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ABSTRACT The eastern boundary region off Angola encompasses a highly productive ecosystem important for the food security of the coastal population. The fish-stock distribution, however, undergoes large variability on intraseasonal, [...]

There is a direct connection between the breach developed within a dam subjected to an overflow and the resulting flood. A normative model based on statistical studies has been developed in the province of Quebec to initialize the process of the flood: it predicts a breach width four times as long as the breach height and a maximal breach discharge that occurs in 30 min. This norm is applied for all the earth and rockfill dams without any consideration of their own particular characteristics. However, the prediction of the breach's characteristics is still uncertain, which explains that this norm is not over yet and is still the most reliable and secure process to use. A theoretical model is presented in this dissertation predicting the dam failure of the first earth and rockfill dam in Quebec using a bituminous core: Nemiscau-1 dam. Three potential damages have been analysed: potential planes of failure; fracturing of the bituminous core; surface erosion. The results are encouraging: the resulting hydrograph seems to predict the degradation of the dam more precisely and more faithfully than the normative model. The proposed model is more suited for hybrid dams than the safety standards of Hydro-Quebec. Key words: dam failure, overflow, earth and rockfill dams, failure hydrograph. Il existe une relation directe entre les caracteristiques de l'inondation qui decoule de la rupture d'un barrage lors de sa submersion et la breche qui se forme au sein de l'ouvrage. Afin d'apprehender le risque de rupture par submersion des barrages en remblai, une approche normative a ete adoptee au Quebec. Cette norme se base sur des ruptures existantes et prevoit, pour les barrages en remblai, la formation, en trente minutes, d'une breche trapezoidale de hauteur H et de largeur au fond 4H. L'utilisation de cette norme ne permet toutefois pas de prendre en compte les caracteristiques propres de chaque barrage et notamment l'utilisation d'un noyau en beton comme element d'etancheite. Seulement, les incertitudes sur la prevision de la breche font que dans l'etat actuel des connaissances, l'utilisation de cette norme reste la solution la plus fiable. Le present article decrit un modele de rupture par submersion du barrage Nemiscau-1, le premier barrage a noyau en beton bitumineux du Quebec. L'etude porte sur trois mecanismes possibles de rupture : le glissement des terres d'amont en aval, des fracturations du rideau en beton bitumineux et l'erosion en surface. Les particularismes du barrage se retrouvent a travers un hydrogramme de rupture par paliers dont la pertinence est superieure a l'hydrogramme obtenu par la norme. Mots-cles : submersion, rupture de barrage, barrage en terre et en enrochement, hydrogramme de rupture., 1. Introduction Il faut entendre par rupture de barrage, la destruction ou le mouvement d'une partie de l'ouvrage, de ses appuis ou de ses fondations, le rendant inapte a retenir [...]

The spring flow of the Mackenzie River into its delta drives the breakup ice jamming and consequent flooding and replenishment of the thousands of lakes on the delta plain. Daily flows for related studies are presently furnished by Water Survey of Canada, based on the records of a hydrometric station located close to the delta entrance. The relative proximity of the Beaufort Sea affects the local water surface slope, amplifying uncertainties that are normally associated with under-ice flow estimates. It is shown that gauge-derived spring flows often do not agree with other evidence, such as past discharge measurements, flows at the next upstream gauge, and hydraulic computations for the 2008 event. This appears to result in inconsistencies between spring flow hydrograph and observed severity of ice breakup. Options for improving spring flow estimates are discussed and installation of an auxiliary water-level gauge near Point Separation is recommended as a practical choice. Key words: flow, gauge, hydroecology, ice breakup, Mackenzie delta, spring, uncertainty. Au printemps, le debit du fleuve Mackenzie dans son delta engendre la formation d'embacles et les inondations qui en decoulent permettent le remplissage de milliers de lacs dans la plaine deltaique. Les debits quotidiens provenant d'etudes associees sont presentement fournis par la division des releves hydrologiques du Canada; ils sont bases sur les registres d'une station hydrometrique situee a l'entree du delta. La proximite relative de la mer de Beaufort affecte la pente locale de la ligne d'eau, amplifiant les incertitudes normalement associees aux estimations des debits sous la glace. Il est demontre que les debits printaniers obtenus des jauges ne concordent souvent pas aux autres donnees, telles que les mesures anterieures de decharge, les debits a la prochaine jauge amont et les calculs hydrauliques de l'evenement de 2008. Cela semble engendrer des discordances entre l'hydrographe du debit printanier et la severite observee de la debacle. Les options pour ameliorer les estimations des debits printaniers sont abordees et il est recommande d'installer une jauge auxiliaire du niveau d'eau pres de Point Separation comme choix pratique. Mots-cles : debit, jauge, hydroecologie, debacle, delta du Mackenzie, printemps, incertitude. [Traduit par la Redaction], Introduction In most Canadian rivers, spring runoff drives the breakup of the winter ice cover and the ensuing ice jams and ice runs. At moderate latitudes, breakup events may also [...]

Every environmental site investigation aims at delineating near-surface (hydro-) stratigraphic units and their characterization. To determine the type and hydraulic properties of sedimentary deposits, direct push (DP) sensor probes and tools are promising methods and are therefore frequently applied to measure high-resolution vertical profiles of soil properties. Given the variety of these tools, the objective of this paper is to compare selected DP tools for the (hydro-) stratigraphic subsurface characterization in a heterogeneous unconsolidated sedimentary aquifer. An overview of current DP applications is given and selected DP tools were tested for reproducibility, as well as their ability to reflect soil variability and to estimate hydraulic conductivity, K. Although resolution differences exist, all of the applied methods captured the main aquifer structure. Correlations of the DP-based K estimates or proxies with DP slug tests (DPST) show that it is possible to describe the aquifer hydraulic structure on less than a metre scale by combining DPST data and continuous DP measurements. Although correlations are site-specific and appropriate DP tools must be chosen, DP is a reliable and efficient alternative for characterizing even strongly heterogeneous sites with complex sedimentary architectures. Key words: direct push, aquifer characterization, hydraulic profiling, cone penetration testing. Les etudes environnementales de sites servent a identifier et caracteriser les unites (hydro-) stratigraphiques pres de la surface. Afin de determiner le type de depots sedimentaires et leurs proprietes hydrauliques, les sondes et outils de poussee directe (PD) font partie des methodes prometteuses, et ainsi sont frequemment appliques pour mesurer a haute resolution les profils verticaux des proprietes des sols. Comme ces outils sont nombreux et varies, l'objectif de cet article est de comparer certains de ces outils de PD pour la caracterisation (hydro-) stratigraphique sous la surface dans un aquifere sedimentaire heterogene et non consolide. Un sommaire des applications courantes de PD est presente, et certains outils ont ete testes pour evaluer leur reproductibilite ainsi que leur capacite a identifier la variabilite des sols et a estimer la conductivite hydraulique, K. Meme si les methodes appliquees different dans leur resolution, elles ont toutes reussi a evaluer la structure de l' aquifere principal. Des correlations entre les estimations de K basees sur la PD ou obtenues indirectement avec des essais de cone en PD (ECPD) demontrent qu'il est possible de decrire la structure hydraulique d'un aquifere a une echelle inferieure au metre en combinant les donnees d' ECPD et les mesures en continu de PD. Malgre que les correlations soient specifiques a un site donne et que les outils de PD appropries doivent etre choisis, la PD est une alternative efficace et fiable pour caracteriser les sites tres heterogenes ayant des architectures sedimentaires complexes. Mots-cles : poussee directe, caracterisation d'aquifere, profilage hydraulique, essai de penetration du cone. [Traduit par la Redaction], Introduction Environmental site investigations require high-resolution information about lithology and hydraulic properties of the subsurface. Knowledge of the spatial distribution of hydraulic conductivity (K) is the prerequisite for understanding flow [...]

Geographers have long been interested in Southern studies and social justice is a common theme in this literature. Traditionally, social justice writing has focused on the plight of the poor [...]

Storage and release functions of western U.S. traditional river valley irrigation systems may counteract early and rapid spring river runoff associated with climate variation. Along the Rio Grande in northern New Mexico, we instrumented a 20-km-long irrigated valley to measure water balance components from 2005 to 2007. Hydrologic processes of the system were incorporated into a system dynamics model to test scenarios of changed water use. Of river water diverted into an earthen irrigation canal system, some was consumed by crop evapotranspiration (7.4%), the rest returned to the fiver as surface return flow (59.3%) and shallow groundwater return flow that originated as seepage from canals (12.1%) and fields (21.2%). The modeled simulations showed that the coupled surface water irrigation system and shallow aquifer act together to store water underground and then release it to the river, effectively retransmitting river flow until later in the year. Water use conversion to nonirrigation purposes and reduced seepage from canals and fields will likely result in higher spring runoff and lower fall and winter river flow. DOI: 10.1061/(ASCE)IR.1943-4774.0000265 CE Database subject headings: Aquifers; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande. Author keywords: River-aquifer interaction; Hydrology; Hydrologic models; Hydrogeology; Irrigation systems; Surface water; Groundwater; Groundwater recharge; Rio Grande.

This paper presents a simplified approach to the characterization of the hydrograph following the partial collapse of concrete gravity dams. The proposed approach uses a simplified representation of the reservoir geometry and is based on the numerical solution of shallow water equations to study the two-dimensional evolution of the water surface within the reservoir. The numerical results are made dimensionless and reorganized so as to compute the peak discharge, the duration and the recession limb of the dam break hydrograph. The proposed practical approach provides a quite satisfactory reproduction of the computed hydrograph for a wide set of realistic situations that have been simulated in detail. DOI: 10.1061/(ASCE)HY.1943-7900.0000231 CE Database subject headings: Dam failure; Shallow water; Numerical models; Simulation; Outflow; Hydrographs. Author keywords: Dam failure; Dam breaches; Shallow water; Numerical simulation; Outflow.

Accounting for transmission losses properly is critical in hydrologic analyses in arid and semiarid climates. The objective of this research was to develop a model that could account for the spatial and temporal variations of transmission losses while routing the flow hydrograph through the channel reach. This model was based on Hortonian infiltration methods and hydrologic channel routing. While most transmission loss models predict flow volumes, the model developed herein uses hydrographs of individual storm events. A numerical optimization procedure was used to identify optimum parameter values for each of Horton's parameters and the routing coefficient, which were then used in modeling transmission losses. Flow gauge data were obtained from the Walnut Gulch Experimental Watershed, which is located near Tucson, Ariz. Testing of this model indicates that it is able to account for transmission losses and predict downstreamflow with reasonable accuracy. To provide a measure of verification, the model was compared to predictions from Lane's model, which is a commonly used method of accounting for transmission losses based on upstreamflow and downstreamflow volumes. Overall the two methods were found to agree fairly well though differing assumptions in the methods influence the results. DOI: 10.1061/(ASCE)IR.1943-4774.0000228 CE Database subject headings: Hydrographs; Optimization; Hydraulic models; Streamflow; Arid lands. Author keywords: Transmission losses; Hydrographs; Optimization; Modeling; Streamflow; Arid lands.

Analytical but approximate invertible equations for time base of gamma unit hydrographs or unit kernel hydrograph (UKH), which are applicable to all catchments, are derived in terms of the parameters of the unit hydrograph. The time base has been linked to the time to peak and lag time for the gamma UKH. The gamma UKH is redefined taking the time base and time to peak as parameters, as these parameters are physically more conceivable than the conventional parameters. The widely used National Resource Conservation Service empirical equations for the time base are found not applicable to all catchments. The proposed equations can also be used for determining the conventional parameters from the known values of the time base and time to peak or lag time. Using the proposed equations for time to peak and time base, the gamma UKH is fitted to few published storm events considering the time base as a parameter. DOI: 10.1061/(ASCE)IR.1943-4774.0000105 CE Database subject headings: Hydrographs; Runoff; Rainfall; Parameters.

A sensitivity analysis of the model presented in the companion paper is made and, on the basis of the results a criterion is proposed for the choice of values to assign to the side slopes of the breach, in order to use the model for prediction. Moreover, the sensitivity analysis shows that the outflow hydrograph and its peak value depend not only on the dam height and the stored volume, but also on the vertical distribution of the water mass in the reservoir. The model is compared with some previously published methods and the disadvantages, limitations, and errors that can be made using parametric models and predictive equations are pointed out. Finally, easy to use equations interpolating the numerical results of the model are provided that predict not only the peak discharge but the whole outflow hydrograph for overtopping failures. DOI: 10.1061/(ASCE)0733-9429(2008)134:12(1697) CE Database subject headings: Dams; Earth; Dam failure; Earthfill; Peak flow; Flash floods; Hydrographs.

This paper proposes a dam-breach model which predicts, in a simple but physically based manner, not only the peak discharge but the whole outflow hydrograph and breach development. The following aspects are taken into account: the geometry of the embankment, the shape of the reservoir, the hydraulic characteristics of the flow through the breach and its erosive capacity, and the shape of the breach. The model needs only one calibration parameter and can be easily applied to real cases. The application of the model with a single value of the calibration parameter produced excellent results in the simulation of 12 historic earthfill dam failures, with a discharge range covering three orders of magnitude. DOI: 10.1061/(ASCE)0733-9429(2008)134:12(1688) CE Database subject headings: Dams, earth; Dam failure; Earthfill; Peak flow; Flash floods; Hydrographs.

In the mid-Atlantic region of the United States, sediment loads from stream runoff generally change more rapidly in the rising limb than in the falling limb of a storm hydrograph. As a result, sediment load reaches its peak prior to flow peak, an observation known as clockwise hysteresis. This dynamic load-flow relationship is poorly reproduced by the existing multivariate linear regression models. This paper explores regressors that attempt to incorporate observed features in a statistical model and thus improve load estimates. These included inverse discharge and flow-change regressors. The load estimates using three regression models for eight rivers are compared, and recommended regression equations are proposed. CE Database subject headings: Regression models; Sediment; Runoff; Hydrographs; Statistics.

The study analyzes the volume conservation problem of the variable parameter Muskingum-Cunge (VPMC) method for which some remedial solutions have been advocated in recent literature. The limitation of the VPMC method to conserve volume is brought out by conducting a total of 6,400 routing experiments. These experiments consist of routing a set of given hypothetical discharge hydrographs for a specified reach length in uniform rectangular and trapezoidal channels using the VPMC method, and comparing the routed solutions with the corresponding benchmark solutions obtained using the full Saint-Venant equations. The study consisted of 3,200 routing experiments carried out each in uniform rectangular and trapezoidal channel reaches. Each experiment was characterized by a unique set of channel bed slope, Manning's roughness coefficient, peak discharge, inflow hydrograph shape factor, and time to peak. A parallel study was carried out using an alternate physically based variable parameter Muskingum discharge hydrograph (VPMD) routing method proposed by Perumal in 1994 under the same routing conditions, and the ability of both the VPMC and VPMD methods to reproduce the benchmark solutions was studied. It is brought out that within its applicability limits, the VPMD method is able to conserve mass more accurately than the VPMC method. The reason for the better performance of the former over the latter method is attributed to the physical basis of its development. It is argued that adoption of artificial remedial measures to overcome the volume conservation problem makes the VPMC method semiempirical in nature, thereby losing the fully physically based characteristics of the method. The paper also dwells on the problems of negative initial outflow or dip in the beginning of the Muskingum solution, and the negative value of the Muskingum weighting parameter. Besides, the effect of incorporating the inertial terms in the estimation of Muskingum parameters and their impact on the overall Muskingum routing solutions is addressed by conducting another set of 6,400 numerical experiments using both the VPMC and VPMD methods. DOI: 10.1061/(ASCE)0733-9429(2008)134:4(475) CE Database subject headings: Hydrographs; Parameters; Conservation; Channels; Routing.

Abstract: A model is developed for the optimal design of storm water networks. The model uses a genetic algorithm (GA) as the search engine and the TRANSPORT module of the [...]

We conducted a combined field and numerical study of the effects of episodic internal Kelvin-type waves on bottom boundary turbulence and the exchange of a passive tracer between the main basin and the side basin of a large lake (Lake Geneva). High-resolution measurements of the vertical current structure near the entrance of the 25-km-long and 70-m-deep side basin revealed that hypolimnetic current speeds frequently exceed 0.2 m [s.sup.-1], leading to a turbulent bottom boundary layer several meters thick with logarithmic current profiles and to a region of strong shear across the thermocline. The time series and vertical structure of the currents were reproduced by a three-dimensional numerical model of the lake. It was demonstrated that, after episodes of strong winds from the northeast and southwest, exchange flows due to internal Kelvin waves were able to temporarily half or double the hypolimnetic volume of the side basin, leading to an irreversible exchange of up to 40% of the hypolimnetic water in the side basin of Lake Geneva within only a few wave cycles. With the help of the numerical model, it was shown that the key mechanisms of exchange are horizontal dispersion by resolved scales and, to a small extent, shear dispersion in the bottom boundary layer. It is suggested that bottom boundary-layer turbulence and the interbasin exchange can explain the structural differences in the oxygen profiles observed in the side basin and the main basin, respectively.

The combination of altimetry data and the geoid height of a state-of-the-art geoid model are not only inaccurate, but also inconsistent with a hydrographic of the flow field, with an analysis of a hydrographic section between Australia and Antarctica. The inconsistent transport estimate and the unrealistic velocity field obtained with the sea-surface height data imply that the smoothed sea-surface height relative to the EGM96 geoid height overestimates the sea-surface drop across the southern ocean and consequently overestimates the total transport as well.

Byline: Takashi Miyao (1), Koichi Ishikawa (2) Keywords: North Pacific Intermediate Water; Kuroshio; Oyashio; volume transport Abstract: In order to examine the formation, distribution and transport of North Pacific Intermediate Water (NPIW), repeated hydrographic observations along several lines in the western North Pacific were carried out in the period from 1996 to 2001. NPIW formation can be described as follows: (1) Oyashio water extends south of the Subarctic Boundary and meets Kuroshio water in intermediate layers (2) active mixing between Oyashio and Kuroshio waters occurs in intermediate layers (3) the mixing of Oyashio and Kuroshio waters and salinity minimum formation around the potential density of 26.8[sigma].sub.I, proceed to the east. It is found that Kuroshio water flows eastward even in the region north of 40degN across the 165degE line, showing that Kuroshio water extends north of the Subarctic Boundary. Volume transports of Oyashio and Kuroshio components (relative to 2000 dbar) integrated in the potential density range of 26.6--27.4[sigma]I, along the Kuroshio Extension across 152degE--165degE are estimated to be 7--8 Sv (10.sup.6 [m.sup.3]s.sup.-1) and 9--10 Sv, respectively, which is consistent with recent work. Author Affiliation: (1) Hakodate Marine Observatory, Hakodate, Hokkaido, 041-0836, Japan (2) Climate and Marine Department, Japan Meteorological Agency, Chiyoda-ku, Tokyo, 100-8122, Japan Article History: Registration Date: 06/10/2004

The Delaunay triangulation is a widely appreciated and investigated mathematical model for topographic surface representation. After a brief theoretical description, six possible basic algorithms to construct a Delaunay triangulation are analyzed and properties that can be exploited for multibeam echosounder data processing are investigated. Two concepts will be treated in more depth: the divide-and-conquer construction algorithm and the incremental method. The calculation speed of the divide-and-conquer method makes it an ideal candidate to construct the initial triangulation of multibeam data. Its runtime performance is compared to that of the incremental algorithm to demonstrate this. The algorithm's merge step appears to be useful also in replacing triangulated areas of existing triangulations by new data. The incremental algorithm does not seem an effective construction method but it can easily be adapted to accommodate insertion of individual vertices into an existing triangulation and as such it is useful for editing purposes. DOI: 10.1061/(ASCE)0733-9453(2003)129:2(79) CE Database subject headings: Triangulation; Algorithms; Hydrographs; Mathematical models; Topography.

The annual advance and retreat of sea ice has been considered a major physical determinant of spatial and temporal changes in the structure of the Antarctic coastal marine ecosystem. However, the role of glacial meltwater on the hydrography of the Antarctic Peninsula ecosystem has been largely ignored, and the resulting biological effects have only been considered within a few kilometers from shore. Through several lines of evidence collected in conjunction with the Palmer Station Long-Term Ecological Research Project, we show that the freshening and warming of the coastal surface water over the summer months is influenced not solely by sea ice melt, as suggested by the literature, but largely by the influx of glacial meltwater. Moreover, the seasonal variability in the amount and extent of the glacial meltwater plume plays a critical role in the functioning of the biota by influencing the physical dynamics of the water (e.g., water column stratification, nearshore turbidity). From nearly a decade of observations (1991-1999), the presence of surface meltwater is correlated not only to phytoplankton blooms nearshore, but spatially over 100 km offshore. The amount of meltwater will also have important secondary effects on the ecosystem by influencing the timing of sea ice formation. Because air temperatures are statistically increasing along the Antarctic Peninsula region, the presence of glacial meltwater is likely to become more prevalent in these surface waters and continue to play an ever-increasing role in driving this fragile ecosystem.

A description of ocean-atmospheric interaction for the Atlantic Ocean is presented. The transport energy of the Deep Western Boundary Current is balanced by a northward recirculation, while Lower Deep Water is a primary component of the deep equatorial Atlantic and generates an upward diapycnal transport.

Byline: Hiroji Onishi (1) Keywords: Alaskan Stream; Subarctic Current; EOF analysis; North Pacific Subarctic Gyre; Ridge Domain water Abstract: In the central North Pacific Subarctic Gyre, CTD hydrographic measurements were carried out yearly in late June from 1990 to 1998 at 9 stations along 180deg meridian from 48degN to 51.2degN. Vertical sections of 9-year means, anomalies for each year and others of potential temperature, salinity, potential density and geostrophic velocity (referred to 3000 m) were calculated based on this data set. Empirical Orthogonal Function (EOF) analysis was adopted in the investigation of spatial characteristics and its temporal variation in vertical sections. The spatial distribution of the 1st mode EOF of velocity shows the westward Alaskan Stream and the eastward Subarctic Current. This mode explains 37.6% of the total variance. Two positive maxims appear in its amplitude in 1991 and 1997, which is similar to the variation in volume transport of the eastward Subarctic Current. These variations are closely related to the vertical movement of Ridge Domain deep water. Author Affiliation: (1) Graduate School of Fisheries Science, Hokkaido University, Minato-cho 3-1-1, Hakodate, Hokkaido, 041-8611, Japan Article History: Registration Date: 08/10/2004

Data are presented on the physical and biogeochemical characteristics of the thermocline found in eastern North Atlantic central waters. Enhanced boundary mixing was found to have an influence on biogeochemical tracer distributions, but diapycnal mixing was not crucial for large-scale tracer distributions.

Ice-affected periods represent a significant portion of the annual hydrograph for most Canadian hydrometric stations. Because the stage-discharge relation is not reliable under ice-cover conditions, Water Survey of Canada subjectively interpolates winter streamflow from as few as two observations of discharge during the ice-covered season, which may last 6 months or longer. An alternative method of producing discharge estimates is proposed that uses a combination of conceptual and statistical hydrological modeling to overcome limitations in both the availability of data and our understanding of relevant processes. A conceptual hydrological model is tested to evaluate the utility of this approach for data-sparse regions. When model predictions were adjusted to fit two winter measurements, 79% of all verification measurements were within 20% of predicted estimates. There was a seasonal bias to the error distribution, with most measurements within the first 30 days after freeze-up being less than predicted and most measurements after April 1 being greater than predicted. These deviations probably result from hydraulic and hydrologic processes not represented within the model.

Research indicates that nitrate limitation, silicate depletion and Southern Ocean Front meandering are the primary factors affecting phytoplankton populations and the presence of chlorophyll-alpha. Variations also occur within meridians and zones.

Research reveals two northward current kernels off the Norwegian coast which impact Atlantic Ocean water transport to the Nordic Seas. Findings also include the discovery of two cores of water which, during the summer, exhibit salinity exceeding 35.25 at a depth of approximately 100 m.

An analysis is presented on source, circulation and composition of the Atlantic Ocean's deep water masses. Sources include the Iceland-Scotland Overflow Water; composition includes salinity, dissolved oxygen, nitrate, phosphate and silicate, which are affected by organic matter mineralization and diapycnal mixing.

A study of the cause and effect links between the hydrographic structure of the west Antarctic Peninsula continental shelf and its phytoplankton community composition is presented. Results indicate an environment-trophic coupling that may occur in other Antarctic regions.

Research findings are presented on the Red Sea's geothermal brines. These include salinity, diffusional transport, density gradients, and the different properties between the deep brine basins and overlying seawater.

An estuarine frontal system was investigated with a series of numerical experiments using a 3D hydrodynamic model. The model results were confirmed with field observations and compared with theoretical analysis. Various factors, singly or jointly, contributing to the frontogenesis were investigated. The numerical computations demonstrate that the theoretical critical densimetric Froude number is exceeded as flood current increases and the front is pushed forward to the deeper water. The numerical experiments indicate that two factors contribute significantly to the flow convergence by advancing the phase of flood current on the shoals relative to that in the channel. They are differential friction resulting from depth contrast between deep channel and shoals, and enhanced surface ebb current in the channel resulting from stratification and density induced circulation. Numerical experiments also show that the front is stronger and lasts longer during neap tide than during spring tide. Weaker salinity contrast during spring tide reduces the buoyancy force that is required for the diving of the denser water mass. Furthermore, the stronger flood current during spring tide causes the densimetric Froude number to exceed its critical value earlier, as predicted by the theoretical analysis, and pushes the front away from the region of steep bottom slope, causing it to dissipate.

The vertical distributions of the hydrographic properties, particularly the meridional and zonal property asymmetries, were analyzed in light of the circulation in the Atlantic region. Results revealed an arrival from the southeast and northwestward crossing of the equator offshore from the deep western boundary current of northern water. A net warming of the intermediate and upper deep waters and cooling of the bottom water was found during a comparison of temperatures along 7 degrees 30 north in 1993 with those at 8 degrees north during the International Geophysical Year in 1957.

Singerland et al. made a creditable study on the hydrodynamics and salinity of the Cretaceous Western Interior seaway. However, it cannot be considered the definitive study inasmuch as it merely complements other studies that come up with their own models. Singerland et al.'s work is evolutionary in character and is not one to supplant the brackish-lid model of seaway hydrography which, despite its many shortcomings, still has its adherents for want of better models.

A hydrographic survey conducted by the UUS Pargo submarine in 1993 produced measurements that gave the upper Arctic Ocean a unique, synoptic description. Data collected from this oceanographic survey has provided evidence that the Arctic Ocean has been significantly influenced by Atlantic Water. This was especially prominent in the Lomonosov and the Mendeleyev Ridges where warm cores of Atlantic Water were found.

The temperature, salinity, and geostrophic velocity in the upper 1200 meters of the northern tropical Atlantic was studied over a 10 year period between 1982 and 1991. The data was based on two experiments, FOCAL/SEQUALsuper2 and WESTRAXsuper3. Strong meandering of the North Equatorial Countercurrent during the summer of 1987 was observed, and there was strong thermocline current transporting water northward in summer 1986.

The features of the Western Boundary Current (WBC) of the east coast of India, or the Bay of Bengal, during Mar 1993 are observed based on its thermohaline structure and estimated geostrophic flow patterns. Results reveal that the flow regime inferred in the western Bay during the said period represented the developing phase of the WBC system, which appeared first at the northwestern Bay.

Geomorphology-based instantaneous unit hydrographs have been proposed by several engineers as a tool to produce runoff hydrographs from rainfall for ungauged watersheds. A difficulty in applying the geomorphology-based unit hydrographs is the determination of travel time that is actually a hydraulic problem. In this paper, kinematic-wave theory is used to analytically determine the travel times for overland and channel flows in a stream-ordering subbasin system. The resultant instantaneous unit hydrograph is a function of the time rate of water input (intensity of rainfall excess in application); hence the linearity restriction of the unit hydrograph theory is relaxed. In applying the instantaneous unit hydrographs for hydrograph simulation, the model deals with temporally nonuniform rainfall through convolution integration of the instantaneous unit hydrographs applied to the rainfall excess of varying intensities with time. The proposed model is tested by comparing the simulated and observed hydrographs of an example watershed for several rainstorms with good results. Sensitivity of surface runoff unit hydrographs to the model parameters is also investigated.

Hydrographic data from two cruises in the central and southern Tyrrhenian basin revealed that there are thermohaline stepped structures lying between the Levantine Intermediate Water and the Deep Water. One staircase, lying 600-2500 meters underwater, was composed of four to eight homogeneous layers, which were separated by thinner interfaces. The staircase's structure was less defined towards the basin boundaries but strongly discernible in the basin's deepest parts. Comparison of the new data with previous data shows that there has been a progressive reduction in step number and a progressive increase in the step thickness.

A new method for calculation of frequency-equivalent storms and hydrographs is presented. This procedure is an extension of the frequency-equivalent nonlinear hydrograph (FENLH) methodology. Streamflow data records for a total of 129 basins in the state of Kansas have been used. A new storm criterion for generating frequency-equivalent storms was selected. Peak flow rates, hydrograph volumes, and peak reduction factors, produced by the storm criterion, were related to the basin physiographic and climatic data. The combination of index flood and multiple regression techniques were used to obtain predictive equations for peak flow rates and hydrograph volumes for six different return intervals. The use of the FENLH model as a prototype and the selection of the criterion utilized in this study to determine frequency-equivalent conditions, provided storm dimensions that appeared realistic. The accuracy of the results obtained indicated that the methodology presented in this study can be applied to other areas.

In hydraulic and hydrologic studies, engineers develop new models or calibrate existing models by various techniques. One is often concerned with the model validity regarding its ability to predict future events. Five potentially useful statistical validation methods are presented. For illustration, they were applied to examine the predictability of unit hydrographs derived by various methods in the framework of the least squares and its variations. It was found that storm-stacking (conventional multistorm analysis) together with storm-scaling yields the most desirable UH. The general framework of these validation methods can also be applied to a validation study of other hydrologic and hydraulic models.

Least squares (LS) methods are frequently used to determine an optimal unit hydrograph (UH) for a watershed. However, the conventionally used ordinary LS method could potentially produce a UH with unwanted fluctuation among hydrograph ordinates. When that occurs, the ridge LS method can be used to reduce noise fluctuation in a derived UH. In the framework of the ridge LS method, a UH can be obtained by minimizing the mean-squared error (MSE) of the estimated UH or direct runoff hydrograph (DRH). Therefore, the ridge LS method theoretically would enhance the predictability of the derived UH. This paper describes methodologies of obtaining the optimal ridge parameter for use in the ridge LS method to estimate a UH. Furthermore, the unit volume constraint is considered in the determination of the optimal ridge parameter. A statistical validation study is also conducted to show that a UH obtained by the ridge LS method has a better predictive capability than the one derived by the ordinary LS method.

Extensive analysis of remotely-sensed images provide insightful information on the spatial coverage, long-crestedness and the development of internal tides in the Bay of Biscay. Further details on aspects including onshelf propagation and wavelength structure of the Celtic shelf can be attained by analyzing data from thermistor chain moorings.

Synoptic surveys reveal the advection of intermediate and deep water masses in the Iceland Basin to be in a cyclonic manner, wherein partial changes occur as a result of topographic steering along ridges on the Icelandic slope. Property-property plots, vertical tracer sections and isopycnal analysis aid in providing insightful details on the meeting and mixing of various water types in the basin.