Water Level Reduction Research Articles

Effect of water level on insect-tadpole predator-prey interactions

Predator-prey interactions are affected by environmental conditions. We examined the effect of changes in water level on the predator-prey interactions in a food web comprising of a top predator (dragonfly naiad), one mesopredator (backswimmer), and prey tadpoles of species that differ in microhabitat occupancy (neustonic and benthic). The results revealed that under high water level conditions (HWL), predators took longer to attack the neustonic tadpoles (Microhyla nilphamariensis) relative to the low-water-level condition (LWL). Dragonfly larvae mostly attacked the benthic tadpoles (Euphlyctis cyanophlyctis) when the water level was high. Nevertheless, under LWL, dragonfly larvae equally attacked both benthic and neustonic tadpoles. Interestingly, dragonfly larvae frequently attacked mesopredators (i.e., backswimmers) when they were presented together with neustonic tadpoles. These results demonstrated that changes in water level influence predator-prey interactions in the pond ecosystem where neustonic tadpoles faced lower risk under HWL. The reduction of water level favored the survival of benthic prey tadpoles. The presence of mesopredator (backswimmers) reduced the predation risk of neustonic tadpoles. These results help to understand how the differences in predation risks shape anti-predator responses in these prey tadpoles.

Bathymetric Monitoring of Alluvial River Bottom Changes for Purposes of Stability of Water Power Plant Structure with a New Methodology for River Bottom Hazard Mapping (Wloclawek, Poland).

The aim of this research was to produce a new methodology for a special river bottom hazard mapping for the stability purposes of the biggest Polish water power plant: Włocławek. During the operation period of the water power plant, an engineering-geological issue in the form of pothole formation on the Wisła River bed in the gravel-sand alluvium was observed. This was caused by increased fluvial erosion resulting from a reduced water level behind the power plant, along with frequent changes in the water flow rates and water levels caused by the varying technological and economic operation needs of the power plant. Data for the research were obtained by way of a 4-year geodetic/bathymetric monitoring of the river bed implemented using integrated GNSS (Global Navigation Satellite System), RTS (Robotized Total Station) and SBES (Single Beam Echo Sounder) methods. The result is a customized river bottom hazard map which takes into account a high, medium, and low risk levels of the potholes for the water power plant structure. This map was used to redevelop the river bed by filling. The findings show that high hazard is related to 5% of potholes (capacity of 4308 m3), medium with 38% of potholes (capacity of 36,455 m3), and low hazard with 57% of potholes (capacity of 54,396 m3). Since the construction of the dam, changes due to erosion identified by the monitoring have concerned approximately 405,252 m3 of the bottom, which corresponds to 130 Olympic-size pools. This implies enormous changes, while a possible solution could be the construction of additional cascades on the Wisła River.

Composition and changes in the spontaneous flora of the Wadi El Rayan Ramsar site, Fayoum, Egypt, in the last 20 years

Abstract Wadi El Rayan is located in Egypt in the Sahara ecoregion the Palearctic ecozone (the world’s largest hot desert). The total area of Wadi El Rayan is 1759km2. The aim of this work was to study the ecosystems, compare species composition, species richness and species diversity of the study sites in the Wadi El Rayan protected area and the distributions of plants in the different landform. The field observations found that there is a low diversity and number of plant species around the lakes, in particular a decline in vegetation cover in accordance with a dramatic decrease in the water level in the lakes compared to earlier studies. The reduction of water levels due to decreased water supply is considered the main threat facing ecosystems and biodiversity in the lake area which requires a continuous survey of flora and measures to be implemented to conserve the natural vegetation in the area. Based on investigations of the spontaneous flora of Wadi El Rayan in 2018, 18 taxa of vascular plants were recorded. This inventory was compared with published records of investigations made in 1998, 2002 and 2014. A total of 18 vascular plant species belonging to 14 families were recorded in the wetland and desert ecosystems around the lakes of Wadi El Rayan. The vegetation mainly consists of sparsely distributed xerophytic and halophytic plants except in the wetland ecosystem around the lakes where it is characterized by some hydrophytic and halophytic plants. The family with the highest number of species was Poaceae followed by Zygophyllaceae. The results showed that a higher number of species was recorded from the Lower Lake (13 species) than the Upper Lake (10 species) and (5 species) for the connecting channel. The most frequently recorded species were Phragmites australis, Tamarix nilotica, Juncus rigidus and Alhagi graecorum: the first two species were the most successful species as they grow in a variety of ecosystems and habitats.

Impact of Inlet Closures on Surge Response in New Jersey Back Bays

Cialone, M.A. and Slusarczyk, G., 2020. Impact of inlet closures on surge response in New Jersey back bays. Journal of Coastal Research, 36(6), 1111–1120. Coconut Creek (Florida), ISSN 0749-0208.The in-depth study presented in this paper includes numerical modeling and analysis of the effects of storm surge barriers (inlet closures) on water levels in the back bays of New Jersey during storm events. Eleven inlet closures were each numerically “closed” singularly and in combination with other inlet closures. Storm surge simulations were run with all 11 inlets “open” as a base condition and for each of the inlet singular closure and combination closure conditions. In this paper, four combinations of inlet barrier positions were selected to demonstrate the ability of surge barriers to potentially prevent surge propagation into the back bays of New Jersey, including: (1) the base condition (all inlets open); (2) closing one of the larger entrances, Barnegat Inlet; (3) all inlets closed except for a small inlet (Corson Inlet) and an extremely wide inlet entrance (Little Egg/Brigantine Inlet); and (4) all inlets closed. A comparison of maximum surge envelopes and water-level time series from simulations of 10 synthetic tropical storms with the inlets in these four configurations was made. Three of the largest bay systems, Barnegat Bay, Manahawkin Bay, and Little Egg Harbor, are the main focus of this paper. As expected, the greatest reduction in water level in the bays occurs when all inlets are closed with surge barriers. The average reduction in water level for the three bays mentioned above with all inlets closed is 0.70 m, with a maximum average reduction in Little Egg Harbor of 0.73 m. Simulations with only Barnegat Inlet closed show the greatest reduction in water level in the northern portion of Barnegat Bay, whereas surge can still propagate into the southern portion of the bay through Little Egg/Brigantine Inlet. However, storms with strong N-to-S wind can inhibit flow entering from the open inlet at Little Egg/Brigantine and therefore show the greatest reduction in maximum water level in the southern portion of Barnegat Bay for these conditions. With some inlets open and some closed, strong alongshore winds can also cause surge to become trapped behind adjacent inlet closures. This demonstrates the importance of considering multiple means of flow propagation into an embayment as well as the timing of implementing surge barriers to optimize surge protection.

Morphometric Analysis and Prioritization of Sub-watersheds for Management of Natural Resources using GIS: a case study of Rajasthan, India

Natural resources management is crucial in water scarce semi-arid regions because of scanty rainfall and over exploitation of ground water resources. The watershed choosen in this study is drained by Bandi River having area of 2162.7 km 2 and located in Pali district of Rajasthan, India. Incessant rainfall, continuous exploitation of ground water results in the reduction of ground water level and recurrent drought conditions in this area. Hence, the watershed had been further divided into 5 sub-watersheds represented as SWS-1 to SWS-5 with geographical area ranging from 98 km 2 to 265 km 2 and perimeter ranging from 47 km to 79 km. These sub watersheds were then prioritized based on morphometric analysis considering the linear, areal and relief aspects of the drainage system in GIS environment using ArcGIS 10.5.5. The analysis showed that the drainage density of sub-watersheds varies between 1.351 km/km 2 to 2.513 km/km 2 and the lowest drainage density was found in SWS-4 that indicated the presence of impermeable sub-soil system with dense vegetation cover and low relief in the sub-watershed. The sub-watershed, SWS-2 has high circularity ratio of 0.6 that indicated the topography at the late maturity stage. Similarly, the Elongation Ratio varied from 0.4007 to 0.9340 in the sub-watersheds indicated comparatively steep ground slope and high relief. After the computation of all morphometric parameters of the sub watersheds, the compound parameter values were calculated and the sub-watershed having the lowest compound parameter value was given the highest priority for conservation measures. In this study, the sub-watershed SWS-1 was found to have the lowest compound value of 1.875 and hence considered for immediate soil conservation and water management measures. https://doi.org/10.23953/cloud.ijarsg.471

Slow and Steady: Gradual Drawdown of Private Wetlands Supports Shorebirds During Northbound Migration

AbstractThe Grasslands Ecological Area is the largest contiguous wetland complex in California's Central Valley and is a stronghold for hundreds of thousands of waterbirds. Primarily managed for waterfowl habitat and forage production, landowners of these privately owned seasonal wetlands in the Grassland Ecological Area typically flood the wetlands in the fall and dewater them the following spring in February and March. These wetlands support large populations of nonbreeding shorebirds and other waterbirds in winter. When the number of migratory shorebirds using the region peaks in mid-April, landowners have already dewatered most wetlands. The mismatch in the timing of available habitat and the habitat needs of migrating shorebirds contributes to the observed deficit of shorebird habitat in the Central Valley in spring. Working with private landowners, we developed and tested a wetland management practice designed to increase the amount of shallow-water habitat available to shorebirds in April by delaying the drawdown and reducing water levels more slowly (gradual drawdown) relative to the traditional management practice. On average, we found that wetlands managed with gradual drawdown provided over twice as much shorebird habitat, contributing up to 26% of the overall shorebird habitat objective for the Central Valley. Wetlands managed with gradual drawdown supported up to 21 times more migratory shorebirds during peak migration and a greater number of shorebird species than traditionally managed wetlands. Our results demonstrate the potential of working with private landowners to implement small changes in wetland management that can have a large impact in meeting regional conservation objectives for migratory shorebirds.

Characteristics of Groundwater Level Fluctuation Due to Groundwater Reservoir for Water Dispute Resolution in Ulsan, Korea

In the Ulsan area, dam development was actively promoted for large-scale industrial and population growth, but the conflict between cultural property preservation and securing water supply security became a longstanding social issue since the discovery of the Bangudae petroglyphs in the Sayeon dam submerged area. This study aims to analyze groundwater level fluctuation in the surrounding area of the Ulsan Teahwa river to evaluate if the groundwater reservoir installed at the mid-stream of the river can resolve water shortage problem in the Ulsan Metropolitan city while preserving the Bangudae petroglyphs. The results show that a water intake facility with the capacity of 30,000㎥/day installed in groundwater reservoir is expected to ensure water intake all year long. It is also estimated that the groundwater level decreases by at least 0.3m in an area within a radius of about 650m from the facility. The groundwater reservoir installed at the mid-stream of the Teahwa river is expected to make up the shortage amount of water due to the reduction of water level for preserving the Bangudae petroglyphs, which could resolve the existing water disputes in Ulsan, Korea.

Wood‐induced backwater effects in lowland streams

AbstractPlacement of wood in streams has become a common method to increase ecological value in river and stream restoration and is widely used in natural environments. Water managers, however, are often hesitant to introduce wood in channels that drain agricultural and urban areas because of backwater effect concerns. This study aims to better understand the dependence of wood‐induced backwater effects on cross‐sectional area reduction and on discharge variation. A newly developed, one‐dimensional stationary model demonstrates how a reduction in water level over the wood patch significantly increases directly after wood insertion. The water level drop is found to increase with discharge, up to a maximum level. If the discharge increases beyond this maximum, the water level drop reduces to a value that may represent the situation without wood. This reduction predominately depends on the obstruction ratio, calculated as the area covered by wood in the channel cross section divided by the total cross‐sectional area. The model was calibrated with data from a field study in four lowland streams in the Netherlands. The field study showed that morphologic adjustments in the stream and reorientation of the woody material reduced the water level reduction over the patches in time. The backwater effects can thus be reduced by optimizing the location where wood patches are placed and by manipulating the obstruction ratio. The model can function as a generic tool to achieve a stream design with wood that optimizes the hydrological and ecological potential of streams.

ANALISA SIFAT FISIK DAN KANDUNGAN NUTRISI TEPUNG TALAS (Colocasia esculenta L.) PADA SUHU PENGERINGAN YANG BERBEDA

Taro flour is one of dried products of taro (Colocasia esculenta L.). The characteristics of taro flour that low water content has an important role in determining the storage time. The presence of water in materials is influenced by internal factors of material, processing, moisture of storage and packaging materials. The water level reduction technique commonly used is by drying process, one of them is by using a tray dryer machine. The aim of the study was to analyze the physical properties, and nutritional content of taro flour produced from drying taro chips using a tray dryer machine at a drying temperature of 50°C, 60°C and 70°C with drying times 5, 6, and 7 hours. The physical parameters observed were water content, density and color, the nutritional parameters observed were protein, fat, ash, carbohydrates and crude fiber. The results of study showed that the water content ranged from 6.14 - 8.34%, density ranged from 0.45 - 0.57 kg/m3 and the lightness parameter values ranged from 69.9 - 72.0, with redness values between 12.2 - 12.8 and yellowness values between 11.5 - 13.1. The highest values of protein, fat and carbohydrate were 8.34%, 0.38% and 86.94%. The highest ash and crude fiber values were 3.84% and 2.99%.

Catastrophic events and estuarine connectivity influence presence of aquatic macrophytes and trophic status of intermittently-open coastal lagoons in eastern Australia

Small intermittently open lagoons are the most common type of estuary in NSW but the majority of them have no seagrass despite apparently suitable physical and water quality conditions. This paper describes the consequences of a catastrophic drought on trophic structure of primary producers in two intermittently open coastal lagoons that have negligible anthropogenic stress. It examines the roles of various factors influencing primary producers and hence ecosystems in intermittently open lagoons, in both short and long timeframes.Two estuarine lagoons with undisturbed catchments (Durras Lake and Nadgee Lake) experienced decadal scale shift in production dominance from benthic to pelagic and back to benthic following a catastrophic reduction in water levels during drought conditions. Water quality deteriorated significantly (high turbidity, ammonia and chlorophyll) after loss of macrophytes and then re-established to “normal” conditions within 2–3 years. Despite this, macrophytes did not re-appear for 6–7 years. The high proportion of intermittent estuaries with no seagrass was concluded to be a consequence of recruitment limitation, and estuarine morphology shapes the ecology of these lagoons, rather than an inherent inability for seagrass and macrophytes to live in the estuaries. Recruitment of macrophytes required coincident occurrence of multiple rare stochastic events, making chance an important aspect of re-establishment of biological assemblages in disturbance driven ecosystems.Conceptual models derived for northern hemisphere, riverine, surface-water fed estuaries tend to dominate thinking about estuaries in the literature, but are clearly inappropriate for typical southern-hemisphere low-flow and groundwater-dominated intermittent estuaries.Climate change is likely to increase the frequency of occurrence of the conditions that led to the loss of seagrass and macrophytes and therefore potentially reduce the number of intermittent estuaries in NSW with macrophytes. In the systems described, maintenance of regional seagrass populations is reliant on the stochastic survival of some populations to act as source populations. Climate change is predicted to make what are currently “extreme” events more common. This could, in turn, mean that the likelihood of the sort of loss described in our two cases studies could become more common, increasing the proportion of systems with no seagrass and progressively closing the window of opportunity for external recruitment. Potentially, this could lead to localised extinction of seagrass in intermittent estuaries.

Simulating Caspian Sea surface water level by artificial neural network and support vector machine models

Reduction in sea water level can make services in nearshore structures difficult, and sea water level rise increases the risk to residential areas or the surrounding fields. For strategic planning, it is vital to take into account the present and future fluctuations of Caspian Sea water level. In this study, support vector machine and artificial neural network are used to estimate water level of the Caspian Sea. A 34-year period dataset is used as input data for water level on the scale based at Anzali, Iran. Performances of these two models are compared according to some statistical indices. Results of this study indicate that support vector machine with an error of 4.782 mm and r = 0.96 simulated the time series better, as compared with artificial neural network with an error of 5.014 mm and r = 0.957; furthermore, the uncertainty of this model is lower than that of the artificial neural network, i.e., 0.04 verses 0.22.

Combining multisource satellite data to estimate storage variation of a lake in the Rift Valley Basin, Ethiopia

Integration of remote sensing data sets from multiple satellites is tested to simulate water storage variation of Lake Ziway, Ethiopia for the period 2009-2018. Sixty Landsat ETM+/OLI images served to trace temporal variation of lake surface area using a water extraction index. Time series of lake levels were acquired from two altimetry databases that were validated by in-situ lake level measurements. Coinciding pairs of optical satellite based lake surface area and radar altimetry based lake levels were related through regression and served for simulating lake storage variation. Indices for extracting lake surface area from images showed 91–99 % overall accuracy. Lake water levels from the altimetry products well agreed to in-situ lake level measurements with R2 = 0.92 and root mean square error of 11.9 cm. Based on this study we conclude that integrating satellite imagery and radar altimetry is a viable approach for frequent and accurate monitoring of lake water volume variation and for long-term change detection. Findings indicate water level reduction (4 cm/annum), surface area shrinkage (0.08km2/annum) and water storage loss (20.4Mm3/annum) of Lake Ziway (2009–2018).

Tide–surge interaction at the head of the Bay of Bengal during Cyclone Aila

Tide–surge interaction serves a critical role in shallow coastal regions in modifying the characteristics of peak water levels during storm events. In the present study, we investigated the tide–surge interaction in the coastal waters at the head of the Bay of Bengal (BoB) during Cyclone Aila, a Category 1 cyclone. The space–time characteristics of the interaction were discussed. The numerical simulation results reveal that the interaction was significant with interaction heights of up to 1 m at many locations that were even a few hundred kilometres away from the maximum surge. The spatial pattern of the interaction exhibited lower values in the central part of the head of the BoB due to the reduction in the width of the continental shelf and the relatively lower tidal amplitudes in this region compared with those in the remaining portion of the head of the BoB. The overall effect of the interaction was the reduction in the peak water levels. Favourable factors such as the extreme shallowness of the coastal waters, tidal contribution, and complex coastline geometry explain the strong tide–surge interaction at the head of the BoB.

Water level instability analysis of Urmia Lake Basin in the northwest of Iran

Water level reduction of Urmia Lake Basin is the main problem in northwest of Iran during 2001–2017. Climate change and human activity have affected the water resources in this basin. In addition, continuing downward trend of water level in the Urmia Lake leads to hazard such as dust storm, lake drying, subsidence in plains, population immigration, and reduced production efficiency. Finding the causes of water level change is one of the challenges as to the unsustainability of the lake. Climate change, drought, dam construction, well drilling, land use change, land cover change, and the pattern of cultivations are inflectional here. The results of the Man-Kendall test indicate that the annual temperature (Z = 2.3, 95%) and frequency of droughts increased, and annual precipitation (Z = − 2.5, 95%) decreased. The results indicate that groundwater extraction increased from 374 to 2263.4 mcm, and the volume of dams increased from 198 to 1758 mcm (1961–2017). Surface water is reduced due to decreasing rainfall, increasing temperature, and drought frequency in the last decade. The comparison of these parameters with each other indicates high contribution of climate change and human activity in water level reduction of the subject lake. Restoration and sustainability of this lake are very important to the water management resources of Urmia Lake Basin.

Spatio-temporal characterisation of droughts using selected indices in Upper Tana River watershed, Kenya

Monitoring and assessment of drought is key to modelling, impact assessment, mitigation and prediction of occurrence. The Upper Tana River watershed hosts two of Kenya's main water towers, Mt. Kenya and Aberdare Ranges, and is increasingly under threat from reduced water levels in the river basins due to unsustainable anthropogenic activities. The occurrence of drought in the region often exacerbates the impact of such activities on the natural resource-base. The study evaluated temporal and spatial characteristics of meteorological drought in Upper Tana Watershed using remotely sensed data from 1981 to 2018. Climate Hazard Group InfraRed Precipitation with Station (CHIRPS) and Modern-Era Retro-Analysis for Research and Applications-Assimilation Model (MERRA) products provided precipitation and temperature data via Google Earth Engine platform. GeoClim was used in the retrieval of Standardised Precipitation Index (SPI), while Standardised Precipitation and Evapotranspiration Index (SPEI) data were downloaded from SPEI Global Drought Monitor. Values for these datasets were plotted against time to facilitate temporal analysis of the drought. Spatially, the most intense meteorological drought period was from 2007 to 2009 in that the years were hit by severe drought for three consecutive years that covered the entire watershed. Temporally, drought incidences were observed in 1982, 1989, 1994, 2000, 2006, and 2011 and 2017. Both SPI and SPEI indices showed similar drought years. Drought mitigation measures should be implemented across the watershed. The findings provide insights that can be used by natural resource management practitioners in; drought forecasting, early warning systems, and in planning and management of water resources within the watershed. We recommend characterisation of the other types of droughts, agricultural and socio-economic droughts, for a holistic understanding of their spatial-temporal manifestations and the impact on the livelihoods of the watershed.

Experimental study of single slope solar still coupled with parabolic trough collector

After a comprehensive review, it was found that very few research has been conducted on single slope solar still coupled with parabolic trough collector. In this research article, the behavior of parabolic trough collector integrated solar still was experimentally evaluated. An experimental study dealing with the energy analysis of a single slope solar still coupled with a parabolic trough collector was investigated for three different brine depths (5 cm, 10 cm and 15 cm) and results are presented. Three different brine depths of 5 cm, 10 cm and 15 cm water level were configured for flow rates of 4.1 l/m2, 3.645 l/m2 and 3.2 l/m2, respectively and daily productivity was investigated. The energy analysis includes annual energy output, energy payback period, CO2 mitigation, and embodied energy. It was observed that the annual energy output, energy payback time and CO2 mitigation decrease with increasing water depth while a reduction in water level from 15 cm to 5 cm showed an increased in daily energy yield of 22%. The embodied energy of the experimental setup is estimated at 856.72 kWh, and 5 cm of water depth resulted in the highest range of carbon credit earned (₹10,169.86–₹40,679.44). Energy and economic analysis were also conducted for parabolic trough collector integrated solar still to evaluate the viability of the developed system. The payback period of the setup was found to be 246 days, 253 days, and 341 days at 5 cm, 10 cm and 15 cm water level, respectively.

Increasing water application efficiency at paddy field plot with application of evaporative irrigation (theoretical study)

Increased awareness of precision agriculture in water management, requires various ideas and methods for its application in the fields. One idea that can be categorized into precision farming as well as appropriate technology, is evaporative irrigation. Evaporative irrigation is an idea to control the provision of irrigation water based on the direct response of plant water needs, namely evapotranspiration. The objectives of this study were to: (1) examine the theoretical aspects of the evaporative irrigation to be applied to plots of rice fields in a plot of plots with irrigation units, (2) laying out design principles for evaporative irrigation valve closures. The results showed that, theoretically, a controller pipe was needed which would be an indicator for thick water in the plot of rice fields. The pipe controller regulates the opening of the irrigation lid to the plot based on the float-ballast principle. The design principle is carried out by simulating the reduction in the controller water level of the controller which illustrates the decrease in thick water plots. Water depth that is still tolerated for rice growth will be the limit for the provision of irrigation water to the plots. Amount of irrigation water provided is equal to the value of plant water needs in the ongoing rice growth phase. One example of the design of the controller pipe water level to start and stop irrigation is at 117.8 mm water level and 300 mm respectively. The total water needs of one crop-season is calculated to be 625 mm. With the application of evaporative irrigation, the initial conditions of sufficient water do not require the provision of irrigation water until the 31st day. Irrigation water application after that, until harvesting, requires only 477 mm. Giving this water follows the plant water requirements calculated on a day-to-day basis.

Features of work of retaining walls made of bored piles in flowing sandy loams

The customers usually try to avoid areas with a high groundwater level in the process of choosing a site for construction. The presence of groundwater significantly increases the cost of construction, if there is necessity of the construction of underground floors. But construction in the conditions of modern megacities is increasingly challenging geotechnical engineers, because of the need not only to build on lands with difficult engineering and geological conditions, and not only to develop reliable foundation`s decisions, but also because of the need to more effectively design the underground spaces with its subsequent operation as underground premises for various purposes.The process of water level reducing is not only technologically complex, but also leads to a changes in the physical and mechanical characteristics of soils, which are difficult to predict.This paper shows the features of numerical modeling of walls in water-saturated soils.The effect of the ability to filter water through walls on the stress-strain state of the system of retaining structures – soil mass is demonstrated.The calculations were performed using numerical modeling, since this approach allows engineers to see (predict) the formation of dangerous processes. Numerical modeling also allows to take into account the change in the physical and mechanical characteristics of the soil during drainage of the pit and take into account the process of water level reduction and the effect of water reduction on the formation of the stress-strain state of the system restraining structures – soil mass.In the framework of design process, there is always appear the opportunity to consider various technical decisions for walls and choose the most effective among those considered.In this paper, the construction of walls with the possibility to use the soil berms to temporarily reduce the free height of walls is considered. In addition, the operation of anchor fasteners in soft (weak) soils is shown. Also, elements of the building frame were used to reduce horizontal movements.It is important to understand that not all measures (the construction decisions) are possible in certain conditions, especially when it is a tight environment of dense urban development.

Variation of the Water Level in the Yangtze River in Response to Natural and Anthropogenic Changes

The water level in the Yangtze River has significantly changed due to the effects of varied precipitation and dam operations, which have exerted significant effects on irrigation, navigation, and ecosystems. Based on the measured data and the proposed calculation method, we analyzed the adjustment mechanisms of the seasonal water level in the whole Yangtze River. The results were as follows. During the dry season, the rising precipitation and dam operation both increased the water level in the upper reaches and in the reaches from the Jianli to Datong stations during 1981–2014. Moreover, dam operations were the dominant factor (except at Datong station). In the reaches from the Yichang to Shashi stations, dam operations are the reason for the reduction of the measured water level in the dry season, while the rising precipitation had an opposite influence. During the flood season, dam operations helped to reduce the water level from the upper reaches to the estuary during 1981–2014, while climate variation stresses adversely affected the entire river basin. In the reaches between the Luoshan and Jianli stations, climate variation is the dominant factor for the increased water level during the flood season, while dam operation is the reason for the reduced water level at the other six hydrological stations.

Forecasting the impacts of climate change on inland waterways

Inland waterways are vulnerable to climate change as river navigation depends on water levels. Droughts can severely disrupt inland navigation services by reducing water levels either to completely non-navigable ones or to levels that oblige operators to reduce vessel load. We analyse the impacts of droughts induced by climate change using projections of river discharge data provided by eleven different climate model runs. We consider location specific characteristics by focusing the analysis on four specific locations of the Rhine and the Danube where a substantial part of the total freight activity in the European Union (EU) takes place. For the majority of the cases and scenarios considered, a decrease of the number of low water level days is projected, leading to fewer drought related disruptions in the operation of the inland waterway transport system. Although the uncertainties from the climate projections should not be neglected, the navigation sector could benefit from global warming which means that European inland waterways might be one of the few sectors where climate change can have negligible, or even positive, impact. The average economic benefit, for the cases considered, from the decrease of low water levels by the end of the century is projected to be almost €8million annually.