimated with MODIS data and meteorological data. The wetland ET partitioning and its relationship with abnormally low water levels were analyzed for 2000–2013. The results showed that the water evaporation rate (Ewater) was larger than the land ET rate (ETland); the ETland/Ewater ranged from 0.77 to 0.99. When the water level was below 12.8 m, the ET partition ratio was larger than 1, which indicates that wetland ET comes from land surface ET more than water evaporation. The negative standardized water level index (SWI) was used to represent an abnormally low water level in the wetland. Although the monthly wetland ET decreased as the negative SWI decreased, ETland was higher than the average under negative SWI conditions from September to December, when the water level decreased. The abnormally low water level induced more water loss from the land surface, especially when the water level decreased, which reduced the available water resources along the wetland shore. [ABSTRACT FROM AUTHOR]

This article presents an overview of selected physical processes and their effects on water quality in Hamilton Harbour. An understanding of circulation and mixing processes are essential to assess the fate and transport of water quality constituents in Hamilton Harbour. Water level measurements showed that in addition to harbour and lake seiches, the Helholtz mode, due to pumping action from Lake Ontario, is important in generating harbour water movements while the circulation patterns in the open waters of the harbour are influenced by prevailing winds. In general, the mean summer circulation consists of two counter-rotating gyres occupying the harbour. Hamilton Harbour physical processes are further characterized by substantial water exchanges with Lake Ontario. These exchange flows play a major role in determining the retention time of the harbour, thereby exerting a large influence on water quality, including hypolimnetic dissolved oxygen concentrations. [ABSTRACT FROM AUTHOR]

Nearly 60% of European wetlands have been lost to drainage or to the cessation of grassland management. Large amounts of resources are put into wetland restoration with the aim to recover biodiversity. However, few studies have simultaneously evaluated effects of management, wetness and flooding dynamics on biodiversity of restored wetlands such as seasonally flooded wet grasslands., We inventoried bird communities over 4 years at 137 sites (each 3·1 ha) within five restored wet grassland areas in Sweden to investigate whether species richness and occurrence of 12 common wet grassland species were related to (i) local conditions such as management (grazing, mowing and unmanaged areas), basic wetness and spring flooding dynamics. Further, we investigated whether (ii) the composition of the adjacent landscape (20 ha) related to local bird diversity and (iii) species turnover (i.e. beta diversity) differed between sites characterized by their basic wetness, degree of flooding and predominant management regime., Local species richness was positively linked to degree of flooding and basic wetness of grasslands but not to type of grassland management. Species richness tended also to be negatively linked to proportion of forest at the landscape scale. Although variable, the same results were also true concerning the probability of the occurrence of a single species at the local scale., Species turnover between sites, and thus total species richness, was distinctly higher in (i) grazed as compared to mowed grasslands except in dry non-flooded grasslands and (ii) flooded as compared to non-flooded sites. Similar patterns held for the subset of 12 red-listed species. We suggest that the high beta diversity in grazed and flooded grasslands is driven by the heterogeneous vegetation structure, resulting in good conditions for foraging and nesting for several wet grassland bird species., Synthesis and applications. The selection of wetlands for conserving wet grassland birds should prioritize temporary flooded grasslands of moderate wetness, preferably far from forest edges. Restoration and management of wet grasslands should include water level management, removal of shrubs and trees, and low-intensity grazing, whereas mowing could be used in non-flooded grasslands of low basic wetness. [ABSTRACT FROM AUTHOR]

The present study is focused on the development of geological setting under the erosional basis of the Early Holocene regression in the upper Northwestern Black Sea continental slope. The new obtained data for the core EUXRo01-1 were correlated with proxy-records from other sedimentary cores from the Northwestern and Western Black Sea upper continental slope and they correspond to the researches of other authors. The deposits in core EUXRo01-1 have recorded Late Pleistocene--Holocene geological setting changes. The new obtained data show that the deposits during the Early Holocene Black Sea regression and subsequent transgression were accumulated in rather variable lithodynamic conditions of the shelf, shelf edge and the continental slope. At some places of the continental slope, the processes of redeposition (e.g. gravity flows, turbiditic currents) were mainly controlled by water-level changes during the Early Holocene and they have played an important role in the forming of the sedimentary sequences. [ABSTRACT FROM AUTHOR]

Fluctuations of groundwater table (GWT) has great role in agriculture through assured supply of irrigation in industry and other fronts. As such, probability of possible GWT also plays an important role in terms of efficient usages of this valuable resource. An attempt has been made to find probability distributions taking seasonal (January, May, August and November for 2005 to 2013) information on GWT for the districts under five agro-climatic zones of West Bengal. The study reveals that 17 districts of West Bengal, India, can be categorised into 6 probability model groups: Weibul, Normal, Weibul (3P), Log Logistic (3P), Log Normal (3P) and Gamma (3P). These models can be used to ascertain the probability of occurrences of GWT in specific district. Cluster analysis, using GWT figures for various seasons over the period of study reveals that the districts could be grouped into four clusters, which in-turn may facilitate clusterwise strategy for restricting the depletion of GWT depth or maintenance of the same. These techniques can be used for intradistrict GWT analysis for efficient monitoring of GWT. [ABSTRACT FROM AUTHOR]

High-altitude inland lakes in High Mountain Asia (HMA) are key indicators to climate change and variability as a result of mostly closed watersheds and minimal disturbance by human activities. However, examination of the spatial and temporal pattern of lake changes, especially for water-level variations, is usually limited by poor accessibility of most lakes. Recently, satellite altimeters have demonstrated their potential to monitor water level changes of terrestrial water bodies including lakes and rivers. By combining multiple satellite altimetry data provided by the Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS) and Geoscience Laser Altimeter System (GLAS) instrument on the NASA Ice, Cloud and land Elevation satellite (ICESat), this study examined water level changes of typical lakes in HMA at a longer timescale (in the 1990s and 2000s) compared with earlier studies on Tibetan lakes. Cross-evaluation of the radar altimetry data from LEGOS and laser altimetry data from ICESat/GLAS shows that they were in good agreement in depicting inter-annual, seasonal and abrupt changes of lake level. The long-term altimetry measurements reveal that water-level changes of the 18 lakes showed remarkable spatial and temporal patterns that were characterized by different trends, onsets of rapid rises and magnitudes of inter-annual variations for different lakes. During the study period, lakes in the central and northern HMA (15 lakes) showed a general growth tendency, while lakes in South Tibet (three lakes) showed significant shrinking tendency. Lakes in Central Tibet experienced rapid and stable water-level rises around mid-1990s followed by slowing growth rates after 2006. In contrast, the water-level rises of lakes in the northern and north-eastern Tibetan Plateau were characterized by abrupt increases in specific years rather than gradual growth. Meteorological data based on station observations indicate that the annual changes of water level showed strongly correlated with precipitation and evaporation but may not evidently related to the glacier melting induced by global warming. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lake Purrumbete is located in western Victoria, Australia, and is highly regarded for its ecological, social, economic and scientific values. Recently, many lakes in the region have been dry or at their lowest level in recorded history, due to a drought that broke in 2010. For this study, a modified difference water budget method was employed to estimate net groundwater flux through the difference between the level of the lake and the water table, along with the specific yield and area of the aquifer. This model successfully modelled the lake level fluctuations. In recent years, Lake Purrumbete has fallen below the outflow level; however, because of its large volume, changes in salinity to date are minor and do not affect its freshwater status. An understanding of how these systems will behave in the future and how they may be best managed in a drying climate is considered an important step to adapt to climate change. Postulated future climatic changes in the region of the lake were used to project the lake level fluctuations to 2030 using the water budget model, and showed that dry conditions would cause the lake level to remain below its outlet elevation, but wet conditions would result in a significant recovery in the lake level. If the level of Lake Purrumbete continues to fall, the main threat to its ecological status will be the potential loss of some significant areas of fringing wetland habitat. The lowering in lake level could cause a shift in the abundance of algal plankton and so influence the whole lake food web. This may reduce the invertebrate diversity of the lake. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Integrated Coastal Zone Management / Revista de Gestão Costeira Integrada is the property of Associacao Portuguesa dos Recursos Hidricos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The results of long-term observations on changes in the relative body conditions of burbot ( Lota lota L.) in the Lower Ob basin during the open channel period (June-September) are analyzed. Statistically significant strong positive dependence of the hepatosomatic index of spawners on the maximum flood level is revealed. An equation predicting the value of the hepatosomatic index of spawners from instrumentally measurable environmental parameters is constructed. [ABSTRACT FROM AUTHOR]

The Qianjiangping landslide is a large planar rock slide which occurred in July 14, 2003 shortly after the water level reached 135 m in the Three Gorges Reservoir, China. The landslide destroyed 4 factories and 129 houses, took 24 lives, and made 1,200 people homeless. Field investigation shows that the contributing factors for the landslide are the geological structure of the slope, the previous surface of rupture, the water level rise, and continuous rainfall. In order to reveal the mechanism and failure process of the landslide, numerical simulation was conducted on Qianjiangping slope before sliding. Based on the characteristics and the engineering conditions of the landslide, the topography and the geological profiles of Qianjiangping slope before sliding is reconstructed. The seepage field of Qianjiangping slope before sliding was simulated with the Geostudio software. The results show that ground water table rises and bends to the slope during the rise of water level, and the slope surface becomes partially saturated within the period of continuous rainfall. Using the ground water table obtained above, the failure process of Qianjiangping slope is simulated with the Flac3D software. The results demonstrate that the shear strain increment, displacement, and shear failure area of the slope increased greatly after the water level rose and continuous rained, and the landslide was triggered by the combined effect both of water level rise and continuous rainfall. The development of shear strain increment, displacement, and shear failure area of the slope shows that the landslide was retrogressive in the lower part of the slope and progressive in the upper part of the slope. [ABSTRACT FROM AUTHOR]

Sea ice limits the interaction of the land and ocean water in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic, the open-water season is increasing in duration and summertime sea-ice extents are decreasing. Sea ice provides a first-order control on the physical vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructures by ocean water. We ask how the changing sea-ice cover has influenced coastal erosion over the satellite record. First, we present a pan-Arctic analysis of satellite-based sea-ice concentration specifically along the Arctic coasts. The median length of the 2012 open-water season, in comparison to 1979, expanded by between 1.5 and 3-fold by Arctic Sea sector, which allows for open water during the stormy Arctic fall. Second, we present a case study of Drew Point, Alaska, a site on the Beaufort Sea, characterized by ice-rich permafrost and rapid coastal-erosion rates, where both the duration of the open-water season and distance to the sea-ice edge, particularly towards the northwest, have increased. At Drew Point, winds from the northwest result in increased water levels at the coast and control the process of submarine notch incision, the rate-limiting step of coastal retreat. When open-water conditions exist, the distance to the sea ice edge exerts control on the water level and wave field through its control on fetch. We find that the extreme values of water-level setup have increased consistently with increasing fetch. [ABSTRACT FROM AUTHOR]

With the rapid development of economy, demand of water resources is becoming larger and larger, and over-exploitation of groundwater is common in many areas. Due to over-exploitation of groundwater over many years, a number of potential adverse hydrogeological problems have raised. To reduce such adverse effects, it is necessary to carry out strict groundwater management in over-exploited areas. And to achieve the strictest management of groundwater, it is critical to determine control levels of groundwater including the blue line levels (proper levels) and red line levels (warning levels). According to the establishment of evaluation model of shallow and deep groundwater exploitation and utilization risks, it can be observed that the groundwater level index factor is included in the evaluation index system in different groundwater function zones. Therefore, there is a corresponding relationship between the risk grade and groundwater level of different underground aquifers. The risk grade of different groundwater function zones in Tianjin is divided into five grades, which contributes to the risk management of groundwater, avoiding the arising of a wide range of risk management measure. However, to determine the key groundwater level, the standard of five grades cannot meet the requirements. The risk grades need to be divided more subtly. Hence, in this paper, the risk grade was divided according to the standard of sixteen grades based on that of five grades in the first place. The higher the grade is, the greater the risk. And then the occurrence frequency of risk grade for each aquifer was counted in each administrative district or country. The corresponding water level of the risk grade, whose occurrence frequency was the highest, served as the base level. The water level of groundwater that would be exploited and utilized in the future cannot be below this base level. In consequence, this water level that served as the red line level was the minimum requirement in the planning years, while the corresponding water levels of other risk grades that were inferior to this risk grade can all be seen as red line levels. And the planning period the long-term corresponding groundwater level of the aquifers under mining-banned condition can be used as blue line control levels of the different planning years. Finally, according to the determinate range of red line level change amplitude in each district or country, as well as the ultimate restoration aim of groundwater levels (blue line levels), corresponding measures were taken step by step to achieve the overall rising of groundwater levels. The obtained determinate control levels can provide a scientific basis for dynamic management of groundwater. [ABSTRACT FROM AUTHOR]

The article discusses the study done on the generation of Lake Baikal, Russia level oscillations by remote strong earthquakes using a Valdai float recorder with the use of a stilling well. Topics discussed include recording the wave velocities and with a three-component broadband accelerometer, lake level oscillations through Sumatran earthquake, and seasonal variations in the Lake Baikal water level.

Using sediment traps, we aimed to elucidate the temporal and spatial variations in sediment fluxes in large and shallow Lake Peipsi, over the May to October 2011 period, and analyze the factors behind those variations. The effects of weather factors (mean and maximum wind velocity, water level and water temperature) on sediment resuspension and the concentrations of suspended solids (SS), total phosphorus (TP), soluble reactive phosphorus (SRP), and chlorophyll a (Chl a) were investigated. Moreover, the internal loading of TP due to sediment resuspension was determined. The sediment resuspension rates were significantly higher in the shallower waters than in the deeper parts of the lake. Resuspension was a major factor in sedimentation dynamics of the lake, which is presently subject to eutrophication. The rates of sediment resuspension followed the same pattern as gross sedimentation during the study period, and their respective values differed significantly between sampling dates. The highest resuspension rates were observed in September (mean 55.4 g dw m day), when the impacts of wind events were particularly pronounced. Weather factors that were recorded approximately 2 weeks before water and sediment sampling affected the gross sedimentation and sediment resuspension. The water quality variables of SS, TP, SRP, Chl a were similarly affected. During the study, TP concentrations of the water were mainly determined by the resuspension of sediments containing a large pool of organic material. Although internal loading of TP due to resuspension was several times greater than external loading, external loading determines the amount of phosphorus that enters the lake and can be resuspended. [ABSTRACT FROM AUTHOR]

An analytical solution to shallow-water nonlinear equations determining the height of tsunami waves leaving the source is obtained. The initial water-level displacement in the source and the distribution of particle velocities are set. The numerical solution showed that analytical estimates fit well with source characteristics varying in a broad range, even if the waves produced by the source collapse. [ABSTRACT FROM AUTHOR]

Water levels in areas with intensive agriculture have often been strictly controlled for decades. Recently, more natural fluctuating water levels have been propagated to improve the ecological quality of wetlands in these areas. This study investigated the effects of water levels on protected base-rich mesotrophic fens during winter and summer., We used a mesocosm approach to simulate water level fluctuations under winter and summer conditions (light and temperature) to test the effects of water level on the biogeochemistry and vegetation of two highly endangered fen types with the brownmosses Scorpidium scorpioides and Hamatocaulis vernicosus as dominant mosses., Both species showed decreased photosynthetic capacity at lower water levels. These levels also resulted in decreased alkalinity due to oxidation processes in the moss layer. High water levels led to increased pH and alkalinity, due to reduction processes and infiltration of base-rich water., For the P-limited S. scorpioides mesocosms, high water levels did not lead to P mobilization or to significant changes in biomass production, P uptake and N:P ratios. However, for the mesocosms with H. vernicosus, where P limitation was not obvious, high water levels did result in P mobilization and increased P availability due to iron reduction. The lower P mobilization for S. scorpioides appeared to be related to lower total soil P content and higher Fe:P and Ca:P ratios. Although high water levels resulted in the accumulation of ammonium under winter conditions, this did not happen under summer conditions, making ammonium toxicity unlikely., Synthesis and applications. Our results suggest that low water levels could hamper protected brownmosses in rich fens, especially during the summer. In contrast, inundations may have a positive effect on rich fens by increasing the alkalinity. However, inundations may lead to eutrophication due to internal P mobilization in soils with a high total P content and low Fe:P ratio. Therefore, we recommend that soils with high total P content and low Fe:P ratios should not be flooded. [ABSTRACT FROM AUTHOR]

Copyright of Knowledge & Management of Aquatic Ecosystems is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Long period waterlevel variations, from 14 d to 1 yr, are examined for Hamanako, a tidal inlet on the Pacific coast of Honshu, Japan. Eleven years of records, prior to the regulation of the entrance to the inlet, are analyzed. At all the frequencies examined there were substantial fluctuations, some periodic and some irregular. Dominant features were abrupt changes in mean waterlevel and tidal range, and regular 14 d and 28 d cycles in most years. These cycles have been related to the role of the entrance constriction in generating spring-tidal pumping (STP). The rapid changes in tidal amplitude and mean waterlevel are explained in terms of changes in the hydraulic resistance of the entrance and have been correlated with outflows from the tidal lagoon caused by typhoons and catchment runoff. An annual cycle of amplitude 12.5 cm has been explained in terms of the annual cycle of the Kuroshio. Novel features of this study are the extensions to conventional time series analysis, and showing that the 14 d periodic fluctuations were caused by STP and that this process also contributed to the 28 d fluctuations. STP is invariably present in estuaries with a shallow inlet but is rarely identified; this paper shows methods to evaluate it and other long period components of the waterlevel record. [ABSTRACT FROM AUTHOR]

This study investigated the water level effects on the dynamic characteristics of a prototype arch dam model using ambient vibration testing were investigated. Achievement of this purpose involved construction of a prototype arch dam-reservoir-foundation model under laboratory. The dam body was constructed with 60 cm height. Ambient vibration tests on the arch dam estimated its natural frequencies, mode shapes and damping ratios for different water levels. In the ambient vibration tests, ambient excitations are provided from small impact effects and the responses of the arch dam are measured. It can be stated from the study that natural frequencies are not overly changed among 0-30 cm water levels; however they are increased for higher water levels. The difference between the first natural frequencies of the arch dam obtained from empty reservoir ( H = 0 cm) and full reservoir ( H = 60 cm) is about 20-25%. [ABSTRACT FROM AUTHOR]

Many contaminated unconfined aquifers are located in proximity to river systems. In groundwater studies, the physical presence of a river is commonly represented as a transient-head boundary that imposes hydrologic responses within the intersected unconfined aquifer. The periodic fluctuation of river-stage height at the boundary produces associated responses within the adjacent aquifer system, the magnitude of which is a function of the existing well, aquifer, boundary conditions, and characteristics of river-stage fluctuations. The presence of well responses induced by the river stage can significantly limit characterization and monitoring of remedial activities within the stress-impacted area. This article demonstrates the use of a time-domain, multiple-regression, convolution (superposition) method to develop well/aquifer river response function (RRF) relationships. Following RRF development, a multiple-regression deconvolution correction approach can be applied to remove river-stage effects from well water-level responses. Corrected well responses can then be analyzed to improve local aquifer characterization activities in support of optimizing remedial actions, assessing the area-of-influence of remediation activities, and determining mean groundwater flow and contaminant flux to the river system. [ABSTRACT FROM AUTHOR]

This paper studies climatic drivers (air and water temperature, precipitation rates, river discharge, sea level and storm patterns) in four Mediterranean regions: the Catalan-Valencia Coast (Spain), the Oran (Algeria) and Gabès (Tunisia) Gulfs and the western Nile Delta (Egypt). The paper also considers the potential hazards that these drivers can induce. It first analyses climatic trends in the drivers, taking into account the available time series of recorded and simulated meteo-oceanographic data from different sources. Next, it presents the general framework to assess biogeophysical hazards (flooding, erosion, droughts and water quality), followed by a simple and yet robust evaluation of those hazards for the four studied coastal sites. Assuming climate change projections under different scenarios and considering the observed trends in drivers, the resulting erosion rates due to sea-level rise and wave storm effects have been estimated. The Nile and Ebro Deltas, together with the Oran Gulf, are more vulnerable than the Gulfs of Valencia and Gabès. Regarding water quality in terms of (a) precipitation and dissolved oxygen in the water column and (b) sea surface temperature, the results show that the most vulnerable zones for the projected conditions (a) are the Gulfs of Oran, Valencia and Gabès, while the Nile Delta is the region where the decrease in water quality will be less pronounced. For the projected conditions (b), the most vulnerable zone is the Ebro Delta, while the impact in the other three cases will be smaller and of comparable magnitude. Finally, the overall future impact of these hazards (associated to climatic change) in the four sites is discussed in comparative terms, deriving some conclusions. [ABSTRACT FROM AUTHOR]

The article discusses the effects of climate changes on Bangladesh, where rising sea levels, climate variability, and extreme weather events such as floods, cyclones, and droughts may cause more severe issues due to meteorological and topological conditions. The incidences of flood related mortalities for women and children due to drowning and diseases such as cholera, fungal infections in the lower legs, and typhoid are examined. Other topics addressed include postflood mental health effects, malnutrition, and soil salinity. Tables and maps are presented with information on the area inundated due to sea-level rise, studies on the impact of flooding on health, and saltwater intrusion in the coastal and delta regions.

The impacts of climate change on hydrology and water resources in the Vuoksi watershed in eastern Finland were studied in order to assess the possibilities to adapt lake regulation to the projected changes. A conceptual watershed model and several climate scenarios were used to estimate the effects of climate change on three lakes in the Vuoksi watershed for 2010–2039, 2040–2069 and 2070–2099. The adaptation possibilities were studied by using alternative regulation strategies. In Lake Pielinen the impacts of these water level changes on social, economic and ecological indicators were assessed with two different outflow strategies. According to the results, climate change will alter snow accumulation and melt and therefore cause large seasonal changes in runoff and water levels. Runoff and water levels will decrease during late spring and summer and increase during late autumn and winter. In some lakes current calendar-based regulation practices and limits, which have been developed based on past hydrology, may not be appropriate in the future. Modifying the regulation practices and limits is a necessary and effective way to adapt to climate change. [ABSTRACT FROM AUTHOR]

Changes in the structure of plant communities may have much more impact on ecosystem carbon (C) cycling than any phenotypic responses to environmental changes. We studied these impacts via the response of plant litter quality, at the level of species and community, to persistent water-level (WL) drawdown in peatlands. We studied three sites with different nutrient regimes, and water-level manipulations at two time scales. The parameters used to characterize litter quality included extractable substances, cellulose, holocellulose, composition of hemicellulose (neutral sugars, uronic acids), Klason lignin, CuO oxidation phenolic products, and concentrations of C and several nutrients. The litters formed four chemically distinct groups: non-graminoid foliar litters, graminoids, mosses and woody litters. Direct effects of WL drawdown on litter quality at the species level were overruled by indirect effects via changes in litter type composition. The pristine conditions were characterized by Sphagnum moss and graminoid litters. Short-term (years) responses of the litter inputs to WL drawdown were small. In long-term (decades), total litter inputs increased, due to increased tree litter inputs. Simultaneously, the litter type composition and its chemical quality at the community level greatly changed. The changes that we documented will strongly affect soil properties and C cycle of peatlands. [ABSTRACT FROM AUTHOR]

Small-bodied fishes constitute an important assemblage in many wetlands. In wetlands that dry periodically except for small permanent waterbodies, these fishes are quick to respond to change and can undergo large fluctuations in numbers and biomasses. An important aspect of landscapes that are mixtures of marsh and permanent waterbodies is that high rates of biomass production occur in the marshes during flooding phases, while the permanent waterbodies serve as refuges for many biotic components during the dry phases. The temporal and spatial dynamics of the small fishes are ecologically important, as these fishes provide a crucial food base for higher trophic levels, such as wading birds. We develop a simple model that is analytically tractable, describing the main processes of the spatio-temporal dynamics of a population of small-bodied fish in a seasonal wetland environment, consisting of marsh and permanent waterbodies. The population expands into newly flooded areas during the wet season and contracts during declining water levels in the dry season. If the marsh dries completely during these times (a drydown), the fish need refuge in permanent waterbodies. At least three new and general conclusions arise from the model: (1) there is an optimal rate at which fish should expand into a newly flooding area to maximize population production; (2) there is also a fluctuation amplitude of water level that maximizes fish production, and (3) there is an upper limit on the number of fish that can reach a permanent waterbody during a drydown, no matter how large the marsh surface area is that drains into the waterbody. Because water levels can be manipulated in many wetlands, it is useful to have an understanding of the role of these fluctuations. [ABSTRACT FROM AUTHOR]

Since the impoundment of the Three Gorges Reservoir in June 2003, a number of new landslides have occurred and existing landslides have been made worse. The 1,260 × 104 m3 Baishuihe landslide, located at 56 km west of the Three Gorges Dam, began to deform more noticeably after the first impoundment in early July 2003. The sliding of the two blocks comprising the landslide, one an active block and the other a relatively stable block, became apparent after approximately 5 years of monitoring. Field recordings show that the landslide displacement is affected by the combined effects of the rainfall and water level in the reservoir. These effects have been investigated in the present paper, including the deformation characteristics (movement pattern, direction, displacement and velocity) earmarking the temporal evolution of the active block. Based on a practical creep model of a large rock slide, alert velocity thresholds for pre-alert, alert and emergency phases have been computed corresponding to the imminence of failure. The alert velocity thresholds are being proposed to be included as a part of an early-warning system of an emergency plan drawn up to minimize the adverse impact in the event of landslide failure. The emergency plan is intended to be implemented as a risk management tool by the relevant authorities of the Three Gorges Reservoir in the near future. [ABSTRACT FROM AUTHOR]

A three-level nested rendering of a high-resolution limited-area model version of the Global Environment Multiscale configuration (GEM-LAM), running quasi-operationally at the Canadian Meteorological Centre, is evaluated for its capabilities in marine fog prediction. The model shows a general underestimation of the cloud water content at lower levels that is utilized as one of the proxies for fog and/or low stratus. A warm and dry tendency also appears at the lowest layer (a few hundreds of meters above the surface) of the vertical profiles and at screen level. The condensation scheme directly generates/dissipates the cloud water content (or fog) while boundary layer processes [such as moist turbulent kinetic energy (MoisTKE)] vertically redistribute it. However, the results presented here emphasize the significance of the accurate initial and vertical velocity fields, as well as the interactions between the condensation scheme and the radiation scheme that interacts fully with clouds. These conclusions suggest that a delicate balance among the different physical processes and dynamics is needed for a successful fog forecast. [ABSTRACT FROM AUTHOR]

Ice jams can sometimes occur in high latitude rivers during winter and the resulting water level rise may generate costly and dangerous flooding such as the recent ice jam flooding in the Nechako River in downtown Prince George in Canada. Thus, the forecast of water level and ice jam thickness is of great importance. This study compares three methods to simulate and forecast water level and ice jam thickness based on field observations of river ice jams in the Quyu Reach of the Yellow River in China. More specifically, simulation results generated by the traditional multivariant regressional method are compared to those of the back propagation neural network and the support vector machine methods. The forecast of ice jam thickness and water level under ice jammed condition have been conducted in two different approaches, 1) simulation of water level and ice jam thickness in the second half of the period of measurement using models developed based on data gained during the first half of the period of measurement, 2) simulation of water level and ice jam thickness at the downstream cross sections using models developed based on data gained at the upstream cross sections. For this reason, as the results of simulation and field observations indicated, the back propagation neural network method and the support vector machine method are superior in terms of accuracy to the multi-variant regressional method. [ABSTRACT FROM AUTHOR]

Collingsworth, PD and Kohler, CC. 2010. Abundance and habitat use of juvenile sunfish among different macrophyte stands. Lake Reserv. Manage. 26:35-42. Juvenile Lepomis sunfish (< 75 mm total length, TL) density, plant stem density and invertebrate density were compared in the 3 most common habitats in the littoral zone of Cedar Lake, a Midwestern North American reservoir: nonvegetated areas, stands of the exotic macrophyte Eurasian watermilfoil (Myriophyllum spicatum) and stands of American pondweed (Potomogeton nodosus). Eurasian watermilfoil stands consistently had significantly higher stem density and invertebrate density than American pondweed stands. Juvenile sunfish densities were significantly higher in vegetated habitats than nonvegetated areas, but no significant differences were observed between the 2 vegetated habitats. Juvenile sunfish densities were initially higher in American pondweed stands than Eurasian watermilfoil stands, but fish density in American pondweed stands declined dramatically as water levels fell in autumn. Juvenile sunfish size structure was related to habitat type, with the smallest fish associated with Eurasian watermilfoil (38.2 mm TL), intermediate fish associated with American pondweed (43.1 mm TL), and the largest fish associated with nonvegetated habitats (51.2 mm TL). We suggest resource agencies should focus vegetation management efforts on eradicating Eurasian watermilfoil stands to provide foraging access for largemouth bass to improve their growth rate and reduce stunting of sunfish. However, management agencies must recognize that a healthy plant community below the depth of water level fluctuation may be the only source of cover for juvenile centrarchids during late summer in reservoirs prone to fluctuating water levels. [ABSTRACT FROM PUBLISHER]

One of the widely acknowledged consequences of global climate change is sea-level rise. Sea-level rise has predictable impacts on human welfare and the environment and the oceans will continue to rise for some time, regardless of the climate change mitigation measures that the countries of the world decide to take. Therefore, some adjustment to sea-level rise—adaptation—is inevitable. However, sea-level rise poses two challenges for leaders trying to formulate adaptation plans. First, sea-level rise is slow, measured in millimeters per year, and the full extent of climate change-driven sea-level rise is expected to take centuries to manifest. This is a planning horizon outside the political ken of most governmental bodies; indeed, planning horizons longer than a few decades are extremely rare. Second, scientists are still uncertain as to the extent of the problem. Specifically, how high will the oceans rise? For both reasons, adaptation to sea-level rise requires some form of adaptive management—an ability to react to new information regarding the extent and speed of sea-level rise as that information becomes more certain and precise for different areas of the country. Moreover, an adaptive management approach to sea-level rise provides a means of avoiding government inaction because of uncertainty. Instead, recognition of the need for an adaptive approach necessarily counsels governments to implement initial adaptation measures that will be beneficial to coastal communities regardless of how far the oceans encroach and how fast they do so. This Article suggests that taking a public health approach to sea-level rise can provide governments and planners with immediately implementable and "no regrets" adaptation measures that will be beneficial to coastal communities regardless of the eventual actual impacts of sea-level rise in particular areas of the country. Specifically, this Article suggests that planners should begin by looking at three specific concerns: (1) availability of drinking water supplies; (2) potential changes in disease exposure, with resultant changes in medical infrastructure and training needs; and (3) the potential for the toxic contamination of sea water as it comes ashore, with resultant changes in allowable land uses in the coastal zone. [ABSTRACT FROM AUTHOR]

The article presents a study that examines the impact of different water table levels on desert riparian forest vegetation. The study uses data from middle and lower reaches of Tarim River, to analyze relationship between vegetation and environmental factors and influence of groundwater level for species diversity. Result shows high species diversity at 2-4 meter levels, in which drop in water level also reduces diversity. It concludes that proper water level for vegetation is from 2-4 meters.

The combination of climate change and natural periodicities in meteorological variables are demonstrating significant impacts on the water resources of Lake Superior within the Laurentian Great Lakes system of North America. Statistical analyses of long-term records are used to demonstrate how changes over time may be interpreted very differently, depending upon the timeframe over which the analyses are made. Non-linear regression modelling shows that, while increasing trends in overland and overlake precipitation, flows and runoff occurred during the first decades of the twentieth century, very different trends are apparent for the period 1970-2005. For this latter period, increasing rates of air overlake temperature and lake evaporation are occurring but all other parameters are demonstrating decreasing trends. The result is a decline in water levels in Lake Superior at the rate of approximately 1 cm per year over the last 35 years. The results are used to show that to avoid decreasing water levels in Lake Superior, the discharge through St Mary's River must be decreased to approximately one-half the long-term annual average, the results of which will have dramatic implications for ships' cargo levels and hydroelectric energy generation. [ABSTRACT FROM AUTHOR]

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The article presents a study which examines the effects of altered water level to the greenhouse gases (GHG) and dissolved reactive phosphorous (DRP) release on soil cores of the Rice Lake Wetland, Minnesota that is being assessed for restoration. It mentions that the intact cores of a sampling site with higher iron (Fe) and lower calcium carbonate contents relinquished more DRP compared to other locations. Moreover, the chemical data proposes that the redox-driven reactions control the DRP levels on the high-Fe location and the calcium carbonate CaCO3 adsorption is more significant in low-Fe site. The study shows that the hydrology restoration of the Rice Lake wetland could possibly affect the local water and global air quality which can intricate cost-to-benefit analysis.

The North Fork Holston River (NFHR) was examined in fall 2005 to determine the potential impact of a brine discharge on benthic macroinvertebrates. Conductivity of the discharge ranged from 5900 to 10,930 μ S/cm with a highest measurement of 18,000 μ S/cm. During normal flow, conductivity dissipates rapidly downstream of the discharge; however, low-flow conditions in 2005 hindered dissipation. Benthic macroinvertebrate surveys determined statistically significant differences (p = .05) in all metrices between sites excluding taxa richness. Hydropsychid caddisflies were the predominant taxa at the first two sites below the brine discharge, accounting for 74.3 and 68.8% of the organisms collected. Therefore, Ephemeroptera-Plecoptera-Trichoptera (EPT) abundance minus Hydropsychidae [EPT-H] was the most predictive parameter measured. When hydropsychids were removed from statistical analyses, mean EPT abundance was highest at upstream reference sites 1 and 2 (256 and 297, respectively) and reduced at all downstream sites, ranging from 24 to 52 EPT organisms. Virginia Stream Condition Index (SCI) scores indicated impairment downstream of the discharge with scores of 46.9, 41.8, and 55.8, well below the impairment threshold of 61. These results suggest subchronic, intermittent toxicity occurs under low-flow and may contribute to altered benthic macroinvertebrate assemblages downstream of the brine discharge for approximately 26 miles. [ABSTRACT FROM AUTHOR]