Analytical solution and numerical model for the interface in a stratified long wave system

For a two layered long wave propagation, linearized governing equations, which were derived earlier from the Euler equations of mass and momentum assuming negligible friction and interfacial mixing are solved analytically using Fourier transform. For the solution, variations of upper layer water level is assumed to be sinosoidal having known amplitude and variations of interface level is solved. As the governing equations are too complex to solve it analytically, density of upper layer fluid is assumed as very close to the density of lower layer fluid to simplify the lower layer equation. A numerical model is developed using the staggered leap-forg scheme for computation of water level and discharge in one dimensional propagation having known amplitude for the variations of upper layer water level and interface level to be solved. For the numerical model, water levels (upper layer and interface) at both the boundaries are assumed to be known from analytical solution. Results of numerical model are verified by comparing with the analytical solutions for different time period. Good agreements between analytical solution and numerical model are found for the stated boundary condition. The reliability of the developed numerical model is discussed, using it for different a (ratio of density of fluid in the upper layer to that in the lower layer) and p (ratio of water depth in the lower layer to that in the upper layer) values. It is found that as ‘CX’ increases amplification of interface also increases for same upper layer amplitude. Again for a constant lower layer depth, as ‘p’ increases amplification of interface. also increases for same upper layer amplitude.

The application of wave induced forces to a two-dimensional finite element long wave hydrodynamic model

This paper describes the modification of a two-dimensional finite element long wave hydrodynamic model in order to predict the net current and water levels attributable to the influences of waves. Tests examine the effects of the application of wave induced forces, including comparisons to a physical experiment. An example of a real river system is presented with comparisons to measured data, which demonstrate the importance of simulating the combined effects of tides and waves upon hydrodynamic behavior. (C) 2002 Elsevier Science Ltd. All rights reserved.

Modelação e monitorização do comportamento dinâmico de barragens abóbada: identificação modal automática

Trabalho Final de Mestrado elaborado no Laboratório de Engenharia Civil (LNEC) para obtenção do grau de Mestre em Engenharia Civil pelo Instituto Superior de Engenharia de Lisboa no âmbito do protocolo de cooperação entre o ISEL e o LNEC

Evaluation of two sweeping methods for estimating the number of immature Aedes aegypti (Diptera: Culicidae) in large containers

Introduction Here, we evaluated sweeping methods used to estimate the number of immature Aedes aegypti in large containers. Methods III/IV instars and pupae at a 9:1 ratio were placed in three types of containers with, each one with three different water levels. Two sweeping methods were tested: water-surface sweeping and five-sweep netting. The data were analyzed using linear regression. Results The five-sweep netting technique was more suitable for drums and water-tanks, while the water-surface sweeping method provided the best results for swimming pools. Conclusions Both sweeping methods are useful tools in epidemiological surveillance programs for the control of Aedes aegypti.

Observations on aquatic Macrophyte Dynamics In the Reservoir Of The Balbina Hydroelectric Powerplant, Amazonas State, Brazil

Between 1991 and 1995 aquatic macrophyte composition was observed in the lower part of the reservoir of the hydroelectric power plant of Balbina (Amazonas, Brazil). After closure of the dam in 1987, vegetation cover - mostly Eichhornia crassipes - was high, but was not quantified. After 1990 it declined rapidly with a characteristic succession pattern: Eichhornia ® Vincularia + Cyperaceae ® Salvinia. The Cyperaceae, and many other less dominant species, were mostly associated with drift wood, produced by the decomposing, emergent forest. Comparison of the chemical data of the Uatumã river before the construction of the dam (1983) with those of later years (1989 - 1995) suggests that the succession was the result of a relatively mild and short period of eutrophication, followed by declining nutrient levels. Annual variation of water levels, followed by aquatic and terrestrial decomposition of the marginal vegetation, may allow for the maintenance of relatively productive vegetation belts along the shore lines of islands and inundated stream valleys.

Previsão de cheias em Barcelos

Dissertação de mestrado integrado em Engenharia Civil

Hazard assessment of storm events for the battery, New York

The environmental and socio-economic importance of coastal areas is widely recognized, but at present these areas face severe weaknesses and high-risk situations. The increased demand and growing human occupation of coastal zones have greatly contributed to exacerbating such weaknesses. Today, throughout the world, in all countries with coastal regions, episodes of waves overtopping and coastal flooding are frequent. These episodes are usually responsible for property losses and often put human lives at risk. The floods are caused by coastal storms primarily due to the action of very strong winds. The propagation of these storms towards the coast induces high water levels. It is expected that climate change phenomena will contribute to the intensification of coastal storms. In this context, an estimation of coastal flooding hazards is of paramount importance for the planning and management of coastal zones. Consequently, carrying out a series of storm scenarios and analyzing their impacts through numerical modeling is of prime interest to coastal decision-makers. Firstly, throughout this work, historical storm tracks and intensities are characterized for the northeastern region of United States coast, in terms of probability of occurrence. Secondly, several storm events with high potential of occurrence are generated using a specific tool of DelftDashboard interface for Delft3D software. Hydrodynamic models are then used to generate ensemble simulations to assess storms' effects on coastal water levels. For the United States’ northeastern coast, a highly refined regional domain is considered surrounding the area of The Battery, New York, situated in New York Harbor. Based on statistical data of numerical modeling results, a review of the impact of coastal storms to different locations within the study area is performed.

The importance of catfish burrows in maintaining fish populations of tropical freshwater streams in western Ecuador / Garrett S. Glodek.

v.73:no.1(1978)

Fish assemblages in two sandy beaches in lower Purus river, Amazonas, Brazil

Fish assemblages from two sandy beaches in the lower Purus river (Amazonas, Brazil) were compared. Four sampling groups were represented by: day and night samples in sandy beach inside the Reserva Biológica de Abufari (biological reserve) and day and night samples in the Reserva de Desenvolvimento Sustentável Piagaçu-Purus (sustainable development reserve). Samples were collected during low water levels (November) in 2007. The fish were sampled by means of seines with mesh size of 5 mm between opposing knots, 11 m long and 6 m wide. A total of 112 fish species belonging to nine orders and 27 families was captured. The vast majority of the dominant forms consisted of small fishes (< 100 mm SL) or juveniles. Samples collected in Abufari at night presented more specimens (3,540), higher richness (84 spp.), larger total biomass (76,614 g) and higher diversity (H'= 2.57) than the other groups. The composition of fish assemblages was significantly different among all analyzed groups (ANOSIM, p < 0.0001, R= 0.71). NMDS analysis also clustered all species in four distinct groups according to species composition per period and site. SIMPER analyses showed that 80% of variation of species composition among the groups examined was due to 12 species. However, fish composition did not show any correlation with the abiotic factors examined. Different levels of use in both reserves may explain differences in fish composition.

1009-004 Lost Island Lake Watershed Final Report

The Lost Island Lake watershed is located in the prairie pothole region, a region dotted with glacial wetlands and shallow lakes. At 1,180 acres, Lost Island Lake is the state's fifth largest natural lake and its watershed is comprised of nearly 1,000 acres of wetland habitat, including Iowa 's largest natural wetland – Barringer Slough. Unfortunately, Lost Island and its associated wetlands are not functioning to their fullest ecological and water quality potential. In 2002 and 2004, Lost Island Lake was categorized as '·impaired'" on Iowa's Impaired Waters List. Frequent algal blooms and suspended solids drastically increase turbidity levels resulting in its impairment. To investigate these concerns, a two-year study and resulting Water Quality Improvement Plan were completed. The water quality study identified an overabundance of non-native common carp (Cyprinus carpio) in the lake and its surrounding wetlands as a primary cause of impairment. The goal of the Lost Island Lake Watershed Enhancement Project is to restore ecological health to Lost Island Lake and its intricate watershed resulting in improved water quality and a diverse native plant and wildlife community. The purpose of this grant is to obtain funding for the construction of two combination fish barriers and water control structures placed at key locations in the watershed within the Blue Wing Marsh complex. Construction of the fish barriers and water control structures would aid restoration efforts by preventing spawning common carp from entering wetlands in the watershed and establishing the ability to manage water levels in large wetland areas. Water level management is crucial in wetland health and exotic fish control. These two structures are part of a larger construction project that involves a total of four combination fish barriers and water control structures and one additional fish barrier. The entire Lost Island Lake Watershed Enhancement Project is a multi-year project, but the construction phase for the fish barriers and water control structures will be completed before December 31, 2011.

Groundwater recharge estimate at Alto Rio Grande - MG watershed

Springs are outcrops of aquifers surface, and the water cycle in this environment pass through the recharge, generally defined as the amount of water added to the aquifer, which may occur locally from rainwater infiltration. This study uses the Water Table Fluctuation (WTF) method to estimate the direct recharge and a groundwater balance to estimate the deep recharge on unconfined aquifers. The WTF method employs data of the aquifer water levels and its specific yield to estimate the direct recharge. The groundwater balance considers the direct recharge estimated by the WTF method, as the water input in the system and outputs as the base flow and deep recharge. The recharge was estimated at four areas at the watershed of Alto Rio Grande city, Minas Gerais (MG) state, in Brazil. The direct recharge estimate was 121.11; 64.62; 83.99; 152.46 (mm/year) for the L1, L2, M1 and M2 areas. The effect of the presence of forest in the recharge area can prevail over slope of relief, allowing more direct recharge, even in sources with steeper relief. The runoff from the springs in the study period exceeded the direct recharge, indicating a situation in which the saturated zone feeds the vadose zone. The annual flow was above the direct recharge pointing a situation of over exploitation of the aquifer, a non sustainable situation. The specific yield of the aquifers could also have been underestimated.

Salon keskusta-alueen tulvasuojelu : Tulvasuojelutoimenpiteiden mitoitus ja arviointi

Uskelanjoki virtaa Salon kaupungin läpi ja varsinkin jääpato tulvatilanteissa tulvavedenkorkeudet uhkaavat nousta maa-alueille. Tässä työssä tutkittiin valittujen tulvasuojelutoimenpiteiden vaikutuksia tulvavedenkorkeuksiin Uskelanjoessa sekä Salon kaupungin keskusta-alueella. Tavoitteena oli löytää Uskelanjoen tulvimisen ehkäisyyn kustannustehokas ratkaisu. Työssä mallinnettiin Uskelanjoen vedenkorkeuksia yksidimensionaalisesti käyttäen HEC-RAS -mallia. Mallinnus suoritettiin mitoitustulvalla tulvasuojelutoimenpiteille, jotka olivat jäidenpidätysrakennelmien rakentaminen, ruoppaus, pengerrys sekä näiden vaihtoehtojen yhdistelmät. Mallinnuksesta saatujen tulvavedenkorkeuksien avulla laadittiin tarkastellulta uomaosuudelta tulvavaarakartat sekä tulvavahinkoarviot. Näiden tietojen pohjalta voitiin vaihtoehtojen hyötyjä vertailla käyttämällä kustannus-hyötyanalyysia. Kustannus-hyötyanalyysin tuloksista havaittiin, että jäidenpidätysrakennelmat osoittautuivat parhaaksi tulvasuojeluvaihtoehdoksi Uskelanjoessa. Muutkin työssä tutkitut vaihtoehdot osoittautuivat kannattaviksi. Epävarmuuden kumuloituminen vedenkorkeuksien mallinnuksesta hyötyjen ja haittojen arviointiin luo oman epävarmuutensa tässä työssä laskettuihin arvoihin. Tätä epävarmuutta on tutkittu työssä käyttämällä herkkyysanalyysia. Herkkyysanalyysin tuloksia tarkastelemalla jäidenpidätysrakennelmien rakentaminen osoittautui kaikkein riskivapaimmaksi vaihtoehdoksi Uskelanjoen tulvasuojelussa.

Similarity among periphyton algal communities in a lentic-lotic gradient of the upper Paraná river floodplain, Brazil

Floristic comparison of periphyton communities from three systems with different hydrodynamic regimes (lentic, semilotic, and lotic) was carried out during high and low water periods on the Upper Paraná River floodplain. For each period and system, glass slides were sampled every two days during 18-day periods, and Eichhornia azurea Kunth petioles were sampled three times. A total of 228 species was collected, representing 12 classes, mainly diatoms and desmids. The highest species-richness was found in communities from lentic system and during high water. Species richness in the lotic system was more stable over succession and hydrological periods. Algal taxonomic structure in river community was clearly separated from the other two systems, with 43% of similarity level. The hydrological period was next in importance, followed last by the substratum type, with communities associated at 65-78% similarity levels, depending on system and hydrological period. The type of system, but not the water levels,was the main factor that influenced community richness, followed by disturbances caused by flood pulses and the operation of reservoirs upstream. The periphyton on artificial and natural substrata presented high degree of similarity.

Impacts of the Belo Monte hydroelectric dam construction on pioneer vegetation formations along the Xingu River, Pará State, Brazil

There is an important pioneer vegetation formation along the Xingu River in the area where the Belo Monte hydroelectric dam is being constructed that is highly adapted to a seasonally fluctuating water levels. The aim of this study was to examine the habitat and flora of the pioneer formations in the Belo Monte area. The area was divided in three sections for study purposes (Reservoir, Low Flow, and Control) that were expected to experience different degrees of impact from the dam project. The calculations of habitat losses were based on satellite imagery classifications, and a total of 111 plots were established in the three areas for vegetation sampling. Habitat losses of the pioneer formations will total 89.7% when the project is fully functional. Forty-five of the 72 recorded species are restricted to single areas. Species richness and diversity were significantly lower in the control area. The completion of the Belo Monte reservoir will result in habitat reductions and will consequently reduce the richness and diversity of pioneer formations. Studies suggest monitoring the populations located in the reduced flow area to determine possible impacts resulting from changes in the regional hydrological cycle caused by the Xingu River dam.

Temporal variations in the primary productivity of Eleocharis acutangula (Cyperaceae) in a tropical wetland environment

Wetland vegetation typically includes aquatic macrophytes with high primary production capacities. The present study investigated how hydrological variations affect biomass allocation and primary productivity in the emergent macrophyte Eleocharis acutangula (Roxb.) Schult. Eleocharis acutangula ramets were collected from the Campelo Lagoon flood plain (21°39'S, 41°12'W and 21°37S, 41°11'W) between March/2005 and February/2006. This region experienced an unusually short rainy period between November/2005 and February/2006 that generated atypically high primary production levels (128gDWm-2month-1) and total biomass gains (447gDWm-2) in May and June/2005 respectively. Our data indicated that primary production and biomass allocation were strongly influenced by variations in wetland water levels and that macrophytes quickly invested in biomass accumulation when surface water levels rised.