Hydrodynamic Modeling

Hydrodynamic and water quality models provide a tool for environmental management
and infrastructure planning in Darwin Harbour, a tropical estuary located in northern Australia. These
models are relied upon by both private industry and government for planning and environmental
problem solving. A validation study using a fluorescent tracer and a number of drogues was carried
out in order to verify and calibrate the models. An Acoustic Doppler Current Profiler was also deployed
close to the outfall locations for the period of the study. The tracer and drogues were released on two
consecutive days and at two locations corresponding to a proposed waste water outfall extension
route. The tracer was released at different depths on each day and the drogues tracked the
subsurface current at 1.5m depth. The movement of the tracer plume body differed somewhat to the
drogues’ paths, revealing a time lag in near field vertical mixing close to the surface. Darwin’s large
tidal range was thought to generate rapid vertical mixing, however field studies in this area have not
been carried out previously. This study confirms that 2-D modelling is appropriate to characterise the
vertical mixing in the study area for the proposed waste water outfall.

Bangladesh is situated at the confluence of GBM basins, with 90% of the basin area locating outside the country. Future climate change will lead to intense, prolonged, and frequent floods in Bangladesh. An integrated flood risk assessment that transforms flood risks from transboundary river basins to the local administrative level is necessary. A 1D/2D hydrodynamic model is developed for flood vulnerable Arial Khan River feed by basin-scale hydrologic model for low (RCP2.6) and high (RCP8.5) climate scenarios. An increasing trend in flood depth, duration, and area is observed from the early (2020s) to the end (2080s) of the century for both scenarios. The difference between both RCPs is minimal from the 2020s to 2050s but becomes very pronounced in the 2080s. The depth-duration-area with equal weightage provides better hazard results for the area. Flood risk is assessed using the IPCC AR5 framework incorporating vulnerability and exposure. Some medium-hazard zones fall into high-ris...

A field study of the tidal currents, cohesive sediment dynamics and transport of organic carbon in a highly vegetated mangrove swamp was carried out at Middle Creek, Cairns, Australia. The interaction of tidal currents and the vegetation generated jets, eddies and zones of stagnant waters which were numerically modelled. A high value of the Manning friction coefficient (n=0·1) was derived by the dense vegetation. About 80% of the suspended sediment brought in from coastal waters at spring flood tide was trapped in the mangroves, corresponding to about 10–12 kg of sediment m−1creek length/spring tide, resulting in a rise of the substrate by about 0·1 cm year−1. The selective trapping of clay was caused by flocculation of the finer particles in the mangroves. There was an indication of a slight inwelling of organic carbon. Creek water was readily differentiated from mangrove water by large differences in the molecular weight distribution of the dissolved organic carbon.

Flood hazard causes great loss to lives and properties leading to disturbance in human society. Flood is the single most hydrometeorological hazard causing substantial losses. To gain better understanding of the flood phenomena especially for planning and mitiga-tion purposes, flood risk analysis is often required. For the present study, the middle part of Panchganga river of Kolhapur district, Maharashtra was selected. The main objective of the present study was to evaluate the potential flood risk areas of Panchganga river using GIS-based multicriteria decision analysis. The flood scenario across the Panchganga river was analysed using RADARSAT SAR data of 5 August 2005. To remove the speckle of SAR image, a median filtered technique was used. Thresholding technique was applied on RADARSAT SAR data to segregate flooded areas from non-flooded areas. Factors considered for evaluation of the flood risk analysis were flood layer, elevation, infrastructure and land use/ land cover analysis. The spatial multicriteria analysis with ranking, rating and analytical hierarchy process (AHP) method was used to compute the priority weights of each criterion. Accuracy assessment reveals that AHP is the most accurate technique to assess flood risk of Panchganga river.

From a human history perspective, the intrinsic characteristics of estuaries have made them preferable sites of occupation and, consequently, intense areas of development. A direct consequence of human occupation of these coastal areas is that estuaries rank among the environments most affected by human presence and activities. The fast expansion of socio-economic activities on coastal and estuarine areas over the last decades, such as tourism, nature conservation, coastal fisheries and industrial and urban development has expanded and complicated the management tasks. In recent years, there has been a growing concern to maintain a steady growth in economical activities and social development in estuarine areas, while preserving their natural features and ecological services.

Given the acceptance by governments of the goal of sustainable development, a more sustainable coastal management strategy requires a more interdisciplinary and integrated management process. There are no easy answers to the question of what is best for a particular system from a resource’s management point of view. It is the task of scientists from different disciplines to present as complete a picture as possible to those who make decisions. The ECOMANAGE (Integrated Ecological Coastal Zone Management System) project described here, funded by the European Commission’s Sixth Framework Programme (Contract nº INCO-CT-2004-003715), aims to provide coastal authorities with the knowledge and tools for such an integrated management approach. The common goal was to work towards a social and environmental sustainable estuarine system management in three distinct transitional waters systems in South America: Santos Estuary in Brazil, Bahía Blanca Estuary in Argentina and Fjord Aysén in Chile. Besides their geographical location, these coastal systems cover a wide spectrum of management challenges because they vary significantly in their ecological state and human pressures, in a gradient that goes from a more pristine state of Fjord Aysén, to the heavily occupied and degraded system in Santos Estuary.

The South American continent is endowed with a unique and valuable marine heritage, which enclose several of the world’s largest and most productive estuaries. The accelerated development in most Latin American countries is posing demanding challenges in the management of natural resources, especially in coastal areas. Integrated coastal management approaches are required, combining all aspects of the human, physical and biological aspects of the coastal zone within a single management framework. Integrated coastal management is presented here as a broad, multi-purpose endeavor aimed at improving the quality of life of communities dependent on estuarine resources and helping local decision maker attaining sustainable development of estuarine areas, from the headwaters of coastal watersheds to the outer marine areas. The work presented in this volume is a step in that direction. Hopefully, the knowledge, experience, tools and results presented here will be used in other places with similar conflicting uses of natural resources.

Interdisciplinary and integration was the major thrust of ECOMANAGE. The project was originally assembled from scientifically promising and socially relevant research fields, with physical modelling and eutrophication as the core. The social sciences, human ecology and management oriented subjects were included to provide the project with the integrative principle. The work developed during the project formed the knowledge pool for this book. The volume is a collection of writings selected on the basis of novelty, relevance in a water resource management framework, and insightfulness. Contributions have also been included in order to survey the strengths and limitations of a range of existing coastal zone management practices operating in different local environmental and socio-economic contexts. The core message that is highlighted is that the management challenges posed are complex and multifaceted, encompassing physical forcing, natural hazard and variability and vulnerability, together with socio-cultural vulnerability problems.

Being the result of a multidisciplinary scientific endeavor, the book will have an audience that range across a wide spectrum of environmental and social disciplines. The book should be of interest for anyone working in the field of ICZM (Integrated Coastal Zone Management), from scientists to decision makers. Dealing with examples from South America, the book has a strong local interest. However, the kind of approach developed in the project and portrayed in the book enables this work to be used as a benchmark for scientists working worldwide in related areas or facing the same challenges.

The book addresses costal zone management in an integrative way, with particular focus on water resources. As such, we hope it will be of interest for scientists working in fields such as aquatic ecology, ecohydrology, ground water, marine sciences in general, water quality, coastal zone management, etc. In addition, the strong component of the modelling approach will target the modelling community, from ecosystem to ground water modelers.

A strategy for adaptive control and energetic optimization of aerobic fermentors was implemented, with both air flow and agitation speed as manipulated variables. This strategy is separable in its components: control, optimization, estimation. We optimized parameter’s estimation (from the usual KLa correlation) using sinusoidal excitation of air flow and agitation speed. We have implemented parameter’s estimation trough recursive least squares algorithm with forgetting factor. We carried separate essays on control, optimization and estimation algorithms. We carried our essays using an original computational simulation environment, with noise and delay generating facilities for data sampling and filtering.

Our results show the convergence and robustness of the estimation algorithm used, improved with use of both forgetting factor and KLa dead-band facilities. Control algorithm used in our work compares favorably with PID using the integrated area criteria for deviation between oxygen molarity and critical molarity (set point). Optimization algorithm clearly reduces energetic consumption, respecting critical molarity. Integration of control, optimization and adaptive algorithms was implemented, but future work is needed for stability. Methods were defined and implemented for stability improvement. We have implemented data acquisition and computer manipulation of air flow and agitation speed for actual fermentors.

Surma is a mountainous river, originating at Manipur hills of India enters Bangladesh through Sylhet district. Due to its location near the foothills of Himalaya, this region has a large rate of precipitation. As a result, the river causes frequent flash flood during early monsoon causing a significant change in peak flow. Being sudden and violent in nature, flash flood causes massive destruction in the agricultural productions, transports, navigations and valuable properties. This concerns for a better understanding of Surma River and its flash Flood. The selected reach is almost 85km and spans from Surma Transit at u/s to Sunamganj at d/s. Different hydrodynamic characteristics such as variation in water level, velocity, discharge and flash flood analysis due to peak flow change at the Chhatak transit for the year 2000 are assessed. The result output shows, maximum water level and discharge of Surma River is obtained during the monsoon. The velocity is also high during this period. During the winter, discharge and velocity are almost zero. Flash Flood analysis of Surma River shows rapid change in water level and flow during the month of April, 2000 with respect to flood level. Due to its development on a short time, the changes in water level and discharge will show its devastating impact. Overall, Hydrodynamic analysis will help to understand the characteristics and features of Surma River and Flash Flood analysis will shows its development and occurrence period in Surma River along with impacts.

En el presente trabajo presentamos un modelo hidrodinámico 3D del Humedal del Rio Cruces en la Región de Los Ríos, Chile. Este humedal es uno de los mas grandes de Chile, está protegido por la convención RAMSAR y soporta una diversidad biológica de importancia continental, sobretodo como sitio de nidificación del Cisne de Cuello Negro (Cygnus melancoryphus). El modelo incluye 3 niveles de modelación anidada, con diferentes escalas geográficas y de definición de su grilla, logrando definiciones de la grilla de menos de 100 m. en su nivel mas anidado. Sobre este sistema de modelos hidrodinámicos se implementó un módulo lagrangiano para calcular el tiempo de residencia del Humedal. Nuestros resultados muestran tiempo de residencia de 3 dias para la zona baja del humedal y de 53 días para la zona alta. Nuestro trabajo muestra la utilidad de este tipo de modelos para conocer la dinámica de los componentes abióticos de este tipo de ecosistemas, la estructura de sus corrientes y la hidrodinámica en general de un sistema. El objetivo de presentar nuestro trabajo es incentivar el uso de este tipo de herramientas informáticas en la toma de decisiones de gestión ambiental de sistemas acuáticos, tanto en el ámbito público como privado, aportando a una visión integrada de este tipo ecosistemas.

A three-dimensional model has been modified to describe the complex interactions between hydrodynamics, sediment dynamics and biological parameters in the presence of Zostera noltei. The model treats seagrass leafs as flexible blades that bend under hydrodynamic forcing and alter the local momentum and turbulence fluxes and, therefore, the benthic shear conditions; these changes cause related changes to the mass balance at the boundary of the bed, in turn affecting the suspended matter in the column and ultimately primary productivity and the growth of the dwarf-grass. Modelling parameters related to the impact of Z. noltei to the local flow and to erosion and deposition rates were calibrated using flume experimental measurements; results from the calibration of the model are presented and discussed. The coupled model is applied in the Arcachon Bay, an area with high environmental significance and large abundance of dwarf-grass meadows. In the present paper, results from preliminary applications of the model are presented and discussed; the effectiveness of the coupled model is assessed comparing modelling results with available field measurements of suspended sediment concentrations and seagrass growth parameters. The model generally reproduces sediment dynamics and dwarf-grass seasonal growth in the domain efficiently. Investigations regarding the effects of the vegetation to the near-bed hydrodynamics and to the sediment suspension in the domain show that dwarf-grass meadows play an important part to velocity attenuation and to sediment stabilisation, with flow and suspended sediment concentrations damping, compared to an unvegetated state, to reach 35–50 and 65 %, respectively, at peak seagrass growth.

In this paper we present the setup, calibration, and validation of an advanced 3-D ocean circulation model to further seek the potential for operational forecasting applications and investigate the coastal hydrodynamic processes in selected areas of the Black Sea. The extents of the studied areas refer to typical mid-range depths in a microtidal open coast environment up to the shelf-break. The effects of short-term changes in meteorological conditions on the coastal eddies' anticyclonic dynamics are explored in conjunction with the effects of the eastern and western cyclonic gyres of the Rim Current in the Black Sea basin. Newly produced field datasets of in situ oceanographic observations in coastal waters are employed for the validation of highresolution hydrodynamic simulations in operational forecast mode to detect the sub-mesoscale effects of prevailing coastal circulation patterns.

Hydro-geology (hydro- meaning water, and -geology meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquifers). The term hydrology is often used interchangeably. Some make the minor distinction between a hydrologist or engineer applying themselves to geology (hydrology), and a geologist applying themselves to hydrology (hydro geology).Hydrogeology is an interdisciplinary subject; it can be difficult to account fully for the chemical, physical, biological and even legal interactions between soil, water, nature and society. The study of the interaction between groundwater movement and geology can be quite complex. Groundwater does not always flow in the subsurface down-hill following the surface topography; groundwater follows pressure gradients (flow from high pressure to low) often following fractures and conduits in circuitous paths. Taking into account the interplay of the different facets of a multi-component system often requires knowledge in several diverse fields at both the experimental and theoretical levels. The following is a more traditional introduction to the methods and nomenclature of saturated subsurface hydrology, or simply the study of ground water content.Hydrogeology, as stated above, is a branch of the earth sciences dealing with the flow of water through aquifers and other shallow porous media (typically less than 450 m or 1,500 ft below the land surface.) The very shallow flow of water in the subsurface (the upper 3 m or 10 ft) is pertinent to the fields of soil science, agriculture and civil engineering, as well as to hydrogeology. The general flow of fluids (water, hydrocarbons, geothermal fluids, etc.) in deeper formations is also a concern of geologists, geophysicists and petroleum geologists. Groundwater is a slow-moving, viscous fluid (with a Reynolds number less than unity); many of the empirically derived laws of groundwater flow can be alternately derived in fluid mechanics from the special case of Stokes flow (viscosity and pressure terms, but no inertial term). The mathematical relationships used to describe the flow of water through porous media are the diffusion and Laplace equations, which have applications in many diverse fields. Steady groundwater flow (Laplace equation) has been simulated using electrical, elastic and heat conduction analogies. Transient groundwater flow is analogous to the diffusion of heat in a solid, therefore some solutions to hydrological problems have been adapted from heat transfer literature.Traditionally, the movement of groundwater has been studied separately from surface water, climatology, and even the chemical and microbiological aspects of hydrogeology (the processes are uncoupled). As the field of hydrogeology matures, the strong interactions between groundwater, surface water, water chemistry, soil moisture and even climate are becoming more clear.For example: Aquifer drawdown or overdrafting and the pumping of fossil water may be a contributing factor to sea-level rise

The paper presents the structure and application of a regional scale operational modelling tool for the West Iberian coast. The forecasting suite includes nested hydrodynamic models forced with up-to-date meteorological forecast data and large scale model results as lateral boundary conditions. The present status of the system and its recent upgrades are reviewed, offering a general description of the main components of the system: circulation model, qualitative and quantitative validation methodology and type of results. Seasonal differences in temperature, salinity and current velocity fields are illustrated with model results, and the validation shows a satisfactory reproduction of the top and deep layers thermodynamics. The system provides boundary forcing for a number of local scale model applications via downscaling of the solution, and its potential for products and services for both scientific and coastal management activities is discussed here.

A hydrodynamic model for Khor Al-Zubair and Shatt Al-Basrah canal was introduced by using the Mike11 routine. The model was run for two months, March and April of 2018 with Δt=40 sec and Δx=300 m. Model calibration and validation were done through a comparison of measurements

The knowledge of the influence of the hydrological regime of river basins on submarine sedimentary processes in deltaic systems may have wider implications from the point of view of global climate change. Under this consideration, the present study aims to analyze morphometric parameters extracted from model simulations of pro-deltaic undulations found off Adra River (Almería, Spain), in the continental shelf of the northern margin of the Alboran Sea.

The main objectives of this work are the presentation of a hydro-biogeochemical model for the Tagus estuary and the study of the interaction between tides and river discharge. Special emphasis will be given to hydrographic, fine sediment dynamics and biogeochemical variations at two different time scales: the tidal cycle and the fortnight cycle. The numerical model validation was performed comparing harmonic analysis results ofmeasured and model predicted sea surface height for 12 stations covering the whole estuary. For the M2 constituent the difference is less than 5% of the local amplitude for almost all the stations. Differences in phase are small, with an average value of 5º. The results show strong salinity and suspended sediments gradients which are advected up and downstream according to the tidal cycle. Moreover, the estuary is divided in three main regions: a marine, a mixing and a freshwater influence area. The suspended sediments and chlorophyll concentrations reveal strong fortnight time dependence near the estuary mouth. Higher concentrations of fine sediments are found during spring tides that on neaps, which induces a decrease (increase) in the chlorophyll concentration during spring (neap) tides. This study presents the first results of the Tagus estuary predictive model, which are consistent with observations and with previously knowledge about the estuary. Preliminary outcomes obtained with this high resolution numerical modeling system are very encouraging to pursuit the development of a numerical tool suitable to deliver products that can be used both in scientific endeavors and in estuarine management, in order to assess the ecological estuarine quality.

The cut-cell finite volume method in hydrodynamic models have become more popular in computational fluid dynamics (CFD). By representing the model boundary as a polygon cutting through grid cells, we expect a better representation of flow field near the boundary, provided that proper treatments are made for distorted cells. This method is implemented in a 2-D explicit-scheme model named XBeach. Despite a more realistic computed flow field, the stability of XBeach as an explicit model has to be considered. Normally when a strict CFL criterion is applied, the presence of very small cells yields prohibitively small time step. But it is also dubious whether the numerical oscillations in small cells could affect the flow pattern in general. A test in ∆t selection with influence on velocity is presented. Result shows that by choosing the time step considering an average small cell instead of the smallest one, we can extend the time step up to the order of 200 times thus increase the efficiency of computation.

Bangladesh is situated at the confluence of GBM basins, with 90% of the basin area locating outside the country. Future climate change will lead to intense, prolonged, and frequent floods in Bangladesh. An integrated flood risk assessment that transforms flood risks from transboundary river basins to the local administrative level is necessary. A 1D/2D hydrodynamic model is developed for flood vulnerable Arial Khan River feed by basin-scale hydrologic model for low (RCP2.6) and high (RCP8.5) climate scenarios. An increasing trend in flood depth, duration, and area is observed from the early (2020s) to the end (2080s) of the century for both scenarios. The difference between both RCPs is minimal from the 2020s to 2050s but becomes very pronounced in the 2080s. The depth-duration-area with equal weightage provides better hazard results for the area. Flood risk is assessed using the IPCC AR5 framework incorporating vulnerability and exposure. Some medium-hazard zones fall into high-ris...

The currently prevalent practice in hydrodynamic research is to assess radial wells by constructing a
hydrodynamic model. Numerical modeling codes tended to limit the possibility of realistically representing
the structural characteristics of a radial well (shaft and laterals), along with the groundwater
abstraction mechanism via the known groundwater level within the laterals and the calibrated coefficient
of their conductivity. Such limitations were offset by various boundary condition modeling techniques in
order to produce a so-called “representative” depiction of the radial well, which did not fail to affect
the results. The objective of the present research is to assess the simulation of radial wells in MODFLOW-
USG code, based on a numerical method of finite volumes. One of the radial wells at Belgrade’s
water supply source was selected for the case study, given that a complex groundwater regime change
had been registered within its zone of influence. The results indicate that the method can be applied to
simulate virtually all aspects and operational conditions of this type of well, with the highest level of
representativeness.

The impoundment of rivers by large dams is the biggest direct anthropogenic impact on the hydrological cycle. However, dams can help solving eutrophication in estuaries by controlling flow pulses, which in turn might enhance the advection of fish larval stages from their spawning and nursery areas. Thus, this work aimed to merge data on the abundance of anchovy eggs with MOHID hydrodynamic model for the Guadiana estuary, allowing dam/basin managers to set river discharge scenarios that might mitigate/prevent eutrophication, without compromising the presence of fish larval stages inside the estuary. Data on anchovy larval stages were assessed in the Guadiana estuary and adjacent coast and three simulation setups were developed. In Simulation A, anchovy eggs abundance was merged in the hydrodynamic model to compare the outputs with data on the abundance, distribution and development stage of anchovy eggs and larvae. In Simulation B, lagrangian particles were incorporated in the model to determine the percentage of particles released from the upper, middle and lower estuary that remain in the estuary along 10 days, in two tidal situations and in seven river discharge scenarios. In Simulation C, the abundance of anchovy eggs was merged in the model to select the discharge scenario(s) that do not compromise the presence of anchovy larval stages in the estuary. Results confirmed the spawning and nursery areas of anchovy and showed that scenarios B (Q max ¼ 20 m 3 s À1 ) and C (Q max ¼ 50 m 3 s À1 ) should be applied during neap tides. The choice between scenarios depends on the degree of eutrophication, the effectiveness of an inexistent monitoring program and on plankton response experiments to flushing and increased nutrient loading. This work produced an easy-to-use management tool for Guadiana managers, serving as an example to other estuarine sites around the world. Ultimately, this work suggests that river flow management must be guided by robust ecological studies, under an adequate sociological framework and adopting sustainable economic principles to maintain and improve the ecosystem services.

We used two-dimensional hydrodynamic models for the assessment of water diversion effects on benthic macroinvertebrates and associated habitat in a montane stream in Yosemite National Park, Sierra Nevada Mountains, CA, USA. We sampled the macroinvertebrate assemblage via Surber sampling, recorded detailed measurements of bed topography and flow, and coupled a twodimensional hydrodynamic model with macroinvertebrate indicators to assess habitat across a range of low flows in 2010 and representative past years. We also made zero flow approximations to assess response of fauna to extreme conditions. The fauna of this montane reach had a higher percentage of Ephemeroptera, Plecoptera, and Trichoptera (%EPT) than might be expected given eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. the relatively low faunal diversity of the study reach. The modeled responses of wetted area and area-weighted macroinvertebrate metrics to decreasing discharge indicated precipitous declines in metrics as flows approached zero. Changes in area-weighted metrics closely approximated patterns observed for wetted area, i.e., area-weighted invertebrate metrics contributed relatively little additional information above that yielded by wetted area alone. Loss of habitat area in this montane stream appears to be a greater threat than reductions in velocity and depth or changes in substrate, and the modeled patterns observed across years support this conclusion. Our models suggest that step function losses of wetted area may begin when discharge in the Merced falls to 0.02 m3/s; proportionally reducing diversions when this threshold is reached will likely reduce impacts in low flow years.

We study the influence of cold fronts on the heat fluxes and thermal structure of a tropical reservoir located in Brazil. The period chosen for this study consisted of 49 days between 28 April 2010 and 15 July 2010 and was defined based on information from the Brazilian Centre for Weather Forecasting and Climate Studies (CPTEC), data collected in situ and the interpretation of remotely sensed images. During the selected time period, five cold front passages were identified, allowing us to analyze the cumulative effect of cold fronts and the reservoir's resilience on the days that elapsed between the passages. To better understand the physical processes that drive changes in heat fluxes and thermal structure, a simulation was performed that utilized a threedimensional hydrodynamic model. The results showed that during the cold front days, the sensible and latent heat fluxes were enhanced by approximately 24 % and 19 %, respectively. The daily average heat loss was up to 167 % higher on the cold front days than on the non-cold front days. The high heat loss and the increased wind intensity that occurred during the cold front passages destabilized the water column and provided partial or complete mixing. The colder waters of the Paranaíba River contributed to reestablish the thermal stratification following the passages of the cold fronts. These results suggest that cold front passages play an important role in the stratification and mixing regimes of Brazilian reservoirs located in southern and southeastern regions.

Flood hazard causes great loss to lives and properties leading to disturbance in human society. Flood is the single most hydrometeorological hazard causing substantial losses. To gain better understanding of the flood phenomena especially for planning and mitigation purposes, flood risk analysis is often required. For the present study, the middle part of Panchganga river of Kolhapur district, Maharashtra was selected. The main objective of the present study was to evaluate the potential flood risk areas of Panchganga river using GIS-based multicriteria decision analysis. The flood scenario across the Panchganga river was analysed using RADARSAT SAR data of 5 August 2005. To remove the speckle of SAR image, a median filtered technique was used. Thresholding technique was applied on RADARSAT SAR data to segregate flooded areas from non-flooded areas. Factors considered for evaluation of the flood risk analysis were flood layer, elevation, infrastructure and land use/ land cover analysis. The spatial multicriteria analysis with ranking, rating and analytical hierarchy process (AHP) method was used to compute the priority weights of each criterion. Accuracy assessment reveals that AHP is the most accurate technique to assess flood risk of Panchganga river.

Building a numerical model in not an easy task. In addition to its need for verification, it requires special skills and experiences in mathematics, computer programming and may take long period to be ready for operation and prediction. On the other hand, artificial neural network ANN) prediction models are more efficient in predictions once they are trained from examples or patterns. These types of ANN models need large amount of data which should be at hand before thinking to develop such models. In this paper, the capability of ANN model to predict suspended sediment in 2-D flow field is investigated. The data used for training the network are generated from a pre-verified 2-D hydrodynamic and a 2-D suspended sediment models which were recently developed by the authors. About two-thirds of the data are used for training the network while the rest of the data are used for validating and testing the developed ANN model. Field data measured by hydraulic research Institute are used to compare the results of the ANN model. A tansh activation function is used at the hidden layer which consisted of 5-10-1. The conjugate gradient learning algorithm is adopted. The results of the developed ANN model proved that the technique is reliable in such field compared to both the results of the previously developed models and the field data provided that the trained network is used to generate prediction within the range of training data.

Building a numerical model in not an easy task. In addition to its need for verification, it requires special skills and experiences in mathematics, computer programming and may take long period to be ready for operation and prediction. On the other hand, artificial neural network ANN) prediction models are more efficient in predictions once they are trained from examples or patterns. These types of ANN models need large amount of data which should be at hand before thinking to develop such models. In this paper, the capability of ANN model to predict suspended sediment in 2-D flow field is investigated. The data used for training the network are generated from a pre-verified 2-D hydrodynamic and a 2-D suspended sediment models which were recently developed by the authors. About two-thirds of the data are used for training the network while the rest of the data are used for validating and testing the developed ANN model. Field data measured by hydraulic research Institute are used to compare the results of the ANN model. A tansh activation function is used at the hidden layer which consisted of 5-10-1. The conjugate gradient learning algorithm is adopted. The results of the developed ANN model proved that the technique is reliable in such field compared to both the results of the previously developed models and the field data provided that the trained network is used to generate prediction within the range of training data.

This study investigates use of water quality (WQ) variables, namely total chromium concentration, total iron concentration, and turbidity for predicting suspended sediment concentration (SSC). For this purpose, the artificial neural networks (ANNs) and regression analysis (RA) models are employed. Seven different RA models are constructed, considering the functional relation between measured WQ variables and SSC. The WQ and SSC data are fortnightly obtained from six monitoring stations, located on the stream Harsit, Eastern Black Sea Basin, Turkey. A total of 132 water samples are collected from April 2009 to February 2010. Model prediction results reveal that ANN is able to predict SSC from WQ data, with mean absolute error (MAE) of 10.30 mg/L and root mean square error (RMSE) of 13.06 mg/L. Among seven RA models, the best one, which has the form including all independent parameters, produces results comparable to those of ANN, with MAE = 14.28 mg/L and RMSE = 15.35 mg/L. The sensitivity analysis results reveal that the most effective parameter on the SSC is total chromium concentration. These results have time-and cost-saving implications.

We critically analyzed a set of ecological models that are used to assess the impact of hydropower dams on water quality and habitat suitability for biological communities. After a literature search, we developed an integrated conceptual model that illustrates the linkages between the main input variables, model approaches, the output variables and biotic-abiotic interactions in the ecosystems related to hydropower dams. We found that variations in water flow and water depth coupled with increased nutrient availability are major variables that contribute to structural and functional ecosystem changes. We also found that ecological models are an important tool to assess the impact of hydropower dams. For instance, model simulation of different scenarios (e.g., with and without the dam, different operation methods) can analyze and predict the related ecosystem shifts. However, one of the remaining shortcomings of these models is the limited capacity to separate dam-related impacts from other anthropogenic influences (e.g., agriculture, urbanization). Moreover, collecting sufficient high-quality data to increase the statistical power remains a challenge. The severely altered conditions (e.g., generation of very deep lakes) also lead to difficulties for standardized data collection. We see future opportunities in the integration of models to improve the understanding of the different processes affected by hydropower dam development and operation, as well as the use of remote sensing methods for data collection.

The Ganges-Brahmaputra-Meghna (GBM) delta is one of the most dynamic tide dominated delta in the world. The flow generated in the upper catchment of the GBM basins is passing through the estuarine systems of the GBM delta. The particular feature of these estuarine systems is characterized by extreme flow concentration in one single estuary, the Lower Meghna Estuary. Due to highly dynamic nature and a huge flow volume, it is difficult to measure the discharge in the Lower Meghna estuary. Till now, there is no measuring station and no reliable estimate of total flow volume which is passing through the Lower Meghna estuary. In this study, a 1D dynamic model (HEC RAS unsteady) is applied to compute the discharge in the Lower Meghna estuary. In the schematized model network, all the major rivers of the delta are included that contribute flow to the Lower Meghna estuary. The model is validated using measured water level available at the Lower Meghna estuary. The validated model is used to generate the temporal variation of discharge and the flow volume passing through the Lower Meghna estuary for different flooding scenario.

In this study, we coupled a three-dimensional hydrodynamic model with an ecosystem model and applied it to the shallow complex floodplain wetland of Chini Lake in Malaysia. Our objective was to provide a better understanding of the lake’s ecosystem dynamics under different forcing mechanisms. Simulations and validation were performed over a dry month period. Wind speed ranged between 0 and 7.7 m s−1, whilst air temperature ranged between 22.0 and 35.6 °C. Advective transport driven by wind stress was the dominant physical force that shaped the water quality variations during the dry season. Convective circulation intermittently influenced the circulation during calm conditions. Nutrient concentration and stratification of dissolved oxygen (DO) varied between the lakes. Wind events saw patterns of the surface DO concentrations move spatially in the direction of the wind. The ecosystem model simulation suggested that the water quality in Chini Lake was influenced by macrophyte production, although the dissolved and particulate organic carbon accounted for the major fraction of organic matter content in the lake.

"The eutrophication phenomenon often leads to undesirable water quality. This paper delineates an unsteady three-dimensional finite difference numerical model for eutrophication dynamics in the coastal waters of Tolo harbour, Hong Kong, employing the numerically generated, boundary-fitted, orthogonal curvilinear grid system as well as a grid "block" technique. It models the transport and interaction of nine water quality constituents. Adjustments of values of some kinetic coefficients in the model are effected through calibration with field data. It is demonstrated that the model can reasonably reproduce the interactions amongst all the water quality constituents, the eutrophication processes and, in particular, the featured bottom water anoxic condition during the summer in Tolo harbour.

Keywords: eutrophication; hydrodynamic modeling; unsteady modeling; Tolo harbour; water quality modeling"

We quantify the role of zooplankton in nutrient cycles in Lake Kinneret, Israel, using field data and a numerical model. A coupled ecological and hydrodynamic model (Dynamic Reservoir Model (DYRESM)-Computational Aquatic Ecosystem Dynamics Model (CAEDYM)) was validated with an extensive field data set to simulate the seasonal dynamics of nutrients, three phytoplankton groups and three zooplankton groups. Parameterization of the model was conducted using field, experimental and literature studies. Sensitivity of simulated output was tested over the full parameter space and established that the most sensitive parameters were related to zooplankton grazing rates, temperature responses and food limitation. The simulated results predict that, on average, 51% of the carbon from phytoplankton photosynthesis is consumed by zooplankton. Excretion of dissolved nutrients by zooplankton accounts for 3-46 and 5-58% of phytoplankton uptake of phosphorus and nitrogen, respectively. Comparison of nutrient fluxes attributable to zooplankton with nutrient loads from inflows and release from bottom sediments shows that the relative contribution by zooplankton to inorganic nutrients in the photic zone varies seasonally in response to the annual hydrodynamic cycle of stratification and mixing. As a percent of total dissolved organic sources relative contributions by zooplankton excretion are highest (62%) during periods of stratification and when inflow nutrient loads are low, and lowest (2%) during the breakdown of stratification and when inflow loads are high. The results illustrate the potential of a lake ecosystem model to extract useful process information to complement field data collection and address questions related to the role of zooplankton in nutrient cycles.

Water renewal in semi-enclosed coastal areas is crucial for the supply of oxygen and seston and for the removal of organic loadings from finfish or shellfish aquaculture sites. Water renewal depends on hydrodynamic processes and can have a complex spatial distribution due to irregular topographic features. This study describes some physical oceanography observations gathered in the Richibucto estuary, New Brunswick, Canada, and provides an estimate of the spatial distribution of water renewal in the North Arm, a location in the estuary where the largest American oyster (Crassostrea virginica) aquaculture operation in eastern Canada is located. The estuary changes from a well mixed estuary to a partially stratified estuary depending on runoff conditions. Tides are mixed but mainly diurnal due to the nearby presence of the second M 2 amphidromic point in the Gulf of St. Lawrence. Tidal amplitudes vary from 0.3 to 0.6 m and show a slight increase some 35 km upstream. Currents in the main channel can reach over 0.60 m s Ϫ1 during ebb and 0.3 m s Ϫ1 during flood, with a slack water period of approximately 8 h. Low frequency sea level fluctuations have a range of 0.5 m at the mouth and are coherent within the estuary. Hydrodynamic and advection-dispersion models are used to calculate the spatial distribution of the local renewal time (LRT) in the North Arm for high and low freshwater discharge conditions, using the dissolved tracer method. Results show that the LRT varies from less than 5 d at the downstream end of the North Arm to over 100 d further upstream. When averaged over the entire North Arm, the integral renewal time (IRT) is estimated to vary only from 8 to 21 d depending on the season. The LRT and IRT estimates are major improvements over conventional renewal estimates using tidal prism methods.

Abstract
Large-scale prototype experiments of regulating flow and sediment have been conducted annually in the Yellow River, China since 2002, with large amounts of observed hydrological data being collected during the experiments. In the present study, a two-dimensional hydrodynamic model based on the finite-volume method has been refined, with an improvement being made in the spatial reconstruction method of the state variables. The enhanced spatial reconstruction method can account for the effect of a wet or dry interface on the calculation of numerical fluxes, especially for low discharges, which can avoid the occurrence of unreal flow fluxes. The refined model was applied to simulate flood routing in the 2004 and 2006 experiments in the lower Yellow River and relatively close agreement between the model predictions and observed data was obtained. The effect of different bed roughness values on the predicted results was investigated using a sensitivity test, and various factors influencing the accuracy of the predicted discharges are presented. The simulated results also show that the refined spatial reconstruction method results in higher predictive accuracy for low discharges, different bed roughness coefficients have only a slight effect on the predicted discharges and the predictive accuracy of the model is also influenced by the resolution of bed topography and the way in which the open boundary conditions are specified.