The purpose of this study explores the sound propagation in very shallow water to understand the environment quality of the Si-Tzi Marine Test Field. Very shallow water acoustics characterized by that sound wave will have a dramatic interaction between the bottoms and the propagation of wave and bottom with a high degree of correlation. Those types of environment are concentrated in the west coast of Taiwan. Analysis of actual acoustic data from the ocean obtain and to use "OASES" simulation that an applied acoustic tool. Expect to understand the phenomenon of water acoustic propagation in the very shallow. The Si-Tzi marine test field had detailed environmental information by previously study. In experiment process, the hydrophone "iTC-6050c" receiving broadband sound source "UW350" signal. The use of personal computer with DAQ card for data acquisition and control. The source in the research vessel was moored 20 m below sea, at the same time to launch three consecutive single (frequency signal 350 Hz, 800 Hz, and 1250 Hz). Reception of signals in order to drift the way. Measured at different frequencies in very shallow water of the transmission loss. The results showed that the results of the current measurement and simulation in line with the follow-up study will be measured "transmission loss" to do to Inversion for geoacoustic parameters in very shallow water. Then obtained "geoacoustic parameters" Comparison of sea-bed surface sampling results. Confirmation "geoacoustic inversion technique" is correct.

Shallow water acoustics is one of the most challenging areas of underwater acoustics; it deals with strong sea bottom and surface interactions, multipath propagation, and it often involves complex variability in the water column. The sea bottom is the dominant environmental influence in shallow water. An accurate solution to the Helmholtz equation in a shallow water waveguide requires accurate seabed acoustic parameters (including seabed sound speed and attenuation) to define the bottom boundary condition. Direct measurement of these bottom acoustic parameters is excessively time consuming, expensive, and spatially limited. Thus, inverted geo-acoustic parameters from acoustic field measurements are desirable. Because of the lack of convincing experimental data, the frequency dependence of attenuation in sandy bottoms at low frequencies is still an open question in the ocean acoustics community. In this thesis, geo-acoustic parameters are inverted by matching different characteristics of a measured sound field with those of a simulated sound field. The inverted seabed acoustic parameters are obtained from long range broadband acoustic measurements in the Yellow Sea '96 experiment and the Shallow Water '06 experiment using the data-derived mode shape, measured modal attenuation coefficients, measured modal arrival times, measured modal amplitude ratios, measured spatial coherence, and transmission loss data. These inverted results can be used to test the validity of many seabed geo-acoustic models (including Hamilton model and Biot-Stoll model) in sandy bottoms at low frequencies. Based on the experimental results in this thesis, the non-linear frequency dependence of seabed effective attenuation is justified.

<p>An investigation to assess the anthropogenic pollutant loads, transport and impact on shallow groundwater in one of Kampala’s peri-urban areas (Bwaise III Parish) was undertaken. Bwaise III is a densely populated informal settlement with a high water table (<1.5 m) and inadequate basic social services infrastructure (e.g, sanitation, safe water supply, roads, etc).</p><p>Field surveys were undertaken to identify, locate and quantify various pollutant sources. Information on the usability and operational aspects of the excreta and solid waste management systems was obtained from consultations with the residents. Water from installed monitoring wells and one operational protected spring and wastewater (sullage) characteristics (quality, discharges for drains and spring, water levels for the wells) as well as soil characteristics (soil stratigraphy, physical and chemical) were determined through field and laboratory measurements. Laboratory batch experiments were undertaken to estimate phosphorus sorption potential of the soils.</p><p>The results reveal that excreta disposal systems, solid waste and sullage are the major contributors to shallow groundwater contamination. High contaminant loads from these sources accumulate within the area resulting in widespread contamination. The water table responds rapidly to short rains (48hr) due to the pervious and shallow (<1 m) vadose zone, which consists of mostly organic fill material. Rapid water quality deterioration (increased thermotolerant coliforms, organic content in the form of total kjedahl nitrogen, phosphorus) following rains potentially follows from leaching, desorption and macropore flow. Spatial variation of the water quality in the area is largely related to anthropogenic activities within the vicinity of the well sources. Animal rearing, solid waste dumps and latrines are seen to result in increased localised microbial and organic content during the rains. The spring discharge with high nitrate levels does not respond to short rains suggesting that this source is fed by regional baseflow. The corresponding high microbial contamination in this case is a result of observed poor maintenance of the protection structure leading to direct ingress of contaminated surface runoff. Natural attenuation of contaminants is very limited. Estimated bacteria die-off rates are very low, about 0.01hr-1, suggesting a high risk for microbial contamination. The soils still have potential to retain additional phosphorus, whose sorption is largely a function of iron, available phosphorus and moisture content of the soils. This is also seen with the model results in which the phosphorus contaminant plume sticks to the surface irrespective of the rainfall infiltration rates. Simulation results show that continuous heavy intense rains (> 0.25mm/min) result in rapid flooding occurring within 1hr to 2 days. With lower rains, the water table does not rise to the surface, and no flooding takes place.</p><p>Protection of the shallow groundwater in the area requires socio-technical measures targeting reduction of pollutant loads within the area as well as a wider spring catchment. Re-protection of the spring, coupled with awareness creation, should be immediately addressed so as to reduce microbial contamination. Community participation in solidwaste management should be encouraged. Resource recovery systems such as composting of the mostly organic waste and use of ecological sanitation toilet systems should be piloted in the area. Successful operation of the systems however depends on continuous sensitisation of the communities.</p><p>An investigation to assess the anthropogenic pollutant loads, transport and impact on shallow groundwater in one of Kampala’s peri-urban areas (Bwaise III Parish) was undertaken. Bwaise III is a densely populated informal settlement with a high water table (<1.5 m) and inadequate basic social services infrastructure (e.g, sanitation, safe water supply, roads, etc).</p><p>Field surveys were undertaken to identify, locate and quantify various pollutant sources. Information on the usability and operational aspects of the excreta and solid waste management systems was obtained from consultations with the residents. Water from installed monitoring wells and one operational protected spring and wastewater (sullage) characteristics (quality, discharges for drains and spring, water levels for the wells) as well as soil characteristics (soil stratigraphy, physical and chemical) were determined through field and laboratory measurements. Laboratory batch experiments were undertaken to estimate phosphorus sorption potential of the soils.</p><p>The results reveal that excreta disposal systems, solid waste and sullage are the major contributors to shallow groundwater contamination. High contaminant loads from these sources accumulate within the area resulting in widespread contamination. The water table responds rapidly to short rains (48hr) due to the pervious and shallow (<1 m) vadose zone, which consists of mostly organic fill material. Rapid water quality deterioration (increased thermotolerant coliforms, organic content in the form of total kjedahl nitrogen, phosphorus) following rains potentially follows from leaching, desorption and macropore flow. Spatial variation of the water quality in the area is largely related to anthropogenic activities within the vicinity of the well sources. Animal rearing, solid waste dumps and latrines are seen to result in increased localised microbial and organic content during the rains. The spring discharge with high nitrate levels does not respond to short rains suggesting that this source is fed by regional baseflow. The corresponding high microbial contamination in this case is a result of observed poor maintenance of the protection structure leading to direct ingress of contaminated surface runoff. Natural attenuation of contaminants is very limited. Estimated bacteria die-off rates are very low, about 0.01hr-1, suggesting a high risk for microbial contamination. The soils still have potential to retain additional phosphorus, whose sorption is largely a function of iron, available phosphorus and moisture content of the soils. This is also seen with the model results in which the phosphorus contaminant plume sticks to the surface irrespective of the rainfall infiltration rates. Simulation results show that continuous heavy intense rains (> 0.25mm/min) result in rapid flooding occurring within 1hr to 2 days. With lower rains, the water table does not rise to the surface, and no flooding takes place.</p><p>Protection of the shallow groundwater in the area requires socio-technical measures targeting reduction of pollutant loads within the area as well as a wider spring catchment. Re-protection of the spring, coupled with awareness creation, should be immediately addressed so as to reduce microbial contamination. Community participation in solidwaste management should be encouraged. Resource recovery systems such as composting of the mostly organic waste and use of ecological sanitation toilet systems should be piloted in the area. Successful operation of the systems however depends on continuous sensitisation of the communities.</p>

Shallow-water hydrothermal vents occur world-wide in regions of volcanic activity. The vents located at Tutum Bay, Ambitle Island, Papua New Guinea are unique in that the vent fluids and surrounding sediments contain some of the highest concentrations of arsenic in a natural system. This study addresses the effects of the vent system on the benthic communities, focusing on the eukaryotes, macrofauna, meiofauna and bacteria. Samples were collected in November 2003 and May/June 2005. Analysis of the 2003 macrofaunal samples indicated that pH, rather than arsenic was influencing the benthic community, and that the hydrothermal influence occurred at a greater distance than expected. Results of more intensive sampling carried out in 2005 are the primary focus of this dissertation. The pore water and sediment characteristics revealed distinct physical habitats corresponding with distance from the vent. There was a trend of decreasing temperature and arsenic concentration and increasing salinity and pH with distance from the vent. The vent sediment was poorly sorted volcanic gravel, while sediments along the transect showed a gradient from fine, well sorted volcanic sands to coarser carbonate sands farther away. The macrofauna showed a trend of increasing diversity with distance from the vent and similar taxa were present in both the 2003 and 2005 samples. The vent community was dominated by the polychaete Capitella cf. capitata. The inner transect from 30 m to 140 m had low diversity. Dominant taxa included thalassinid shrimp and the amphipod Platyischnopus sp.A. The 180 m to 300 m sites had significantly higher diversity. The Danlum Bay reference site had relatively higher diversity than the nearshore transect sites and was dominated by deposit feeding polychaetes. Macrofaunal community structure was influenced by the sediment characteristics, notably by CaCO3 content, sorting and median grain size. The meiofaunal community also showed changes with distance from the vent. Chromadorid nematodes were dominant at the vent site and were a major component of the meiofauna at most sites, along with copepods. The meiofaunal community at the reference site showed greater similarity to the vent community and both sites had low abundances. Nematodes were more abundant than copepods near the vent, but copepods were more abundant farther offshore and at the reference site. Meiofaunal community structure was influenced primarily by the pore water temperature and salinity. Biological interactions with the macrofaunal community through physical disturbance and predation may also influence the meiofaunal community.  The molecular analysis of eukaryotic and bacterial diversity also revealed changes with distance from the vent. The 0 m and reference sites grouped together due to the presence of fungal sequences and the 140 m and 300 m sites grouped together due to a common molluscan sequence. Metazoans and fungi dominated the eukaryote sequences. The most abundant eukaryotic OTUs included fungi matching Paecilomyces sp. and Cladosporium cladosporioides and metazoans matching Viscosia viscosa (Nematoda) and Astarte castanea represented by 24 phyla and was dominated by Actinobacteria and γ-Proteobacteria. More bacterial phyla were present near the vent, while more overall OTUs were found at the intermediate sites along the transect. The most distant site had much lower diversity dominated by Firmicutes. The macrofaunal community had the strongest correlation with environmental variables. Comparison between the meiofauna and the metazoan sequences showed the proportion of nematodes found in both datasets were comparable, but the meiofauna analysis found a higher proportion of arthropods, while the molecular results were disproportionally high for platyhelminthes. Overall, the vents increased the complexity of the system by creating unique habitats. The extreme environment created by the hydrothermal activity maintained the surrounding habitat at an early successional stage colonized by a few opportunistic species. There was a gradation in the benthic communities away from the vent towards a more carbonate based climax community. The low pH environment had an effect on the sediment composition, which in turn influenced the benthic community. These findings can serve as a model for studying the potential effects of ocean acidification and climate change on benthic communities and marine biocomplexity.

Waves and circulation processes interact in daily wind and tide driven flows as well as in more extreme events such as hurricanes. Currents and water levels affect wave propagation and the location of wave-breaking zones, while wave forces induce setup and currents. Despite this interaction, waves and circulation processes are modeled separately using different approaches. Circulation processes are represented by the shallow water equations, which conserve mass and momentum. This approach for wind-generated waves is impractical for large geographic scales due to the fine resolution that would be required. Therefore, wind-waves are instead represented in a spectral sense, governed by the action balance equation, which propagates action density through both geographic and spectral space. Even though wind-waves and circulation are modeled separately, it is important to account for their interactions by coupling their respective models. In this dissertation we use discontinuous-Galerkin (DG) methods to couple spectral wave and circulation models to model wave-current interactions. We first develop, implement, verify and validate a DG spectral wave model, which allows for the implementation of unstructured meshes in geographic space and the utility of adaptive, higher-order approximations in both geographic and spectral space. We then couple the DG spectral wave model to an existing DG circulation model, which is run on the same geographic mesh and allows for higher order information to be passed between the two models. We verify and validate coupled wave/circulation model as well as analyzing the error of the coupled wave/circulation model. / text

This dissertation focuses on a variety of vadose zone processes that impact water table fluctuations. The development of vadose zone process conceptualization has been limited due to both the lack of recognition of the importance of the vadose zone and the absence of suitable field data. Recent studies have, however, shown that vadose zone soil moisture dynamics, especially in shallow water table environments, can have a significant effect on processes such as infiltration, recharge to the water table, and evapotranspiration. This dissertation, hence, attempts to elucidate approaches for modeling vadose zone soil moisture dynamics. The ultimate objective is to predict different vertical and horizontal hydrological fluxes. The first part of the dissertation demonstrates a new methodology using soil moisture and water table data collected along a flow transect. The methodology was found to be successful in the estimation of hydrological fluxes such as evapotranspiration, infiltration, runoff, etc. The observed dataset was also used to verify an exponential model developed to quantify the ground water component of total evapotranspiration. This analysis was followed by a study which analyzed the impact of soil moisture variability in the vadose zone on water table fluctuations. It was found that antecedent soil moisture conditions in the vadose zone greatly affected the specific yield values, causing a broad range of water table fluctuations for similar boundary fluxes. Hence, use of a constant specific yield value can produce inaccurate results. Having gained insight into the process of evapotranspiration and specific yield, a threshold based model to determine evapotranspiration and subsequent water table fluctuation was conceptualized and validated. A discussion of plant root water uptake and its impact on vadose zone soil moisture dynamics is presented in the latter half of this dissertation. A methodology utilizing soil moisture and water table data to determine the root water uptake from different sections of roots is also described. It was found that, unlike traditional empirical root water uptake models, the uptake was not only proportional to the root fraction, but was also dependent on the ambient soil moisture conditions. A modeling framework based on root hydraulic characteristics is provided as well. Lastly, a preliminary analysis of observed data indicated that, under certain field conditions, air entrapment and air pressurization can significantly affect the observed water table values. A modeling technique must be developed to correct such observations.

A new methodology is proposed for estimation of evapotranspiration (ET) flux at small spatial and temporal scales. The method involves simultaneous measurement of soil moisture (SM) profiles and water table heads along transects flow paths. The method has been applied in a shallow water table field site in West-Central Florida for data collected from January 2002 through June 2004. Capacitance shift type moisture sensors were used for this research, placed at variable depth intervals starting at approximately 4 in. (10 cm) below land surface and extending well below the seasonal low water table depth of 59 in. (1.5 m). Vegetation included grassland and wetland forested flatwoods. The approach includes the ability to resolve multiple ET components including shallow and deep vadose zone, surface interception capture and depression storage ET. Other components of the water budget including infiltration, total and saturation rainfall excess runoff, net runoff, changes in storage and lateral groundwater flows are also derived from the approach. One shortcoming of the method is the reliance on open pan or other potential ET estimation techniques when the water table is at or near land surface. Results are compared with values derived for the two vegetative covers from micrometeorological and Bowen ratio methods. Advantages of the SM method include resolving component ET.

Storm surge, the pileup of seawater occurring as a result of high surface stresses and strong currents generated by extreme storm events such as hurricanes, is known to cause greater loss of life than these storms' associated winds. For example, inland flooding from the storm surge along the Gulf Coast during Hurricane Katrina killed hundreds of people. Previous storms produced even larger death tolls. Simultaneously, dune, barrier island, and channel erosion taking place during a hurricane leads to the removal of major flow controls, which significantly affects inland inundation. Also, excessive sea bed scouring around pilings can compromise the structural integrity of bridges, levees, piers, and buildings. Modeling these processes requires tightly coupling a bed morphology equation to the shallow water equations (SWE). Discontinuous Galerkin finite element methods (DGFEMs) are a natural choice for modeling this coupled system, given the need to solve these problems on large, complicated, unstructured computational meshes, as well as the desire to implement hp-adaptivity for capturing the dynamic features of the solution. Comprehensive modeling of these processes in the coastal zone presents several challenges and open questions. Most existing hydrodynamic models use a fixed-bed approach; the bottom is not allowed to evolve in response to the fluid motion. With respect to movable-bed models, there is no single, generally accepted mathematical model in use. Numerical challenges include coupling models of processes that exhibit disparate time scales during fair weather, but possibly similar time scales during intense storms. The main goals of this dissertation include implementing a robust, efficient, tightly-coupled morphological model using the local discontinuous Galerkin (LDG) method within the existing Advanced Circulation (ADCIRC) modeling framework, performing systematic code and model verification (using test cases with known solutions, proven convergence rates, or well-documented physical behavior), analyzing the stability and accuracy of the implemented numerical scheme by way of a priori error estimates, and ultimately laying some of the necessary groundwork needed to simultaneously model storm surges and bed morphodynamics during extreme storm events. / text

Η λίμνη Παμβώτιδα των Ιωαννίνων είναι μια τυπική εύτροφη ρηχή λίμνη που παρουσιάζει μεγάλο οικολογικό ενδιαφέρον (ανήκει στο δίκτυο «ΦΥΣΗ 2000» , αποτελεί ενδιαίτημα πολλών ελληνικών ενδημικών ειδών ) . Ο ευτροφισμός και η εισαγωγή πολλών αλλόχθονων κυπρινοειδών ειδών τα τελευταία χρόνια έχουν προκαλέσει τα τελευταία χρόνια δραματική μείωση της αφθονίας της υδρόβιας βλάστησης. Στα πλαίσια αυτής της μεταπτυχιακής διατριβής μελετήθηκε η δομή της υπάρχουσας υδρόβιας βλάστησης και αξιολογήθηκε η επίδραση της παρόχθιας ζώνης στα φυσικοχημικά χαρακτηριστικά του νερού κατά τη δειγματοληπτική περίοδο 2004-2005. Εφαρμόστηκαν οι μέθοδοι TWINSPAN και NMS προκειμένου η υδρόβια βλάστηση να ταξινομηθεί σε ευδιάκριτες ομάδες βλάστησης και η CCA ώστε να διαπιστωθούν συσχετίσεις μεταξύ των υδρόβιων μακροφύτων και των περιβαλλοντικών παραμέτρων. Πραγματοποιήθηκε ανάλυση διασποράς (one-way ANOVA) προκειμένου να διαπιστωθούν στατιστικά σημαντικές διαφορές μεταξύ των φυσικοχημικών χαρακτηριστικών του νερού της παρόχθιας ζώνης ,του νερού υδρόβιας βλάστησης εκτός παρόχθιας ζώνης και των ανοικτών νερών. Επιπλέον διερευνήθηκαν πιθανά εποχιακά πρότυπα στη διακύμανση των φυσικοχημικών παραμέτρων ενώ διερευνήθηκαν και πιθανές συσχετίσεις μεταξύ των παραμέτρων. Χρησιμοποιήθηκαν οι τροφικοί δείκτες Carlson για την αξιολόγηση της τροφικής κατάστασης της λίμνης και την εξαγωγή χρήσιμων συμπερασμάτων. Τα αποτελέσματα των αναλύσεων έδειξαν πως η υφυδατική βλάστηση έχει μειωθεί σε δραματικά επίπεδα ,ενώ έχουν απομείνει ελάχιστα είδη που παρουσιάζουν μέγιστη τιμή πληθοκάλυψης την άνοιξη. Διακρίθηκαν 4 ομάδες υδρόβιας βλάστησης εκ των οποίων οι 3 αντιστοιχούν σε ομάδες εφυδατικής βλάστησης. Η παρόχθια ζώνη παρουσίασε χαμηλότερα επίπεδα SRP ,pH ,διαλυμένου οξυγόνου ,ανθρακικών και διαφάνειας και υψηλότερα επίπεδα όξινων ανθρακικών ,αγωγιμότητας και λόγου διαφάνειας προς βάθος σε σχέση με τους άλλους δύο οικότυπους. Τα φωσφορικά και τα αμμωνιακά κυμάνθηκαν σε υψηλά επίπεδα το καλοκαίρι ενώ τα νιτρικά εμφάνισαν την υψηλότερη συγκέντρωσή τους το φθινόπωρο. Ο λόγος DIN /SRP κυμάνθηκε σε χαμηλές τιμές ( <15) υποδεικνύοντας περιοριστικές συνθήκες αζώτου ενώ η τροφική κατάσταση της λίμνης κατατάσσεται ως εύτροφη σύμφωνα με τον τροφικό δείκτη Carlson. Σύμφωνα με τα παραπάνω υπάρχουν ενδείξεις πως η παρόχθια ζώνη, είτε λόγω των υδρόβιων μακροφύτων είτε λόγω άλλων μηχανισμών ,επηρεάζει με διάφορους τρόπους ορισμένα φυσικοχημικά χαρακτηριστικά του νερού. Τα αυξημένα επίπεδα φωσφόρου το καλοκαίρι υποδεικνύουν την ύπαρξη μηχανισμών απελευθέρωσης φωσφόρου από το ίζημα ,ενώ οι χαμηλές τιμές του λόγου DIN/SRP αποτελούν ένδειξη για την επικράτηση αζωτοδεσμευτικών κυανοβακτηρίων με δυσμενείς επιπτώσεις για την υδρόβια ζωή. / Lake Pamvotis is a shallow eutrophic lake situated in northwestern Greece (Region of Epirus). The lake has been stocked with grass carp and common carp during the last years and since then a serious decline of submerged vegetation has been observed. The aquatic vegetation of the lake was studied during the sampling period 2004 –2005 and was classified in groups using TWINSPAN and NMS. CCA was performed in order to examine relationships between the aquatic macrophyte species abundance and the environmental variables. Moreover ,it was investigated the effect of the littoral zone on physical and chemical characteristics of water quality and the seasonal patterns of the environmental variables. One –way ANOVA was used to determine statistical significant differences of environmental variables between the littoral zone and the non –littoral plots with aquatic vegetation and without aquatic vegetation. The trophic state index of Carlson was calculated to evaluate the trophic state of the lake. The results showed a great decline of submerged aquatic vegetation and only a few submersed species were recorded (Ranunculus trichophyllus ,Potamogeton crispus ,Callitriche stagnalis). One-way ANOVA showed that SRP ,pH ,surface D.O ,carbonates and transparency were lower in the littoral zone while bicarbonates ,conductivity and transparency /depth ratio were higher. Higher SRP was recorded during the summer due to increased internal loading from the sediment ,while higher nitrate concentrations were occured during the autumn. The ratio DIN/SRP ranged in low values (<15) from spring to autumn indicating N limiting conditions where cyanobacteria blooms are likely to be dominant. The trophic state of the lake is classified as eutrophic according to the Kratzer and Brezonik classification system.

Research report on the dynamics of nitric compounds in different water levels of shallow wells, located in Pypliai, Kaunas District, is given in the thesis. Subject of research – water quality indicators: nitrates (NO3-), nitrites (NO2-) and ammonium (NH3). Aim of research – to define variation of nitrates concentrations in different water levels of shallow wells. Methodology: analysis of scientific literature; chemical water quality analyzes methods: spectral and electrochemical methods; statistical analysis using EXCEL, STATISTICA programs. Results of research: the results of scientific research showed, that nitrates concentrations in deeper levels of shallow wells vary differently; the tendencies of these variations depend on seasons. Seasons make no impact to nitrites and ammonium concentrations in deeper levels of shallow wells. The following statistically relevant water indicators were determined to influence nitrate concentration in shallow well water: oxygen quantity and electrical conductivity. Nitrite concentrations are inversely proportional to oxygen amount. Ammonium concentrations depend on organic compound quantity. Statistically relevant links between nitrites and ammonium were estimated.