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The Mandovi and Zuari are two tropical estuaries along the west coast of India, characterized by mixed tides with semidiurnal dominance and heavy fresh water influx during the southwest monsoon (June to September). Previous observations of tides in these estuaries show that the tidal effects in the upstream regions are subject to decay due to freshwater influx during the southwest monsoon. The longitudinal distribution of salinity in these estuaries undergoes large variations between the southwest monsoon and the dry season (February to May). The main objectives of the present study were to simulate the tidal circulation, the longitudinal distribution of salinity, and the freshwater influence on tides and the salinity distribution. Another objective was to study the intraseasonal variations of salinity during the breaks in the southwest monsoon. A hybrid network numerical model was used for the present study to simulate the tidal circulation and the salinity distribution in these estuaries. The model reproduced observed tides accurately during the dry and wet seasons. The model could reproduce the longitudinal distribution of salinity well during the dry season and the simulation of salinity distribution was reasonably well during the wet season. The simulated tidally averaged salinities over the [M.sub.2] tidal period for varying fiver discharges show that even a small freshwater influx can affect the longitudinal distribution of salinity to a great extent in this type of estuaries. DOI: 10.1061/(ASCE)0733-950X(2009)135:6(278) CE Database subject headings: Tidal currents; Salinity; Fresh water; Coastal environment; India; Monsoon.

This research investigated the sorption and transport of MS-2 in saturated sand under a wide range of salinities using one-dimensional column experiments. The salinity varied from 0 ppt (fresh water) to 30 ppt. The MS-2 in the fresh water showed very weak adsorption due to having the same negative charge as the sand. Increasing the salinity concentrations dramatically enhanced MS-2 adsorption. The MS-2 breakthrough revealed the existence of reversible and irreversible sorption sites in the sand. Salinity increased MS-2 attachment by compressing the double layers of MS-2 and reversible sorption sites. The salinity also changed some reversible sorption sites into irreversible sorption sites by reversing to positive surface charges of silica powder. An advection-dispersion-sorption model with a two-site reversible-irreversible kinetic sorption was developed to describe MS-2 breakthrough under different salinity conditions. The sorption parameters were estimated and their independence was evaluated by minimizing the total squared error of the MS-2 data. The proposed model showed good agreement with the experimental data for a wide range of salinity levels from fresh water to near seawater. The strong sorption shown in the MS-2 breakthrough at high salinity levels above 8 ppt was able to distinguish the proposed model from other sorption models. This study promotes the understanding of the viral sorption with salinity and provides a useful model for coastal management of viral migration in saline coastal groundwater. DOI: 10.1061/(ASCE)0733-9372(2009)135:10(1041) CE Database subject headings: Salinity; Sorption; Saturated soils; Sand; Models.

The essence of three case studies in relation to the global problem of surface and groundwater contamination by inorganic salts and biodegradation-resistant ('hard') nonionic surfactants (APEOs) is presented and the results analyzed as far as the long-term consequent water salt and APEO profiles are concerned. The main conclusion derived is that sustainable large-scale reuse/recycling and reclamation in semiarid zones requires a combined desalination-biological treatment of APEO-free sewage/wastewaters before their reuse. This should be done without delay in order to ensure the quality of the supplied water from the scarce resources and to avoid, most probably, an irreversible process of aquifer contamination in these zones. DOI: 10.1061/(ASCE)0733-9372(2006)132:6(683) CE Database subject headings: Water reuse; Recycling; Reclamation; Salinity; Ground-water pollution; Aquifers; Israel; Arid lands.

This paper presents a model to estimate the soil salinity for different on-farm management strategies under irrigated conditions. It is based on research in the Manitoba irrigation scheme in northeast Brazil, where upward flow from the shallow water table is the main cause of soil salinization. The model calculates soil water and salt balances for the topsoil. It is calibrated for the topsoil of abandoned plots and for the root zone (0.9 m) of mango trees. Simulating the effect of different management scenarios on soil salinity may help to organize the switch from intensive surface irrigation to more efficient irrigation practices. DOI: 10.1061/(ASCE)0733-9437(2005)131:4(351) CE Database subject headings: Irrigation systems; Irrigation efficiency; Saline ground water; Salinity; Simulation models; Water balance; Brazil.

The performance of the Chesapeake Bay Environmental Model Package is examined in four steps of model development. The steps include initial application, grid refinements, addition of living resources, and grid refinements with recalibration. Performance statistics are presented for the mainstem bay and for the James River, a major tributary. Computed salinity has the lowest relative error. Computed total phosphorus and surface chlorophyll have the greatest relative error. Errors in the bay are lower than in the James River. The capacity of the model has increased substantially over more than a decade but quantitative performance, measured by the summary statistics, has reached a plateau. Limited spatial sampling, uncertainty in loading, and difficulty in assigning boundary conditions are among the factors that limit the accuracy that can be attained with the model. CE Database subject headings: Model accuracy; Chesapeake Bay; Eutrophication; Nutrients; Salinity; Chlorophyll; Dissolved oxygen.

Devils Lake, a terminal, saline lake, of glacial origin, in North Dakota has experienced a 7.5 m rise in lake elevation resulting in the flooding of over 243 [km.sup.2] from 1992 to 2002. At lower water surface elevations, Devils Lake functions as a series of connected basins with salinity increasing in an eastward direction due to evaporation. The recent increase in water depth provides an opportunity for increased dispersive exchange flows and mixing between the lake's basins due to wind and buoyancy forces. This increased mixing will change the future water quality distribution in Devils Lake, and may therefore have an impact on plans for lake level stabilization. In this paper, a model based on energy and conservation of mass principles is applied to estimate the potential redistribution of sulfate within Devils Lake. The rate of redistribution may affect the lake's ecosystem and the design of a possible water diversion to the Red River of the North for the purpose of stabilizing the water surface elevation. Included in the paper is the selection of model input parameters, model calibration with field measurements, and application of the model to five future scenarios. DOI: 10.1061/(ASCE)0733-9496(2003)129:5(399) CE Database subject headings: Dispersion; Floods; Lakes; North Dakota; Salinity; Water quality.

This paper presents the results from a detailed field experiment of water movement on a border-irrigated bay in northern Victoria, Australia, an area characterized by shallow ground-water tables and salinization problems. The objective of the study was to quantify the impact of changes in irrigation management on salt and water movement within and from the bay and on recharge to the region's shallow ground-water table. Results showed that the evapotranspiration volume almost wholly explained the soil moisture changes between irrigation events and that deep drainage was negligible. Infiltration was mainly confined to the advanced stages of irrigation, with the soil rapidly becoming saturated across the bay, due to the presence of soil cracks. Such findings suggest that more efficient management of border irrigation supply to the bay will not lead to the lowering of the shallow ground-water table--conclusions that have important implications for irrigation management.

Subsurface flow and salinity patterns in a tidal marsh plain determine the character and health of the wetland ecosystem. The presence of a flow field with both saturated and unsaturated regions requires that the governing equations and the associated equations of state transition smoothly between the two regions. The fluid density in the marsh plain is not constant; it responds to changes in both pressure head and salinity. These considerations lead to the development of the marsh plain equations, the coupled field equations for subsurface flow and salinity transport in the continuous saturated/unsaturated flow domain of a tidal wetland.

Record low flow on the Mississippi River in 1988 created a potential for record prior movement of the saltwater wedge from the Gulf of Mexico, threatening water supply for the city of New Orleans and nearby communities. The U.S. Army Corps of Engineers employed one-dimensional and two-dimensional numerical models to design temporary underwater sill that would limit upstream salinity intrusion. The sill was constructed and successfully protected the freshwater supplies of the New Orleans area with cost savings of over $50,000,000. Postdrought analysis showed that the models accurately predicted behavior of the salt wedge and the sill.

Circulatory change and alteration of salinity in Galveston Bay is investigated numerically by using a three-dimensional hydrodynamic and transport model. Galveston Bay is an extremely complex and dynamic estuarine system. Tides, freshwater inflows, wind, and bathymetry all affect the circulation patterns and salinity distribution. A thorough understanding of the physical hydrodynamic and environmental impact on the estuary, due to the influences of stream inflows, wind, tides, bathymetry, and pollutant transport, is essential to develop a rich and healthy estuarine ecosystem. A three-dimensional hydrodynamic and salinity transport model is applied to simulate the whole Galveston Bay. This model solves coupled full Navier-Stokes equations and salinity transport equations in a curvilinear coordinate system. By inputting freshwater inflows, tide, and wind data into the model, the time variation of the three-dimensional circulation patterns, free-surface elevations and salinity profiles are obtained to describe this dynamic system. A curvilinear grid of the Galveston Bay is generated for computation. A monthly simulation has been conducted to study the tide and freshwater induced circulation. The free-surface elevations and salinity distribution are also presented. The predicted free-surface elevations in the bay are in good agreement with the field measurements. The results also indicate that the bottom salinity in the bay increases during a monthly tidal-forcing. The impact of velocity and the salinity field caused by the freshwater inflows are discussed.

The companion paper by the writers developed a model for the determination of optimal freshwater inflows into bays and estuaries for the purpose of balancing freshwater demands with the various types of fish harvests. This model has been applied to determine the freshwater inflow needs into the Lavaca-Tres Palacios Estuary in Texas for various scenarios. The results of the model application are analyzed for various management alternatives, treatment of salinity constraints, and the desired levels of certainty for harvest regression equations. The comparison of the application results with previous models further illustrates the advancement of this new model. The new methodology can provide a powerful tool for analysis of 'what if' type scenarios for decision makers to quantitatively analyze various water resources management strategies.

A study to determine the salinity and monthly streamflow of water in four stations along the Ebro River, Spain, was conducted using transfer function-noise models. Results indicate that the residual variance of the models are of the same magnitude in all stations. The models explain the 80% variance in salinity for two stations and 60% variance in the other two probably caused by resevoir effects.

Several advective transport schemes are considered in the context of two-dimensional scalar transport. To review the properties of these transport schemes, results are presented for simple advective test cases. Wide variation in accuracy and computational cost is found. The schemes are then applied to simulate salinity fields in South San Francisco Bay using a depth-averaged approach. Our evaluation of the schemes in the salinity simulation leads to some different conclusions than those for the simple test cases. First, testing of a stable, but nonconservative Eulerian-Lagrangian scheme does not produce accurate results, showing the importance of mass conservation. Second, the conservative schemes that are stable in the simulation reproduce salinity data accurately independent of the order of accuracy of each scheme. Third, the leapfrog-central scheme was stable for the model problems but not stable in the unsteady, free surface computations. Thus, for the simulation of salinity in a strongly dispersive setting, the most important properties of a scalar advection scheme are stability and mass conservation.

Several advective transport schemes are considered in the context of two-dimensional scalar transport. To review the properties of these transport schemes, results are presented for simple advective test cases. Wide variation in accuracy and computational cost is found. The schemes are then applied to simulate salinity fields in South San Francisco Bay using a depth-averaged approach. Our evaluation of the schemes in the salinity simulation leads to some different conclusions than those for the simple test cases. First, testing of a stable, but nonconservative Eulerian-Lagrangian scheme does not produce accurate results, showing the importance of mass conservation. Second, the conservative schemes that are stable in the simulation reproduce salinity data accurately independent of the order of accuracy of each scheme. Third, the leapfrog-central scheme was stable for the model problems but not stable in the unsteady, free surface computations. Thus, for the simulation of salinity in a strongly dispersive setting, the most important properties of a scalar advection scheme are stability and mass conservation.