Reservoir releases for generating power need to be reconciled with efforts to maintain healthy ecosystems in regulated rivers having irregular channel topography. Fluctuating, complex flow patterns near river obstructions such as boulders and large woody debris provide unique habitat for many aquatic organisms. Numerical modeling of the flow structures surrounding these obstructions is challenging, yet it represents an important tool for aquatic habitat assessment. Moreover, efforts for modeling the morphologically and biologically important transient flows, as well as quantifying their impacts on physical fish habitat during the unsteady-flow period remain rare. In this dissertation, the ability of two- (2-D) and three-dimensional (3-D) hydraulic models to reproduce the localized complex flow features at steady base and peak flows is examined first. The performance of the two hydraulic models is evaluated by comparing the numerical results with measurements of flow around a laboratory hemisphere and boulders located at a reach of the Smith River in Virginia. Close agreement between measured values and the velocity profiles predicted by the two models is obtained outside the wakes behind these obstructions. However, results suggest that in the vicinity of theses obstructions the 3-D model is better suited for reproducing the circulation flow behavior favored by many aquatic species over a broad range of flows. Further, time-dependent flow features affecting channel morphology and aquatic physical habitat are investigated using the numerical models for the same reach in the Smith River. Temporal variation measurements of water surface elevation and velocity profile obtained in the field during a reservoir release are in good agreement with the numerical results. A hypothetical "staggering" flow release scenario simulated by the 3-D model leads to reduced erosional area and longer refugia availability for juvenile brown trout during hydropeaking. Finally, an unsteadiness parameter β is proposed for determining whether an unsteady flow regime can be either modeled using a truly dynamic flow approach or a quasi-steady flow method. / Ph. D.

Made available in DSpace on 2014-07-29T16:21:16Z (GMT). No. of bitstreams: 1 Dissertacao_Vieira_2011.pdf: 1523509 bytes, checksum: 3cdad6bc2c4962ae82afe2a1ffbc4501 (MD5) Previous issue date: 2011-03-11 / The presence of riparian vegetation is an important factor that strongly influences such river characteristics, which consequently maintain local habitat heterogeneity and contributes to the input of allochthonous materials. Therefore, this dissertation has two objectives: 1) to compare the interaction of fish assemblages with riparian vegetation that belongs to the streamlet Santa Maria, Meia Ponte, Piracanjuba Rivers basins, rivers located in the Northern portion of the Paraná River basin, Central Brasil, identifying possible structures relating basins and rivers orders to the vegetation cover percentage, availability of allochthonous and authochthonus matters and water turbidity; 2) determine which habitat variables (geomorphology, riparian vegetation, limnological, physical-chemical and hydrological aspects) influence streamlet fish assemblages found within in the Northern Paraná River Basin. In order to do so, during April and September 2009 samples were performed in 27 streamlets of first and second orders from Meia Ponte River (seven tributaries), Piracanjuba River (14 tributaries) and Santa Maria Streamlet (six tributaries) located in the Southeastern region of the state of Goias (Northern Paraná Basin). By the end of the samples, 4879 specimens from 59 species and 19 families were collected. Species richness, individual abundances by guilds and total biomass did not presented significant differences among the three basins considered. However,when the streamlets order were considered, such difference was significant. The difference between first and second order streamlets when considering species richness was, on average, of eight species and the highest species richness was found among second order streamlets. Individual abundances found by trophic guilds presented differences among, carnivorous, herbivorous and insectivorous species, and in all cases, the species richness was higher in the second order streamlets. Total biomass presented an average increase of 131g in the second order streamlets. From the 18 habitat descriptive variables analyzed, eight influenced the local fish assemblages: two of them were quantitative ones (margins cover type and deposited matter in the streamlet bed) and six were quantitative (stream velocity, river width, dissolved oxygen, water conductivity, water temperature and water turbidity). / A presença da mata ripária e um fator que influencia nas características físico-químicas das redes de drenagem, além de promover a manutenção da heterogeneidade de habitat local e contribuir com a entrada de material alóctone. Esta dissertação objetivaresponder à três perguntas : (a) a riqueza, abundância e biomassa por grupo trófico das assembléias de peixes difere entre bacias e é maior em cursos de água de segunda ordem?, (b) a riqueza, abundância e biomassa por grupo trófico está relacionada com as características cobertura vegetal, disponibilidade de matéria alóctone e autóctone e turbidez da água? (2) quais variáveis de habitat (geomorfológicos, mata ripária, limnológicos, físico-químicos e hidrológicos) influenciam na estrutura das assembléias de peixes dos riachos amostrados?. As coletas foram realizadas entre abril e setembro de 2009 em 27 riachos de primeira e segunda ordem. Foram coletados 4879 indivíduos distribuídos em 59 espécies e 19 famílias. A riqueza de espécies, abundância de indivíduos por guildas trófica e biomassa total não apresentaram diferenças significativas entre as três bacias consideradas e sim quando considerada a ordem dos riachos. Das 18 variáveis descritoras do habitat analisadas, oito apresentaram influência sobre a estruturação da assembléia de peixes local, sendo duas qualitativas (tipo de cobertura da margem e materiais depositados na calha do riacho) e seis variáveis quantitativas (velocidade da correnteza, largura do riacho, oxigênio dissolvido, condutividade, temperatura da água e turbidez).

In addition to the hydromorphological pressure on the ecological conditions of free-flowing river courses, increasing water temperature is affecting the water bodies, particularly by changing freshwater community compositions. The low discharge of numerous European rivers in the dry and hot hydrological year 2022 proves this relevance. Therefore, ecological assessment tools such as habitat modeling should take these factors into account when assessing the quantity and quality of habitats. In this paper, the habitat modeling tool “Transient River Habitat Modeling for Macrozoobenthos” (TRiMM) is improved by incorporating a fuzzy logic approach and adding water temperature to the set of parameters determining habitat suitability for macrozoobenthos. Habitat-relevant parameters, including hydromorphological factors (depth, velocity, mineral and organic substrate) and a water quality factor (temperature), are combined in the habitat model so that it can more broadly characterize river physical conditions and their interactions with biological indicators. Habitat modeling employed the mentioned parameters to simulate suitability for the macrozoobenthos in a small river in central Saxony, Germany. Due to its deteriorated condition, this river was selected as a representative for thousands of kilometers of small rivers across the region, which have been restored. The model simulated the status quo of river conditions from spring to summer for three macrozoobenthos species (Ancylus fluviatilis, Ephemera danica and Gammarus fossarum). The results showed that the natural flow resulted in dynamic habitat suitability both spatially and temporally, which differs for each species. Remarkably, the five-parameter model (depth, velocity, temperature, mineral, and organic substrate) generally performed better compared to a similar model without temperature.

<div>Agricultural headwater streams in the Midwestern United States are subject to contaminants from fields, increased sedimentation, and degradation of natural habitat. Previous research has shown that physical instream habitat degradation better explained variation in fish community structure than water chemistry. However, these studies did not include total suspended solids (TSS), which are considered a major freshwater contaminant. The objective of this study is to determine whether total suspended solids better explains fish community structure than other variables in agricultural headwater streams. Mixed linear effects modeling was used to determine the set of independent variables that best predicts each of the fish response variables of species richness, Shannon diversity index, fish density, and index of biotic integrity. Standardized coefficients were used to determine which independent variable in each of the models had the largest influence on fish response metrics. The set of independent variables that best explained species richness were mean total suspended solids, imidacloprid, discharge, and substrate richness. Shannon diversity index was explained best by the combination of maximum total suspended solids, mean total suspended solids, atrazine, total nitrogen, and discharge. Fish density was explained best by the percentage of silt and clay, dissolved oxygen, the percentage of canopy cover, cover type richness, and discharge. IBI was explained best by the combination of the percentage of silt and clay, total phosphorus, mean total suspended solids, and dissolved oxygen. Total suspended solids was the most influential independent variable for fish species richness and Shannon diversity, however the percentage of silt and clay in benthic sediments was the most influential independent variable for fish density and IBI. Results also indicate discharge and total phosphorus as being influential to fish community metrics. The results from this study suggest that models containing a combination of different types of independent variables best explain fish community structure. This study supports the use of conservation and restoration practices that reduce total suspended solids and the amount of silt and clay present in bed sediments to increase fish community integrity of agricultural headwater streams of the Midwestern United States.</div>

In this study Bradford’s (2008) approach for setting ecological flow and water level targets is tested and refined through application within the Lake Simcoe Region Conservation Authority’s (LSRCA) subwatershed of Lover’s Creek. A method for defining subwatershed objectives and identifying habitat specialists through expert input is proposed and tested. The natural regime of each streamflow and wetland site is characterized along with the hydrological alteration at each site. Potential ecological responses to the hydrologic alterations are then hypothesized for the different types of changes calculated at each site. Methods for setting overall ecosystem health and specific ecological objective flow targets are proposed and tested. These targets are integrated into a flow regime for each site and a process for using this information for decision making is suggested. Flow magnitude quantification is attempted using hydraulic modelling and sediment transport equations, however the data used were found to be inadequate for this application. The accuracy of the targets developed using the method presented in this paper is mainly limited by the accuracy of the hydrological model and quantified flow magnitudes. Recommendations for improving these components of the assessment are made. The unique approach and recommendations presented in this paper provide explicit steps for developing flow targets for subwatersheds within the LSRCA. This research contributes toward the advancement of EFA within the LSRCA, which provides opportunity for enhanced protection and restoration of ecosystem health across the watershed. / Lake Simcoe Region Conservation Authority