HYDROGEOLOIC SIGNIFICANCE OF OGALLALA FLUVIAL ENVIRONMENTS, THE GANGPLANK

1981 ◽  
pp. 89-94 ◽  
Author(s):  
RUSSELL G. SHEPHERD ◽  
WILLARD G. OWENS
Keyword(s):  
Fluvial Environments

QUALIDADE DAS ÁGUAS E NÍVEL TRÓFICO DA BACIA DO RIO PACIÊNCIA NA ILHA DO MARANHÃO, BRASIL

2019 ◽  
Vol 21 (2) ◽  
pp. 437-453
Author(s):  
Elna Lucilia Santos Corrêa ◽  
Karina Suzana Feitosa Pinheiro ◽  
Cláudio José Da Silva de Sousa ◽  
Luiz Jorge Bezerra da Silva Dias
Keyword(s):  
Water Quality ◽  
Trophic Status ◽  
The Body ◽  
Chemical Parameters ◽  
Public Supply ◽  
Physico Chemical ◽  
Great Availability ◽  
Del Rio ◽  
Fluvial Environments

O Brasil apresenta grande disponibilidade de água doce em seus mananciais. Fazendo parte desse recurso encontra-se, o rio Paciência, localizado na Ilha do Maranhão destacado pela sua importância local, principalmente por contribuir com suas águas para recarga dos mananciais subterrâneos, fonte de abastecimento público de vários bairros de São Luís, capital do estado. No entanto, este rio vem sofrendo comprometimento da qualidade de suas águas, consequência do processo de uso e ocupação dos espaços em sua bacia. Destacando-se como um dos principais problemas relacionados a qualidade de ambientes fluviais,  a eutrofização, que consiste no processo em que o corpo d’água adquire elevados níveis de nutrientes (fosfatos e nitratos), é um indicador determinante da qualidade da água. Neste sentido, o objetivo deste trabalho foi caracterizar a qualidade da água e do estado trófico na bacia hidrográfica do rio Paciência atráves dos parâmetros fisico-químico evidenciando os trechos mais comprometidos conforme os valores alcançados nas análises. Os resultados das análises foram comparados com a CONAMA No. 357/05 que indicaram uma situação preocupante quanto à qualidade da água no local de estudo.Palavras-chave: Qualidade de água; Eutrofização; Ilha do Maranhão. ABSTRACTThe Brazil has great availability of fresh water in its springs. Within these contexts, the Paciência River, located on the Island of Maranhão stands out for its local importance, mainly for contributing its waters to the recharge of the underground springs, source of public supply of several districts of São Luís, capital of the state. However, this river has been compromising the quality of its waters, a consequence of the process of use and occupation of the spaces in its basin. Highlighting as one of the main problems related to the quality of fluvial environments, eutrophication, which consists of the process in which the body of water acquires high levels of nutrients (phosphates and nitrates), is a determinant indicator of water quality. In this sense, the objective of this work was to characterize the water quality and trophic status in the Paciência river basin through the physico-chemical parameters, showing the most compromised stretches according to the values reached in the analyzes. The results of the analyzes were compared with CONAMA No. 357/05 which indicated a worrying situation regarding the quality of the water at the place of study.Keywords: Water quality; Eutrophication; Island of Maranhão. RESUMENBrasil tiene gran disponibilidad de agua dulce en sus manantiales. Parte de este recurso es el río Paciencia, ubicado en la isla de Maranhão, que destaca por su importancia local, principalmente porque contribuye con sus aguas a recargar las fuentes subterráneas, fuente de suministro público de varios barrios de São Luís, capital del estado. Sin embargo, este río se ha visto afectado por la calidad de sus aguas, como consecuencia del proceso de uso y ocupación de los espacios en su cuenca. Destacando como uno de los principales problemas relacionados con la calidad de los ambientes fluviales, la eutrofización, que consiste en el proceso en el que el cuerpo de agua adquiere altos niveles de nutrientes (fosfatos y nitratos), es un indicador determinante de la calidad del agua. En este sentido, el objetivo de este trabajo fue caracterizar la calidad del agua y el estado trófico en la cuenca del río Paciência a través de los parámetros fisicoquímicos, mostrando las secciones más comprometidas de acuerdo con los valores alcanzados en los análisis. Los resultados de los análisis se compararon con CONAMA N°. 357/05, que indicó una situación preocupante con respecto a la calidad del agua en el sitio de estudio.Palabras clave: Calidad del agua; Eutrofización, Isla Maranhão.

Morphodynamic stability and characteristic length scales of bifurcations and confluences loops

2021 ◽  
Author(s):  
Niccolò Ragno ◽  
Marco Redolfi ◽  
Marco Tubino
Keyword(s):  
Froude Number ◽  
Water Surface ◽  
Characteristic Length ◽  
Coupled Model ◽  
Surface Elevation ◽  
Momentum Balance ◽  
Water Surface Elevation ◽  
Control Volumes ◽  
Almost All ◽  
Fluvial Environments

<p>The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.</p>

scholarly journals On some local restricted Maastrichtian environments of the "Hațeg Island" (Transylvania, Romania)

2016 ◽  
Vol 47 (1) ◽  
pp. 82 ◽  
Author(s):  
V. Codrea ◽  
Al. Solomon ◽  
C. Fărcaș ◽  
O. Barbu
Keyword(s):  
Case Studies ◽  
Oxygen Content ◽  
Fossil Record ◽  
Sedimentary Rocks ◽  
Red Beds ◽  
Abandoned Channels ◽  
Fluvial Environments ◽  
Haţeg Basin

The continental Maastrichtian formations from Transylvania are notorious mainlyfor bearing peculiar fossils related to an island realm known as the "Hațeg Island". The thick piles of sedimentary rocks accumulated in fluvial environments. The "red beds" are in dominance. However, local peculiar environments are of interest for specific types of fossilization (plants, invertebrates or vertebrates), i.e. ox-bow lakes or fluvial temporary abandoned channels. In such deposits the fossil record can be different compared to the red beds, especially when the oxygen content was low. Case studies as the ones from Pui (Hațeg Basin) or Oarda de Jos (SW Transylvanian Basin) are exposed. The relationships of fossil taxa and these restricted environments are discussed.

Depositional Environments of Plant Bearing Sediments

1988 ◽  
Vol 3 ◽  
pp. 1-13 ◽  
Author(s):  
Scott L. Wing
Keyword(s):  
Mass Flow ◽  
Depositional Environments ◽  
Fluvial Systems ◽  
Volcanic Origin ◽  
Sedimentary Environments ◽  
Plant Remains ◽  
Mass Flow Deposits ◽  
Fluvial Environments

Plants can become incorporated into the sediments of virtually any environment, from the oozes of abyssal plains to the silts and sands of delta fronts to brecciated mudflows of volcanic origin. However there is a much narrower range of sedimentary environments in which identifiable plant remains are found in abundance. Generally speaking these are the very shallow or subaerial portions of deltas and estuaries, the channels and floodplains of fluvial systems, lakes of all sizes, ash-falls, and mass-flow deposits such as mudflows. For the purposes of this paper peat swamps are considered as unusual subtypes of deltaic and fluvial environments in which clastic input is low relative to organic accumulation.

scholarly journals Drift-Ice Abrasion Marks along Rocky Shores

1985 ◽  
Vol 31 (109) ◽  
pp. 237-241 ◽  
Author(s):  
Jean-Claude Dionne
Keyword(s):  
Hudson Bay ◽  
Rocky Shores ◽  
Tidal Zone ◽  
Cold Regions ◽  
Lawrence Estuary ◽  
Soft Rocks ◽  
Rock Fragments ◽  
Ice Floes ◽  
St Lawrence Estuary ◽  
Fluvial Environments

AbstractDrift-ice abrasion marks are common along present-day rocky shorelines in cold regions. They include polished surfaces, scratches, striations, small grooves, and minor friction cracks. Most are found on relatively soft rocks like shale, sandstone, limestone, dolomite, and basalt, and occasionally on harder rocks like granite and gneiss. They were made by rock fragments frozen at the base of ice cover or by ice floes pushed onshore by wind or dragged along the bottom by waves, tides, and currents. They are found both in the modern and Pleistocene marine, lacustrine, and fluvial environments. Along the Hudson Bay eastern shoreline, these abrasion marks are superimposed on glacially polished and striated surfaces. Along the St. Lawrence Estuary, they are more common on boulders in the tidal zone. Characteristics of drift-ice abrasion marks are described and their significance is pointed out.

The nature of the Late Paleozoic glaciation in Gondwana as determined from an analysis of garnets and other heavy minerals

1979 ◽  
Vol 16 (6) ◽  
pp. 1137-1153 ◽  
Author(s):  
C. P. Gravenor
Keyword(s):  
South Africa ◽  
North America ◽  
Heavy Minerals ◽  
Late Paleozoic ◽  
Glacial Sediments ◽  
Mechanical Abrasion ◽  
Long Period ◽  
Glaciogenic Sediments ◽  
Fluvial Environments

Heavy mineral suites from Late Paleozoic sediments from South Africa, Australia, and Antarctica are dominated by garnet. The enrichment of garnet is attributed to the loss of unstable minerals such as pyroxenes and amphiboles by mechanical abrasion in beach and fluvial environments during periods of deglaciation.An analysis of chattermark trails found on the surface of the garnets shows that the percentage of chattermarked garnets is roughly twice that from samples of Pleistocene glacial sediments of North America. As the percentage of garnets with chattermark trails is a function of the distance of glacial transport, it is concluded that the garnets found in the Late Paleozoic glaciogenic sediments have been transported over very long distances, probably as a result of having been recycled many times. As these glacially mature garnets are found in tillite and other glaciogenic deposits which directly overlie bedrock, it is suggested that much of Gondwana was covered for a long period of time by glaciers of continental dimensions and that much of the record of the early part of the Late Paleozoic glaciation is missing due to glacial erosion.

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