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Abstract. — Since the end of the XIXe century, the mean values of annual discharges of the Rhône in the water gaging station of Sault Brénaz, have been relatively constant. They have been influenced only by climatological changes (for example the draught period 1940-1949). But the evolution of monthly hydrological regimes and particularly the daily regimes (studied by the frequency of occurrence analysis for caracteristic discharges and the sequences of following days of discharges > to given values), shows the joint influence of climatological and human parameters (hydroelectric settlements). These changes in the rhythm of the stream have been to be correlated with the observations made in the near environment (level of undreground sheets, of water biological changes, etc. . .).

Summary. — Between Lyon and Geneva, dams, reservoirs, embankments and channels built within the framework of french Upper- Rhone hydro-electric management produce strong modifications in hydrology and, consequently, in vegetation dynamism of the river-system. The author considers the consequential effects on vegetal communities, their future and their spatial organization. The difficulties in doing a previsionnal diagnosis are brought out.

Summary. — The man-induced impacts, perceptible in 1980-1981, on the natural vegetation are described. The example of a small part of the french Upper-Rhone river-basin near Geneva is choosen. The changes induced by : — Hydro-electric dam and reservoir (1948). — Railway embankments (1860). — Stream gravel extraction activities (1970).

Abstract. — A set of piezometers located on the left bank of the Rhône river are studied. Two main objectives are pursued : a statistical classification of the underground water levels, following their cross- correlations or their cross-corelations with the explicative variables (temperature ; rainfall ; river flow) ; the construction of a mathematical dynamic model relating the measurements at various instants, for short-term forecasting of the water levels evolution.

Abstract. — The method of grain size image (Passega) is applied to the study of fine-grained alluvial deposits in the plains of the French upper Rhône river. It provides a simple criterion for discriminating the ecological units, demonstrates the spatial variability of grain-size distribution (influence of slope and fluvial models) and the thining of the load since the 19th century.

Abstract. — The inventory of French Alpine lakes, completed from the I.G.N. topographic map — 1/25 000 — , indexes more than 3 000 natural, fited and artificial, permanent and temporary lakes ; the surface of 583 of these lakes is above 0,005 km 2. A preliminary description of three morphometric caracteristics (altitude, area, depth) is proposed.

Abstract. — The lake of Aiguebelette (Savoie) is, in summer, chimicaly and biologicaly polluted by the bathers (june, July, august) and in winter, by the waters of the salt— leaching on the motor — way A 43. These brined waters are reaching the lake. The ratio of the sodium chloride remains in reasonable norms, but is requiring future evolution watching.

Abstract. — Saint-Bon-Tarentaise is an exceptional case among alpine ski resorts. In 1946 it launched the first of a series of facilities ; from 1950 to 1960 it was the empirical « laboratory »for new types of mountain resort tourist facilities. With more than 30 years running, it provides the means to observe social change in the local population.