The voluminous limnological literature contains few studies of mountain streams. Though there are a few papers on the benthic algae (see Budde 1928, Raabe 1951) only Pennak (1943) reports year-round quantitative data on the phytoplankton. Brinley (1950) gives some phytoplankton information in a summer study of streams in Rocky Mountain National Park.

A study to determine habitat differences of benthic macroinvertebrates was conducted on the upper Strawberry River, Utah. The investigation was part of a large scale project to determine minimum stream flow requirements for trout. The effects of time, habitat, depth and velocity on the distribution of benthic fauna were evaluated. Samples of benthic invertebrates (146 total) were collected every 2 months at 8 stations on the river from November, 1975 through August, 1976. Representatives of 59 taxa were collected. Eight taxa comprised 90 percent of the mean annual community standing crop in numbers. Biomass was not dominated by any group of taxa. Community standing crop decreased from late Fall 1975 until early Summer 1976. The largest increase in standing crop occurred during August. Prediction of benthic distribution through the use of depth and velocity categories was unsuccessful. Three-dimensional plots of the relative density of a taxon versus depth and velocity indicated the contagious nature of the animals' distributions but their preference for specific categories could not be demonstrated. The results suggested that macroinvertebrates could tolerate large variations in current and depth and that these physical factors are only indirectly related to faunal distribution. Results of analysis of variance and covariance showed time to be the factor which influenced the distribution of most taxa (85%), followed by the time x habitat interaction (20%), velocity (18%), habitat (11%), and depth (9%). Comparisons in animal abundance were made between 4 riffles and 4 ''pools". These two habitats did not differ significantly in substrate type or velocity, however depth did show significant differences. Results of nonparametric tests suggested that the majority of taxa migrated into "pools" during periods of snow, ice, and low flows, an indication that "pools" may provide refuge to macroinvertebrates during periods of stream dewatering and diversion.

Five groups of 400 hatchery rainbow trout, (Salmo gairdneri), were stocked in a small, mountain stream at )-week intervals from June to September, 1972. A fish trap captured any fish moving out of a 500 m study section. Fish began moving at high levels during the first day of each stocking and continued at high rates for 5-8 days (Early Phase), after which movement decreased to low levels for 6-9 days (Late Phase). Early Phase fish moved primarily at night, possibly due to their disoriented state and high subjectivity to stream conditions. Fish moving during Late Phase did so mainly during daylight, probably in response to diurnal periodicity of a day-active food organism in the drift. Forced movement due to social behavior did not seem to be an influencing factor, but the duration of visible light seemed important to moving fish.

Estimates of the brown trout (Salmo trutta) population were made in two areas of the Blacksmith Fork River, Cache County, Utah, from June 1972 to June 1973. Additional data were obtained on movement, growth, mortality, biomass, production, and yield. Population density was highly variable in the area where habitat alterations had occurred, but was relatively uniform where the habitat was undisturbed. The brown trout exhibited little movement except during spawning season. Instantaneous growth and mortality rates are provided for each age group. Mean annual biomass in the two areas was 12.0 and 10.2 grams per square meter and production was estimated at 9.2 and 7.7 grams per square meter per y ear in the two study areas. Gametes comprised approximately 5 percent of the annual production and angler harvest removed 39 percent of production.

La Durance est une large rivière méditerranéenne à charge grossière et à lit divagant. Le fonctionnement hydro-sédimentaire de son bassin versant a été profondément modifié par la mise en place d'aménagements hydro-électriques et par les extractions de graviers, qui ont entraîné une rétraction de sa bande active et une incision marquée de son lit. Ces évolutions morphologiques correspondent à des enjeux majeurs en termes de gestion du territoire en moyenne et basse Durance, du fait de la nécessité du maintien d'une capacité d'écoulement du lit en crue, et de la mobilité latérale du lit, souvent incompatible avec l'occupation de la vallée. Cette thèse, basée sur la collecte de données de terrain, vise à développer un schéma de fonctionnement du transport sédimentaire dans les rivières à charge grossière de grande largeur, en intégrant les différentes échelles spatiales (et donc temporelles). Elle a également pour objectif de donner des clefs de compréhension pour la gestion des flux sédimentaires en Durance. Les mécanismes de la mobilité des particules sédimentaires et des formes fluviales sont étudiés dans une démarche ascendante de reformulation scientifique de questionnements opérationnels. / The Durance River (South-Eastern France) is a large and steep wandering gravel-bed river, deeply impacted by gravel mining and flow diversion in its whole catchment area. The Durance River is characterized by a sediment deficit that led to a reduction of active channel width and river bed degradation. These lateral and vertical dynamics lead to important issues in terms of landscape management, because of (i) maintaining the bed hydraulic capacity to evacuate flood discharges and (ii) planform evolution of the river that conflicts with landscape use. This field-based thesis aims at developing a functioning scheme of bedload transport in large gravel bed rivers at various spatial (and consequently temporal) scales and gives keys to understanding for sediment fluxes management on the Durance River. Particle and bedform mobility mechanisms are studied with a scientific approach closely linked to management issues.