In alpine catchments, the nature of hydrological sources and stores varies in both space and time. This thesis presents an investigation of the processes controlling the stream hydrograph in three nested sub-catchments within a small alpine catchment (the TaillonlGabietous catchment) in the French Pyrenees. The study conducts fieldwork and modelling in parallel to allow the independent corroboration of hypotheses from different sets of analytical and field techniques. Meteorological. hydrological and hydrochemical data were collected during the 1996 and 1997 summer ablation seasons. Three key observations are made following analysis of this data. First, a temporal compensation effect is observed between summer meltwater runoff and the more prolonged discharge of groundwater throughout the winter. Second. the importance of precipitation events over the ablation season in this climatically sensitive area is recognised. Third. it is suggested that it is unrealistic to assume watertight catchments in many alpine areas. A conceptual model is presented of the hydrological processes controlling the stream hydrograph in an alpine glacierized catchment with an underlying groundwater system. Links to concurrent projects on glacier hydrometeorology. climate change. and stream ecology significantly enhanced the overall conclusions of the thesis.

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Thesis (Ph. D.)--University of Adelaide, Dept. of Civil Engineering, 1984. / Includes bibliographical references (leaves 390-404).

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 18, 2008). Includes bibliographical references (p. 42-47).

No description available.

The recession portion of the ephemeral stream hydrograph is modeled as a conceptual analog of the discharge from a single leaky reservoir. Physically, the reservoir may be considered to approximate that portion of the ephemeral stream channel that is flowing at the beginning of recession. The discharging reservoir is described by a continuity equation and by discharge-stage and storage-stage relations. No input is routed through the reservoir. It is assumed that initially (at the beginning of recession) the reservoir has water in storage. The discharge-stage relation for the reservoir is defined by the rating curve for the stream and storage-stage depends on reservoir configuration. A good agreement between observed and model curves is obtained by optimizing two parameters, reservoir leakage rate and initial storage, The agreement is most sensitive to changes in initial storage. Best parameter values are physically realistic and best reservoir configuration has leakage that varies directly with stage (depth) and storage that varies as the square of stage.

No description available.

The movement of organisms and resources within ecosystems are essential elements in the productivity, stability, and distribution of communities. This thesis examines how water velocity, a defining factor of lotic systems, influences the dispersion of benthic organisms and particulate organic matter in small stream ecosystems. Variation in movement-related behaviours in two rheophilous (‘flow-loving’) mayflies (Epeorus and Baetis) and two rheophobic (‘flow-avoiding’) mayflies (Ameletus and Paraleptophlebia) were compared to determine how benthic organisms disperse between and within habitat patches in hydrodynamically complex landscapes. The degree to which water velocity and particle shape influence the retention of organic matter (including deciduous leaves, conifer needles, red-cedar fronds, and branch fragments) was examined to determine how physical factors determine detrital resource availability in streams. Although water velocity did not influence the crawling rates of Baetis and Ameletus in daylight conditions, both mayflies dispersed rapidly upstream in low-velocity flows in dark conditions. Drift rates of both mayflies were lower in daylight than dark conditions, and were generally inversely related to their habitat preferences. Escape responses in grazing Epeorus, Baetis, and Ameletus larvae in a range of flow conditions showed that retreat distance was more sensitive than flight initiation distance to variation in water velocity, suggesting that hydrodynamics mediate the risks of predation and the costs of flight in stream systems. Comparisons of the transport distances of live larvae, dead larvae, and passive tracer particles in low and high water velocities showed that drift distance varied substantially among taxa, and that behavioural control over drift distance generally declined as water velocity increased. While organic matter particles generally travelled further in high-velocity reaches, leaves were retained in riffles when they impacted on protruding clasts, while ‘stiff’ particles were retained when they settled into streambed interstices. Leaves placed in high-velocity microhabitats were broken down more slowly than leaves in low-flow areas, likely due to the exclusion of large-bodied detritivores. In conclusion, this thesis supports the view that hydrodynamic forces control trophic interactions and local population dynamics in stream ecosystems by directly altering the physical – and sometimes behavioural – processes of particle entrainment, transport, and deposition.

Intraguild (IG) predation, where species within the same guild prey on each other, is common in aquatic communities. I used the abundance and distributional patterns of three species of Rhyacophila (Trichoptera), derived from a survey of 25 streams in Nova Scotia, Canada, to test several predictions of IG theory. I first sampled microhabitats and conducted behavioural observations to establish that the species do co-occur and prey on each other. Abundance patterns did not conform to two key model predictions: (1) Neither of the IG prey (R. minor, R. vibox) was excluded from the most productive streams, and (2) IG prey densities were not inversely related to productivity in streams with the IG predator (R. fuscula). It remains possible that intraguild predation occurs between these species of Rhyacophilia, the measured abundances do not indicate any measurable effects from IGP, the abundance being determined instead by the availability of prey.