Water Level Dynamics Research Articles

BOILER DRUM-LEVEL MODELING

In this paper, a mathematical model is developed to describe the dynamics of the drum-level of a natural circulation boiler. A boiler-drum is divided into two parts; the upper part contains saturated steam while the lower part contains a steam/water mixture. The ratio of the steam in that mixture is defined in this work as the steam volumetric ratio. On the other hand, balance equations are applied to the drum. The resulting equations are used to model the drum-level. The importance of the resulting model comes from the direct modeling of drum level which is usually computed off-line with the aid of empirical formulas and assumptions. Safe operation of boilers requires perfect level controller which cannot be designed without proper modeling. Simulation of the water level dynamics for step changes in heat rate and steam demand are compared with those in the literature. The results show that the drum level can be obtained from the basic balance equations.

Coasts, water levels, and climate change: A Great Lakes perspective

The North American Laurentian Great Lakes hold nearly 20 % of the earth’s unfrozen fresh surface water and have a length of coastline, and a coastal population, comparable to frequently-studied marine coasts. The surface water elevations of the Great Lakes, in particular, are an ideal metric for understanding impacts of climate change on large hydrologic systems, and for assessing adaption measures for absorbing those impacts. In light of the importance of the Great Lakes to the North American and global economies, the Great Lakes and the surrounding region also serve as an important benchmark for hydroclimate research, and offer an example of successful adaptive management under changing climate conditions. Here, we communicate some of the important lessons to be learned from the Great Lakes by examining how the coastline, water level, and water budget dynamics of the Great Lakes relate to other large coastal systems, along with implications for water resource management strategies and climate scenario-derived projections of future conditions. This improved understanding fills a critical gap in freshwater and marine global coastal research.

Deducing transmissivity from specific capacity in the heterogeneous upper aquifer system of Jifarah Plain, NW-Libya

The hydraulic characterisation of aquifer systems is important for the development of exploitation scenarios and management strategies. Especially in lithologically heterogeneous aquifers, local scale variations in transmissivity (T) may not be neglected. Field scale transmissivity values are usually derived from pumping tests, but in most cases their number and availability is rather limited. Therefore T values are often estimated from specific well capacities (SC) which can easily be measured in exploitation wells based on static and dynamic water levels. Empirical relations allow T to be calculated from SC values using a power law relation of the form T=A*SCN. In this paper this relation is investigated for three aquifers in north-west Lybia, using the results from step-drawdown tests which allow determination of well efficiencies, which can be incorporated into the regression analysis. The obtained fitting coefficients of the power law relations were compared with published values from other studies. Both parameters of the power law relation (scale factor and power coefficient) seem to be highly correlated following an exponential relationship (R2=0.89), reducing the T–SC relation to a single parameter equation, which is mainly related to lithology.

Assessing hyporheic exchange and associated travel times by hydraulic, chemical, and isotopic monitoring at the Steinlach Test Site, Germany

First results of a multi-disciplinary hyporheic monitoring study are presented from the newly established Steinlach Test Site in Southern Germany. The site is located in a bend of the River Steinlach (mean discharge of 1.8 m³/s) underlain by an alluvial sandy gravel aquifer connected to the stream. The overall objective is a better understanding of hyporheic exchange processes at the site and their interrelations with microbial community dynamics and biochemical reactions at the stream–groundwater interface. The present paper focuses on the distribution of lateral hyporheic exchange fluxes and their associated travel times at the Steinlach Test Site. Water level dynamics in various piezometers correspond to the different domains of hydraulic conductivity in the shallow aquifer and confirms hyporheic exchange of infiltrated stream water across the test site. Hydrochemical compositions as well as increased damping of continuous time series of electrical conductivity (EC) and temperature at the respective piezometers confirmed the inferred distribution of hyporheic flowpaths. Mean travel times ranging from 0.5 days close to the stream to more than 8 days in the upstream part of the test site could be estimated from deconvolution of EC and δ18O–H2O data. The travel times agree well with the presumed flowpaths. Mg/Ca ratios as well as model fits to the EC and δ18O data indicate the presence of an additional water component in the western part of the test site which most likely consists of hillslope water or groundwater. Based on the mean travel times, the total lateral hyporheic exchange flux at the site was estimated to be of the order of 1–2 L/s.

Complex interactions between pre-spawning water level increase, trophic state and spawning stock biomass determine year-class strength in a shallow-water-spawning fish

Summary Pre-spawning water level increase (PWLI) is a recently discovered parameter of water level dynamics affecting juvenile year-class strength (YCS) in shallow-water-spawning fish. By analysing a time series of commercial common bream (Abramis brama) yields in Lake Constance from 1950 through 2007, this study showed that the differences in juvenile YCS are conserved until the adult life stage. Adult YCS was best explained by complex interactions of PWLI with both stock-intrinsic and extrinsic environmental variables. The correlation between PWLI and YCS of adult bream became more pronounced as the trophic state of the lake increased. It is argued that this mediator effect of the trophic state results from increased growth of the algal biofilms during high trophic state periods. These biofilms are known to impair safe attachment of the eggs to the substratum and affect mortality rates of the eggs. Furthermore, reproductive stock size exhibited a positive effect on the resulting YCS. However, a marginally significant interaction between reproductive stock size and PWLI indicates that the two positive effects of PWLI and reproductive stock size on YCS were not fully additive, probably because the very large year-classes resulting from the combined positive effects suffered from strong intra-specific competition. This study demonstrates that anthropogenic water level regulation, e.g. for flood protection or for the generation of hydroelectric power, and climate change altering PWLI have the potential to affect YCS throughout the whole life cycle of bream, particularly in eutrophic water bodies. Similar effects of PWLI are anticipated in other shallow water spawning species.

A new insight on the water level dynamics of the Danube Delta using a high spatial density of SAR measurements

Summary In this work, an interferometric ALOS PalSAR dataset acquired between 2007 and 2010 is used to measure water level changes for the first time within a hydrographical unit of the Danube Delta in Romania at the Black Sea. When the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique was applied, it revealed a previously unknown and spectacular dynamic of the water levels in Danube Delta. The results are presented in the form of water level change maps for different periods of time. The DInSAR measurements for a number of locations are compared with extrapolated water level change values obtained from an existing mathematical model of the hydrological regime in the Danube Delta. The comparison shows a very good correlation between DInSAR measurements and the mathematical model, showing that this method using L-band ALOS PalSAR data and applied to a wetland area of Danube Delta can be used to increase the spatial density of water level measurements and contributes to a better understanding of hydrological processes.

The Application of EMD in Dynamic Water Level Measurement

Due to the water liquidity and undulation in irrigation channel as well as the vary kinds of external disturbances, the value of water change couldn’t be smooth. The signal of water level measuring is a nonlinear, non-stationary signal. In order to improve the measuring precision of water level, in the processing of water level measurement signal, the algorithm of Empirical Mode Decomposition is introduced. It can optimize the water level measured values and reduce the influence of the water wave to the water level measurement. Experiment shows this method is effective to improve the measuring precision of water level.

Multisensor Monitoring System for Assessment of Locust Hazard Risk in the Lake Balkhash Drainage Basin

Satellite and ground-based data were combined in a monitoring system to quantify the link between climate conditions and the risk of locust infestations in the southern part of Lake Balkhash’s drainage basin in the Republic of Kazakhstan. In this monitoring system, the Normalized Difference Vegetation Index (NDVI), derived from the SPOT-VGT satellite, was used for mapping potential locust habitats and monitoring their area throughout 1998 to 2007. TOPEX/Poseidon and Jason 1 altimeter data were used to track the interannual dynamics of water level in Balkhash Lake. Climate conditions were represented by weather records for air temperature and precipitation during the same period. The classification procedure, based on an analysis of multitemporal dynamics of SPOT-VGT NDVI values observed by individual vegetation classes, generated annual areas of ten land-cover types, which were then categorized as areas with low, medium, and high risk for locust infestation. Statistical analyses showed significant influences of the climatic parameters and the Balkhash Lake hydrological regime on the spatial extend of annual areas of potential locust habitats. The results also indicate that the linkages between locust infestation risk and environmental factors are characterized by time lags. The expansion of locust risk areas are usually preceded by dry, hot years and lower water levels in Balkhash Lake when larger areas of reed grass are free from seasonal flooding. Years with such conditions are favourable for locust outbreaks due to expansion of the habitat areas suitable for locust oviposition and nymphal development. In contrast, years with higher water levels in Balkhash Lake and lower temperature decrease the potential locust habitat area.

Artificial Regulation of Water Level and Its Effect on Aquatic Macrophyte Distribution in Taihu Lake

Management of water levels for flood control, water quality, and water safety purposes has become a priority for many lakes worldwide. However, the effects of water level management on the distribution and composition of aquatic vegetation has received little attention. Relevant studies have used either limited short-term or discrete long-term data and thus are either narrowly applicable or easily confounded by the effects of other environmental factors. We developed classification tree models using ground surveys combined with 52 remotely sensed images (15–30 m resolution) to map the distributions of two groups of aquatic vegetation in Taihu Lake, China from 1989–2010. Type 1 vegetation included emergent, floating, and floating-leaf plants, whereas Type 2 consisted of submerged vegetation. We sought to identify both inter- and intra-annual dynamics of water level and corresponding dynamics in the aquatic vegetation. Water levels in the ten-year period from 2000–2010 were 0.06–0.21 m lower from July to September (wet season) and 0.22–0.27 m higher from December to March (dry season) than in the 1989–1999 period. Average intra-annual variation (CVa) decreased from 10.21% in 1989–1999 to 5.41% in 2000–2010. The areas of both Type 1 and Type 2 vegetation increased substantially in 2000–2010 relative to 1989–1999. Neither annual average water level nor CVa influenced aquatic vegetation area, but water level from January to March had significant positive and negative correlations, respectively, with areas of Type 1 and Type 2 vegetation. Our findings revealed problems with the current management of water levels in Taihu Lake. To restore Taihu Lake to its original state of submerged vegetation dominance, water levels in the dry season should be lowered to better approximate natural conditions and reinstate the high variability (i.e., greater extremes) that was present historically.

Analysis of the water level dynamics simulated by a global river model: A case study in the Amazon River

Water level dynamics in continental‐scale rivers is an important factor for surface water studies and flood hazard management. However, most continental‐scale river models have not focused on the reproduction of water level because the storage and movement of surface waters are regulated by smaller‐scale topography than their grid resolutions. Here we analyzed the water level dynamics simulated by a state‐of‐the‐art global river model, CaMa‐Flood, with subgrid representation of floodplain topography. As a case study, hydrodynamics simulation in the Amazon River was accomplished, and the simulated water surface elevations along the main stem were compared against Envisat altimetry. The seasonal cycles of the simulated water surface elevations are in agreement with the altimetry (correlation coefficient >0.69, annual amplitude error <1.6 m). The accuracy of absolute water surface elevations was also good (averaged RMSE of 1.83 m), and the associated errors were within the range of the model uncertainty due to channel cross‐section parameters. Then the ocean tide variation at river mouth was incorporated for simulating the tidal effect in the inland Amazon basin, which requires realistic representation of absolute water surface elevations. By applying power spectra analysis to the simulated water level variations, the 15 day cycle due to spring and neap tides was detected at Obidos, located 800 km upstream from the river mouth. The reproduction of the ocean tide propagation to the inland region suggests that CaMa‐Flood includes the main physical processes needed to accurately simulate the water level dynamics in continental‐scale rivers.

Finite element investigation of the poroelastic effect on the Xinfengjiang Reservoir-triggered earthquake

Coulomb failure stress changes (ΔCFS) are used in the study of reservoir-induced seismicity (RIS) generation. The threshold value of ΔCFS that can trigger earthquakes is an important issue that deserves thorough research. The Ms6.1 earthquake in the Xinfengjiang Reservoir in 1962 is well acknowledged as the largest reservoir-induced earthquake in China. Therefore, it is a logical site for quantitative calculation of ΔCFS induced by the filling of the reservoir and for investigating the magnitude of ΔCFS that can trigger reservoir seismic activities. To better understand the RIS mechanism, a three-dimensional poroelastic finite element model of the Xinfengjiang Reservoir is proposed here, taking into consideration of the precise topography and dynamic water level. We calculate the instant changes of stress and pore pressure induced by water load, and the time variation of effective stresses due to pore water diffusion. The ΔCFS on the seismogenesis faults and the accumulation of strain energy in the reservoir region are also calculated. Primary results suggest that the reservoir impoundment increases both pore pressure and ΔCFS on the fault at the focal depth. The diffusion of pore pressure was likely the main factor that triggered the main earthquake, whereas the elastic stress owing to water load was relatively small. The magnitude of ΔCFS on seismogenesis fault can reach approximately 10 kPa, and the ΔCFS values at the hypocenter can be about 0.7–3.0 kPa, depending on the fault diffusion coefficient. The calculated maximum vertical subsidence caused by the water load in the Xinfengjiang Reservoir is 17.5 mm, which is in good agreement with the observed value of 15 mm. The accumulated strain energy owing to water load was only about 7.3×1011 J, even less than 1% of the seismic wave energy released by the earthquake. The reservoir impoundment was the only factor that triggered the earthquake.

Application of Resistivity Sounding In Groundwater Investigation: A Case Study of Rimin Gado and Tofa Local Government Areas of Kano State, Nigeria

Over thirty Vertical Electrical Sounding survey were carried out in Tofa and Rimin Gado local government areas of Kano state. Dynamic water level from open wells was also collected and was used as a guide for the selection of the electrode spread. The schlumberger array with a maximum electrode spread of 100 m was employed in all the points. Results from the sounding data indicates that the area is generally underlain by five geoelectric or geologic section which include Lateritic top soil or Lateritic sand, Silty sand or Sandy clay, Weathered basement or Clayey sand, Fractured basement and Fresh basement. Based on the result obtained the weathered as well as the fractured basements forms the aquiferous zone within the study area, with the weathered being more promising. The resistivity of these zones varies from 9 to 1640 Ωm with an average value 255 Ωm, while the thickness varies from a value of 1.66 to 28 m with an average value of 10.67 m. Depth to this zone varies from 5 to 31 m with an average value of 8.1 m. The study also shows that the Rimin Gado area appears to have more potential for groundwater development as compared with the Tofa area.

Differentiation of temporal water level dynamics in the Besko and Klimkówka Reservoirs (The Low Beskids, Poland)

Differentiation of temporal water level dynamics in the Besko and Klimkówka Reservoirs (The Low Beskids, Poland)

Water level dynamics of Amazon wetlands at the watershed scale by satellite altimetry

In this study we used satellite altimetry to characterize the time and space variations in water stored in or circulating through rivers, floodplains, wetlands and lakes in the major sub-basins of the Amazon basin. Using a specific methodology to rigorously select original three-dimensional (3D) data from an Environmental Satellite (ENVISAT) mission, water level time series were calculated at the crossing path of the satellite tracks with the water bodies. We took advantage of the continuous sampling of the water level along the satellite track segments that cross the watershed to analyse both spatial and temporal relationships between: (i) the river and its floodplain and (ii) different basins. This work evidences in particular the existence of water leaking between the Negro and Solimões basins at the high water stage. It highlights that the phenomenon of a secondary flood peak occurring in the water level series in the Solimões basin at rising water, known as repiquete, is caused by the rain equatorial regime of the northern upstream tributaries of the Solimões River, but is disconnected from the same phenomenon occurring within the Rio Negro basin.

Importance of water level dynamics for vegetation patterns in a natural percolation mire (Rospuda fen, NE Poland)

Although conservation of percolation mires is very important for the European biodiversity, our understanding of their functioning is still insufficient, as most of the studied sites are to some extent degraded. We present a study on the relationship between vegetation patterns, hydrochemical gradients and water level fluctuations carried out in the Rospuda valley (NE Poland), which was recently discovered for science as a uniquely preserved fully functioning percolation mire. Vegetation composition, mire water chemistry and water level dynamics were studied along five transects perpendicular to the valley. Eight major vegetation types were identified: brown moss-small and slender sedge fens, Sphagnum-small sedge fens, brown moss-tall sedge fens, tall sedge-reed fens, pine-birch fen woodlands and shrublands, spruce fen woodlands, inundated alder woodlands, alder spring fen woodlands. The seasonal dynamics of water table was revealed as the major factor explaining vegetation patterns. The studied chemical parameters were relatively homogeneous in the whole mire—there is a rather uniform type of mineral-rich nutrient-poor subsurface water all across the fen.

Taizhou Bridge South Anchor Caisson Construction Drainage System Optimization Model of Settlement and Deformation as Constraint Conditions

Since construction drainage will inevitably cause ground settlement, it is necessary that a system optimization model is established with source (sink) distribution and intensity being the object function, minimum requirements of settlement and deformation of surroundings caused by draining and dynamic water levels during different working procedures being constraints, and the design parameter of pumping (injection) wells being the variable. The system optimization model solved the problem of which Taizhou bridge south anchor caisson foundation construction drainage induced settlement, so as to lower the damage of surrounding buildings. So the system optimization model provides a new method for active control over settlement during draining. Such a method of drainage based on system optimization model should be of significance for similar projects involving drainage.

Soft Water Level Sensors for Characterizing the Hydrological Behaviour of Agricultural Catchments

An innovative soft water level sensor is proposed to characterize the hydrological behaviour of agricultural catchments by measuring rainfall and stream flows. This sensor works as a capacitor coupled with a capacitance to frequency converter and measures water level at an adjustable time step acquisition. It was designed to be handy, minimally invasive and optimized in terms of energy consumption and low-cost fabrication so as to multiply its use on several catchments under natural conditions. It was used as a stage recorder to measure water level dynamics in a channel during a runoff event and as a rain gauge to measure rainfall amount and intensity. Based on the Manning equation, a method allowed estimation of water discharge with a given uncertainty and hence runoff volume at an event or annual scale. The sensor was tested under controlled conditions in the laboratory and under real conditions in the field. Comparisons of the sensor to reference devices (tipping bucket rain gauge, hydrostatic pressure transmitter limnimeter, Venturi channels…) showed accurate results: rainfall intensities and dynamic responses were accurately reproduced and discharges were estimated with an uncertainty usually acceptable in hydrology. Hence, it was used to monitor eleven small agricultural catchments located in the Mediterranean region. Both catchment reactivity and water budget have been calculated. Dynamic response of the catchments has been studied at the event scale through the rising time determination and at the annual scale by calculating the frequency of occurrence of runoff events. It provided significant insight into catchment hydrological behaviour which could be useful for agricultural management perspectives involving pollutant transport, flooding event and global water balance.

USDA conservation program and practice effects on wetland ecosystem services in the Prairie Pothole Region

Implementation of the U.S. Department of Agriculture (USDA) Conservation Reserve Program (CRP) and Wetlands Reserve Program (WRP) has resulted in the restoration of >2 million ha of wetland and grassland habitats in the Prairie Pothole Region (PPR). Restoration of habitats through these programs provides diverse ecosystem services to society, but few investigators have evaluated the environmental benefits achieved by these programs. We describe changes in wetland processes, functions, and ecosystem services that occur when wetlands and adjacent uplands on agricultural lands are restored through Farm Bill conservation programs. At the scale of wetland catchments, projects have had positive impacts on water storage, reduction in sedimentation and nutrient loading, plant biodiversity, carbon sequestration, and wildlife habitat. However, lack of information on the geographic location of restored catchments relative to landscape‐level factors (e.g., watershed, proximity to rivers and lakes) limits interpretation of ecosystem services that operate at multiple scales such as floodwater retention, water quality improvement, and wildlife habitat suitability. Considerable opportunity exists for the USDA to incorporate important landscape factors to better target conservation practices and programs to optimize diverse ecosystem services. Restoration of hydrologic processes within wetlands (e.g., hydroperiod, water level dynamics) also requires a better understanding of the influence of conservation cover composition and structure, and management practices that occur in uplands surrounding wetlands. Although conservation programs have enhanced delivery of ecosystem services in the PPR, the use of programs to provide long‐term critical ecosystem services is uncertain because when contracts (especially CRP) expire, economic incentives may favor conversion of land to crop production, rather than reenrollment. As demands for agricultural products (food, fiber, biofuel) increase, Farm Bill conservation programs will become increasingly important to ensure provisioning of ecosystem services to society, especially in agriculturally dominated landscapes. Thus, continued development and support for conservation programs legislated through the Farm Bill will require a more comprehensive understanding of wetland ecological services to better evaluate program achievements relative to conservation goals.

Sinkholes related to discontinuous pumping: susceptibility mapping based on geophysical studies. The case of Crestatx (Majorca, Spain)

The Crestatx aquifer is the main source of water supply to the Bay of Alcudia, one of the largest resorts on the island of Majorca (Spain). This water has been used since the 1970s using several pumping wells, which draw an annual volume of 1.5 hm3. The seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level (up to 120 m) and dynamic water levels of down to 87 m below sea level. At the end of the 1990s, several sinkholes and subsidence depressions started being detected in a highly karstified area. Twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70,000 m2, with diameters up to 23 m and depth more than 15 m. The intense and continuous rainfall during recent years (2008–2010) has considerably accelerated the process, increasing the dimensions of existing sinkholes and the appearance of new morphologies. By means of electrical tomography techniques, a ground study was carried out. Numerous cavities have been identified in the upper 30 m. Using a map of the surface morphologies and the geophysical profiles, we can determine that the propagation and orientation of the sinkholes lie along three main directions: N30°E, N130°E and N60°E. The first is the most relevant, which is parallel to the main tectonic structures in the area. The interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas, which is an effective tool to assess risk in the area, as there are roads and a housing development nearby. The high, but discontinuous, exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions, as it causes large variations of pressure and accelerates the dissolution process in the underlying rock.

Dynamics of wetland vegetation under multiple stresses: a case study of changes in sawgrass trait, structure, and productivity under coupled plant‐soil‐ microbe dynamics

AbstractThis paper quantifies wetland vegetation dynamics under drought, waterlogging, shading, and nutrient stresses within the coupled plant‐soil‐microbe system. A plant is characterized by three independent traits, namely leaf nitrogen (N) content, specific leaf area (SLA), and allometric carbon (C) allocation to rhizome storage, while plant growth is modelled through a dynamic plant allocation scheme. The modelling of N focuses on the internal cycle in which the aerobic and anaerobic processes are determined by the dynamics of oxygen controlled by plants, microbial aerobic processes, and hydrologic dynamics. The dynamics of water levels and soil moisture are described by a simple hydrologic model with stochastic rainfall and are decoupled from the plant‐soil‐microbe dynamics. Using the model to investigate the dynamics of sawgrass, the results, which are consistent with field observations in the southern Everglades, indicate that SLA decreases with increasing anaerobic condition. The lower SLA maintains high stomatal opening, while at the same time prevents cavitational collapse when sawgrass lowers its root:shoot ratio to reduce C cost in root anaerobic respiration. Given a naturally low but not too scarce level of phosphorus, net N mineralization is higher in the wetter hydrologic regimes because the increase in anaerobic decomposition and N mineralization compensate for the decline in those of aerobes; and the slower growing, more nitrogen efficient anaerobes compete less with plants for N. The optimal traits are the results of several counteracting trends of trade‐offs in C and N economy differently influenced by trait combinations in different wetland environments. Copyright © 2010 John Wiley & Sons, Ltd.