In this study, I examined the influence of hydrological seasonality on spatiotemporal variation of algal biomass and shrimp abundance on sandbanks of the Cinaruco River in southwestern Venezuela. Seasonal variations of abiotic and biotic variables in the Cinaruco were driven by the hydrological regime. During the highwater periods, river sites in the main channel and lagoon sites were similar in water physicochemical variables and algal biomass. In contrast, physicochemical variables and algal biomass differed between river and lagoon sites during the low-water period. The absence of flow in lagoons and consistently low algal biomass on river sandbanks were the most important features of the spatial variability between main-channel and lagoon sandbanks during low-water phases. Benthic algal biomass was highly uniform at small spatial scales and significantly heterogeneous at large spatial scales. In the second major part of this dissertation, I found a relatively species-rich shrimp assemblage with seven species inhabiting the sandbanks of the Cinaruco. I also observed clear patterns of temporal and spatial variation in shrimp abundance on the Cinaruco sandbanks. Abundance of shrimp on the sandbanks presented remarkable diel variation, showing almost exclusive use of this habitat at nights. Seasonally, shrimp were more abundant during rising- and falling-water periods, when rapid changes of environmental conditions occur. Shrimp abundance was high on those sandbanks with absence of troughs and presence of submerged vegetation. These environmental features presumably promote colonization/establishment and survival/persistence of shrimp in the sandbanks. In a patch-dynamic view of communities, a mobility control model seems to apply to shrimp of the sandbanks in the Cinaruco during the period of rapid changes in hydrology and habitat structure. During low-water periods, when habitat structure of sandbanks is relatively constant, low shrimp abundance appears to be heavily controlled by high fish predation. The annual flood regime of the Cinaruco, which drives the concentrations of dissolved materials, affects material interchanges between aquatic and terrestrial systems, and modifies aquatic habitat structural complexity, is responsible for creating strong patterns of seasonal and spatial variation in benthic algal crops and shrimp abundance on the sandbanks of this large floodplain river.

Thesis (M. Sc.)--York University, 1998. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 82-88). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ39192.

This dissertation presents an investigation of the effects of a stochastic component of sediment transport in sandy rivers in an attempt to gain information about the transport system and its implications for the evolution of Earth's surface topography. First, a method for characterizing the geometries of bed forms is introduced and compared to previously proposed methods. This new method is then implemented on a field dataset as well as laboratory dataset and the results are compared to those obtained by traditional methods. Second, a method for characterizing the dynamic evolution of the bed geometries is demonstrated. It produces a velocity scale, the mean migration rate of the bed topography, and a deformation scale, the evolutionary departures of the bed topography from pure migration. These scales are calculated for the field and laboratory data and are compared. The flux of bed sediment is then shown to depend on the stochastic component of bed evolution. The fluxes for each dataset are calculated, they are related to the environmental conditions causing the transport of sediment, and suggestions are made for the design of field campaigns that attempt to measure sediment transport by repeated surveys of bed topography. Finally, the implications of stochasticity for sediment transport are investigated. A null hypothesis is formulated for topographic change by a stochastic process. Then the effects of measurement and field collection methods on the null hypothesis are evaluated. The most important prediction is non-trivial behaviors in measurable rates of surface change at short timescales. This prediction is then evaluated with field data from a growing sandy channel network whose behaviors can be determined at timescales of decades to centuries (dendrochronology), tens of thousands of years (cosmogenic radiochemistry), and hundreds of thousands to millions of years (age of channel system and sediments through which it cuts). These three investigations create a coherent account of the expressions and implications of variability in the transport of sediment, and therefore the evolution of topography, in sandy river systems that can then be generalized to changes across Earth's surface. / text

Located in central Brazil, the Araguaia River is the largest river flowing through the Cerrado, the Brazilian savanna. The thesis presented here assesses the hydro-geomorphology of the middle Araguaia River-floodplain system by characterizing flooding patterns and linking these patterns to the geomorphology of the floodplain. It also determines the response of floodplain lake morphometry and surface water connectivity to the annual flooding of the river, and describes how different floodplain geomorphologic units influence changes in open water areas in the floodplain from the dry season to the wet season. Peak discharges along the middle Araguaia River can be reduced downstream despite large increases in drainage area and the contribution of tributary inputs. After analyzing average daily discharge measurements from 1975 to 2007 along an upstream reach and a downstream reach in the middle Araguaia River, four main flooding types are characterized based on the magnitude of the peak discharge and the pattern of peak discharge reduction that occurs as the flood wave moves downstream. Short-term losses of channel discharge during the flooding peak and over the flooding season from November to May are estimated, with the downstream reach displaying more short-term channel loss compared to the upstream study reach. Differences in floodplain geomorphological characteristics between the two study reaches, including the proportions of distinct geomorphologic units (a lower elevation impeded floodplain, a unit dominated by paleomeanders, and a unit of accreted banks and islands), influence the patterns of peak reduction and channel loss. Short-term losses of channel discharge during flooding peaks are usually re-gained by the channel by the end of the flooding season, although in two years about 10% of the volume input into the downstream reach was lost from the channel over the flooding season. Using satellite imagery and an open water index, changes in lake area, perimeter, and surface water connectivity with the main channel between dry season and the wet season are determined for 32 floodplain lakes. The changes in lake morphometry and connectivity are linked to how fluvial processes formed the floodplain lakes. Spatial variations in the floodplain areas that became open water from the dry season to the wet season demonstrate that distinct floodplain geomorphologic units influence the extent and location of open water areas during flooding. Floodplain lakes that expand in area and in depth and are connected to the river channel via surface water likely provide storage areas for the channel losses and peak discharge reductions observed in some of the flooding types for the middle Araguaia River. Although there have been attempts to plan the placement of dams on the Araguaia River, the river is not impounded, allowing for the analysis of a river system with an unaltered flow regime. This thesis contributes to knowledge of a large and understudied tropical river in an ecologically sensitive region. / text

published_or_final_version / Civil Engineering / Master / Master of Philosophy

No description available.

Project Completion Report, Office of Water Resources Research Project A-047-ARIZ / Period of Investigation: July 1973 - June 1974 / The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Resources Research, as authorized under the Water Resources Research Act of 1964. / A means of referencing various entities along a given stream course is the river mile index. This gives the location relative to the coordinate geometry of the river system. This type of referencing is very useful to a number of agencies both within the State and at higher levels. Detailed map coverage of the State has not been available until recently with the production of 7-1/2 minute orthophoto maps of the entire State of Arizona. Since these maps were produced from imagery obtained during 1972-73, the State has a fairly definite point in time with which the maps were produced. The existing U. S. Geological Survey maps varied by up to 50 years in their generation. A scheme was worked out and six orthophoto maps were annotated using that method for an area around Tucson, Arizona. The problem of developing a computer software package to produce river mile indices was begun but soon shown to be too vast in scope to accomplish all that was desired. Several existing similar programs were examined. The U. S. Environmental Protection Agency (EPA) has a program AUTOMAP which is designed to do all that was sought to be done and much more. The development of a small, crude, local computer program was abandoned. Linkage to the EPA program AUTOMAP was sought and will be effected soon. The enlargement of project scope and envolvement meant that the pilot project was absorbed into a now ongoing activity to digitize the main stream channels and ancillary data. This new enlarged project, with funding from other sources, should be completed this year. The OWRR project may be thought of as the seed of the large project now being conducted. Without the seed the present status would not have been realized.

The overall objectives of a study initiated in 1972 by the Water Resources Research Center (Univ. of Arizona), in cooperation with the Pima County Dept. of Sanitation, are to examine the possibility of interactions between recharged river water and deposits in adjoining landfills, and if such interactions occur to evaluate the effect on native groundwater quality. Corresponding to these objectives, the principal function of a monitoring program initiated during the project was to characterize background water levels and native groundwater quality during normal low flows (i.e., sewage flows) in the river, and to monitor changes, if such occur, during flood flows. As it turns out, data from the project should also be applicable to the anticipated irrigation of farmland near Marana, using effluent from the Impending Ina Rd Treatment Facility. In particular, clues will be provided on transformations in sewage effluent quality during infiltration and deep percolation. The first phase of the project was conducted at the Ina Rd landfill and the second involved both the Ina Rd and Ruthrauff Rd fills. Results of the first phase were reported in a paper by Wilson and Small. This report will review the results of the second study phase. Specific objectives of the studies during the second phase included (1) obtaining river water and well water samples for chemical and microbiological analysis, (2) monitoring water level changes in available wells and (3) characterizing general features of the geohydrology in the vicinity of the landfills.

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No description available.